from collections import defaultdict

def map_func(inputs):
    results = defaultdict(list)
    for input in inputs:
        words = input.split()
        for word in words:
            results[word].append(1)
    return results.items()

def reduce_func(item):
    word, occurrences = item
    return (word, sum(occurrences))

def map_reduce(inputs):
    mapped = map_func(inputs)
    grouped = defaultdict(list)
    for key, value in mapped:
        grouped[key].append(value)
    return [reduce_func(group) for group in grouped.items()]

inputs = ["apple pear banana", "pear banana", "apple pear", "apple", "pear banana apple"]
print(map_reduce(inputs))

from flask import Flask, jsonify
from threading import Lock

app = Flask(__name__)
lock = Lock()

# a list to store the events
events = []

# endpoint to retrieve the events
@app.route("/poll")
def poll():
    # lock the events list to ensure that no events are added while being read
    with lock:
        # if there are no events, hold the request open until there are
        if not events:
            lock.release()
            sleep(60)
            lock.acquire()
        # return the events as a JSON object
        return jsonify(events)

# endpoint to add events
@app.route("/add_event", methods=["POST"])
def add_event():
    # lock the events list to ensure that no events are added while being read
    with lock:
        # add the new event to the events list
        events.append("new event")
    return "Event added."

if __name__ == "__main__":
    app.run()

import queue

class MessagingService:
    def __init__(self):
        self.request_queue = queue.Queue()
        self.response_queues = {}

    def add_response_queue(self, key, response_queue):
        self.response_queues[key] = response_queue

    def get_request_queue(self):
        return self.request_queue

    def get_response_queue(self, key):
        return self.response_queues.get(key)

class SyncService:
    def __init__(self, messaging_service):
        self.messaging_service = messaging_service
        self.files = {}

    def update_file(self, file_name, content):
        self.files[file_name] = content
        response_queue = self.messaging_service.get_response_queue("notification_service")
        response_queue.put(f"File {file_name} was updated")

    def get_files(self):
        return self.files

class NotificationService:
    def __init__(self, messaging_service):
        self.messaging_service = messaging_service
        self.response_queue = queue.Queue()
        self.messaging_service.add_response_queue("notification_service", self.response_queue)

    def get_updates(self):
        while True:
            try:
                yield self.response_queue.get(block=False)
            except queue.Empty:
                break

import flask
import gridfs
import pymongo

app = flask.Flask(__name__)

# Connect to the database
client = pymongo.MongoClient("mongodb://localhost:27017/")
db = client["dropbox"]
fs = gridfs.GridFS(db)

# Define an endpoint for uploading a file
@app.route("/files", methods=["POST"])
def upload_file():
    # Retrieve the file from the request
    file = flask.request.files["file"]

    # Save the file to the database
    file_id = fs.put(file)

    # Return the ID of the saved file
    return flask.jsonify({"file_id": str(file_id)})

# Define an endpoint for downloading a file
@app.route("/files/<file_id>", methods=["GET"])
def download_file(file_id):
    # Retrieve the file from the database
    file = fs.get(file_id)

    # Return the file
    return flask.send_file(file)

# Example usage
if __name__ == "__main__":
    app.run(port=5002)

import java.util.*;

class User {
    private String username;
    private List<String> files;

    public User(String username) {
        this.username = username;
        this.files = new ArrayList<>();
    }

    public String getUsername() {
        return username;
    }

    public List<String> getFiles() {
        return files;
    }

    public void uploadFile(String filename) {
        files.add(filename);
        System.out.println("File '" + filename + "' uploaded successfully.");
    }

    public void downloadFile(String filename) {
        if (files.contains(filename)) {
            System.out.println("Downloading file '" + filename + "'...");
            // Logic for downloading the file
            System.out.println("File '" + filename + "' downloaded successfully.");
        } else {
            System.out.println("File '" + filename + "' not found.");
        }
    }
}

class DropboxSystem {
    private Map<String, User> users;

    public DropboxSystem() {
        this.users = new HashMap<>();
    }

    public void registerUser(String username) {
        if (!users.containsKey(username)) {
            User newUser = new User(username);
            users.put(username, newUser);
            System.out.println("User '" + username + "' registered successfully.");
        } else {
            System.out.println("Username '" + username + "' is already taken.");
        }
    }

    public User getUser(String username) {
        return users.get(username);
    }
}

public class DropboxApp {
    public static void main(String[] args) {
        DropboxSystem dropbox = new DropboxSystem();

        // Register users
        dropbox.registerUser("user1");
        dropbox.registerUser("user2");

        // Upload files
        User user1 = dropbox.getUser("user1");
        user1.uploadFile("file1.txt");
        user1.uploadFile("file2.txt");

        // Download files
        User user2 = dropbox.getUser("user2");
        user2.downloadFile("file1.txt");
        user2.downloadFile("file3.txt");
    }
}

from flask import Flask, jsonify, request
import dropbox

app = Flask(__name__)

# Initialize Dropbox API client
ACCESS_TOKEN = "YOUR_ACCESS_TOKEN"
dbx = dropbox.Dropbox(ACCESS_TOKEN)

# Endpoint for uploading a file to Dropbox
@app.route('/upload', methods=['POST'])
def upload_file():
    # Get file from request
    file = request.files['file']
    
    # Upload file to Dropbox
    dbx.files_upload(file.read(), '/' + file.filename)
    
    # Return success message
    return jsonify({'message': 'File uploaded successfully'})

# Endpoint for getting metadata of a file on Dropbox
@app.route('/metadata/<path:path>', methods=['GET'])
def get_file_metadata(path):
    # Get file metadata from Dropbox
    metadata = dbx.files_get_metadata('/' + path)
    
    # Return file metadata
    if isinstance(metadata, dropbox.files.FileMetadata):
        file_metadata = {
            'name': metadata.name,
            'size': metadata.size,
            'client_modified': metadata.client_modified,
            'server_modified': metadata.server_modified,
            'path_lower': metadata.path_lower,
            'path_display': metadata.path_display
        }
        return jsonify(file_metadata)
    else:
        folder_metadata = {
            'name': metadata.name,
            'path_lower': metadata.path_lower,
            'path_display': metadata.path_display,
            'contents': []
        }
        for entry in metadata.entries:
            if isinstance(entry, dropbox.files.FileMetadata):
                file_metadata = {
                    'name': entry.name,
                    'size': entry.size,
                    'client_modified': entry.client_modified,
                    'server_modified': entry.server_modified,
                    'path_lower': entry.path_lower,
                    'path_display': entry.path_display
                }
                folder_metadata['contents'].append(file_metadata)
            else:
                folder_metadata['contents'].append({'name': entry.name})
        return jsonify(folder_metadata)

# Endpoint for downloading a file from Dropbox
@app.route('/download/<path:path>', methods=['GET'])
def download_file(path):
    # Download file from Dropbox
    _, file = dbx.files_download('/' + path)
    
    # Return file data
    return file.content

# Endpoint for deleting a file from Dropbox
@app.route('/delete/<path:path>', methods=['DELETE'])
def delete_file(path):
    # Delete file from Dropbox
    dbx.files_delete('/' + path)
    
    # Return success message
    return jsonify({'message': 'File deleted successfully'})

if __name__ == '__main__':
    app.run(debug=True)

import flask
import gridfs
import pymongo

app = flask.Flask(__name__)

# Connect to the database
client = pymongo.MongoClient("mongodb://localhost:27017/")
db = client["dropbox"]
fs = gridfs.GridFS(db)

# Define an endpoint for uploading a file
@app.route("/files", methods=["POST"])
def upload_file():
    # Retrieve the file from the request
    file = flask.request.files["file"]

    # Save the file to the database
    file_id = fs.put(file)

    # Return the ID of the saved file
    return flask.jsonify({"file_id": str(file_id)})

# Define an endpoint for downloading a file
@app.route("/files/<file_id>", methods=["GET"])
def download_file(file_id):
    # Retrieve the file from the database
    file = fs.get(file_id)

    # Return the file
    return flask.send_file(file)

# Example usage
if __name__ == "__main__":
    app.run(port=5002)

with open("example.txt", "rb") as f:
    dbx.files_upload(f.read(), "/example.txt")

_, res = dbx.files_download("/example.txt")
data = res.content
with open("example.txt", "wb") as f:
    f.write(data)

import os

LOCAL_FOLDER = "my_folder"

if not os.path.exists(LOCAL_FOLDER):
    os.makedirs(LOCAL_FOLDER)

result = dbx.files_list_folder("/" + LOCAL_FOLDER)

for entry in result.entries:
    local_path = os.path.join(LOCAL_FOLDER, entry.name)
    if not os.path.exists(local_path) or entry.server_modified > os.path.getmtime(local_path):
        _, res = dbx.files_download(entry.path_lower)
        data = res.content
        with open(local_path, "wb") as f:
            f.write(data)

import dropbox
from dropbox.paper import PaperDocCreateUpdatePolicy

TOKEN = 'YOUR_ACCESS_TOKEN'

dbx = dropbox.Dropbox(TOKEN)
paper_api = dropbox.paper.PaperApi(dbx)

title = "My new Paper document"
content = "This is my new Paper document."

doc = paper_api.docs_create(title, import_format="markdown")
paper_api.docs_update(
    doc.doc_id,
    revision=PaperDocCreateUpdatePolicy.overwrite.any(),
    contents=content
)

link = dbx.sharing_create_shared_link_with_settings("/example.txt").url
print(link)

results = dbx.files_search("", "example").matches

for result in results:
    print(result.metadata.path_display)

class User:
    def __init__(self, username, password):
        self.username = username
        self.password = password

class UserManager:
    def __init__(self):
        self.users = []

    def register_user(self, username, password):
        new_user = User(username, password)
        self.users.append(new_user)

    def authenticate_user(self, username, password):
        for user in self.users:
            if user.username == username and user.password == password:
                return True
        return False

    def authorize_user(self, username, role):
        # Implement your authorization logic here
        pass

class UserProfile:
    def __init__(self, user):
        self.user = user
        self.bio = ""
        self.profile_picture = ""

    def update_bio(self, new_bio):
        self.bio = new_bio

    def update_profile_picture(self, new_picture):
        self.profile_picture = new_picture

    def get_profile_info(self):
        return {
            "username": self.user.username,
            "bio": self.bio,
            "profile_picture": self.profile_picture
        }

class ConnectionManager:
    def __init__(self):
        self.connections = {}

    def add_connection(self, user1, user2):
        if user1.username not in self.connections:
            self.connections[user1.username] = []
        if user2.username not in self.connections:
            self.connections[user2.username] = []

        self.connections[user1.username].append(user2)
        self.connections[user2.username].append(user1)

    def get_connections(self, user):
        if user.username in self.connections:
            return self.connections[user.username]
        else:
            return []

    def remove_connection(self, user1, user2):
        if user1.username in self.connections and user2 in self.connections[user1.username]:
            self.connections[user1.username].remove(user2)
        if user2.username in self.connections and user1 in self.connections[user2.username]:
            self.connections[user2.username].remove(user1)

class File:
    def __init__(self, file_id, file_name, content):
        self.file_id = file_id
        self.file_name = file_name
        self.content = content

class FileStorageSystem:
    def __init__(self):
        self.files = []

    def upload_file(self, file_id, file_name, content):
        new_file = File(file_id, file_name, content)
        self.files.append(new_file)

    def download_file(self, file_id):
        for file in self.files:
            if file.file_id == file_id:
                return file

    def delete_file(self, file_id):
        for file in self.files:
            if file.file_id == file_id:
                self.files.remove(file)
                break

class FileVersion:
    def __init__(self, file_id, version_number, content):
        self.file_id = file_id
        self.version_number = version_number
        self.content = content

class FileVersioningSystem:
    def __init__(self):
        self.file_versions = {}

    def upload_file_version(self, file_id, content):
        if file_id not in self.file_versions:
            self.file_versions[file_id] = []

        version_number = len(self.file_versions[file_id]) + 1
        new_version = FileVersion(file_id, version_number, content)
        self.file_versions[file_id].append(new_version)

    def download_file_version(self, file_id, version_number):
        if file_id in self.file_versions:
            for version in self.file_versions[file_id]:
                if version.version_number == version_number:
                    return version

    def get_latest_file_version(self, file_id):
        if file_id in self.file_versions:
            return self.file_versions[file_id][-1]

    def delete_file_versions(self, file_id):
        if file_id in self.file_versions:
            del self.file_versions[file_id]

class ConflictResolver:
    def __init__(self):
        self.conflicts = []

    def detect_conflict(self, file_id):
        # Implement conflict detection logic here
        pass

    def resolve_conflict(self, file_id):
        # Implement conflict resolution logic here
        pass

class FileChunk:
    def __init__(self, chunk_id, content):
        self.chunk_id = chunk_id
        self.content = content

class FileChunkingSystem:
    def __init__(self):
        self.file_chunks = {}

    def break_file_into_chunks(self, file_id, content):
        if file_id not in self.file_chunks:
            self.file_chunks[file_id] = []

        # Logic to break the file into smaller chunks
        # ...

        # Create and store file chunks
        chunk_id = 1
        for chunk_content in chunks:
            chunk = FileChunk(chunk_id, chunk_content)
            self.file_chunks[file_id].append(chunk)
            chunk_id += 1

    def get_file_chunks(self, file_id):
        if file_id in self.file_chunks:
            return self.file_chunks[file_id]
        else:
            return []

    def delete_file_chunks(self, file_id):
        if file_id in self.file_chunks:
            del self.file_chunks[file_id]

class DeduplicationSystem:
    def __init__(self):
        self.unique_chunks = {}

    def deduplicate_chunks(self, file_chunks):
        deduplicated_chunks = []

        for chunk in file_chunks:
            if chunk.content not in self.unique_chunks:
                self.unique_chunks[chunk.content] = chunk
                deduplicated_chunks.append(chunk)
            else:
                deduplicated_chunks.append(self.unique_chunks[chunk.content])

        return deduplicated_chunks

    def delete_chunk(self, chunk):
        if chunk.content in self.unique_chunks:
            del self.unique_chunks[chunk.content]

class DataCenter:
    def __init__(self, data_center_id, location):
        self.data_center_id = data_center_id
        self.location = location
        self.data = {}

    def store_data(self, key, value):
        self.data[key] = value

    def retrieve_data(self, key):
        if key in self.data:
            return self.data[key]
        else:
            return None

class DataReplicationSystem:
    def __init__(self):
        self.data_centers = []

    def add_data_center(self, data_center):
        self.data_centers.append(data_center)

    def replicate_data(self, key, value):
        for data_center in self.data_centers:
            data_center.store_data(key, value)

    def retrieve_data(self, key):
        for data_center in self.data_centers:
            data = data_center.retrieve_data(key)
            if data:
                return data

        return None

class DataDistributionSystem:
    def __init__(self):
        self.data_centers = []

    def add_data_center(self, data_center):
        self.data_centers.append(data_center)

    def distribute_file(self, file_id):
        for data_center in self.data_centers:
            data_center.store_file(file_id)

    def access_file(self, file_id):
        for data_center in self.data_centers:
            file = data_center.retrieve_file(file_id)
            if file:
                return file

        return None

class DataConsistencyManager:
    def __init__(self):
        self.data_centers = []

    def add_data_center(self, data_center):
        self.data_centers.append(data_center)

    def synchronize_data(self, key, value):
        for data_center in self.data_centers:
            data_center.store_data(key, value)

    def maintain_consistency(self):
        for data_center in self.data_centers:
            data_center.update_data_from_other_centers(self.data_centers)

class DataCenter:
    def __init__(self, data_center_id, location):
        self.data_center_id = data_center_id
        self.location = location
        self.data = {}

    def store_data(self, key, value):
        self.data[key] = value

    def retrieve_data(self, key):
        if key in self.data:
            return self.data[key]
        else:
            return None

    def update_data_from_other_centers(self, other_centers):
        for center in other_centers:
            if center.data_center_id != self.data_center_id:
                self.data.update(center.data)

class File:
    def __init__(self, file_id, file_name, content):
        self.file_id = file_id
        self.file_name = file_name
        self.content = content
        self.shared_with = []

    def share_with_user(self, user):
        if user not in self.shared_with:
            self.shared_with.append(user)

    def unshare_with_user(self, user):
        if user in self.shared_with:
            self.shared_with.remove(user)

class User:
    def __init__(self, username):
        self.username = username

class FileManager:
    def __init__(self):
        self.files = []

    def create_file(self, file_id, file_name, content):
        new_file = File(file_id, file_name, content)
        self.files.append(new_file)

    def share_file_with_user(self, file_id, user):
        file = self.find_file(file_id)
        if file:
            file.share_with_user(user)

    def unshare_file_with_user(self, file_id, user):
        file = self.find_file(file_id)
        if file:
            file.unshare_with_user(user)

    def find_file(self, file_id):
        for file in self.files:
            if file.file_id == file_id:
                return file

        return None

class File:
    def __init__(self, file_id, file_name, content):
        self.file_id = file_id
        self.file_name = file_name
        self.content = content
        self.shared_with = {}
    
    def share_with_user(self, user, access_level):
        self.shared_with[user.username] = access_level
    
    def unshare_with_user(self, user):
        if user.username in self.shared_with:
            del self.shared_with[user.username]
    
    def get_access_level(self, user):
        if user.username in self.shared_with:
            return self.shared_with[user.username]
        else:
            return None

class User:
    def __init__(self, username):
        self.username = username

class FileManager:
    def __init__(self):
        self.files = []
    
    def create_file(self, file_id, file_name, content):
        new_file = File(file_id, file_name, content)
        self.files.append(new_file)
    
    def share_file_with_user(self, file_id, user, access_level):
        file = self.find_file(file_id)
        if file:
            file.share_with_user(user, access_level)
    
    def unshare_file_with_user(self, file_id, user):
        file = self.find_file(file_id)
        if file:
            file.unshare_with_user(user)
    
    def get_access_level(self, file_id, user):
        file = self.find_file(file_id)
        if file:
            return file.get_access_level(user)
        else:
            return None
    
    def find_file(self, file_id):
        for file in self.files:
            if file.file_id == file_id:
                return file
    
        return None

class Comment:
    def __init__(self, comment_id, user, message):
        self.comment_id = comment_id
        self.user = user
        self.message = message

class Annotation:
    def __init__(self, annotation_id, user, content):
        self.annotation_id = annotation_id
        self.user = user
        self.content = content

class File:
    def __init__(self, file_id, file_name, content):
        self.file_id = file_id
        self.file_name = file_name
        self.content = content
        self.shared_with = []
        self.comments = []
        self.annotations = []

    def share_with_user(self, user):
        if user not in self.shared_with:
            self.shared_with.append(user)

    def unshare_with_user(self, user):
        if user in self.shared_with:
            self.shared_with.remove(user)

    def add_comment(self, comment_id, user, message):
        comment = Comment(comment_id, user, message)
        self.comments.append(comment)

    def delete_comment(self, comment_id):
        for comment in self.comments:
            if comment.comment_id == comment_id:
                self.comments.remove(comment)

    def add_annotation(self, annotation_id, user, content):
        annotation = Annotation(annotation_id, user, content)
        self.annotations.append(annotation)

    def delete_annotation(self, annotation_id):
        for annotation in self.annotations:
            if annotation.annotation_id == annotation_id:
                self.annotations.remove(annotation)

    def get_comments(self):
        return self.comments

    def get_annotations(self):
        return self.annotations

class User:
    def __init__(self, username):
        self.username = username

class FileManager:
    def __init__(self):
        self.files = []

    def create_file(self, file_id, file_name, content):
        new_file = File(file_id, file_name, content)
        self.files.append(new_file)

    def share_file_with_user(self, file_id, user):
        file = self.find_file(file_id)
        if file:
            file.share_with_user(user)

    def unshare_file_with_user(self, file_id, user):
        file = self.find_file(file_id)
        if file:
            file.unshare_with_user(user)

    def add_comment_to_file(self, file_id, comment_id, user, message):
        file = self.find_file(file_id)
        if file:
            file.add_comment(comment_id, user, message)

    def delete_comment_from_file(self, file_id, comment_id):
        file = self.find_file(file_id)
        if file:
            file.delete_comment(comment_id)

    def add_annotation_to_file(self, file_id, annotation_id, user, content):
        file = self.find_file(file_id)
        if file:
            file.add_annotation(annotation_id, user, content)

    def delete_annotation_from_file(self, file_id, annotation_id):
        file = self.find_file(file_id)
        if file:
            file.delete_annotation(annotation_id)

    def find_file(self, file_id):
        for file in self.files:
            if file.file_id == file_id:
                return file

        return None

class File:
    def __init__(self, file_id, file_name, content):
        self.file_id = file_id
        self.file_name = file_name
        self.content = content
        self.versions = []

    def update_content(self, new_content, user):
        version = Version(len(self.versions) + 1, new_content, user)
        self.versions.append(version)
        self.content = new_content

    def restore_to_version(self, version_number):
        for version in self.versions:
            if version.version_number == version_number:
                self.content = version.content
                break

class Version:
    def __init__(self, version_number, content, user):
        self.version_number = version_number
        self.content = content
        self.user = user

class User:
    def __init__(self, username):
        self.username = username

class FileManager:
    def __init__(self):
        self.files = []

    def create_file(self, file_id, file_name, content):
        new_file = File(file_id, file_name, content)
        self.files.append(new_file)

    def find_file(self, file_id):
        for file in self.files:
            if file.file_id == file_id:
                return file

        return None

    def update_file_content(self, file_id, new_content, user):
        file = self.find_file(file_id)
        if file:
            file.update_content(new_content, user)

    def restore_file_to_version(self, file_id, version_number):
        file = self.find_file(file_id)
        if file:
            file.restore_to_version(version_number)

class File:
    def __init__(self, file_id, file_name, content):
        self.file_id = file_id
        self.file_name = file_name
        self.content = content

class SearchEngine:
    def __init__(self):
        self.index = {}

    def index_file(self, file):
        keywords = self.extract_keywords(file)
        for keyword in keywords:
            if keyword in self.index:
                self.index[keyword].append(file)
            else:
                self.index[keyword] = [file]

    def search_files_by_keyword(self, keyword):
        if keyword in self.index:
            return self.index[keyword]
        else:
            return []

    def extract_keywords(self, file):
        # Perform keyword extraction logic here
        # This can be based on full-text search or metadata extraction
        # Return a list of keywords for the file
        return []

class FileManager:
    def __init__(self):
        self.files = []
        self.search_engine = SearchEngine()

    def create_file(self, file_id, file_name, content):
        new_file = File(file_id, file_name, content)
        self.files.append(new_file)
        self.search_engine.index_file(new_file)

    def search_files_by_keyword(self, keyword):
        return self.search_engine.search_files_by_keyword(keyword)

import hashlib

class File:
    def __init__(self, file_id, file_name, content):
        self.file_id = file_id
        self.file_name = file_name
        self.content = content

class EncryptionManager:
    @staticmethod
    def encrypt_data(data):
        # Implement encryption logic here
        # Return encrypted data
        return hashlib.sha256(data.encode()).hexdigest()

    @staticmethod
    def decrypt_data(encrypted_data):
        # Implement decryption logic here
        # Return decrypted data
        return encrypted_data

class FileManager:
    def __init__(self):
        self.files = []
        self.encryption_manager = EncryptionManager()

    def create_file(self, file_id, file_name, content):
        encrypted_content = self.encryption_manager.encrypt_data(content)
        new_file = File(file_id, file_name, encrypted_content)
        self.files.append(new_file)

    def get_file_content(self, file_id):
        file = self.find_file(file_id)
        if file:
            encrypted_content = file.content
            decrypted_content = self.encryption_manager.decrypt_data(encrypted_content)
            return decrypted_content
        else:
            return None

    def find_file(self, file_id):
        for file in self.files:
            if file.file_id == file_id:
                return file

        return None

class User:
    def __init__(self, username, password):
        self.username = username
        self.password = password

class AuthenticationManager:
    def __init__(self):
        self.users = []

    def register_user(self, username, password):
        new_user = User(username, password)
        self.users.append(new_user)

    def authenticate_user(self, username, password):
        for user in self.users:
            if user.username == username and user.password == password:
                return True

        return False

# Usage example
auth_manager = AuthenticationManager()
auth_manager.register_user("user1", "password123")

file_manager = FileManager()
file_manager.create_file(1, "example.txt", "Hello, World!")

username = "user1"
password = "password123"

if auth_manager.authenticate_user(username, password):
    file_content = file_manager.get_file_content(1)
    print(file_content)
else:
    print("Authentication failed.")

class ClientApplication:
    def __init__(self, platform):
        self.platform = platform

class API:
    def __init__(self):
        self.endpoints = {}

    def register_endpoint(self, endpoint, handler):
        self.endpoints[endpoint] = handler

    def handle_request(self, endpoint, request):
        if endpoint in self.endpoints:
            handler = self.endpoints[endpoint]
            return handler(request)
        else:
            return "Endpoint not found."

class AuthenticationManager:
    def __init__(self):
        self.users = {}

    def register_user(self, username, password):
        self.users[username] = password

    def authenticate_user(self, username, password):
        if username in self.users and self.users[username] == password:
            return True
        else:
            return False

# API endpoint handlers
def handle_login(request):
    username = request["username"]
    password = request["password"]
    auth_manager = AuthenticationManager()
    if auth_manager.authenticate_user(username, password):
        return "Login successful."
    else:
        return "Login failed."

def handle_file_upload(request):
    # Handle file upload logic here
    return "File uploaded successfully."

# Usage example
api = API()
api.register_endpoint("/login", handle_login)
api.register_endpoint("/upload", handle_file_upload)

# Client application example
desktop_app = ClientApplication("Desktop")

# Handling login request
login_request = {
    "username": "user1",
    "password": "password123"
}
login_response = api.handle_request("/login", login_request)
print(login_response)

# Handling file upload request
upload_request = {
    "file_name": "example.txt",
    "file_data": "Lorem ipsum dolor sit amet."
}
upload_response = api.handle_request("/upload", upload_request)
print(upload_response)

class DataStore:
    def __init__(self):
        self.data = {}

    def get(self, key):
        return self.data.get(key)

    def set(self, key, value):
        self.data[key] = value

class BackupManager:
    def __init__(self, data_store):
        self.data_store = data_store
        self.backup = {}

    def perform_backup(self):
        self.backup = self.data_store.data.copy()

    def restore_backup(self):
        self.data_store.data = self.backup

class DisasterRecoveryManager:
    def __init__(self, data_store, backup_manager):
        self.data_store = data_store
        self.backup_manager = backup_manager

    def handle_system_failure(self):
        self.backup_manager.restore_backup()

# Usage example
datastore = DataStore()
backup_manager = BackupManager(datastore)
dr_manager = DisasterRecoveryManager(datastore, backup_manager)

# Storing data in the data store
datastore.set("key1", "value1")

# Performing backup
backup_manager.perform_backup()

# Simulating system failure
datastore.set("key1", "corrupted_value")

# Handling system failure and restoring backup
dr_manager.handle_system_failure()

# Retrieving data from the data store after recovery
recovered_value = datastore.get("key1")
print(recovered_value)

[Mobile Clients] <--> [Load Balancer] <--> [Application Servers] <--> [Cache]
                                         |        |        |
                                  [User Service] [Restaurant Service] [Order Service]
                                                        |
                                                [Payment Service]
                                                        |
                                                [Notifications Service]
                                                        |
                                                [Database (RDBMS)]
                                                        |
                                                [Storage (HDFS/S3)]
                                                        |
                                               [CDN (Content Delivery Network)]

import java.util.*;

class User {
    private String userId;
    private String username;
    private String password;
    // other user attributes
    
    public User(String userId, String username, String password) {
        this.userId = userId;
        this.username = username;
        this.password = password;
        // initialize other attributes
    }
    
    // Getters and setters for attributes
    public String getUserId() {
        return userId;
    }
    
    public String getUsername() {
        return username;
    }
    
    public String getPassword() {
        return password;
    }
    
    // ...
}

class Restaurant {
    private String restaurantId;
    private String name;
    // other restaurant attributes
    
    public Restaurant(String restaurantId, String name) {
        this.restaurantId = restaurantId;
        this.name = name;
        // initialize other attributes
    }
    
    // Getters and setters for attributes
    public String getRestaurantId() {
        return restaurantId;
    }
    
    public String getName() {
        return name;
    }
    
    // ...
}

class Order {
    private String orderId;
    private User user;
    private Restaurant restaurant;
    // other order attributes
    
    public Order(String orderId, User user, Restaurant restaurant) {
        this.orderId = orderId;
        this.user = user;
        this.restaurant = restaurant;
        // initialize other attributes
    }
    
    // Getters and setters for attributes
    public String getOrderId() {
        return orderId;
    }
    
    public User getUser() {
        return user;
    }
    
    public Restaurant getRestaurant() {
        return restaurant;
    }
    
    // ...
}

class DoorDash {
    private Map<String, User> users;
    private Map<String, Restaurant> restaurants;
    private List<Order> orders;
    
    public DoorDash() {
        this.users = new HashMap<>();
        this.restaurants = new HashMap<>();
        this.orders = new ArrayList<>();
    }
    
    public void addUser(User user) {
        users.put(user.getUserId(), user);
    }
    
    public User getUserById(String userId) {
        return users.get(userId);
    }
    
    public void addRestaurant(Restaurant restaurant) {
        restaurants.put(restaurant.getRestaurantId(), restaurant);
    }
    
    public Restaurant getRestaurantById(String restaurantId) {
        return restaurants.get(restaurantId);
    }
    
    public void createOrder(String userId, String restaurantId) {
        User user = getUserById(userId);
        Restaurant restaurant = getRestaurantById(restaurantId);
        
        if (user == null || restaurant == null) {
            System.out.println("User or restaurant not found");
            return;
        }
        
        String orderId = generateOrderId(); // Generate a unique order ID
        Order order = new Order(orderId, user, restaurant);
        orders.add(order);
        
        // Additional logic for order processing, payment, etc.
        // ...
    }
    
    // Additional methods for retrieving user orders, restaurant orders, etc.
    // ...
}

public class Main {
    public static void main(String[] args) {
        DoorDash doorDash = new DoorDash();
        
        User user1 = new User("1", "Alice", "password");
        User user2 = new User("2", "Bob", "password");
        
        doorDash.addUser(user1);
        doorDash.addUser(user2);
        
        Restaurant restaurant1 = new Restaurant("1", "Pizza Hut");
        Restaurant restaurant2 = new Restaurant("2", "McDonald's");
        
        doorDash.addRestaurant(restaurant1);
        doorDash.addRestaurant(restaurant2);
        
        doorDash.createOrder("1", "1");
        
        // Additional code for retrieving orders, displaying information, etc.
        // ...
    }
}

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/api/register', methods=['POST'])
def register_user():
    # Handle registration logic and store user details
    return jsonify({'message': 'User registered successfully'})

@app.route('/api/login', methods=['POST'])
def login_user():
    # Handle authentication logic and generate access token
    return jsonify({'access_token': 'your_access_token'})

if __name__ == '__main__':
    app.run()

@app.route('/api/restaurants', methods=['GET'])
def get_restaurants():
    # Retrieve and return a list of restaurants
    return jsonify({'restaurants': ['Restaurant A', 'Restaurant B']})

@app.route('/api/restaurants/<restaurant_id>', methods=['GET'])
def get_restaurant(restaurant_id):
    # Retrieve and return details of the specified restaurant
    return jsonify({'restaurant': restaurant_id})

@app.route('/api/orders', methods=['POST'])
def place_order():
    # Handle order placement logic
    return jsonify({'message': 'Order placed successfully'})

if __name__ == '__main__':
    app.run()

@app.route('/api/orders/<order_id>/status', methods=['GET'])
def get_order_status(order_id):
    # Retrieve and return the status of the specified order
    return jsonify({'status': 'In Progress'})

if __name__ == '__main__':
    app.run()

@app.route('/api/users/<user_id>', methods=['GET'])
def get_user(user_id):
    # Retrieve and return details of the specified user
    return jsonify({'user': user_id})

@app.route('/api/users/<user_id>', methods=['PUT'])
def update_user(user_id):
    # Update the details of the specified user
    return jsonify({'message': 'User updated successfully'})

@app.route('/api/users/<user_id>', methods=['DELETE'])
def delete_user(user_id):
    # Delete the specified user
    return jsonify({'message': 'User deleted successfully'})

if __name__ == '__main__':
    app.run()

@app.route('/api/drivers', methods=['GET'])
def get_drivers():
    # Retrieve and return a list of drivers
    return jsonify({'drivers': ['Driver A', 'Driver B']})

@app.route('/api/drivers/<driver_id>', methods=['GET'])
def get_driver(driver_id):
    # Retrieve and return details of the specified driver
    return jsonify({'driver': driver_id})

@app.route('/api/drivers', methods=['POST'])
def create_driver():
    # Create a new driver account
    return jsonify({'message': 'Driver created successfully'})

if __name__ == '__main__':
    app.run()

Restaurant Selection:

class Restaurant:
    def __init__(self, name, cuisine):
        self.name = name
        self.cuisine = cuisine

class DoorDash:
    def __init__(self):
        self.restaurants = []

    def add_restaurant(self, name, cuisine):
        restaurant = Restaurant(name, cuisine)
        self.restaurants.append(restaurant)

    def get_restaurants(self):
        return self.restaurants


# Example usage
doordash = DoorDash()
doordash.add_restaurant("Restaurant A", "Italian")
doordash.add_restaurant("Restaurant B", "Mexican")
doordash.add_restaurant("Restaurant C", "Japanese")

restaurants = doordash.get_restaurants()
for restaurant in restaurants:
    print(f"Name: {restaurant.name}, Cuisine: {restaurant.cuisine}")

Real-time Tracking:
class Order:
    def __init__(self, order_id, status):
        self.order_id = order_id
        self.status = status

class DoorDash:
    def __init__(self):
        self.orders = []

    def track_order(self, order_id):
        for order in self.orders:
            if order.order_id == order_id:
                return order.status
        return None

    def update_order_status(self, order_id, status):
        for order in self.orders:
            if order.order_id == order_id:
                order.status = status
                break

    def place_order(self, order_id):
        order = Order(order_id, "In Progress")
        self.orders.append(order)


# Example usage
doordash = DoorDash()
doordash.place_order("12345")
print(doordash.track_order("12345"))  # Output: In Progress

doordash.update_order_status("12345", "Delivered")
print(doordash.track_order("12345"))  # Output: Delivered

Seamless Ordering:

class Order:
    def __init__(self, order_id, items, discounts, payment):
        self.order_id = order_id
        self.items = items
        self.discounts = discounts
        self.payment = payment

class DoorDash:
    def __init__(self):
        self.orders = []

    def place_order(self, order_id, items, discounts, payment):
        order = Order(order_id, items, discounts, payment)
        self.orders.append(order)
        return order

    def get_order_details(self, order_id):
        for order in self.orders:
            if order.order_id == order_id:
                return {
                    'order_id': order.order_id,
                    'items': order.items,
                    'discounts': order.discounts,
                    'payment': order.payment
                }
        return None


# Example usage
doordash = DoorDash()
order = doordash.place_order("12345", ["Pizza", "Burger"], ["10% off"], "Credit Card")
order_details = doordash.get_order_details("12345")
print(order_details)

Ratings and Reviews:

class Restaurant:
    def __init__(self, name):
        self.name = name
        self.reviews = []

    def add_review(self, review):
        self.reviews.append(review)

class DoorDash:
    def __init__(self):
        self.restaurants = []

    def add_restaurant(self, name):
        restaurant = Restaurant(name)
        self.restaurants.append(restaurant)

    def leave_review(self, restaurant_name, review):
        for restaurant in self.restaurants:
            if restaurant.name == restaurant_name:
                restaurant.add_review(review)
                break

    def get_reviews(self, restaurant_name):
        for restaurant in self.restaurants:
            if restaurant.name == restaurant_name:
                return restaurant.reviews
        return None


# Example usage
doordash = DoorDash()
doordash.add_restaurant("Restaurant A")
doordash.leave_review("Restaurant A", "Great food and service!")
doordash.leave_review("Restaurant A", "Highly recommended!")

reviews = doordash.get_reviews("Restaurant A")
print(reviews)

Customer Support:
class CustomerSupport:
    def __init__(self):
        self.inquiries = []

    def submit_inquiry(self, inquiry):
        self.inquiries.append(inquiry)
        return inquiry

    def get_inquiry_details(self, inquiry_id):
        for inquiry in self.inquiries:
            if inquiry['inquiry_id'] == inquiry_id:
                return inquiry
        return None


# Example usage
customer_support = CustomerSupport()
inquiry = customer_support.submit_inquiry({
    'inquiry_id': '9876',
    'message': 'I have an issue with my order.'
})
inquiry_details = customer_support.get_inquiry_details('9876')
print(inquiry_details)

from flask import Flask, request, jsonify

app = Flask(__name__)

# Placeholder data for restaurants, orders, and delivery drivers
restaurants = [
    {
        'id': 1,
        'name': 'Restaurant A',
        'location': 'Location A',
        'cuisine': 'Cuisine A',
        'menu': {
            'item1': 'Description 1',
            'item2': 'Description 2'
        }
    },
    {
        'id': 2,
        'name': 'Restaurant B',
        'location': 'Location B',
        'cuisine': 'Cuisine B',
        'menu': {
            'item3': 'Description 3',
            'item4': 'Description 4'
        }
    }
]

orders = [
    {
        'id': 1,
        'user_id': 1,
        'restaurant_id': 1,
        'order_items': ['item1', 'item2'],
        'total_amount': 25.99,
        'order_status': 'In Progress'
    },
    {
        'id': 2,
        'user_id': 2,
        'restaurant_id': 2,
        'order_items': ['item3', 'item4'],
        'total_amount': 32.50,
        'order_status': 'Delivered'
    }
]

drivers = [
    {
        'id': 1,
        'name': 'Driver A',
        'availability': True,
        'assigned_deliveries': []
    },
    {
        'id': 2,
        'name': 'Driver B',
        'availability': False,
        'assigned_deliveries': [1]
    }
]

ratings_reviews = [
    {
        'restaurant_id': 1,
        'rating': 4.5,
        'review': 'Great food and service!'
    },
    {
        'restaurant_id': 2,
        'rating': 3.8,
        'review': 'Decent food, but late delivery.'
    }
]

# Restaurant Search and Ordering API
@app.route('/api/restaurants', methods=['GET'])
def get_restaurants():
    return jsonify({'restaurants': restaurants})

@app.route('/api/restaurants/<int:restaurant_id>', methods=['GET'])
def get_restaurant(restaurant_id):
    restaurant = next((r for r in restaurants if r['id'] == restaurant_id), None)
    if restaurant:
        return jsonify({'restaurant': restaurant})
    else:
        return jsonify({'message': 'Restaurant not found'})

@app.route('/api/orders', methods=['POST'])
def place_order():
    # Handle order placement logic
    return jsonify({'message': 'Order placed successfully'})

# Real-time Tracking API
@app.route('/api/orders/<int:order_id>/status', methods=['GET'])
def get_order_status(order_id):
    order = next((o for o in orders if o['id'] == order_id), None)
    if order:
        return jsonify({'status': order['order_status']})
    else:
        return jsonify({'message': 'Order not found'})

# User Management API
@app.route('/api/users/<int:user_id>', methods=['GET'])
def get_user(user_id):
    # Retrieve and return details of the specified user
    return jsonify({'user': user_id})

@app.route('/api/users/<int:user_id>', methods=['PUT'])
def update_user(user_id):
    # Update the details of the specified user
    return jsonify({'message': 'User updated successfully'})

@app.route('/api/users/<int:user_id>', methods=['DELETE'])
def delete_user(user_id):
    # Delete the specified user
    return jsonify({'message': 'User deleted successfully'})

# Delivery Driver Management API
@app.route('/api/drivers', methods=['GET'])
def get_drivers():
    return jsonify({'drivers': drivers})

@app.route('/api/drivers/<int:driver_id>', methods=['GET'])
def get_driver(driver_id):
    driver = next((d for d in drivers if d['id'] == driver_id), None)
    if driver:
        return jsonify({'driver': driver})
    else:
        return jsonify({'message': 'Driver not found'})

@app.route('/api/drivers', methods=['POST'])
def create_driver():
    # Create a new driver account
    return jsonify({'message': 'Driver created successfully'})

if __name__ == '__main__':
    app.run()

class PayPalSystem:
    def __init__(self):
        self.users = {}
        self.transactions = []

    def create_user(self, user_id):
        # Logic to create a new user
        pass

    def process_transaction(self, user_id, amount):
        # Logic to process a transaction for a user
        pass

    def get_transaction_history(self, user_id):
        # Logic to retrieve transaction history for a user
        pass


# Usage example:
paypal_system = PayPalSystem()

# Create users
for i in range(100_000_000):
    user_id = f"user_{i}"
    paypal_system.create_user(user_id)

# Process transactions
for i in range(1_000_000):
    user_id = f"user_{i % 100_000_000}"
    amount = i % 10
    paypal_system.process_transaction(user_id, amount)

# Get transaction history for a user
user_id = "user_12345"
transaction_history = paypal_system.get_transaction_history(user_id)
print(transaction_history)

class User:
    def __init__(self, userId, username, email, password):
        self.userId = userId
        self.username = username
        self.email = email
        self.password = password

class PaymentSource:
    def __init__(self, sourceId, userId, type, details):
        self.sourceId = sourceId
        self.userId = userId
        self.type = type
        self.details = details

class Transaction:
    def __init__(self, transactionId, userId, amount, currency, timestamp):
        self.transactionId = transactionId
        self.userId = userId
        self.amount = amount
        self.currency = currency
        self.timestamp = timestamp

class Like:
    def __init__(self, likeId, userId, transactionId, timestamp):
        self.likeId = likeId
        self.userId = userId
        self.transactionId = transactionId
        self.timestamp = timestamp

class Comment:
    def __init__(self, commentId, transactionId, userId, caption, timestamp):
        self.commentId = commentId
        self.transactionId = transactionId
        self.userId = userId
        self.caption = caption
        self.timestamp = timestamp

class PayPalSystem:
    def __init__(self):
        self.users = {}
        self.paymentSources = {}
        self.transactions = []
        self.likes = []
        self.comments = []

    def create_user(self, userId, username, email, password):
        user = User(userId, username, email, password)
        self.users[userId] = user

    def get_user(self, userId):
        return self.users.get(userId)

    def link_payment_source(self, sourceId, userId, type, details):
        paymentSource = PaymentSource(sourceId, userId, type, details)
        self.paymentSources[sourceId] = paymentSource

    def create_transaction(self, transactionId, userId, amount, currency, timestamp):
        transaction = Transaction(transactionId, userId, amount, currency, timestamp)
        self.transactions.append(transaction)

    def create_like(self, likeId, userId, transactionId, timestamp):
        like = Like(likeId, userId, transactionId, timestamp)
        self.likes.append(like)

    def create_comment(self, commentId, transactionId, userId, caption, timestamp):
        comment = Comment(commentId, transactionId, userId, caption, timestamp)
        self.comments.append(comment)

{
  "name": "John Doe",
  "email": "[email protected]",
  "password": "mysecretpassword"
}

{
  "user_id": "1234567890",
  "message": "User registered successfully"
}

{
  "sender_id": "1234567890",
  "receiver_id": "0987654321",
  "amount": 100.00,
  "currency": "USD",
  "description": "Payment for services"
}

{
  "transaction_id": "abcdef123456",
  "message": "Funds transferred successfully"
}

{
  "transactions": [
    {
      "transaction_id": "abcdef123456",
      "sender_id": "1234567890",
      "receiver_id": "0987654321",
      "amount": 100.00,
      "currency": "USD",
      "description": "Payment for services",
      "timestamp": "2023-07-07 10:30:00"
    },
    {
      "transaction_id": "xyz987654321",
      "sender_id": "0987654321",
      "receiver_id": "1234567890",
      "amount": 50.00,
      "currency": "USD",
      "description": "Refund for purchase",
      "timestamp": "2023-07-06 15:45:00"
    }
  ]
}

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/users/register', methods=['POST'])
def register_user():
    name = request.json.get('name')
    email = request.json.get('email')
    password = request.json.get('password')
    
    # Validate and process registration logic
    # Store user details in the database
    
    return jsonify({
        "user_id": "1234567890",
        "message": "User registered successfully"
    })

if __name__ == '__main__':
    app.run()

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/transactions/transfer', methods=['POST'])
def transfer_funds():
    sender_id = request.json.get('sender_id')
    receiver_id = request.json.get('receiver_id')
    amount = request.json.get('amount')
    currency = request.json.get('currency')
    description = request.json.get('description')
    
    # Validate and process fund transfer logic
    # Update sender and receiver account balances
    # Log the transaction details
    
    return jsonify({
        "transaction_id": "abcdef123456",
        "message": "Funds transferred successfully"
    })

if __name__ == '__main__':
    app.run()

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/users/<user_id>/transactions', methods=['GET'])
def get_transaction_history(user_id):
    # Fetch transaction history for the given user_id from the database
    
    transactions = [
        {
            "transaction_id": "abcdef123456",
            "sender_id": "1234567890",
            "receiver_id": "0987654321",
            "amount": 100.00,
            "currency": "USD",
            "description": "Payment for services",
            "timestamp": "2023-07-07 10:30:00"
        },
        {
            "transaction_id": "xyz987654321",
            "sender_id": "0987654321",
            "receiver_id": "1234567890",
            "amount": 50.00,
            "currency": "USD",
            "description": "Refund for purchase",
            "timestamp": "2023-07-06 15:45:00"
        }
    ]
    
    return jsonify({
        "transactions": transactions
    })

if __name__ == '__main__':
    app.run()

class User:
    def __init__(self, user_id, username, email, password):
        self.user_id = user_id
        self.username = username
        self.email = email
        self.password = password
        self.payment_sources = []

    def add_payment_source(self, payment_source):
        self.payment_sources.append(payment_source)

    def get_payment_sources(self):
        return self.payment_sources

class PaymentSource:
    def __init__(self, source_id, type, details):
        self.source_id = source_id
        self.type = type
        self.details = details

class PayPal:
    def __init__(self):
        self.users = {}

    def register_user(self, user_id, username, email, password):
        user = User(user_id, username, email, password)
        self.users[user_id] = user

    def get_user(self, user_id):
        return self.users.get(user_id)

    def link_payment_source(self, user_id, source_id, type, details):
        user = self.get_user(user_id)
        if user:
            payment_source = PaymentSource(source_id, type, details)
            user.add_payment_source(payment_source)

# User Registration and Account Management
paypal = PayPal()
paypal.register_user("123", "John", "[email protected]", "password")

# Linking Payment Sources
paypal.link_payment_source("123", "1", "bank_account", "1234567890")
paypal.link_payment_source("123", "2", "credit_card", "************1234")

# Fund Transfer
def transfer_funds(sender_id, receiver_id, amount):
    sender = paypal.get_user(sender_id)
    receiver = paypal.get_user(receiver_id)
    if sender and receiver:
        # Perform fund transfer logic
        print(f"Transfer {amount} from {sender.username} to {receiver.username}")

transfer_funds("123", "456", 100.0)

# Buyer and Seller Protection
def enable_protection(transaction_id):
    # Enable buyer and seller protection for the transaction
    print(f"Protection enabled for transaction {transaction_id}")

enable_protection("789")

# International Payments
def make_international_payment(user_id, amount, currency):
    user = paypal.get_user(user_id)
    if user:
        # Perform international payment logic
        print(f"Payment of {amount} {currency} made by {user.username}")

make_international_payment("123", 50.0, "USD")

# Mobile Support
def make_mobile_payment(user_id, amount):
    user = paypal.get_user(user_id)
    if user:
        # Perform mobile payment logic
        print(f"Mobile payment of {amount} made by {user.username}")

make_mobile_payment("123", 20.0)

# Payment APIs
class PaymentAPI:
    def process_payment(self, user_id, amount):
        user = paypal.get_user(user_id)
        if user:
            # Process payment using PayPal's API
            print(f"Payment of {amount} processed for user {user.username}")

payment_api = PaymentAPI()
payment_api.process_payment("123", 50.0)

from flask import Flask, jsonify, request

app = Flask(__name__)
paypal_system = PayPalSystem()

@app.route("/users", methods=["POST"])
def create_user():
    data = request.get_json()
    userId = data["userId"]
    username = data["username"]
    email = data["email"]
    password = data["password"]
    paypal_system.create_user(userId, username, email, password)
    return jsonify({"message": "User created successfully"}), 201

@app.route("/users/<userId>", methods=["GET"])
def get_user(userId):
    user = paypal_system.get_user(userId)
    if user:
        return jsonify(user.__dict__), 200
    else:
        return jsonify({"message": "User not found"}), 404

@app.route("/payment-sources", methods=["POST"])
def link_payment_source():
    data = request.get_json()
    sourceId = data["sourceId"]
    userId = data["userId"]
    type = data["type"]
    details = data["details"]
    paypal_system.link_payment_source(sourceId, userId, type, details)
    return jsonify({"message": "Payment source linked successfully"}), 201

@app.route("/transactions", methods=["POST"])
def create_transaction():
    data = request.get_json()
    transactionId = data["transactionId"]
    userId = data["userId"]
    amount = data["amount"]
    currency = data["currency"]
    timestamp = data["timestamp"]
    paypal_system.create_transaction(transactionId, userId, amount, currency, timestamp)
    return jsonify({"message": "Transaction created successfully"}), 201

@app.route("/likes", methods=["POST"])
def create_like():
    data = request.get_json()
    likeId = data["likeId"]
    userId = data["userId"]
    transactionId = data["transactionId"]
    timestamp = data["timestamp"]
    paypal_system.create_like(likeId, userId, transactionId, timestamp)
    return jsonify({"message": "Like created successfully"}), 201

@app.route("/comments", methods=["POST"])
def create_comment():
    data = request.get_json()
    commentId = data["commentId"]
    transactionId = data["transactionId"]
    userId = data["userId"]
    caption = data["caption"]
    timestamp = data["timestamp"]
    paypal_system.create_comment(commentId, transactionId, userId, caption, timestamp)
    return jsonify({"message": "Comment created successfully"}), 201

class User:
    def __init__(self, user_id, username, password):
        self.user_id = user_id
        self.username = username
        self.password = password
        # Other user attributes

class Video:
    def __init__(self, video_id, user, title, url, description):
        self.video_id = video_id
        self.user = user
        self.title = title
        self.url = url
        self.description = description
        # Other video attributes

class Hotstar:
    def __init__(self):
        self.users = {}
        self.videos = {}

    def add_user(self, user):
        self.users[user.user_id] = user

    def get_user_by_id(self, user_id):
        return self.users.get(user_id)

    def upload_video(self, user_id, title, url, description):
        user = self.get_user_by_id(user_id)
        if user:
            video_id = len(self.videos) + 1
            video = Video(video_id, user, title, url, description)
            self.videos[video_id] = video
            return video
        return None

    def get_video_by_id(self, video_id):
        return self.videos.get(video_id)

    # Additional methods for handling likes, comments, follow/unfollow, etc.
    # ...

from flask import Flask, request, jsonify, abort

app = Flask(__name__)

users = []
videos = []

# User Management API

@app.route('/users', methods=['POST'])
def create_user():
    data = request.get_json()
    username = data.get('username')
    password = data.get('password')
    email = data.get('email')

    # Validate request body
    if not username or not password or not email:
        abort(400, 'Missing required fields')

    # Create new user
    user = {
        'username': username,
        'password': password,
        'email': email
        # Other user attributes
    }
    users.append(user)

    return jsonify(message='User created successfully'), 201

@app.route('/users/<int:user_id>', methods=['GET'])
def get_user(user_id):
    for user in users:
        if user['id'] == user_id:
            return jsonify(user), 200

    abort(404, 'User not found')

@app.route('/users/<int:user_id>/videos', methods=['POST'])
def upload_video(user_id):
    data = request.get_json()
    title = data.get('title')
    url = data.get('url')
    description = data.get('description')

    # Validate request body
    if not title or not url:
        abort(400, 'Missing required fields')

    # Find user
    user = None
    for u in users:
        if u['id'] == user_id:
            user = u
            break

    if not user:
        abort(404, 'User not found')

    # Create new video
    video = {
        'title': title,
        'url': url,
        'description': description,
        # Other video attributes
    }
    videos.append(video)

    return jsonify(video), 201

# Content Management API

@app.route('/videos/<int:video_id>', methods=['GET'])
def get_video(video_id):
    for video in videos:
        if video['id'] == video_id:
            return jsonify(video), 200

    abort(404, 'Video not found')

@app.route('/videos/<int:video_id>', methods=['DELETE'])
def delete_video(video_id):
    for video in videos:
        if video['id'] == video_id:
            videos.remove(video)
            return jsonify(message='Video deleted successfully'), 204

    abort(404, 'Video not found')

# Likes API

@app.route('/videos/<int:video_id>/likes', methods=['POST'])
def like_video(video_id):
    # Check if video exists
    video = next((v for v in videos if v['id'] == video_id), None)
    if not video:
        abort(404, 'Video not found')

    # Perform like operation (e.g., update video object, add like to database, etc.)

    return jsonify(message='Video liked successfully'), 200

@app.route('/videos/<int:video_id>/likes', methods=['GET'])
def get_likes(video_id):
    # Check if video exists
    video = next((v for v in videos if v['id'] == video_id), None)
    if not video:
        abort(404, 'Video not found')

    # Retrieve list of likes for the video (e.g., from database)

    likes = []  # Placeholder for demonstration
    return jsonify(likes), 200

# Comments API

@app.route('/videos/<int:video_id>/comments', methods=['POST'])
def add_comment(video_id):
    # Check if video exists
    video = next((v for v in videos if v['id'] == video_id), None)
    if not video:
        abort(404, 'Video not found')

    data = request.get_json()
    user_id = data.get('user_id')
    comment_text = data.get('comment_text')

    # Validate request body
    if not user_id or not comment_text:
        abort(400, 'Missing required fields')

    # Perform comment operation (e.g., update video object, add comment to database, etc.)

    return jsonify(message='Comment added successfully'), 200

@app.route('/videos/<int:video_id>/comments', methods=['GET'])
def get_comments(video_id):
    # Check if video exists
    video = next((v for v in videos if v['id'] == video_id), None)
    if not video:
        abort(404, 'Video not found')

    # Retrieve list of comments for the video (e.g., from database)

    comments = []  # Placeholder for demonstration
    return jsonify(comments), 200

if __name__ == '__main__':
    app.run()

class Content:
    def __init__(self, id, title, genre, release_date, language):
        self.id = id
        self.title = title
        self.genre = genre
        self.release_date = release_date
        self.language = language

class ContentLibrary:
    def __init__(self):
        self.contents = []

    def add_content(self, content):
        self.contents.append(content)

    def get_contents(self):
        return self.contents

# Example usage:
content_library = ContentLibrary()
content1 = Content(1, "Movie 1", "Action", "2023-01-01", "English")
content2 = Content(2, "Movie 2", "Comedy", "2023-02-01", "Hindi")
content_library.add_content(content1)
content_library.add_content(content2)
all_contents = content_library.get_contents()
for content in all_contents:
    print(content.title)

class LiveStreaming:
    def __init__(self):
        self.live_events = []

    def add_live_event(self, event):
        self.live_events.append(event)

    def get_live_events(self):
        return self.live_events

# Example usage:
live_streaming = LiveStreaming()
event1 = "Cricket Match"
event2 = "Football Match"
live_streaming.add_live_event(event1)
live_streaming.add_live_event(event2)
all_events = live_streaming.get_live_events()
for event in all_events:
    print(event)

class Device:
    def __init__(self, name):
        self.name = name

class DeviceSupport:
    def __init__(self):
        self.devices = []

    def add_device(self, device):
        self.devices.append(device)

    def get_devices(self):
        return self.devices

# Example usage:
device_support = DeviceSupport()
device1 = Device("Smartphone")
device2 = Device("Tablet")
device3 = Device("Smart TV")
device4 = Device("Web Browser")
device_support.add_device(device1)
device_support.add_device(device2)
device_support.add_device(device3)
device_support.add_device(device4)
all_devices = device_support.get_devices()
for device in all_devices:
    print(device.name)

class User:
    def __init__(self, id, name):
        self.id = id
        self.name = name

class Recommendation:
    def __init__(self, content, user):
        self.content = content
        self.user = user

class RecommendationEngine:
    def __init__(self):
        self.recommendations = []

    def add_recommendation(self, recommendation):
        self.recommendations.append(recommendation)

    def get_recommendations(self, user):
        user_recommendations = []
        for recommendation in self.recommendations:
            if recommendation.user.id == user.id:
                user_recommendations.append(recommendation.content)
        return user_recommendations

# Example usage:
recommendation_engine = RecommendationEngine()
user1 = User(1, "John")
user2 = User(2, "Emma")
content1 = Content(1, "Movie 1", "Action", "2023-01-01", "English")
content2 = Content(2, "Movie 2", "Comedy", "2023-02-01", "Hindi")
recommendation1 = Recommendation(content1, user1)
recommendation2 = Recommendation(content2, user2)
recommendation_engine.add_recommendation(recommendation1)
recommendation_engine.add_recommendation(recommendation2)
user1_recommendations = recommendation_engine.get_recommendations(user1)
for recommendation in user1_recommendations:
    print(recommendation.title)

class Language:
    def __init__(self, name):
        self.name = name

class LanguageSupport:
    def __init__(self):
        self.languages = []

    def add_language(self, language):
        self.languages.append(language)

    def get_languages(self):
        return self.languages

# Example usage:
language_support = LanguageSupport()
language1 = Language("English")
language2 = Language("Hindi")
language3 = Language("Spanish")
language_support.add_language(language1)
language_support.add_language(language2)
language_support.add_language(language3)
all_languages = language_support.get_languages()
for language in all_languages:
    print(language.name)

from datetime import datetime

class LikeService:
    def __init__(self):
        self.likes = []

    def like_post(self, user_id, video_id):
        like_id = len(self.likes) + 1
        timestamp = datetime.now()
        like = {
            'like_id': like_id,
            'user_id': user_id,
            'video_id': video_id,
            'timestamp': timestamp
        }
        self.likes.append(like)
        print('Post liked successfully!')

    def get_likes(self, video_id):
        video_likes = []
        for like in self.likes:
            if like['video_id'] == video_id:
                video_likes.append(like)
        return video_likes


class FollowService:
    def __init__(self):
        self.followers = []

    def follow_user(self, user_id, follower_id):
        follow = {
            'user_id': user_id,
            'follower_id': follower_id
        }
        self.followers.append(follow)
        print('User followed successfully!')

    def get_followers(self, user_id):
        user_followers = []
        for follow in self.followers:
            if follow['user_id'] == user_id:
                user_followers.append(follow)
        return user_followers


class CommentService:
    def __init__(self):
        self.comments = []

    def add_comment(self, user_id, video_id, comment_text):
        comment_id = len(self.comments) + 1
        timestamp = datetime.now()
        comment = {
            'comment_id': comment_id,
            'user_id': user_id,
            'video_id': video_id,
            'comment_text': comment_text,
            'timestamp': timestamp
        }
        self.comments.append(comment)
        print('Comment added successfully!')

    def get_comments(self, video_id):
        video_comments = []
        for comment in self.comments:
            if comment['video_id'] == video_id:
                video_comments.append(comment)
        return video_comments


class VideoUploadService:
    def __init__(self):
        self.videos = []

    def upload_video(self, user_id, video_title, video_url, description, duration):
        video_id = len(self.videos) + 1
        timestamp = datetime.now()
        video = {
            'video_id': video_id,
            'user_id': user_id,
            'video_title': video_title,
            'video_url': video_url,
            'description': description,
            'duration': duration,
            'upload_timestamp': timestamp
        }
        self.videos.append(video)
        print('Video uploaded successfully!')

    def get_user_videos(self, user_id):
        user_videos = []
        for video in self.videos:
            if video['user_id'] == user_id:
                user_videos.append(video)
        return user_videos


class GenerateFeedService:
    def __init__(self):
        self.videos = []

    def add_video(self, video):
        self.videos.append(video)

    def generate_feed(self, user_id):
        followed_users_videos = []
        for video in self.videos:
            if video['user_id'] in FollowService().get_followers(user_id):
                followed_users_videos.append(video)
        sorted_videos = sorted(followed_users_videos, key=lambda x: x['upload_timestamp'], reverse=True)
        return sorted_videos[:50]

class SongService:
    def __init__(self):
        self.songs = {}

    def get_song_details(self, song_id):
        if song_id in self.songs:
            return self.songs[song_id]
        else:
            return None

    def upload_song(self, title, artist, duration):
        song_id = len(self.songs) + 1
        song = {'song_id': song_id, 'title': title, 'artist': artist, 'duration': duration}
        self.songs[song_id] = song
        return song_id

    def update_song_metadata(self, song_id, metadata):
        if song_id in self.songs:
            song = self.songs[song_id]
            song['title'] = metadata['title']
            song['artist'] = metadata['artist']
            song['duration'] = metadata['duration']
            self.songs[song_id] = song
            return True
        else:
            return False


class UserService:
    def __init__(self):
        self.users = {}
        self.user_id_counter = 1

    def authenticate_user(self, username, password):
        for user_id, user in self.users.items():
            if user['username'] == username and user['password'] == password:
                return user_id
        return None

    def register_user(self, username, email, password):
        user_id = self.user_id_counter
        user = {'user_id': user_id, 'username': username, 'email': email, 'password': password}
        self.users[user_id] = user
        self.user_id_counter += 1
        return user_id

    def update_profile(self, user_id, profile_data):
        if user_id in self.users:
            user = self.users[user_id]
            user['username'] = profile_data['username']
            user['email'] = profile_data['email']
            self.users[user_id] = user
            return True
        else:
            return False


class PlaylistService:
    def __init__(self):
        self.playlists = {}
        self.playlist_id_counter = 1

    def create_playlist(self, user_id, name):
        playlist_id = self.playlist_id_counter
        playlist = {'playlist_id': playlist_id, 'name': name, 'owner': user_id, 'songs': []}
        self.playlists[playlist_id] = playlist
        self.playlist_id_counter += 1
        return playlist_id

    def add_song_to_playlist(self, playlist_id, song_id):
        if playlist_id in self.playlists:
            playlist = self.playlists[playlist_id]
            playlist['songs'].append(song_id)
            self.playlists[playlist_id] = playlist
            return True
        else:
            return False

    def remove_song_from_playlist(self, playlist_id, song_id):
        if playlist_id in self.playlists:
            playlist = self.playlists[playlist_id]
            if song_id in playlist['songs']:
                playlist['songs'].remove(song_id)
                self.playlists[playlist_id] = playlist
                return True
        return False

    def get_playlist_details(self, playlist_id):
        if playlist_id in self.playlists:
            return self.playlists[playlist_id]
        else:
            return None


class LikeService:
    def __init__(self):
        self.likes = {}
        self.like_id_counter = 1

    def like_song(self, user_id, song_id):
        like_id = self.like_id_counter
        like = {'like_id': like_id, 'user_id': user_id, 'song_id': song_id}
        self.likes[like_id] = like
        self.like_id_counter += 1
        return like_id

    def unlike_song(self, like_id):
        if like_id in self.likes:
            del self.likes[like_id]
            return True
        else:
            return False


class CommentService:
    def __init__(self):
        self.comments = {}
        self.comment_id_counter = 1

    def add_comment(self, user_id, song_id, comment_text):
        comment_id = self.comment_id_counter
        comment = {'comment_id': comment_id, 'user_id': user_id, 'song_id': song_id, 'comment_text': comment_text}
        self.comments[comment_id] = comment
        self.comment_id_counter += 1
        return comment_id

    def reply_to_comment(self, parent_comment_id, user_id, song_id, comment_text):
        reply_id = self.comment_id_counter
        reply = {'comment_id': reply_id, 'user_id': user_id, 'song_id': song_id, 'comment_text': comment_text}
        self.comments[reply_id] = reply
        self.comment_id_counter += 1


# Example usage of the services

song_service = SongService()
user_service = UserService()
playlist_service = PlaylistService()
like_service = LikeService()
comment_service = CommentService()

# Upload a song
song_id = song_service.upload_song('Song Title', 'Artist Name', 180)

# Register a user
user_id = user_service.register_user('username', '[email protected]', 'password')

# Create a playlist
playlist_id = playlist_service.create_playlist(user_id, 'My Playlist')

# Add the song to the playlist
playlist_service.add_song_to_playlist(playlist_id, song_id)

# Like the song
like_id = like_service.like_song(user_id, song_id)

# Add a comment
comment_id = comment_service.add_comment(user_id, song_id, 'Great song!')

# Reply to a comment
reply_id = comment_service.reply_to_comment(comment_id, user_id, song_id, 'Thank you!')

# Get song details
song_details = song_service.get_song_details(song_id)
print(song_details)

# Get playlist details
playlist_details = playlist_service.get_playlist_details(playlist_id)
print(playlist_details)

class User:
    def __init__(self, user_id, username, email, password):
        self.user_id = user_id
        self.username = username
        self.email = email
        self.password = password
        self.playlists = []

class Playlist:
    def __init__(self, playlist_id, name, owner_id):
        self.playlist_id = playlist_id
        self.name = name
        self.owner_id = owner_id
        self.songs = []

class Song:
    def __init__(self, song_id, title, artist, duration):
        self.song_id = song_id
        self.title = title
        self.artist = artist
        self.duration = duration

    def __str__(self):
        return f"{self.title} by {self.artist}"

class Spotify:
    def __init__(self):
        self.users = {}
        self.playlists = {}
        self.songs = {}
        self.user_id_counter = 1
        self.playlist_id_counter = 1
        self.song_id_counter = 1

    def create_user(self, username, email, password):
        user_id = str(self.user_id_counter)
        user = User(user_id, username, email, password)
        self.users[user_id] = user
        self.user_id_counter += 1
        return user

    def get_user_by_id(self, user_id):
        return self.users.get(user_id)

    def create_playlist(self, user_id, name):
        owner = self.get_user_by_id(user_id)
        if owner:
            playlist_id = str(self.playlist_id_counter)
            playlist = Playlist(playlist_id, name, owner.user_id)
            owner.playlists.append(playlist)
            self.playlists[playlist_id] = playlist
            self.playlist_id_counter += 1
            return playlist

    def get_playlist_by_id(self, playlist_id):
        return self.playlists.get(playlist_id)

    def add_song_to_playlist(self, playlist_id, song_id):
        playlist = self.get_playlist_by_id(playlist_id)
        song = self.get_song_by_id(song_id)
        if playlist and song:
            playlist.songs.append(song)
            return True
        return False

    def create_song(self, title, artist, duration):
        song_id = str(self.song_id_counter)
        song = Song(song_id, title, artist, duration)
        self.songs[song_id] = song
        self.song_id_counter += 1
        return song

    def get_song_by_id(self, song_id):
        return self.songs.get(song_id)

# Low-Level API Design and Python Code Implementation

# Playlist Management API

@app.route('/playlists', methods=['POST'])
def create_playlist():
    # Create a new playlist
    data = request.get_json()
    # Process the request and store playlist information in the database
    # Return the newly created playlist information
    playlist = {'playlist_id': '456', 'name': data['name'], 'songs': []}
    return jsonify(playlist), 201

@app.route('/playlists/<playlist_id>', methods=['PUT'])
def update_playlist(playlist_id):
    # Update playlist details
    data = request.get_json()
    # Process the request and update playlist information in the database
    # Return the updated playlist information
    playlist = {'playlist_id': playlist_id, 'name': data['name'], 'songs': data['songs']}
    return jsonify(playlist)

@app.route('/playlists/<playlist_id>', methods=['DELETE'])
def delete_playlist(playlist_id):
    # Delete a playlist
    # Process the request and remove the playlist from the database
    return '', 204

@app.route('/playlists/<playlist_id>/songs', methods=['POST'])
def add_song_to_playlist(playlist_id):
    # Add a song to a playlist
    data = request.get_json()
    # Process the request and update the playlist in the database by adding the song
    # Return the updated playlist information
    playlist = {'playlist_id': playlist_id, 'name': 'My Playlist', 'songs': ['song1', 'song2', 'song3', data['song_id']]}
    return jsonify(playlist)

@app.route('/playlists/<playlist_id>/songs/<song_id>', methods=['DELETE'])
def remove_song_from_playlist(playlist_id, song_id):
    # Remove a song from a playlist
    # Process the request and update the playlist in the database by removing the song
    playlist = {'playlist_id': playlist_id, 'name': 'My Playlist', 'songs': ['song1', 'song2', 'song3']}
    if song_id in playlist['songs']:
        playlist['songs'].remove(song_id)
    return jsonify(playlist)

# Social Interaction API

@app.route('/social/friends/<user_id>', methods=['POST'])
def add_friend(user_id):
    # Add a friend for a given user
    data = request.get_json()
    # Process the request and update the user's friend list in the database
    return '', 204

@app.route('/social/friends/<user_id>/<friend_id>', methods=['DELETE'])
def remove_friend(user_id, friend_id):
    # Remove a friend for a given user
    # Process the request and update the user's friend list in the database
    return '', 204

@app.route('/social/activities/<user_id>', methods=['GET'])
def get_friend_activities(user_id):
    # Retrieve the recent activities of a user's friends
    # Process the request and fetch the activities from the database
    activities = ['activity1', 'activity2', 'activity3']
    return jsonify(activities)

# Audio Streaming API

@app.route('/audio/<song_id>/stream', methods=['GET'])
def stream_audio(song_id):
    # Stream the audio content of a song
    # Implement audio streaming logic here
    return 'Streaming audio for song ID: ' + song_id

if __name__ == '__main__':
    app.run()

class Song:
    def __init__(self, title, artist, duration):
        self.title = title
        self.artist = artist
        self.duration = duration

class Album:
    def __init__(self, title, artist, release_date, songs):
        self.title = title
        self.artist = artist
        self.release_date = release_date
        self.songs = songs

class MusicCatalog:
    def __init__(self):
        self.songs = []
        self.albums = []

    def add_song(self, title, artist, duration):
        song = Song(title, artist, duration)
        self.songs.append(song)

    def add_album(self, title, artist, release_date, songs):
        album = Album(title, artist, release_date, songs)
        self.albums.append(album)

    def search_song(self, query):
        result = []
        for song in self.songs:
            if query.lower() in song.title.lower():
                result.append(song)
        return result

    def get_recommendations(self, user):
        # Logic to generate personalized song recommendations based on user preferences
        recommendations = []
        # Recommendation generation logic goes here
        return recommendations

class Playlist:
    def __init__(self, name, owner):
        self.name = name
        self.owner = owner
        self.songs = []

    def add_song(self, song):
        self.songs.append(song)

    def remove_song(self, song):
        self.songs.remove(song)

class User:
    def __init__(self, username):
        self.username = username
        self.playlists = []

    def create_playlist(self, name):
        playlist = Playlist(name, self)
        self.playlists.append(playlist)
        return playlist

    def add_song_to_playlist(self, playlist, song):
        if playlist in self.playlists:
            playlist.add_song(song)

    def remove_song_from_playlist(self, playlist, song):
        if playlist in self.playlists:
            playlist.remove_song(song)

class User:
    def __init__(self, username):
        self.username = username
        self.following = []
        self.playlists = []
        self.friends = []

    def follow_playlist(self, playlist):
        if playlist not in self.playlists:
            self.following.append(playlist)

    def unfollow_playlist(self, playlist):
        if playlist in self.following:
            self.following.remove(playlist)

    def add_friend(self, friend):
        if friend not in self.friends:
            self.friends.append(friend)

    def remove_friend(self, friend):
        if friend in self.friends:
            self.friends.remove(friend)

class User:
    def __init__(self, username):
        self.username = username
        self.downloaded_songs = []
        self.downloaded_playlists = []

    def download_song(self, song):
        if song not in self.downloaded_songs:
            self.downloaded_songs.append(song)

    def remove_downloaded_song(self, song):
        if song in self.downloaded_songs:
            self.downloaded_songs.remove(song)

    def download_playlist(self, playlist):
        if playlist not in self.downloaded_playlists:
            self.downloaded_playlists.append(playlist)

    def remove_downloaded_playlist(self, playlist):
        if playlist in self.downloaded_playlists:
            self.downloaded_playlists.remove(playlist)

from flask import Flask, request

app = Flask(__name__)
spotify = Spotify()

# User Management API
@app.route('/users', methods=['POST'])
def create_user():
    data = request.get_json()
    username = data.get('username')
    email = data.get('email')
    password = data.get('password')
    user = spotify.create_user(username, email, password)
    return f"User created with ID: {user.user_id}", 201

@app.route('/users/<user_id>', methods=['GET'])
def get_user(user_id):
    user = spotify.get_user_by_id(user_id)
    if user:
        return f"User: {user.username}, Email: {user.email}", 200
    return "User not found", 404

# Playlist API
@app.route('/users/<user_id>/playlists', methods=['POST'])
def create_playlist(user_id):
    data = request.get_json()
    name = data.get('name')
    playlist = spotify.create_playlist(user_id, name)
    if playlist:
        return f"Playlist created with ID: {playlist.playlist_id}", 201
    return "User not found", 404

@app.route('/playlists/<playlist_id>', methods=['GET'])
def get_playlist(playlist_id):
    playlist = spotify.get_playlist_by_id(playlist_id)
    if playlist:
        return f"Playlist: {playlist.name}, Owner: {playlist.owner_id}", 200
    return "Playlist not found", 404

# Song API
@app.route('/songs', methods=['POST'])
def create_song():
    data = request.get_json()
    title = data.get('title')
    artist = data.get('artist')
    duration = data.get('duration')
    song = spotify.create_song(title, artist, duration)
    return f"Song created with ID: {song.song_id}", 201

@app.route('/songs/<song_id>', methods=['GET'])
def get_song(song_id):
    song = spotify.get_song_by_id(song_id)
    if song:
        return f"Song: {song.title}, Artist: {song.artist}", 200
    return "Song not found", 404

# Add song to playlist API
@app.route('/playlists/<playlist_id>/songs/<song_id>', methods=['POST'])
def add_song_to_playlist(playlist_id, song_id):
    success = spotify.add_song_to_playlist(playlist_id, song_id)
    if success:
        return "Song added to playlist", 200
    return "Playlist or song not found", 404

class User:
    def __init__(self, user_id, username, password, email, bio=None):
        self.user_id = user_id
        self.username = username
        self.password = password
        self.email = email
        self.bio = bio
        self.followers = []
        self.following = []
        self.posts = []

class Post:
    def __init__(self, post_id, user, caption, image_url, timestamp):
        self.post_id = post_id
        self.user = user
        self.caption = caption
        self.image_url = image_url
        self.timestamp = timestamp

class WeChat:
    def __init__(self):
        self.users = {}
        self.posts = []

    def add_user(self, user):
        self.users[user.user_id] = user

    def get_user_by_id(self, user_id):
        return self.users.get(user_id)

    def create_post(self, user_id, caption, image_url, timestamp):
        user = self.get_user_by_id(user_id)

        if user is None:
            print("User not found")
            return

        post_id = len(self.posts) + 1
        post = Post(post_id, user, caption, image_url, timestamp)
        self.posts.append(post)
        user.posts.append(post)

    def get_user_feed(self, user_id):
        user = self.get_user_by_id(user_id)

        if user is None:
            print("User not found")
            return []

        feed = []
        for post in self.posts:
            if post.user.user_id in user.following:
                feed.append(post)

        return feed

class User:
    def __init__(self, username, password):
        self.username = username
        self.password = password
        self.user_id = generate_user_id()

def register_user(username, password):
    # Validate input data
    if not username or not password:
        return {
            "error": "Invalid username or password."
        }

    # Check if the user already exists
    if is_user_exists(username):
        return {
            "error": "User already exists."
        }

    # Create a new user object
    new_user = User(username, password)

    # Store the user in the database or perform any necessary operations

    return {
        "message": "User registration successful.",
        "user_id": new_user.user_id
    }

def login(username, password):
    # Validate credentials
    if not username or not password:
        return {
            "error": "Invalid username or password."
        }

    # Check if the user exists in the database
    user = get_user_by_username(username)
    if not user:
        return {
            "error": "User does not exist."
        }

    # Verify the password
    if user.password != password:
        return {
            "error": "Incorrect password."
        }

    # Generate authentication token
    auth_token = generate_auth_token()

    # Return token or error response
    return {
        "message": "Login successful.",
        "auth_token": auth_token
    }

def get_user_profile(user_id):
    # Retrieve user profile from the database
    user = get_user_by_id(user_id)

    if not user:
        return {
            "error": "User not found."
        }

    # Return user profile or error response
    return {
        "username": user.username,
        "user_id": user.user_id
    }

class Message:
    def __init__(self, sender_id, receiver_id, content):
        self.message_id = generate_message_id()
        self.sender_id = sender_id
        self.receiver_id = receiver_id
        self.content = content
        self.timestamp = get_current_timestamp()

def send_message(sender_id, receiver_id, content):
    # Validate sender and receiver IDs
    if not sender_id or not receiver_id:
        return {
            "error": "Invalid sender or receiver ID."
        }

    # Create a new message object
    new_message = Message(sender_id, receiver_id, content)

    # Store the message in the database or perform any necessary operations

    # Send a notification to the receiver

    return {
        "message": "Message sent successfully.",
        "message_id": new_message.message_id
    }

def get_conversation(conversation_id):
    # Retrieve conversation from the database
    conversation = get_conversation_by_id(conversation_id)

    if not conversation:
        return {
            "error": "Conversation not found."
        }

    # Return conversation or error response
    return {
        "conversation_id": conversation.conversation_id,
        "messages": conversation.messages
    }

def get_unread_message_count(user_id):
    # Retrieve unread message count from the database
    unread_count = get_unread_message_count_by_user_id(user_id)

    # Return count or error response
    return {
        "unread_count": unread_count
    }

class Moment:
    def __init__(self, user_id, content):
        self.moment_id = generate_moment_id()
        self.user_id = user_id
        self.content = content
        self.timestamp = get_current_timestamp()

def post_moment(user_id, content):
    # Validate user ID
    if not user_id:
        return {
            "error": "Invalid user ID."
        }

    # Create a new moment object
    new_moment = Moment(user_id, content)

    # Store the moment in the database or perform any necessary operations

    return {
        "message": "Moment posted successfully.",
        "moment_id": new_moment.moment_id
    }

def get_moments_feed(user_id):
    # Retrieve moments from friends and connections
    moments_feed = get_moments_feed_by_user_id(user_id)

    # Return moments feed or error response
    return {
        "moments": moments_feed
    }

class MiniProgram:
    def __init__(self, program_id, program_name):
        self.program_id = program_id
        self.program_name = program_name

def get_mini_programs():
    # Retrieve available mini-programs from the database
    mini_programs = get_all_mini_programs()

    # Return mini-programs list or error response
    return {
        "mini_programs": mini_programs
    }

def launch_mini_program(program_id, user_id):
    # Validate program ID and user ID
    if not program_id or not user_id:
        return {
            "error": "Invalid program ID or user ID."
        }

    # Launch the mini-program or perform any necessary operations

    return {
        "message": "Mini-program launched successfully."
    }

class PaymentRequest:
    def __init__(self, user_id, amount, description):
        self.payment_id = generate_payment_id()
        self.user_id = user_id
        self.amount = amount
        self.description = description
        self.timestamp = get_current_timestamp()
        self.status = "pending"

def create_payment_request(user_id, amount, description):
    # Validate user ID, amount, and description
    if not user_id or not amount or not description:
        return {
            "error": "Invalid user ID, amount, or description."
        }

    # Create a new payment request object
    new_payment_request = PaymentRequest(user_id, amount, description)

    # Store the payment request in the database or perform any necessary operations

    return {
        "message": "Payment request created successfully.",
        "payment_id": new_payment_request.payment_id
    }

def process_payment_callback(transaction_id, status):
    # Validate transaction ID and status
    if not transaction_id or not status:
        return {
            "error": "Invalid transaction ID or status."
        }

    # Update payment status in the database or perform any necessary operations

    return {
        "message": "Payment callback processed successfully."
    }

class Message:
    def __init__(self, sender_id, receiver_id, content, message_type):
        self.sender_id = sender_id
        self.receiver_id = receiver_id
        self.content = content
        self.message_type = message_type
        self.timestamp = get_current_timestamp()

def send_message(sender_id, receiver_id, content, message_type):
    new_message = Message(sender_id, receiver_id, content, message_type)
    # Implement the logic to send the message in real-time
    return "Message sent successfully."

def receive_message(message):
    # Implement the logic to receive and process the message in real-time
    print("Received message:", message.content)

class Call:
    def __init__(self, caller_id, receiver_id, call_type):
        self.caller_id = caller_id
        self.receiver_id = receiver_id
        self.call_type = call_type
        self.timestamp = get_current_timestamp()

def make_call(caller_id, receiver_id, call_type):
    new_call = Call(caller_id, receiver_id, call_type)
    # Implement the logic to initiate the voice or video call
    return "Call initiated successfully."

def receive_call(call):
    # Implement the logic to handle and process the incoming call
    print("Incoming", call.call_type, "call from", call.caller_id)

class Post:
    def __init__(self, user_id, content, media):
        self.user_id = user_id
        self.content = content
        self.media = media
        self.timestamp = get_current_timestamp()

class User:
    def __init__(self, user_id, username):
        self.user_id = user_id
        self.username = username
        self.posts = []

def create_post(user_id, content, media):
    new_post = Post(user_id, content, media)
    # Store the post in the user's profile or perform any necessary operations
    return "Post created successfully."

def get_user_posts(user_id):
    # Retrieve the user's posts from the database or user's profile
    user = get_user_by_id(user_id)
    if user:
        return user.posts
    else:
        return []

def like_post(user_id, post_id):
    # Implement the logic to handle post likes
    return "Post liked successfully."

class Moment:
    def __init__(self, user_id, content, media):
        self.user_id = user_id
        self.content = content
        self.media = media
        self.timestamp = get_current_timestamp()

class User:
    def __init__(self, user_id, username):
        self.user_id = user_id
        self.username = username
        self.moments = []

def post_moment(user_id, content, media):
    new_moment = Moment(user_id, content, media)
    # Store the moment in the user's moments or perform any necessary operations
    return "Moment posted successfully."

def get_user_moments(user_id):
    # Retrieve the user's moments from the database or user's profile
    user = get_user_by_id(user_id)
    if user:
        return user.moments
    else:
        return []

def delete_moment(user_id, moment_id):
    # Implement the logic to delete a specific moment
    return "Moment deleted successfully."

class MiniProgram:
    def __init__(self, program_id, program_name):
        self.program_id = program_id
        self.program_name = program_name

def launch_mini_program(user_id, program_id):
    # Implement the logic to launch the specified mini-program for the user
    return "Mini-program launched successfully."

def get_available_mini_programs():
    # Retrieve the list of available mini-programs from the database or any source
    return ["Program 1", "Program 2", "Program 3"]

def uninstall_mini_program(user_id, program_id):
    # Implement the logic to uninstall the specified mini-program for the user
    return "Mini-program uninstalled successfully."

class Payment:
    def __init__(self, user_id, amount, description):
        self.user_id = user_id
        self.amount = amount
        self.description = description
        self.timestamp = get_current_timestamp()
        self.status = "pending"

def make_payment(user_id, amount, description):
    new_payment = Payment(user_id, amount, description)
    # Implement the logic to process the payment and update the status
    return "Payment processed successfully."

def get_payment_status(payment_id):
    # Retrieve the payment status from the database or any source
    return "Success"  # Or "Pending", "Failed", etc.

from flask import Flask, request, jsonify

app = Flask(__name__)
wechat = WeChat()

# Endpoint for creating a user
@app.route("/users", methods=["POST"])
def create_user():
    data = request.get_json()
    user_id = data.get("user_id")
    username = data.get("username")
    password = data.get("password")
    email = data.get("email")
    bio = data.get("bio")

    user = User(user_id, username, password, email, bio)
    wechat.add_user(user)

    return jsonify({"message": "User created successfully"}), 201

# Endpoint for creating a post
@app.route("/users/<user_id>/posts", methods=["POST"])
def create_post(user_id):
    user = wechat.get_user_by_id(user_id)

    if user is None:
        return jsonify({"message": "User not found"}), 404

    data = request.get_json()
    caption = data.get("caption")
    image_url = data.get("image_url")
    timestamp = data.get("timestamp")

    wechat.create_post(user_id, caption, image_url, timestamp)

    return jsonify({"message": "Post created successfully"}), 200

# Endpoint for getting the user's feed
@app.route("/users/<user_id>/feed", methods=["GET"])
def get_feed(user_id):
    user = wechat.get_user_by_id(user_id)

    if user is None:
        return jsonify({"message": "User not found"}), 404

    feed = wechat.get_user_feed(user_id)

    feed_data = []
    for post in feed:
        feed_data.append({
            "post_id": post.post_id,
            "user_id": post.user.user_id,
            "caption": post.caption,
            "image_url": post.image_url,
            "timestamp": post.timestamp
        })

    return jsonify({"feed": feed_data}), 200

from flask import Flask, request

app = Flask(__name__)

# Sample data to be stored in the server
users = {}
posts = {}
comments = {}
comment_id_counter = 1

# Low-Level Design Classes
class User:
    def __init__(self, user_id, username, password):
        self.user_id = user_id
        self.username = username
        self.password = password
        self.followers = []
        self.following = []

class Post:
    def __init__(self, post_id, user, content):
        self.post_id = post_id
        self.user = user
        self.content = content
        self.likes = []
        self.comments = []

class Comment:
    def __init__(self, comment_id, user, content):
        self.comment_id = comment_id
        self.user = user
        self.content = content
        self.replies = []

# API Endpoints

# User Management API
@app.route("/users", methods=["POST"])
def create_user():
    data = request.get_json()
    user_id = data["user_id"]
    username = data["username"]
    password = data["password"]
    user = User(user_id, username, password)
    users[user_id] = user
    return {"message": "User created successfully"}, 201

@app.route("/users/<user_id>", methods=["GET"])
def get_user(user_id):
    if user_id in users:
        user = users[user_id]
        return {
            "user_id": user.user_id,
            "username": user.username,
            "password": user.password,
            "followers": user.followers,
            "following": user.following
        }, 200
    else:
        return {"message": "User not found"}, 404

# Post API
@app.route("/posts", methods=["POST"])
def create_post():
    data = request.get_json()
    user_id = data["user_id"]
    content = data["content"]

    if user_id in users:
        user = users[user_id]
        post_id = len(posts) + 1
        post = Post(post_id, user, content)
        posts[post_id] = post
        return {"message": "Post created successfully"}, 201
    else:
        return {"message": "User not found"}, 404

@app.route("/posts/<post_id>", methods=["GET"])
def get_post(post_id):
    if post_id in posts:
        post = posts[post_id]
        return {
            "post_id": post.post_id,
            "user_id": post.user.user_id,
            "content": post.content,
            "likes": post.likes,
            "comments": post.comments
        }, 200
    else:
        return {"message": "Post not found"}, 404

# Like API
@app.route("/posts/<post_id>/likes", methods=["POST"])
def like_post(post_id):
    data = request.get_json()
    user_id = data["user_id"]

    if post_id in posts and user_id in users:
        post = posts[post_id]
        user = users[user_id]
        post.likes.append(user_id)
        return {"message": "Post liked successfully"}, 200
    else:
        return {"message": "Post or user not found"}, 404

# Comment API
@app.route("/posts/<post_id>/comments", methods=["POST"])
def add_comment(post_id):
    data = request.get_json()
    user_id = data["user_id"]
    content = data["content"]

    if post_id in posts and user_id in users:
        post = posts[post_id]
        user = users[user_id]
        comment_id = comment_id_counter
        comment = Comment(comment_id, user, content)
        comments[comment_id] = comment
        post.comments.append(comment_id)
        comment_id_counter += 1
        return {"message": "Comment added successfully"}, 200
    else:
        return {"message": "Post or user not found"}, 404

@app.route("/comments/<comment_id>/replies", methods=["POST"])
def reply_to_comment(comment_id):
    data = request.get_json()
    user_id = data["user_id"]
    content = data["content"]

    if comment_id in comments and user_id in users:
        comment = comments[comment_id]
        user = users[user_id]
        reply_id = comment_id_counter
        reply = Comment(reply_id, user, content)
        comments[reply_id] = reply
        comment.replies.append(reply_id)
        comment_id_counter += 1
        return {"message": "Reply added successfully"}, 200
    else:
        return {"message": "Comment or user not found"}, 404

# Follow API
@app.route("/users/<follower_id>/follow/<following_id>", methods=["POST"])
def follow_user(follower_id, following_id):
    if follower_id in users and following_id in users:
        follower = users[follower_id]
        following = users[following_id]
        follower.following.append(following_id)
        following.followers.append(follower_id)
        return {"message": "User followed successfully"}, 200
    else:
        return {"message": "User not found"}, 404

# Search API
@app.route("/search/posts", methods=["GET"])
def search_posts():
    keyword = request.args.get("q")
    matching_posts = []
    for post in posts.values():
        if keyword in post.content:
            matching_posts.append({
                "post_id": post.post_id,
                "user_id": post.user.user_id,
                "content": post.content
            })
    return {"posts": matching_posts}, 200

if __name__ == "__main__":
    app.run()

# User API

users = {}  # In-memory storage for user data

def register_user(username, password, email):
    user_id = generate_user_id()  # Generate a unique user ID
    user = {
        'user_id': user_id,
        'username': username,
        'password': password,
        'email': email,
        'profile': {}
    }
    users[user_id] = user  # Store user data in the users dictionary
    return user_id

def login_user(username, password):
    for user_id, user in users.items():
        if user['username'] == username and user['password'] == password:
            return user_id
    return None

def get_user_profile(user_id):
    if user_id in users:
        return users[user_id]['profile']
    return None

def update_user_profile(user_id, profile_data):
    if user_id in users:
        users[user_id]['profile'] = profile_data


# Post API

posts = {}  # In-memory storage for post data

def create_post(user_id, content):
    post_id = generate_post_id()  # Generate a unique post ID
    post = {
        'post_id': post_id,
        'user_id': user_id,
        'content': content,
        'comments': []
    }
    posts[post_id] = post  # Store post data in the posts dictionary
    return post_id

def get_post(post_id):
    if post_id in posts:
        return posts[post_id]
    return None

def delete_post(post_id):
    if post_id in posts:
        del posts[post_id]

def get_user_posts(user_id):
    user_posts = []
    for post_id, post in posts.items():
        if post['user_id'] == user_id:
            user_posts.append(post)
    return user_posts


# Comment API

comments = {}  # In-memory storage for comment data

def add_comment(user_id, post_id, content):
    comment_id = generate_comment_id()  # Generate a unique comment ID
    comment = {
        'comment_id': comment_id,
        'user_id': user_id,
        'post_id': post_id,
        'content': content
    }
    if post_id in posts:
        posts[post_id]['comments'].append(comment_id)  # Add comment ID to the post's comments list
    comments[comment_id] = comment  # Store comment data in the comments dictionary
    return comment_id

def delete_comment(comment_id):
    if comment_id in comments:
        comment = comments[comment_id]
        if comment['post_id'] in posts:
            posts[comment['post_id']]['comments'].remove(comment_id)  # Remove comment ID from the post's comments list
        del comments[comment_id]

def get_post_comments(post_id):
    if post_id in posts:
        comment_ids = posts[post_id]['comments']
        post_comments = []
        for comment_id in comment_ids:
            if comment_id in comments:
                post_comments.append(comments[comment_id])
        return post_comments
    return None


# Relationship API

follow_relationships = {}  # In-memory storage for follow relationships

def follow_user(user_id, target_user_id):
    follow_relationships.setdefault(user_id, set()).add(target_user_id)

def unfollow_user(user_id, target_user_id):
    if user_id in follow_relationships and target_user_id in follow_relationships[user_id]:
        follow_relationships[user_id].remove(target_user_id)

def get_user_followers(user_id):
    return follow_relationships.get(user_id, set())

def get_user_following(user_id):
    following = set()
    for user, targets in follow_relationships.items():
        if user_id in targets:
            following.add(user)
    return following


# Search API

def search_posts(keyword):
    matched_posts = []
    for post_id, post in posts.items():
        if keyword in post['content']:
            matched_posts.append(post)
    return matched_posts

def search_users(keyword):
    matched_users = []
    for user_id, user in users.items():
        if keyword in user['username'] or keyword in user['profile']:
            matched_users.append(user)
    return matched_users

def get_trending_topics():
    # Implementation to retrieve trending topics
    ...

import psycopg2

# Database Connection Setup
conn = psycopg2.connect(
    host="your_host",
    database="your_database",
    user="your_username",
    password="your_password"
)
cur = conn.cursor()

# User Operations
def create_user(user_data):
    query = "INSERT INTO users (username, password, email) VALUES (%s, %s, %s) RETURNING user_id"
    cur.execute(query, (user_data['username'], user_data['password'], user_data['email']))
    user_id = cur.fetchone()[0]
    conn.commit()
    return user_id

def get_user(user_id):
    query = "SELECT * FROM users WHERE user_id = %s"
    cur.execute(query, (user_id,))
    user_data = cur.fetchone()
    return user_data

def update_user(user_id, updated_data):
    query = "UPDATE users SET username = %s, password = %s, email = %s WHERE user_id = %s"
    cur.execute(query, (updated_data['username'], updated_data['password'], updated_data['email'], user_id))
    conn.commit()

# Post Operations
def create_post(post_data):
    query = "INSERT INTO posts (user_id, content) VALUES (%s, %s) RETURNING post_id"
    cur.execute(query, (post_data['user_id'], post_data['content']))
    post_id = cur.fetchone()[0]
    conn.commit()
    return post_id

def get_post(post_id):
    query = "SELECT * FROM posts WHERE post_id = %s"
    cur.execute(query, (post_id,))
    post_data = cur.fetchone()
    return post_data

def delete_post(post_id):
    query = "DELETE FROM posts WHERE post_id = %s"
    cur.execute(query, (post_id,))
    conn.commit()

# Comment Operations
def create_comment(comment_data):
    query = "INSERT INTO comments (user_id, post_id, content) VALUES (%s, %s, %s) RETURNING comment_id"
    cur.execute(query, (comment_data['user_id'], comment_data['post_id'], comment_data['content']))
    comment_id = cur.fetchone()[0]
    conn.commit()
    return comment_id

def delete_comment(comment_id):
    query = "DELETE FROM comments WHERE comment_id = %s"
    cur.execute(query, (comment_id,))
    conn.commit()

def get_post_comments(post_id):
    query = "SELECT * FROM comments WHERE post_id = %s"
    cur.execute(query, (post_id,))
    comments = cur.fetchall()
    return comments

# Relationship Operations
def add_follower(user_id, target_user_id):
    query = "INSERT INTO followers (user_id, follower_user_id) VALUES (%s, %s)"
    cur.execute(query, (target_user_id, user_id))
    conn.commit()

def remove_follower(user_id, target_user_id):
    query = "DELETE FROM followers WHERE user_id = %s AND follower_user_id = %s"
    cur.execute(query, (target_user_id, user_id))
    conn.commit()

def get_user_followers(user_id):
    query = "SELECT follower_user_id FROM followers WHERE user_id = %s"
    cur.execute(query, (user_id,))
    followers = cur.fetchall()
    return [follower[0] for follower in followers]

def get_user_following(user_id):
    query = "SELECT user_id FROM followers WHERE follower_user_id = %s"
    cur.execute(query, (user_id,))
    following = cur.fetchall()
    return [followed[0] for followed in following]

# Search Operations
def search_posts(keyword):
    query = "SELECT * FROM posts WHERE content LIKE %s"
    cur.execute(query, ('%' + keyword + '%',))
    matched_posts = cur.fetchall()
    return matched_posts

def search_users(keyword):
    query = "SELECT * FROM users WHERE username LIKE %s OR email LIKE %s"
    cur.execute(query, ('%' + keyword + '%', '%' + keyword + '%'))
    matched_users = cur.fetchall()
    return matched_users

def get_trending_topics():
    # Implementation to retrieve the currently trending topics from the database
    ...

# User Registration and Authentication
users = {}

def register_user(username, password, email):
    if username in users:
        return "Username already exists"
    user_id = generate_user_id()
    users[username] = {
        'user_id': user_id,
        'username': username,
        'password': password,
        'email': email
    }
    return "User registered successfully"

def login_user(username, password):
    if username in users and users[username]['password'] == password:
        return "Login successful"
    return "Invalid credentials"


# Posting and Sharing
posts = {}

def create_post(user_id, content):
    post_id = generate_post_id()
    post = {
        'post_id': post_id,
        'user_id': user_id,
        'content': content
    }
    posts[post_id] = post
    return "Post created successfully"

def share_post(user_id, post_id):
    if post_id in posts:
        shared_post = posts[post_id].copy()
        shared_post['user_id'] = user_id
        posts[generate_post_id()] = shared_post
        return "Post shared successfully"
    return "Invalid post ID"


# Following and Followers
follow_relationships = {}

def follow_user(user_id, target_user_id):
    follow_relationships.setdefault(user_id, set()).add(target_user_id)
    return "User followed successfully"

def unfollow_user(user_id, target_user_id):
    if user_id in follow_relationships and target_user_id in follow_relationships[user_id]:
        follow_relationships[user_id].remove(target_user_id)
        return "User unfollowed successfully"
    return "Invalid user or relationship does not exist"

def get_followers(user_id):
    if user_id in follow_relationships:
        return follow_relationships[user_id]
    return []

def get_following(user_id):
    following = set()
    for user, targets in follow_relationships.items():
        if user_id in targets:
            following.add(user)
    return following


# Comments and Likes
comments = {}
likes = {}

def add_comment(user_id, post_id, content):
    comment_id = generate_comment_id()
    comment = {
        'comment_id': comment_id,
        'user_id': user_id,
        'post_id': post_id,
        'content': content
    }
    if post_id in posts:
        posts[post_id].setdefault('comments', []).append(comment_id)
        comments[comment_id] = comment
        return "Comment added successfully"
    return "Invalid post ID"

def delete_comment(comment_id):
    if comment_id in comments:
        comment = comments[comment_id]
        if comment['post_id'] in posts:
            posts[comment['post_id']]['comments'].remove(comment_id)
        del comments[comment_id]
        return "Comment deleted successfully"
    return "Invalid comment ID"

def like_post(user_id, post_id):
    if post_id in posts:
        likes.setdefault(post_id, set()).add(user_id)
        return "Post liked successfully"
    return "Invalid post ID"

def unlike_post(user_id, post_id):
    if post_id in likes and user_id in likes[post_id]:
        likes[post_id].remove(user_id)
        return "Post unliked successfully"
    return "Invalid post ID or user has not liked the post"

def get_post_comments(post_id):
    if post_id in posts:
        return posts[post_id].get('comments', [])
    return []

def get_post_likes(post_id):
    if post_id in likes:
        return likes[post_id]
    return []


# Trending Topics
trending_topics = []

def add_trending_topic(topic):
    trending_topics.append(topic)
    return "Trending topic added successfully"

def remove_trending_topic(topic):
    if topic in trending_topics:
        trending_topics.remove(topic)
        return "Trending topic removed successfully"
    return "Trending topic not found"

def get_trending_topics():
    return trending_topics


# Direct Messaging
messages = {}

def send_message(sender_id, receiver_id, message):
    message_id = generate_message_id()
    message_data = {
        'message_id': message_id,
        'sender_id': sender_id,
        'receiver_id': receiver_id,
        'message': message
    }
    messages.setdefault(receiver_id, []).append(message_data)
    return "Message sent successfully"

def get_messages(user_id):
    if user_id in messages:
        return messages[user_id]
    return []

# Search Functionality
def search_posts(keyword):
    matched_posts = []
    for post_id, post in posts.items():
        if keyword in post['content']:
            matched_posts.append(post)
    return matched_posts

def search_users(keyword):
    matched_users = []
    for username, user_data in users.items():
        if keyword in username:
            matched_users.append(user_data)
    return matched_users

def search_trending_topics(keyword):
    matched_topics = []
    for topic in trending_topics:
        if keyword in topic:
            matched_topics.append(topic)
    return matched_topics