| from flask import Flask, request, jsonify import pymysql import bcrypt   app = Flask(__name__)   # Database connection configuration db_config = {     'host': 'localhost',     'user': 'root',     'password': '123456',     'database': 'chat_db' }     def get_db_connection():     return pymysql.connect(**db_config)     @app.route('/register', methods=['POST']) def register():     data = request.json     username = data['username']     password = data['password']       hashed = bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt())       conn = get_db_connection()     cursor = conn.cursor()       try:         cursor.execute("INSERT INTO users (username, password) VALUES (%s, %s)", (username, hashed))         conn.commit()         return jsonify({'message': 'Registration successful!'}), 201     except pymysql.IntegrityError:         return jsonify({'message': 'Username already exists!'}), 400     finally:         cursor.close()         conn.close()     @app.route('/login', methods=['POST']) def login():     data = request.json     username = data['username']     password = data['password']       conn = get_db_connection()     cursor = conn.cursor()       try:         cursor.execute("SELECT password FROM users WHERE username = %s", (username,))         result = cursor.fetchone()           if result and bcrypt.checkpw(password.encode('utf-8'), result[0].encode('utf-8')):             return jsonify({'message': 'Login successful!'}), 200         else:             return jsonify({'message': 'Incorrect username or password!'}), 401     finally:         cursor.close()         conn.close()     @app.route('/send_message', methods=['POST']) def send_message():     data = request.json     sender = data['sender']     receiver = data['receiver']     message = data['message']       conn = get_db_connection()     cursor = conn.cursor()       cursor.execute("INSERT INTO messages (sender, receiver, message) VALUES (%s, %s, %s)", (sender, receiver, message))     conn.commit()     cursor.close()     conn.close()       return jsonify({'message': 'Message sent successfully!'}), 201     @app.route('/get_messages', methods=['GET']) def get_messages():     user1 = request.args.get('user1')     user2 = request.args.get('user2')       conn = get_db_connection()     cursor = conn.cursor()       cursor.execute('''SELECT sender, receiver, message, timestamp FROM messages                       WHERE (sender = %s AND receiver = %s) OR (sender = %s AND receiver = %s)                       ORDER BY timestamp''', (user1, user2, user2, user1))       messages = cursor.fetchall()     cursor.close()     conn.close()       return jsonify(messages), 200     if __name__ == '__main__':     app.run(debug=True) |