app/init.py

"""
Flask OpenAI Chat Application
Modern Flask app with proper structure and error handling
"""
import os
import logging
from flask import Flask
from flask_cors import CORS
from dotenv import load_dotenv

def create_app():
    """Application factory pattern"""
    # Load environment variables
    load_dotenv()
    
    app = Flask(__name__)
    
    # Configuration
    app.config['SECRET_KEY'] = os.getenv('SECRET_KEY', 'dev-secret-key-change-in-production')
    app.config['OPENAI_API_KEY'] = os.getenv('OPENAI_API_KEY')
    
    # Validate required environment variables
    if not app.config['OPENAI_API_KEY']:
        raise ValueError("❌ OPENAI_API_KEY is not set. Please add it to your .env file.")
    
    # Enable CORS for all routes
    CORS(app, origins=["*"])  # In production, specify allowed origins
    
    # Setup logging
    setup_logging(app)
    
    # Register blueprints
    from app.routes.chat import chat_bp
    from app.routes.health import health_bp
    
    app.register_blueprint(chat_bp)
    app.register_blueprint(health_bp)
    
    # Error handlers
    register_error_handlers(app)
    
    return app

def setup_logging(app):
    """Configure application logging"""
    if not app.debug:
        # Production logging
        if not os.path.exists('logs'):
            os.mkdir('logs')
        
        file_handler = logging.handlers.RotatingFileHandler(
            'logs/app.log', maxBytes=10240, backupCount=10
        )
        file_handler.setFormatter(logging.Formatter(
            '%(asctime)s %(levelname)s: %(message)s [in %(pathname)s:%(lineno)d]'
        ))
        file_handler.setLevel(logging.INFO)
        app.logger.addHandler(file_handler)
        app.logger.setLevel(logging.INFO)
        app.logger.info('Flask OpenAI Chat startup')

def register_error_handlers(app):
    """Register global error handlers"""
    
    @app.errorhandler(400)
    def bad_request(error):
        return {'error': 'Bad request', 'message': str(error)}, 400
    
    @app.errorhandler(404)
    def not_found(error):
        return {'error': 'Not found', 'message': 'The requested resource was not found'}, 404
    
    @app.errorhandler(500)
    def internal_error(error):
        app.logger.error(f'Server Error: {error}')
        return {'error': 'Internal server error', 'message': 'Something went wrong'}, 500