import os
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from flask_cors import CORS

from config.settings import config

db = SQLAlchemy()
migrate = Migrate()


def create_app(config_name=None):
    """Application factory pattern"""
    if config_name is None:
        config_name = os.environ.get('FLASK_ENV', 'development')
    
    app = Flask(__name__)
    app.config.from_object(config[config_name])
    
    # Initialize extensions
    db.init_app(app)
    migrate.init_app(app, db)
    CORS(app)
    
    # Create upload directories
    os.makedirs(app.config.get('UPLOAD_FOLDER', 'uploads'), exist_ok=True)
    os.makedirs(app.config.get('REPORTS_FOLDER', 'reports'), exist_ok=True)
    
    # Register blueprints
    from app.api import api_bp
    app.register_blueprint(api_bp, url_prefix='/api')
    
    # Register error handlers
    from app.errors import register_error_handlers
    register_error_handlers(app)
    
    return app