import os
from flask import Flask, send_from_directory
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')
    
    # Check if static folder exists (for Docker deployment)
    static_folder = os.path.join(os.path.dirname(os.path.dirname(__file__)), 'static')
    if os.path.exists(static_folder):
        app = Flask(__name__, static_folder=static_folder, static_url_path='')
    else:
        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)
    
    # Serve frontend static files (for Docker deployment)
    # This must be registered AFTER error handlers to properly catch SPA routes
    if app.static_folder and os.path.exists(app.static_folder):
        @app.route('/')
        def serve_index():
            return send_from_directory(app.static_folder, 'index.html')
        
        # Catch-all route for SPA - must be the last route registered
        @app.errorhandler(404)
        def serve_spa(error):
            # Check if this is an API request
            from flask import request
            if request.path.startswith('/api/'):
                # Return JSON error for API requests
                return {'error': {'code': 'RESOURCE_NOT_FOUND', 'message': 'Resource not found'}}, 404
            # For non-API requests, serve index.html for SPA routing
            return send_from_directory(app.static_folder, 'index.html')
    
    return app