import os
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from flask_login import LoginManager
from flask_bcrypt import Bcrypt
from app.config import config

# Initialize extensions
db = SQLAlchemy()
migrate = Migrate()
login_manager = LoginManager()
bcrypt = Bcrypt()


def create_app(config_name='default'):
    """Application factory pattern."""
    app = Flask(__name__)
    
    # Load configuration
    app.config.from_object(config[config_name])
    
    # Initialize extensions
    db.init_app(app)
    migrate.init_app(app, db)
    bcrypt.init_app(app)
    
    # Configure Flask-Login
    login_manager.init_app(app)
    login_manager.login_view = 'auth.login'
    login_manager.login_message = 'Please log in to access this page.'
    login_manager.login_message_category = 'info'
    
    # User loader for Flask-Login
    from app.models.user import User
    
    @login_manager.user_loader
    def load_user(user_id):
        return User.query.get(int(user_id))
    
    # Register blueprints
    from app.routes.auth import auth_bp
    from app.routes.main import main_bp
    from app.routes.sets import sets_bp
    from app.routes.instructions import instructions_bp
    from app.routes.admin import admin_bp
    from app.routes.extra_files import extra_files_bp
    
    app.register_blueprint(auth_bp)
    app.register_blueprint(main_bp)
    app.register_blueprint(sets_bp)
    app.register_blueprint(instructions_bp)
    app.register_blueprint(admin_bp)
    app.register_blueprint(extra_files_bp)
    
    # Import models to ensure they're registered with SQLAlchemy
    from app.models.user import User
    from app.models.set import Set
    from app.models.instruction import Instruction
    from app.models.extra_file import ExtraFile
    
    # Create upload directories
    os.makedirs(os.path.join(app.config['UPLOAD_FOLDER'], 'pdfs'), exist_ok=True)
    os.makedirs(os.path.join(app.config['UPLOAD_FOLDER'], 'images'), exist_ok=True)
    os.makedirs(os.path.join(app.config['UPLOAD_FOLDER'], 'covers'), exist_ok=True)
    os.makedirs(os.path.join(app.config['UPLOAD_FOLDER'], 'thumbnails'), exist_ok=True)
    os.makedirs(os.path.join(app.config['UPLOAD_FOLDER'], 'extra_files'), exist_ok=True)
    
    # Context processor for global template variables
    @app.context_processor
    def inject_global_vars():
        from app.services.brickset_api import BricksetAPI
        return {
            'app_name': 'LEGO Instructions Manager',
            'brickset_available': BricksetAPI.is_configured()
        }
    
    return app