from flask import Flask, request, session
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from flask_login import LoginManager
from flask_cors import CORS
from flask_babel import Babel, gettext as _
from config.config import Config

# Initialize extensions
db = SQLAlchemy()
migrate = Migrate()
login_manager = LoginManager()
cors = CORS()
babel = Babel()

def create_app(config_class=Config):
    app = Flask(__name__)
    app.config.from_object(config_class)
    
    # Initialize extensions with app
    db.init_app(app)
    migrate.init_app(app, db)
    login_manager.init_app(app)
    cors.init_app(app)
    
    # Login manager configuration
    login_manager.login_view = 'auth.login'
    login_manager.login_message = 'Por favor inicia sesión para acceder a esta página.'
    login_manager.login_message_category = 'info'
    
# Import models to ensure they are registered
    from app.models import user
    
# Register blueprints
    from app.routes import auth_bp, classrooms_bp, main_bp, schedule_bp, genetic_bp, genetic_web_bp
    
    app.register_blueprint(auth_bp, url_prefix="/")
    app.register_blueprint(classrooms_bp, url_prefix="/classrooms")
    app.register_blueprint(main_bp, url_prefix="/")
    app.register_blueprint(schedule_bp, url_prefix="/schedule")
    app.register_blueprint(genetic_bp)
    app.register_blueprint(genetic_web_bp)
    
    # Language selector function
    def get_locale():
        # 1. Check if language is explicitly set in URL parameters
        lang = request.args.get('lang')
        if lang and lang in app.config['LANGUAGES']:
            return lang
        
        # 2. Check if user is authenticated and has a configured language in profile
        from flask_login import current_user
        if current_user.is_authenticated and getattr(current_user, 'preferred_language', None):
            if current_user.preferred_language in app.config['LANGUAGES']:
                return current_user.preferred_language
        
        # 3. Check if language is stored in session (e.g. manual switcher)
        if 'language' in session and session['language'] in app.config['LANGUAGES']:
            return session['language']
        
        # 4. Check browser language preference by default (especially on login/guest)
        return request.accept_languages.best_match(app.config['LANGUAGES']) or app.config['BABEL_DEFAULT_LOCALE']

    # Babel context processor
    @app.context_processor
    def inject_conf_vars():
        return dict(
            languages=app.config['LANGUAGES'],
            current_lang=str(get_locale())
        )

    
    # Configure Babel
    babel.init_app(app, locale_selector=get_locale)
    
    return app