from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_login import LoginManager
from dotenv import load_dotenv
from pathlib import Path
import os

db = SQLAlchemy()
login_manager = LoginManager()

def create_app():
    # --- Chemins ---
    base_dir = Path(__file__).resolve().parent
    template_dir = base_dir.parent / 'frontend' / 'templates'
    static_dir = base_dir.parent / 'frontend' / 'static'
    instance_path = base_dir.parent / 'instance'
    instance_path.mkdir(parents=True, exist_ok=True)

    # --- Chargement des variables d'environnement ---
    env_path = base_dir.parent / '.env'
    load_dotenv(env_path)

    # --- Vérification de la clé secrète ---
    secret = os.getenv('FLASK_SECRET')
    if not secret:
        raise RuntimeError("FLASK_SECRET must be set in environment")

    # --- Création de l'application ---
    app = Flask(
        __name__,
        template_folder=str(template_dir),
        static_folder=str(static_dir),
        instance_path=str(instance_path)
    )

    # --- Configuration ---
    app.config.update(
        SECRET_KEY=secret,
        SQLALCHEMY_DATABASE_URI=f"sqlite:///{instance_path / 'users.db'}",
        SQLALCHEMY_TRACK_MODIFICATIONS=False,
        SESSION_COOKIE_HTTPONLY=True,
        SESSION_COOKIE_SAMESITE='Lax',
        SESSION_COOKIE_SECURE=os.getenv("FLASK_ENV") == "production"
    )

    # --- Initialisation des extensions ---
    db.init_app(app)
    login_manager.init_app(app)
    login_manager.login_view = "login"
    login_manager.session_protection = "strong"
    login_manager.login_message = "Veuillez vous connecter pour accéder à cette page."
    login_manager.login_message_category = "warning"

    from backend import routes
    from backend.models import User

    # Loader pour Flask-Login
    @login_manager.user_loader
    def load_user(user_id):
        return User.query.get(int(user_id))
    
    # --- Chargement différé des modèles et routes ---
    with app.app_context():

        # Création de la DB si nécessaire
        db.create_all()
    
    # Initialisation des routes
    routes.init_app(app)

    return app