from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime
import os

db = SQLAlchemy()

def create_app():
    app = Flask(__name__)
    
    # ========================================================================
    # CONFIGURATION - Environment-based for Docker compatibility
    # ========================================================================
    
    # Secret key for session management
    # CRITICAL: Set SECRET_KEY environment variable in production!
    app.config['SECRET_KEY'] = os.getenv('SECRET_KEY', 'your_secret_key_change_in_production')
    
    # Database configuration - supports both SQLite (legacy) and MariaDB (Docker)
    database_type = os.getenv('DATABASE_TYPE', 'mariadb')  # 'sqlite' or 'mariadb'
    
    if database_type == 'sqlite':
        # SQLite mode (legacy/development)
        app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///users.db'
        app.logger.warning('Using SQLite database - not recommended for production!')
    else:
        # MariaDB mode (Docker/production) - recommended
        db_user = os.getenv('DB_USER', 'trasabilitate')
        db_password = os.getenv('DB_PASSWORD', 'Initial01!')
        db_host = os.getenv('DB_HOST', 'localhost')
        db_port = os.getenv('DB_PORT', '3306')
        db_name = os.getenv('DB_NAME', 'trasabilitate')
        
        # Construct MariaDB connection string
        # Format: mysql+mariadb://user:password@host:port/database
        app.config['SQLALCHEMY_DATABASE_URI'] = (
            f'mysql+mariadb://{db_user}:{db_password}@{db_host}:{db_port}/{db_name}'
        )
        app.logger.info(f'Using MariaDB database: {db_user}@{db_host}:{db_port}/{db_name}')
    
    # Disable SQLAlchemy modification tracking (improves performance)
    app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
    
    # Connection pool settings for MariaDB
    if database_type == 'mariadb':
        app.config['SQLALCHEMY_ENGINE_OPTIONS'] = {
            'pool_size': int(os.getenv('DB_POOL_SIZE', '10')),
            'pool_recycle': int(os.getenv('DB_POOL_RECYCLE', '3600')),  # Recycle connections after 1 hour
            'pool_pre_ping': True,  # Verify connections before using
            'max_overflow': int(os.getenv('DB_MAX_OVERFLOW', '20')),
            'echo': os.getenv('SQLALCHEMY_ECHO', 'false').lower() == 'true'  # SQL query logging
        }
    
    # Initialize SQLAlchemy with app
    db.init_app(app)

    # Register blueprints
    from app.routes import bp as main_bp, warehouse_bp
    app.register_blueprint(main_bp, url_prefix='/')
    app.register_blueprint(warehouse_bp)

    # Add 'now' function to Jinja2 globals for templates
    app.jinja_env.globals['now'] = datetime.now

    # Create database tables if they don't exist
    # Note: In Docker, schema is created by setup_complete_database.py
    # This is kept for backwards compatibility
    with app.app_context():
        try:
            db.create_all()
            app.logger.info('Database tables verified/created')
        except Exception as e:
            app.logger.error(f'Error creating database tables: {e}')
            # Don't fail startup if tables already exist or schema is managed externally

    return app