"""Flask application factory for Work Statistics System."""
import os
from flask import Flask, send_from_directory
from flask_sqlalchemy import SQLAlchemy
from flask_cors import CORS

db = SQLAlchemy()


def create_app(config_name='default'):
    """Create and configure the Flask application.
    
    Args:
        config_name: Configuration name ('default', 'testing', 'production')
    
    Returns:
        Configured Flask application instance
    """
    # Check if static folder exists (for production with frontend build)
    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__)
    
    # Load configuration
    from app.config import config
    app.config.from_object(config[config_name])
    
    # Initialize extensions
    db.init_app(app)
    CORS(app)
    
    # Register API routes
    from app.routes import register_routes
    register_routes(app)
    
    # Serve frontend for non-API routes (SPA support)
    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')
        
        @app.errorhandler(404)
        def not_found(e):
            # Return index.html for SPA client-side routing
            return send_from_directory(app.static_folder, 'index.html')
    
    # Create database tables and initialize default admin
    with app.app_context():
        db.create_all()
        _init_default_admin()
    
    return app


def _init_default_admin():
    """Initialize default admin account if none exists.
    
    This ensures there is always at least one admin account
    available for login when the application starts.
    """
    from flask import current_app
    from app.services.admin_service import AdminService
    
    # Skip default admin creation in testing mode
    if current_app.config.get('TESTING', False):
        return
    
    created, message = AdminService.create_default_admin()
    if created:
        print(f"[Init] {message}")
    # Silently skip if admins already exist