"""Team Tryouts Application - Flask Application Factory.

This module provides the application factory for creating and configuring
the Flask application instance with comprehensive security hardening.
"""

import os
from flask import Flask, request, redirect, jsonify, render_template, url_for
from flask_cors import CORS
from app.extensions import db, login_manager, csrf, hash_password, check_password, limiter
from sqlalchemy import text
from werkzeug.exceptions import HTTPException
import markupsafe
from dotenv import load_dotenv

load_dotenv()


def nl2br(value):
    """Convert newlines to HTML line breaks.

    Args:
        value: String value to convert.

    Returns:
        Markup: HTML-safe string with line breaks.
    """
    if value:
        return markupsafe.Markup('<br>'.join(str(value).splitlines()))
    return ''


def create_app():
    """Create and configure the Flask application.

    Initializes Flask with:
        - Secret key for session security
        - Database configuration
        - CSRF protection
        - CORS with restricted origins
        - Login manager
        - Rate limiting
        - All route blueprints
        - Security headers and HTTPS redirects
        - Custom error handlers
        - Health check endpoint
        - Structured logging

    Handles database initialization and seeding with sample data if empty.

    Returns:
        Flask: Configured Flask application instance.
    """
    app = Flask(__name__)
    app.config['SECRET_KEY'] = os.getenv('SECRET_KEY')
    if not app.config['SECRET_KEY']:
        raise RuntimeError('SECRET_KEY environment variable must be set for security')
    app.config['SQLALCHEMY_DATABASE_URI'] = os.getenv('DATABASE_URL')
    if not app.config['SQLALCHEMY_DATABASE_URI']:
        raise RuntimeError(
            'DATABASE_URL environment variable must be set to a PostgreSQL connection string'
        )
    app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
    app.config['WTF_CSRF_ENABLED'] = True

    # File upload size limit (16 MB)
    app.config['MAX_CONTENT_LENGTH'] = 16 * 1024 * 1024

    # Secure session cookie settings
    app.config['SESSION_COOKIE_SECURE'] = os.getenv('SESSION_COOKIE_SECURE', 'true').lower() == 'true'
    app.config['SESSION_COOKIE_HTTPONLY'] = True
    app.config['SESSION_COOKIE_SAMESITE'] = 'Lax'
    app.config['PERMANENT_SESSION_LIFETIME'] = 3600  # 1 hour session timeout

    # Configure CORS - restrict to specific origins in production
    allowed_origins = os.getenv('CORS_ALLOWED_ORIGINS', '').split(',')
    allowed_origins = [origin.strip() for origin in allowed_origins if origin.strip()]
    
    if allowed_origins:
        CORS(
            app,
            origins=allowed_origins,
            supports_credentials=True,
            methods=['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'OPTIONS'],
            max_age=3600,  # Cache preflight for 1 hour
        )
    else:
        # When no origins specified, allow all (development) or none (production)
        # In production with a reverse proxy, CORS is handled at the Nginx level
        CORS(
            app,
            supports_credentials=True,
            methods=['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'OPTIONS'],
            max_age=3600,
        )

    db.init_app(app)
    login_manager.init_app(app)
    csrf.init_app(app)
    limiter.init_app(app)

    # Configure structured logging
    from app.logging_config import configure_logging
    configure_logging(app)

    from app.routes.auth import auth_bp
    from app.routes.tryouts import tryouts_bp
    from app.routes.evaluations import evaluations_bp
    from app.routes.users import users_bp
    from app.routes.main import main_bp
    from app.routes.teams import teams_bp
    from app.routes.matches import matches_bp
    from app.routes.team_matches import team_matches_bp

    app.register_blueprint(auth_bp)
    app.register_blueprint(tryouts_bp)
    app.register_blueprint(evaluations_bp)
    app.register_blueprint(users_bp)
    app.register_blueprint(main_bp)
    app.register_blueprint(teams_bp)
    app.register_blueprint(matches_bp)
    app.register_blueprint(team_matches_bp)

    # Register custom Jinja filters
    app.jinja_env.filters['nl2br'] = nl2br

    # =========================================================================
    # Security Headers
    # =========================================================================
    @app.after_request
    def add_security_headers(response):
        """Add security headers to all responses.

        Implements defense-in-depth with comprehensive HTTP security headers.
        These complement the headers set by Nginx in production.

        HSTS is only sent in production (non-debug) to avoid breaking
        local development over plain HTTP.
        """
        response.headers['X-Content-Type-Options'] = 'nosniff'
        response.headers['X-Frame-Options'] = 'DENY'
        response.headers['X-XSS-Protection'] = '1; mode=block'
        response.headers['Referrer-Policy'] = 'strict-origin-when-cross-origin'
        response.headers['Permissions-Policy'] = (
            'camera=(), microphone=(), geolocation=(), '
            'interest-cohort=(), payment=(), usb=()'
        )
        response.headers['Cross-Origin-Opener-Policy'] = 'same-origin'
        response.headers['Content-Security-Policy'] = (
            "default-src 'self'; "
            "script-src 'self' 'unsafe-inline' https://cdn.jsdelivr.net; "
            "style-src 'self' 'unsafe-inline' https://cdnjs.cloudflare.com https://cdn.jsdelivr.net; "
            "font-src 'self' https://cdnjs.cloudflare.com; "
            "img-src 'self' data:; "
            "connect-src 'self'; "
            "frame-ancestors 'none'; "
            "base-uri 'self'; "
            "form-action 'self'"
        )

        # Only enable HSTS when HTTPS is actually being used
        # (either direct TLS or behind a proxy that terminates TLS)
        is_https = request.is_secure or request.headers.get('X-Forwarded-Proto') == 'https'
        if is_https:
            response.headers['Strict-Transport-Security'] = (
                'max-age=31536000; includeSubDomains; preload'
            )

        return response

    # =========================================================================
    # HTTPS Redirect (Production only)
    # =========================================================================
    @app.before_request
    def force_https():
        """Redirect all HTTP requests to HTTPS in production.

        Respects the X-Forwarded-Proto header from reverse proxies.
        Can be disabled via FORCE_HTTPS environment variable.
        """
        if not app.debug:
            if not request.is_secure and request.headers.get('X-Forwarded-Proto') != 'https':
                if os.getenv('FORCE_HTTPS', 'true').lower() == 'true':
                    return redirect(request.url.replace('http://', 'https://'), code=301)

    # =========================================================================
    # Health Check Endpoint
    # =========================================================================
    @app.route('/health')
    def health_check():
        """Health check endpoint for monitoring and load balancers.

        Verifies database connectivity and application health.
        Returns 200 with basic status info or 503 if unhealthy.

        Returns:
            Response: JSON health status.
        """
        health_data = {
            'status': 'healthy',
            'app': 'team-tryouts',
            'version': '1.0.0',
        }

        # Check database connectivity
        try:
            db.session.execute(text('SELECT 1'))
            health_data['database'] = 'connected'
        except Exception as e:
            health_data['status'] = 'unhealthy'
            health_data['database'] = f'error: {str(e)}'
            return jsonify(health_data), 503

        return jsonify(health_data), 200

    # =========================================================================
    # Custom Error Handlers
    # =========================================================================
    @app.errorhandler(400)
    def bad_request(error):
        """Handle 400 Bad Request errors.

        Args:
            error: The error object.

        Returns:
            Response: Rendered error page or JSON for API requests.
        """
        if request.path.startswith('/users/disponibilities') or \
           request.path.startswith('/users/coach-availability') or \
           request.path.startswith('/users/api/'):
            return jsonify({'error': 'Bad request', 'message': str(error)}), 400
        return render_template('errors/400.html', error=error), 400

    @app.errorhandler(401)
    def unauthorized(error):
        """Handle 401 Unauthorized errors.

        Args:
            error: The error object.

        Returns:
            Response: Redirect to login for pages, JSON for API.
        """
        if request.path.startswith('/users/disponibilities') or \
           request.path.startswith('/users/api/'):
            return jsonify({'error': 'Unauthorized'}), 401
        from flask import flash as _flash
        _flash('Please log in to access this page.', 'warning')
        return redirect(url_for('auth.login'))

    @app.errorhandler(403)
    def forbidden(error):
        """Handle 403 Forbidden errors.

        Args:
            error: The error object.

        Returns:
            Response: Rendered error page or JSON for API requests.
        """
        if request.path.startswith('/users/disponibilities') or \
           request.path.startswith('/users/api/'):
            return jsonify({'error': 'Forbidden', 'message': str(error)}), 403
        return render_template('errors/403.html', error=error), 403

    @app.errorhandler(404)
    def not_found(error):
        """Handle 404 Not Found errors.

        Args:
            error: The error object.

        Returns:
            Response: Rendered error page or JSON for API requests.
        """
        if request.path.startswith('/users/disponibilities') or \
           request.path.startswith('/users/api/'):
            return jsonify({'error': 'Not found'}), 404
        return render_template('errors/404.html', error=error), 404

    @app.errorhandler(429)
    def too_many_requests(error):
        """Handle 429 Too Many Requests errors.

        Args:
            error: The error object.

        Returns:
            Response: JSON error for API or rendered page.
        """
        if request.path.startswith('/users/disponibilities') or \
           request.path.startswith('/users/api/'):
            return jsonify({
                'error': 'Too many requests',
                'message': 'Please try again later.'
            }), 429
        return render_template('errors/429.html', error=error), 429

    @app.errorhandler(500)
    def internal_error(error):
        """Handle 500 Internal Server Error.

        Never exposes stack traces to users. Logs the full error internally.

        Args:
            error: The error object.

        Returns:
            Response: Generic error page or JSON.
        """
        # Log the full error for debugging
        app.logger.error('Internal Server Error: %s', str(error), exc_info=True)

        # Roll back any failed database session
        db.session.rollback()

        if request.path.startswith('/users/disponibilities') or \
           request.path.startswith('/users/api/'):
            return jsonify({
                'error': 'Internal server error',
                'message': 'An unexpected error occurred. Please try again later.'
            }), 500
        return render_template('errors/500.html'), 500

    @app.errorhandler(HTTPException)
    def handle_http_exception(error):
        """Catch-all handler for any unhandled HTTP exceptions.

        Args:
            error: The HTTPException object.

        Returns:
            Response: JSON error for API, re-raises for others.
        """
        if request.path.startswith('/users/disponibilities') or \
           request.path.startswith('/users/api/'):
            return jsonify({
                'error': error.name,
                'message': error.description,
                'code': error.code
            }), error.code
        return error

    # =========================================================================
    # Database Initialization
    # =========================================================================
    with app.app_context():
        import app.models as models  # noqa: F401 — registers all models with SQLAlchemy
        from app.models import User
        db.create_all()

        # Seed database if empty
        if User.query.count() == 0:
            from app.supporting_scrits.seed import seed_database
            seed_database()

    # Start the Discord bot for notifications
    try:
        from app.discord_bot import start_bot
        start_bot()
    except Exception as e:
        app.logger.warning('Could not start Discord bot: %s', e)

    return app


if __name__ == '__main__':
    # Only used for development - production uses wsgi.py (Waitress)
    app = create_app()
    debug_mode = os.getenv('FLASK_DEBUG', 'false').lower() == 'true'
    if debug_mode:
        app.logger.warning(
            'Running in DEBUG mode with Flask built-in server. '
            'This is NOT suitable for production. Use wsgi.py instead.'
        )
    app.run(debug=debug_mode, host='127.0.0.2', port=5000)