import helmet from 'helmet';
import cors from 'cors';
import hpp from 'hpp';
import mongoSanitize from 'express-mongo-sanitize';
import { logger } from '../utils/logger.js';
import { config } from '../config/index.js';
import crypto from 'crypto';

/**
 * Configure CORS
 */
export const corsOptions = {
    origin: function (origin, callback) {
        const allowedOrigins = config.cors?.allowedOrigins || [
            'http://localhost:8080',
            'http://localhost:3000',
            'https://app.marketing-agent.com'
        ];

        // Allow requests with no origin (like mobile apps or Postman)
        if (!origin) return callback(null, true);

        if (allowedOrigins.indexOf('*') !== -1 || allowedOrigins.indexOf(origin) !== -1) {
            callback(null, true);
        } else {
            logger.warn('CORS blocked request', { origin, ip: origin });
            callback(new Error('Not allowed by CORS'));
        }
    },
    credentials: true,
    methods: ['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'OPTIONS'],
    allowedHeaders: ['Content-Type', 'Authorization', 'X-API-Key', 'X-Request-ID'],
    exposedHeaders: ['X-Request-ID', 'X-RateLimit-Limit', 'X-RateLimit-Remaining', 'X-RateLimit-Reset'],
    maxAge: 86400 // 24 hours
};

/**
 * Configure Helmet security headers
 */
export const helmetConfig = helmet({
    contentSecurityPolicy: {
        directives: {
            defaultSrc: ["'self'"],
            scriptSrc: ["'self'", "'unsafe-inline'"],
            styleSrc: ["'self'", "'unsafe-inline'"],
            imgSrc: ["'self'", "data:", "https:"],
            connectSrc: ["'self'"],
            fontSrc: ["'self'"],
            objectSrc: ["'none'"],
            mediaSrc: ["'self'"],
            frameSrc: ["'none'"],
            upgradeInsecureRequests: config.environment === 'production' ? [] : null
        }
    },
    hsts: {
        maxAge: 31536000,
        includeSubDomains: true,
        preload: true
    }
});

/**
 * Request ID middleware
 */
export function requestId(req, res, next) {
    const id = req.get('X-Request-ID') || crypto.randomUUID();
    req.id = id;
    res.setHeader('X-Request-ID', id);
    next();
}

/**
 * IP whitelist/blacklist middleware
 */
export function ipFilter(options = {}) {
    const whitelist = options.whitelist || [];
    const blacklist = options.blacklist || [];

    return (req, res, next) => {
        const clientIp = req.ip || req.connection.remoteAddress;

        // Check blacklist first
        if (blacklist.length > 0 && blacklist.includes(clientIp)) {
            logger.warn('Blacklisted IP attempted access', { ip: clientIp });
            return res.status(403).json({
                success: false,
                error: 'Access denied'
            });
        }

        // Check whitelist if configured
        if (whitelist.length > 0 && !whitelist.includes(clientIp)) {
            logger.warn('Non-whitelisted IP attempted access', { ip: clientIp });
            return res.status(403).json({
                success: false,
                error: 'Access denied'
            });
        }

        next();
    };
}

/**
 * Security headers middleware
 */
export function securityHeaders(req, res, next) {
    // Additional security headers
    res.setHeader('X-Frame-Options', 'DENY');
    res.setHeader('X-Content-Type-Options', 'nosniff');
    res.setHeader('X-XSS-Protection', '1; mode=block');
    res.setHeader('Referrer-Policy', 'strict-origin-when-cross-origin');
    res.setHeader('Permissions-Policy', 'geolocation=(), microphone=(), camera=()');
    
    // Remove potentially sensitive headers
    res.removeHeader('X-Powered-By');
    res.removeHeader('Server');
    
    next();
}

/**
 * API version check middleware
 */
export function apiVersionCheck(supportedVersions = ['v1']) {
    return (req, res, next) => {
        const version = req.headers['api-version'] || req.query.apiVersion;
        
        if (version && !supportedVersions.includes(version)) {
            return res.status(400).json({
                success: false,
                error: 'Unsupported API version',
                supportedVersions
            });
        }
        
        req.apiVersion = version || supportedVersions[0];
        next();
    };
}

/**
 * Prevent parameter pollution
 */
export const preventParamPollution = hpp({
    whitelist: ['sort', 'fields', 'filter', 'page', 'limit']
});

/**
 * MongoDB injection prevention
 */
export const preventMongoInjection = mongoSanitize({
    replaceWith: '_',
    onSanitize: ({ req, key }) => {
        logger.warn('MongoDB injection attempt prevented', {
            ip: req.ip,
            path: req.path,
            key
        });
    }
});

/**
 * Request logging middleware
 */
export function requestLogger(req, res, next) {
    const start = Date.now();

    res.on('finish', () => {
        const duration = Date.now() - start;
        
        logger.info('Request processed', {
            requestId: req.id,
            method: req.method,
            path: req.path,
            statusCode: res.statusCode,
            duration,
            ip: req.ip,
            userAgent: req.get('user-agent'),
            userId: req.user?.id
        });
    });

    next();
}

/**
 * Error logging middleware
 */
export function errorLogger(err, req, res, next) {
    logger.error('Request error', {
        requestId: req.id,
        error: err.message,
        stack: err.stack,
        method: req.method,
        path: req.path,
        ip: req.ip,
        userId: req.user?.id
    });

    next(err);
}

/**
 * Security audit middleware
 */
export function securityAudit(eventType) {
    return (req, res, next) => {
        logger.info('Security event', {
            eventType,
            requestId: req.id,
            userId: req.user?.id,
            ip: req.ip,
            path: req.path,
            method: req.method,
            timestamp: new Date().toISOString()
        });

        next();
    };
}

/**
 * Trusted proxy configuration
 */
export function configureTrustedProxies(app) {
    // Trust proxies for accurate IP detection
    app.set('trust proxy', config.trustProxy || ['loopback', 'linklocal', 'uniquelocal']);
}

/**
 * Session fixation prevention
 */
export function preventSessionFixation(req, res, next) {
    if (req.session && req.user) {
        // Regenerate session ID on login
        if (req.path.includes('/login') && res.statusCode === 200) {
            req.session.regenerate((err) => {
                if (err) {
                    logger.error('Session regeneration failed', { error: err });
                }
                next();
            });
            return;
        }
    }
    next();
}

/**
 * CSRF protection for state-changing operations
 */
export function csrfProtection(options = {}) {
    const excludePaths = options.exclude || ['/api/v1/auth/login', '/api/v1/auth/register'];
    
    return (req, res, next) => {
        // Skip for excluded paths
        if (excludePaths.some(path => req.path.includes(path))) {
            return next();
        }

        // Skip for safe methods
        if (['GET', 'HEAD', 'OPTIONS'].includes(req.method)) {
            return next();
        }

        const token = req.headers['x-csrf-token'] || req.body._csrf;
        const sessionToken = req.session?.csrfToken;

        if (!token || !sessionToken || token !== sessionToken) {
            return res.status(403).json({
                success: false,
                error: 'Invalid CSRF token'
            });
        }

        next();
    };
}

/**
 * Apply all security middleware
 */
export function applySecurityMiddleware(app) {
    // Basic security
    app.use(helmetConfig);
    app.use(cors(corsOptions));
    app.use(requestId);
    app.use(securityHeaders);
    
    // Request processing
    app.use(express.json({ limit: '10mb' }));
    app.use(express.urlencoded({ extended: true, limit: '10mb' }));
    
    // Injection prevention
    app.use(preventMongoInjection);
    app.use(preventParamPollution);
    
    // Logging
    app.use(requestLogger);
    
    // Configure trusted proxies
    configureTrustedProxies(app);
}