/**
 * Rate Limiting Middleware
 * Implements comprehensive rate limiting with Redis backend and flexible configuration
 */

const rateLimit = require('express-rate-limit');
const { getRedisClient } = require('../config/redis');
const logger = require('../utils/logger');

// Rate limiting configuration
const RATE_LIMIT_CONFIG = {
  // Global API rate limits
  global: {
    windowMs: parseInt(process.env.RATE_LIMIT_WINDOW_MS) || 15 * 60 * 1000, // 15 minutes
    max: parseInt(process.env.RATE_LIMIT_MAX_REQUESTS) || 1000, // 1000 requests per window
    standardHeaders: true,
    legacyHeaders: false,
    skipSuccessfulRequests: false,
    skipFailedRequests: false,
  },

  // Authentication endpoints (more restrictive)
  auth: {
    windowMs: 15 * 60 * 1000, // 15 minutes
    max: 10, // 10 attempts per window
    standardHeaders: true,
    legacyHeaders: false,
    skipSuccessfulRequests: true, // Don't count successful logins
    skipFailedRequests: false,
  },

  // Player API endpoints
  player: {
    windowMs: 1 * 60 * 1000, // 1 minute
    max: 120, // 120 requests per minute
    standardHeaders: true,
    legacyHeaders: false,
    skipSuccessfulRequests: false,
    skipFailedRequests: false,
  },

  // Admin API endpoints (more lenient for legitimate admin users)
  admin: {
    windowMs: 1 * 60 * 1000, // 1 minute
    max: 300, // 300 requests per minute
    standardHeaders: true,
    legacyHeaders: false,
    skipSuccessfulRequests: false,
    skipFailedRequests: false,
  },

  // Game action endpoints (prevent spam)
  gameAction: {
    windowMs: 30 * 1000, // 30 seconds
    max: 30, // 30 actions per 30 seconds
    standardHeaders: true,
    legacyHeaders: false,
    skipSuccessfulRequests: false,
    skipFailedRequests: true,
  },

  // Message sending (prevent spam)
  messaging: {
    windowMs: 5 * 60 * 1000, // 5 minutes
    max: 10, // 10 messages per 5 minutes
    standardHeaders: true,
    legacyHeaders: false,
    skipSuccessfulRequests: false,
    skipFailedRequests: true,
  },
};

/**
 * Create Redis store for rate limiting if Redis is available
 * @returns {Object|null} Redis store or null if Redis unavailable
 */
function createRedisStore() {
  // Check if Redis is disabled first
  if (process.env.DISABLE_REDIS === 'true') {
    logger.info('Redis disabled for rate limiting, using memory store');
    return null;
  }
  
  try {
    const redis = getRedisClient();
    if (!redis) {
      logger.warn('Redis not available for rate limiting, using memory store');
      return null;
    }

    // Create Redis store for express-rate-limit
    try {
      const { RedisStore } = require('rate-limit-redis');

      return new RedisStore({
        sendCommand: (...args) => redis.sendCommand(args),
        prefix: 'rl:', // Rate limit prefix
      });
    } catch (error) {
      logger.warn('Failed to create RedisStore, falling back to memory store', {
        error: error.message,
      });
      return null;
    }

  } catch (error) {
    logger.warn('Failed to create Redis store for rate limiting', {
      error: error.message,
    });
    return null;
  }
}

/**
 * Create key generator for rate limiting
 * @param {string} prefix - Key prefix
 * @returns {Function} Key generator function
 */
function createKeyGenerator(prefix = 'global') {
  return (req) => {
    const ip = req.ip || req.connection.remoteAddress || 'unknown';
    const userId = req.user?.playerId || req.user?.adminId || 'anonymous';
    return `${prefix}:${userId}:${ip}`;
  };
}

/**
 * Create rate limit handler
 * @param {string} type - Rate limit type for logging
 * @returns {Function} Rate limit handler function
 */
function createRateLimitHandler(type) {
  return (req, res) => {
    const correlationId = req.correlationId;
    const ip = req.ip || req.connection.remoteAddress;
    const userId = req.user?.playerId || req.user?.adminId;
    const userType = req.user?.type || 'anonymous';

    logger.warn('Rate limit exceeded', {
      correlationId,
      type,
      ip,
      userId,
      userType,
      path: req.path,
      method: req.method,
      userAgent: req.get('User-Agent'),
      retryAfter: res.get('Retry-After'),
    });

    return res.status(429).json({
      error: 'Too Many Requests',
      message: 'Rate limit exceeded. Please try again later.',
      type,
      retryAfter: res.get('Retry-After'),
      correlationId,
    });
  };
}

/**
 * Create skip function for rate limiting
 * @param {Array<string>} skipPaths - Paths to skip rate limiting
 * @param {Array<string>} skipIPs - IPs to skip rate limiting
 * @returns {Function} Skip function
 */
function createSkipFunction(skipPaths = [], skipIPs = []) {
  return (req) => {
    const ip = req.ip || req.connection.remoteAddress;

    // Skip health checks
    if (req.path === '/health' || req.path === '/api/health') {
      return true;
    }

    // Skip specified paths
    if (skipPaths.some(path => req.path.startsWith(path))) {
      return true;
    }

    // Skip specified IPs (for development/testing)
    if (skipIPs.includes(ip)) {
      return true;
    }

    // Skip if rate limiting is disabled
    if (process.env.DISABLE_RATE_LIMITING === 'true') {
      return true;
    }

    return false;
  };
}

/**
 * Create rate limiter middleware
 * @param {string} type - Type of rate limiter
 * @param {Object} customConfig - Custom configuration
 * @returns {Function} Rate limiter middleware
 */
function createRateLimiter(type, customConfig = {}) {
  const config = { ...RATE_LIMIT_CONFIG[type], ...customConfig };
  const store = createRedisStore();

  const rateLimiter = rateLimit({
    ...config,
    store,
    keyGenerator: createKeyGenerator(type),
    handler: createRateLimitHandler(type),
    skip: createSkipFunction(),
    // Note: onLimitReached is deprecated in express-rate-limit v7
    // Removed for compatibility
  });

  // Log rate limiter creation
  logger.info('Rate limiter created', {
    type,
    windowMs: config.windowMs,
    max: config.max,
    useRedis: !!store,
  });

  return rateLimiter;
}

/**
 * Pre-configured rate limiters
 */
const rateLimiters = {
  global: createRateLimiter('global'),
  auth: createRateLimiter('auth'),
  player: createRateLimiter('player'),
  admin: createRateLimiter('admin'),
  gameAction: createRateLimiter('gameAction'),
  messaging: createRateLimiter('messaging'),
};

/**
 * Middleware to add rate limit headers even when not limiting
 * @param {Object} req - Express request object
 * @param {Object} res - Express response object
 * @param {Function} next - Express next function
 */
function addRateLimitHeaders(req, res, next) {
  // Add custom headers for client information
  res.set({
    'X-RateLimit-Policy': 'See API documentation for rate limiting details',
  });

  next();
}

/**
 * Custom rate limiter for WebSocket connections
 * @param {number} maxConnections - Maximum connections per IP
 * @param {number} windowMs - Time window in milliseconds
 * @returns {Function} WebSocket rate limiter function
 */
function createWebSocketRateLimiter(maxConnections = 10, windowMs = 60000) {
  const connections = new Map();

  return (socket, next) => {
    const ip = socket.handshake.address;
    const now = Date.now();

    // Clean up old connections
    if (connections.has(ip)) {
      const connectionTimes = connections.get(ip).filter(time => now - time < windowMs);
      connections.set(ip, connectionTimes);
    }

    // Check rate limit
    const currentConnections = connections.get(ip) || [];
    if (currentConnections.length >= maxConnections) {
      logger.warn('WebSocket connection rate limit exceeded', {
        ip,
        currentConnections: currentConnections.length,
        maxConnections,
      });

      return next(new Error('Connection rate limit exceeded'));
    }

    // Add current connection
    currentConnections.push(now);
    connections.set(ip, currentConnections);

    logger.debug('WebSocket connection allowed', {
      ip,
      connections: currentConnections.length,
      maxConnections,
    });

    next();
  };
}

/**
 * Middleware to apply different rate limits based on user type
 * @param {Object} req - Express request object
 * @param {Object} res - Express response object
 * @param {Function} next - Express next function
 */
function dynamicRateLimit(req, res, next) {
  const userType = req.user?.type;

  let limiter;
  if (userType === 'admin') {
    limiter = rateLimiters.admin;
  } else if (userType === 'player') {
    limiter = rateLimiters.player;
  } else {
    limiter = rateLimiters.global;
  }

  return limiter(req, res, next);
}

module.exports = {
  rateLimiters,
  createRateLimiter,
  createWebSocketRateLimiter,
  addRateLimitHeaders,
  dynamicRateLimit,
  RATE_LIMIT_CONFIG,
};