/**
 * Tenant Limits Middleware
 * Enforces tenant subscription limits for users, devices, API rate limits, etc.
 */

const { securityLogger } = require('./logger');

// Initialize multi-tenant auth
const MultiTenantAuth = require('./multi-tenant-auth');
const multiAuth = new MultiTenantAuth();

/**
 * Redis-like in-memory store for rate limiting (replace with Redis in production)
 */
class RateLimitStore {
  constructor() {
    this.store = new Map();
    this.cleanup();
  }

  get(key) {
    const data = this.store.get(key);
    if (!data) return null;
    
    // Check if expired
    if (Date.now() > data.expires) {
      this.store.delete(key);
      return null;
    }
    
    return data;
  }

  set(key, value, ttlMs) {
    this.store.set(key, {
      ...value,
      expires: Date.now() + ttlMs
    });
  }

  delete(key) {
    this.store.delete(key);
  }

  // Clean up expired entries every minute
  cleanup() {
    setInterval(() => {
      const now = Date.now();
      for (const [key, data] of this.store.entries()) {
        if (now > data.expires) {
          this.store.delete(key);
        }
      }
    }, 60000);
  }
}

const rateLimitStore = new RateLimitStore();

/**
 * Get tenant and validate access
 */
async function getTenantFromRequest(req) {
  const tenantId = await multiAuth.determineTenant(req);
  if (!tenantId) {
    throw new Error('Unable to determine tenant');
  }

  const { Tenant } = require('../models');
  const tenant = await Tenant.findOne({ where: { slug: tenantId } });
  if (!tenant) {
    throw new Error('Tenant not found');
  }

  return tenant;
}

/**
 * Check if tenant has reached user limit
 */
async function checkUserLimit(tenantId, excludeUserId = null) {
  const { User } = require('../models');
  
  const whereClause = { tenant_id: tenantId };
  if (excludeUserId) {
    whereClause.id = { [require('sequelize').Op.ne]: excludeUserId };
  }
  
  const userCount = await User.count({ where: whereClause });
  return userCount;
}

/**
 * Check if tenant has reached device limit
 */
async function checkDeviceLimit(tenantId, excludeDeviceId = null) {
  const { Device } = require('../models');
  
  const whereClause = { tenant_id: tenantId };
  if (excludeDeviceId) {
    whereClause.id = { [require('sequelize').Op.ne]: excludeDeviceId };
  }
  
  const deviceCount = await Device.count({ where: whereClause });
  return deviceCount;
}

/**
 * Middleware to enforce user creation limits
 */
function enforceUserLimit() {
  return async (req, res, next) => {
    try {
      const tenant = await getTenantFromRequest(req);
      const maxUsers = tenant.features?.max_users;
      
      // -1 means unlimited
      if (maxUsers === -1) {
        return next();
      }
      
      const currentUserCount = await checkUserLimit(tenant.id);
      
      if (currentUserCount >= maxUsers) {
        securityLogger.logSecurityEvent('warning', 'User creation blocked due to tenant limit', {
          action: 'user_creation_limit_exceeded',
          tenantId: tenant.id,
          tenantSlug: tenant.slug,
          currentUserCount,
          maxUsers,
          userId: req.user?.id,
          username: req.user?.username,
          ip: req.ip,
          userAgent: req.get('User-Agent')
        });
        
        return res.status(403).json({
          success: false,
          message: `Tenant has reached the maximum number of users (${maxUsers}). Please upgrade your subscription or remove existing users.`,
          error_code: 'TENANT_USER_LIMIT_EXCEEDED',
          current_count: currentUserCount,
          max_allowed: maxUsers
        });
      }
      
      next();
    } catch (error) {
      console.error('Error checking user limit:', error);
      res.status(500).json({
        success: false,
        message: 'Failed to validate user limit'
      });
    }
  };
}

/**
 * Middleware to enforce device creation limits
 */
function enforceDeviceLimit() {
  return async (req, res, next) => {
    try {
      const tenant = await getTenantFromRequest(req);
      const maxDevices = tenant.features?.max_devices;
      
      // -1 means unlimited
      if (maxDevices === -1) {
        return next();
      }
      
      const currentDeviceCount = await checkDeviceLimit(tenant.id);
      
      if (currentDeviceCount >= maxDevices) {
        securityLogger.logSecurityEvent('warning', 'Device creation blocked due to tenant limit', {
          action: 'device_creation_limit_exceeded',
          tenantId: tenant.id,
          tenantSlug: tenant.slug,
          currentDeviceCount,
          maxDevices,
          userId: req.user?.id,
          username: req.user?.username,
          ip: req.ip,
          userAgent: req.get('User-Agent')
        });
        
        return res.status(403).json({
          success: false,
          message: `Tenant has reached the maximum number of devices (${maxDevices}). Please upgrade your subscription or remove existing devices.`,
          error_code: 'TENANT_DEVICE_LIMIT_EXCEEDED',
          current_count: currentDeviceCount,
          max_allowed: maxDevices
        });
      }
      
      next();
    } catch (error) {
      console.error('Error checking device limit:', error);
      res.status(500).json({
        success: false,
        message: 'Failed to validate device limit'
      });
    }
  };
}

/**
 * Middleware to enforce API rate limits per tenant
 * Tracks actual API requests (not page views) shared among all tenant users
 */
function enforceApiRateLimit(windowMs = 60000) { // Default 1 minute window
  return async (req, res, next) => {
    try {
      const tenant = await getTenantFromRequest(req);
      const maxRequests = tenant.features?.api_rate_limit;
      
      // -1 means unlimited
      if (maxRequests === -1) {
        return next();
      }
      
      const key = `api_rate_limit:${tenant.id}`;
      const now = Date.now();
      const windowStart = now - windowMs;
      
      // Get current rate limit data
      let rateLimitData = rateLimitStore.get(key);
      
      if (!rateLimitData) {
        rateLimitData = {
          requests: [],
          totalRequests: 0
        };
      }
      
      // Remove old requests outside the window
      rateLimitData.requests = rateLimitData.requests.filter(timestamp => timestamp > windowStart);
      
      // Check if limit exceeded
      if (rateLimitData.requests.length >= maxRequests) {
        const resetTime = rateLimitData.requests[0] + windowMs;
        const retryAfter = Math.ceil((resetTime - now) / 1000);
        
        securityLogger.logSecurityEvent('warning', 'API rate limit exceeded for tenant', {
          action: 'api_rate_limit_exceeded',
          tenantId: tenant.id,
          tenantSlug: tenant.slug,
          currentRequests: rateLimitData.requests.length,
          maxRequests,
          windowMs,
          userId: req.user?.id,
          username: req.user?.username,
          endpoint: req.path,
          method: req.method,
          ip: req.ip,
          userAgent: req.get('User-Agent')
        });
        
        res.set({
          'X-RateLimit-Limit': maxRequests,
          'X-RateLimit-Remaining': 0,
          'X-RateLimit-Reset': Math.ceil(resetTime / 1000),
          'Retry-After': retryAfter
        });
        
        return res.status(429).json({
          success: false,
          message: `API rate limit exceeded. Maximum ${maxRequests} requests per ${windowMs/1000} seconds for your tenant.`,
          error_code: 'TENANT_API_RATE_LIMIT_EXCEEDED',
          max_requests: maxRequests,
          window_seconds: windowMs / 1000,
          retry_after_seconds: retryAfter
        });
      }
      
      // Add current request
      rateLimitData.requests.push(now);
      rateLimitData.totalRequests++;
      
      // Store updated data
      rateLimitStore.set(key, rateLimitData, windowMs);
      
      // Set rate limit headers
      res.set({
        'X-RateLimit-Limit': maxRequests,
        'X-RateLimit-Remaining': Math.max(0, maxRequests - rateLimitData.requests.length),
        'X-RateLimit-Reset': Math.ceil((now + windowMs) / 1000)
      });
      
      next();
    } catch (error) {
      console.error('Error checking API rate limit:', error);
      // Don't block on rate limit errors, but log them
      next();
    }
  };
}

/**
 * Get tenant limits status
 */
async function getTenantLimitsStatus(tenantId) {
  try {
    const { Tenant } = require('../models');
    const tenant = await Tenant.findByPk(tenantId);
    
    if (!tenant) {
      throw new Error('Tenant not found');
    }
    
    const [userCount, deviceCount] = await Promise.all([
      checkUserLimit(tenantId),
      checkDeviceLimit(tenantId)
    ]);
    
    const rateLimitKey = `api_rate_limit:${tenantId}`;
    const rateLimitData = rateLimitStore.get(rateLimitKey);
    const currentApiRequests = rateLimitData ? rateLimitData.requests.length : 0;
    
    return {
      users: {
        current: userCount,
        limit: tenant.features?.max_users || 0,
        unlimited: tenant.features?.max_users === -1
      },
      devices: {
        current: deviceCount,
        limit: tenant.features?.max_devices || 0,
        unlimited: tenant.features?.max_devices === -1
      },
      api_requests: {
        current_minute: currentApiRequests,
        limit_per_minute: tenant.features?.api_rate_limit || 0,
        unlimited: tenant.features?.api_rate_limit === -1
      },
      data_retention: {
        days: tenant.features?.data_retention_days || 90,
        unlimited: tenant.features?.data_retention_days === -1
      }
    };
  } catch (error) {
    console.error('Error getting tenant limits status:', error);
    throw error;
  }
}

module.exports = {
  enforceUserLimit,
  enforceDeviceLimit,
  enforceApiRateLimit,
  getTenantLimitsStatus,
  checkUserLimit,
  checkDeviceLimit,
  rateLimitStore
};