const Notification = require('../models/notificationModel');
const { getIO } = require('./socket');

/**
 * Emit unread count to a specific user
 */
const emitUnreadCount = async (userId) => {
  try {
    const unreadCount = await Notification.countDocuments({
      user: userId,
      isRead: false,
    });
    getIO().to(userId.toString()).emit('unreadCountUpdate', unreadCount);
    return unreadCount;
  } catch (err) {
    // eslint-disable-next-line no-console
    console.error('Error emitting unread count:', err);
    return 0;
  }
};

/**
 * Check if a user has enabled a specific notification type
 */
const checkUserPreference = async (
  userId,
  type,
  channel = 'app',
  timestamp = null,
) => {
  try {
    const User = require('../models/userModel');
    // Use lean() for faster reading and plain object access
    const user = await User.findById(userId)
      .select('notificationPreferences role permissions')
      .lean();
    if (!user || !user.notificationPreferences) return true;

    const { notificationPreferences, role, permissions = [] } = user;

    // Map notification types to preference categories and required permissions
    let category = 'general';
    if (type && typeof type === 'string') {
      if (type.startsWith('order_')) {
        category = 'orderUpdates';
      } else if (type === 'newsletter') {
        category = 'newsletters';
      } else if (type === 'promo_code') {
        category = 'promotions';
      } else if (type.startsWith('product_')) {
        category = 'productUpdates';
      }
    }

    // Admins always receive all store-critical notifications via app
    if (role === 'admin' && channel === 'app') {
      if (category === 'orderUpdates' || category === 'productUpdates')
        return true;
    }

    // Employees only receive notifications relevant to their permissions
    if (role === 'employee' && channel === 'app') {
      if (category === 'orderUpdates')
        return permissions.includes('manage_orders');
      if (category === 'productUpdates')
        return permissions.includes('manage_products');
    }

    // 1. Check if the specific channel is enabled for this category
    const categoryPref = notificationPreferences[category];
    const isChannelEnabled =
      categoryPref && categoryPref[channel] !== undefined
        ? Boolean(categoryPref[channel])
        : true;

    if (!isChannelEnabled) return false;

    // 2. For vendors, check specific vendorOrderVisibility for order updates
    if (role === 'vendor' && category === 'orderUpdates') {
      const visibility = notificationPreferences.vendorOrderVisibility || {};

      // If a timestamp is provided, check if it falls within any blackout period
      if (timestamp) {
        const orderTime = new Date(timestamp).getTime();

        // Check historical blackout periods
        const blackoutPeriods = visibility.blackoutPeriods || [];
        const isInHistoricalBlackout = blackoutPeriods.some((p) => {
          const start = new Date(p.start).getTime();
          const end = new Date(p.end).getTime();
          return orderTime >= start && orderTime <= end;
        });

        if (isInHistoricalBlackout) return false;

        // Check current active blackout if visibility is OFF
        if (visibility[channel] === false && visibility.disabledAt) {
          const disabledAtTime = new Date(visibility.disabledAt).getTime();
          if (orderTime >= disabledAtTime) return false;
        }
      } else if (visibility[channel] === false) {
        // Fallback to active state if no timestamp provided
        return false;
      }
    }

    return true;
  } catch (err) {
    // eslint-disable-next-line no-console
    console.error('Error checking user preference:', err);
    return true;
  }
};

/**
 * Create a notification for a specific user and emit via socket
 */
const createNotification = async ({
  userId,
  title,
  message,
  type = 'general',
  relatedId = null,
  relatedModel = null,
  priority = 'medium',
  metadata = {},
  timestamp = null,
}) => {
  try {
    // Check user preference for the specific channel
    const isEnabled = await checkUserPreference(userId, type, 'app', timestamp);
    if (!isEnabled) {
      return null;
    }

    const notification = await Notification.create({
      user: userId,
      title,
      message,
      type,
      relatedId,
      relatedModel,
      priority,
      metadata,
    });

    // Real-time socket emission to the specific user
    const io = getIO();
    io.to(userId.toString()).emit('newNotification', notification);

    // Update the user's unread count
    await emitUnreadCount(userId);

    return notification;
  } catch (error) {
    // eslint-disable-next-line no-console
    console.error('Error creating notification:', error);
    // Don't throw to avoid breaking the main flow (e.g. order creation)
    return null;
  }
};

/**
 * Broadcast an order update to all admin/vendor dashboards
 */
const emitOrderUpdate = (order, type) => {
  try {
    const io = getIO();
    io.emit('orderUpdated', {
      orderId: order._id,
      type: type,
      status: order.orderStatus || null,
    });
  } catch (error) {
    // eslint-disable-next-line no-console
    console.error('Error emitting order update:', error);
  }
};

/**
 * Create notifications for multiple users and emit via socket
 */
const createBulkNotifications = async (
  userIds,
  notificationData,
  timestamp = null,
) => {
  try {
    const { type } = notificationData;

    // Filter users based on their preferences for 'app' channel
    const User = require('../models/userModel');
    // Important: Use lean() to get plain objects for easier filtering
    const usersWithPrefs = await User.find({ _id: { $in: userIds } })
      .select('notificationPreferences role permissions')
      .lean();

    const allowedUserIds = usersWithPrefs
      .filter((user) => {
        if (!user || !user.notificationPreferences) return true;

        const { notificationPreferences, role, permissions = [] } = user;
        let category = 'general';

        if (type && typeof type === 'string') {
          if (type.startsWith('order_')) {
            category = 'orderUpdates';
          } else if (type === 'newsletter') {
            category = 'newsletters';
          } else if (type === 'promo_code') {
            category = 'promotions';
          } else if (type.startsWith('product_')) {
            category = 'productUpdates';
          }
        }

        // Admins always receive all store-critical notifications
        if (role === 'admin') {
          if (category === 'orderUpdates' || category === 'productUpdates')
            return true;
        }

        // Employees only receive notifications matching their permissions
        if (role === 'employee') {
          if (category === 'orderUpdates')
            return permissions.includes('manage_orders');
          if (category === 'productUpdates')
            return permissions.includes('manage_products');
        }

        // 1. Check if the specific channel ('app') is enabled for this category
        const categoryPref = notificationPreferences[category];
        const isChannelEnabled =
          categoryPref && categoryPref.app !== undefined
            ? Boolean(categoryPref.app)
            : true;

        if (!isChannelEnabled) return false;

        // Note: vendorOrderVisibility only controls order visibility in the table,
        // not notifications. Notifications are controlled by orderUpdates.app above.
        // So we don't check vendorOrderVisibility here for notifications.

        return true;
      })
      .map((user) => user._id);

    if (allowedUserIds.length === 0) return [];

    const notifications = allowedUserIds.map((userId) => ({
      user: userId,
      ...notificationData,
    }));

    const result = await Notification.insertMany(notifications);

    // Real-time socket emission for each user
    const io = getIO();
    result.forEach((notif) => {
      io.to(notif.user.toString()).emit('newNotification', notif);
      emitUnreadCount(notif.user); // Don't await in loop
    });

    // Emit once to the admin global dashboard using the first notification as a sample
    if (result.length > 0) {
      io.emit('newNotificationAdmin', result[0]);
    }

    return result;
  } catch (error) {
    // eslint-disable-next-line no-console
    console.error('Error creating bulk notifications:', error);
    return [];
  }
};

/**
 * Create order-related notifications (Localized in Arabic)
 */
const notifyOrderCreated = async (order, userId) => {
  const orderIdShort = order._id.toString().slice(-6).toUpperCase();
  return createNotification({
    userId,
    title: 'تم استلام طلبك بنجاح',
    message: `تم استلام طلبك رقم #${orderIdShort} بنجاح. سنقوم بمراجعته وتجهيزه في أقرب وقت.`,
    type: 'order_created',
    relatedId: order._id,
    relatedModel: 'Order',
    priority: 'high',
    metadata: {
      orderId: order._id,
      totalAmount: order.totalAmount,
    },
    timestamp: order.createdAt,
  });
};

const notifyOrderProcessing = async (order, userId) => {
  const orderIdShort = order._id.toString().slice(-6).toUpperCase();
  return createNotification({
    userId,
    title: 'تم تأكيد طلبك',
    message: `تم تأكيد طلبك رقم #${orderIdShort} وهو الآن قيد التجهيز.`,
    type: 'order_confirmed',
    relatedId: order._id,
    relatedModel: 'Order',
    priority: 'high',
    metadata: {
      orderId: order._id,
    },
    timestamp: order.createdAt,
  });
};

const notifyOrderShipped = async (order, userId) => {
  const orderIdShort = order._id.toString().slice(-6).toUpperCase();
  return createNotification({
    userId,
    title: 'تم شحن الطلب',
    message: `طلبك رقم #${orderIdShort} في الطريق إليك الآن عبر شركة الشحن.`,
    type: 'order_shipped',
    relatedId: order._id,
    relatedModel: 'Order',
    priority: 'high',
    metadata: {
      orderId: order._id,
      trackingNumber: order.trackingNumber || null,
    },
    timestamp: order.createdAt,
  });
};

const notifyOrderCompleted = async (order, userId) => {
  const orderIdShort = order._id.toString().slice(-6).toUpperCase();
  return createNotification({
    userId,
    title: 'تم توصيل الطلب',
    message: `تم توصيل طلبك رقم #${orderIdShort} بنجاح. شكراً لتسوقك معنا!`,
    type: 'order_delivered',
    relatedId: order._id,
    relatedModel: 'Order',
    priority: 'high',
    metadata: {
      orderId: order._id,
    },
    timestamp: order.createdAt,
  });
};

const notifyOrderCancelled = async (order, userId, reason = '') => {
  const orderIdShort = order._id.toString().slice(-6).toUpperCase();
  return createNotification({
    userId,
    title: 'تم إلغاء الطلب',
    message: `تم إلغاء طلبك رقم #${orderIdShort}. ${reason ? `السبب: ${reason}` : ''}`,
    type: 'order_cancelled',
    relatedId: order._id,
    relatedModel: 'Order',
    priority: 'high',
    metadata: {
      orderId: order._id,
      reason,
    },
    timestamp: order.createdAt,
  });
};

/**
 * Notify vendor about new order
 */
const notifyVendorNewOrder = async (order, providerId) => {
  try {
    const User = require('../models/userModel');
    const vendorUsers = await User.find({
      provider: providerId,
      role: 'vendor',
      isActive: true,
    }).select('_id');

    if (vendorUsers && vendorUsers.length > 0) {
      const userIds = vendorUsers.map((u) => u._id);
      const orderIdShort = order._id.toString().slice(-6).toUpperCase();
      return createBulkNotifications(
        userIds,
        {
          title: 'طلب جديد للمتجر',
          message: `لقد تلقيت طلباً جديداً برقم #${orderIdShort}. يرجى البدء في تجهيز المنتجات.`,
          type: 'order_created',
          relatedId: order._id,
          relatedModel: 'Order',
          priority: 'high',
          metadata: {
            orderId: order._id,
            totalPrice: order.totalPrice,
          },
        },
        order.createdAt,
      );
    }
    return null;
  } catch (error) {
    console.error('Error in notifyVendorNewOrder:', error);
    return null;
  }
};

/**
 * Product-related notifications
 */
const notifyProductOutOfStock = async (product, providerId) => {
  try {
    const User = require('../models/userModel');
    const vendorUsers = await User.find({
      provider: providerId,
      role: 'vendor',
      isActive: true,
    }).select('_id');

    if (vendorUsers && vendorUsers.length > 0) {
      const userIds = vendorUsers.map((u) => u._id);
      return createBulkNotifications(userIds, {
        title: 'منتج نفد من المخزون',
        message: `نعتذر، ولكن المنتج "${product.nameAr || product.nameEn}" غير متوفر حالياً ونفد من المخزون.`,
        type: 'product_out_of_stock',
        relatedId: product._id,
        relatedModel: 'Product',
        priority: 'medium',
        metadata: {
          productId: product._id,
          productName: product.nameAr || product.nameEn,
        },
      });
    }
    return null;
  } catch (error) {
    console.error('Error in notifyProductOutOfStock:', error);
    return null;
  }
};

const notifyProductBackInStock = async (product, userIds) =>
  createBulkNotifications(userIds, {
    title: 'المنتج متوفر الآن!',
    message: `خبر سعيد! المنتج "${
      product.nameAr || product.nameEn
    }" الذي اشتريته سابقاً متوفر الآن مرة أخرى.`,
    type: 'product_back_in_stock',
    relatedId: product._id,
    relatedModel: 'Product',
    priority: 'medium',
    metadata: {
      productId: product._id,
      productName: product.nameAr || product.nameEn,
    },
  });

/**
 * Notify all users who have previously purchased this product that it's back in stock
 */
const notifyPastBuyersProductBackInStock = async (product) => {
  try {
    // eslint-disable-next-line global-require
    const Order = require('../models/orderModel');

    // Find all users who have this product in their orders
    const orders = await Order.find({
      'items.product': product._id,
      user: { $exists: true, $ne: null },
    }).distinct('user');

    if (orders && orders.length > 0) {
      return notifyProductBackInStock(product, orders);
    }
    return null;
  } catch (error) {
    // eslint-disable-next-line no-console
    console.error('Error in notifyPastBuyersProductBackInStock:', error);
    return null;
  }
};

/**
 * Promo code notifications
 */
const notifyPromoCode = async (userId, promoCode, discount) =>
  createNotification({
    userId,
    title: 'كود خصم جديد متاح!',
    message: `استخدم كود "${promoCode}" للحصول على خصم ${discount}% على مشترياتك القادمة!`,
    type: 'promo_code',
    priority: 'medium',
    metadata: {
      promoCode,
      discount,
    },
  });

/**
 * Review-related notifications
 */
const notifyReviewResponse = async (review, userId) =>
  createNotification({
    userId,
    title: 'تم الرد على تقييمك',
    message: 'لقد قام المتجر بالرد على التقييم الذي تركته للمنتج.',
    type: 'review_response',
    relatedId: review._id,
    relatedModel: 'Review',
    priority: 'low',
    metadata: {
      reviewId: review._id,
    },
  });

/**
 * Auto-delete old notifications to keep database clean
 * Rules:
 * - Unread: Delete after 15 days
 * - Read: Delete after 7 days
 */
const deleteOldNotifications = async () => {
  try {
    const now = new Date();
    const fifteenDaysAgo = new Date(now.getTime() - 15 * 24 * 60 * 60 * 1000);
    const sevenDaysAgo = new Date(now.getTime() - 7 * 24 * 60 * 60 * 1000);

    const result = await Notification.deleteMany({
      $or: [
        // Unread and older than 15 days
        { isRead: false, createdAt: { $lt: fifteenDaysAgo } },
        // Read and older than 7 days (using updatedAt as proxy for readAt date)
        { isRead: true, updatedAt: { $lt: sevenDaysAgo } },
      ],
    });

    return result;
  } catch (error) {
    // eslint-disable-next-line no-console
    console.error('Error in periodic notification cleanup:', error);
    return null;
  }
};

/**
 * Notify all admins and employees about product out of stock
 */
const notifyAdminsProductOutOfStock = async (product) => {
  try {
    const User = require('../models/userModel');
    const staff = await User.find({
      role: { $in: ['admin', 'employee'] },
      isActive: true,
    }).select('_id role permissions');

    // Admins always get notified; employees only if they have manage_products permission
    const eligible = staff.filter(
      (u) =>
        u.role === 'admin' ||
        (u.permissions && u.permissions.includes('manage_products')),
    );

    if (eligible.length > 0) {
      const eligibleIds = eligible.map((a) => a._id);
      return createBulkNotifications(eligibleIds, {
        title: 'منتج نفد من المخزون',
        message: `تنبيه: المنتج "${product.nameAr || product.nameEn}" نفد من المخزون.`,
        type: 'product_out_of_stock',
        relatedId: product._id,
        relatedModel: 'Product',
        priority: 'high',
        metadata: {
          productId: product._id,
          productName: product.nameAr || product.nameEn,
        },
      });
    }
    return null;
  } catch (error) {
    console.error('Error in notifyAdminsProductOutOfStock:', error);
    return null;
  }
};

/**
 * Notify all admins and employees about a new order
 */
const notifyAdminsNewOrder = async (order) => {
  try {
    const User = require('../models/userModel');
    const staff = await User.find({
      role: { $in: ['admin', 'employee'] },
      isActive: true,
    }).select('_id role permissions');

    // Admins always get notified; employees only if they have manage_orders permission
    const eligible = staff.filter(
      (u) =>
        u.role === 'admin' ||
        (u.permissions && u.permissions.includes('manage_orders')),
    );

    if (eligible.length > 0) {
      const eligibleIds = eligible.map((a) => a._id);
      const orderIdShort = order._id.toString().slice(-6).toUpperCase();
      return createBulkNotifications(
        eligibleIds,
        {
          title: 'طلب جديد في المتجر',
          message: `لقد تم استلام طلب جديد رقم #${orderIdShort} بقيمة ${order.totalPrice} ج.م`,
          type: 'order_created',
          relatedId: order._id,
          relatedModel: 'Order',
          priority: 'high',
          metadata: {
            orderId: order._id,
            totalPrice: order.totalPrice,
          },
        },
        order.createdAt,
      );
    }
    return null;
  } catch (error) {
    console.error('Error in notifyAdminsNewOrder:', error);
    return null;
  }
};

/**
 * Notify users who explicitly subscribed to be notified when this product is back in stock.
 * Marks subscriptions as notified so they don't receive duplicate notifications.
 */
const notifyStockSubscribers = async (product) => {
  try {
    const StockSubscription = require('../models/stockSubscriptionModel');

    // Find all pending (not yet notified) subscriptions for this product
    const subscriptions = await StockSubscription.find({
      product: product._id,
      notifiedAt: null,
    });

    if (!subscriptions || subscriptions.length === 0) return null;

    const userIds = subscriptions.map((s) => s.user);

    const result = await createBulkNotifications(userIds, {
      title: 'المنتج متوفر الآن! 🎉',
      message: `خبر سعيد! المنتج "${product.nameAr || product.nameEn}" الذي طلبت إشعاره متوفر الآن. لا تفوّت الفرصة!`,
      type: 'product_back_in_stock',
      relatedId: product._id,
      relatedModel: 'Product',
      priority: 'high',
      metadata: {
        productId: product._id,
        productName: product.nameAr || product.nameEn,
        productSlug: product.slug,
      },
    });

    // Mark all subscriptions as notified so they don't get notified again
    await StockSubscription.updateMany(
      { product: product._id, notifiedAt: null },
      { notifiedAt: new Date() },
    );

    return result;
  } catch (error) {
    // eslint-disable-next-line no-console
    console.error('Error in notifyStockSubscribers:', error);
    return null;
  }
};

module.exports = {
  createNotification,
  createBulkNotifications,
  notifyOrderCreated,
  notifyOrderProcessing,
  notifyOrderShipped,
  notifyOrderCompleted,
  notifyOrderCancelled,
  notifyVendorNewOrder,
  notifyProductOutOfStock,
  notifyProductBackInStock,
  notifyPastBuyersProductBackInStock,
  notifyStockSubscribers,
  notifyPromoCode,
  notifyReviewResponse,
  deleteOldNotifications,
  emitOrderUpdate,
  notifyAdminsProductOutOfStock,
  notifyAdminsNewOrder,
};