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

// Helper to emit and get unread count
const getAndEmitUnreadCount = async (userId) => {
  try {
    const unreadCount = await Notification.countDocuments({
      user: userId,
      isRead: false,
    });
    getIO().to(userId.toString()).emit('unreadCountUpdate', unreadCount);
    return unreadCount;
  } catch (err) {
    console.error('Error emitting unread count:', err);
    return 0;
  }
};

// Get all notifications for the authenticated user
exports.getMyNotifications = async (req, res) => {
  try {
    if (!req.user) {
      return res.status(401).json({
        status: 'fail',
        message: 'You must be logged in to view notifications',
      });
    }

    const page = parseInt(req.query.page, 10) || 1;
    const limit = parseInt(req.query.limit, 10) || 20;
    const skip = (page - 1) * limit;

    // Filter options
    const filter = { user: req.user._id };

    if (req.query.isRead !== undefined) {
      filter.isRead = req.query.isRead === 'true';
    }

    if (req.query.type) {
      filter.type = req.query.type;
    }

    const notifications = await Notification.find(filter)
      .sort({ createdAt: -1 })
      .skip(skip)
      .limit(limit)
      .populate('relatedId');

    const total = await Notification.countDocuments(filter);
    const unreadCount = await Notification.countDocuments({
      user: req.user._id,
      isRead: false,
    });

    res.status(200).json({
      status: 'success',
      results: notifications.length,
      data: {
        notifications,
        pagination: {
          page,
          limit,
          total,
          pages: Math.ceil(total / limit),
        },
        unreadCount,
      },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Get unread notification count
exports.getUnreadCount = async (req, res) => {
  try {
    if (!req.user) {
      return res.status(401).json({
        status: 'fail',
        message: 'You must be logged in',
      });
    }

    const count = await Notification.countDocuments({
      user: req.user._id,
      isRead: false,
    });

    res.status(200).json({
      status: 'success',
      data: { unreadCount: count },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Mark a notification as read
exports.markAsRead = async (req, res) => {
  try {
    if (!req.user) {
      return res.status(401).json({
        status: 'fail',
        message: 'You must be logged in',
      });
    }

    const notification = await Notification.findOneAndUpdate(
      { _id: req.params.id, user: req.user._id },
      { isRead: true, readAt: new Date() },
      { new: true },
    );

    if (!notification) {
      return res.status(404).json({
        status: 'fail',
        message: 'Notification not found',
      });
    }

    const unreadCount = await getAndEmitUnreadCount(req.user._id);

    // Sync admin dashboard: Notify admins that this notification was read
    getIO().emit('notificationReadAdmin', {
      notificationId: notification._id,
      userId: req.user._id,
      isRead: true,
    });

    res.status(200).json({
      status: 'success',
      data: { notification, unreadCount },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Mark all notifications as read
exports.markAllAsRead = async (req, res) => {
  try {
    if (!req.user) {
      return res.status(401).json({
        status: 'fail',
        message: 'You must be logged in',
      });
    }

    await Notification.updateMany(
      { user: req.user._id, isRead: false },
      { isRead: true, readAt: new Date() },
    );

    await getAndEmitUnreadCount(req.user._id);

    // Sync admin dashboard: Notify admins that ALL user notifications were read
    getIO().emit('notificationAllReadAdmin', {
      userId: req.user._id,
    });

    res.status(200).json({
      status: 'success',
      message: 'All notifications marked as read',
      data: { unreadCount: 0 },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Delete a notification
exports.deleteNotification = async (req, res) => {
  try {
    if (!req.user) {
      return res.status(401).json({
        status: 'fail',
        message: 'You must be logged in',
      });
    }

    const notification = await Notification.findOneAndDelete({
      _id: req.params.id,
      user: req.user._id,
    });

    if (!notification) {
      return res.status(404).json({
        status: 'fail',
        message: 'Notification not found',
      });
    }

    const unreadCount = await getAndEmitUnreadCount(req.user._id);

    // Sync admin dashboard: Notify admins that this notification was deleted
    getIO().emit('notificationDeletedAdmin', notification._id);

    res.status(200).json({
      status: 'success',
      data: { unreadCount },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Delete all read notifications
exports.deleteAllRead = async (req, res) => {
  try {
    if (!req.user) {
      return res.status(401).json({
        status: 'fail',
        message: 'You must be logged in',
      });
    }

    await Notification.deleteMany({
      user: req.user._id,
      isRead: true,
    });

    // Sync admin dashboard: Notify admins that ALL user read notifications were deleted
    getIO().emit('notificationAllDeletedReadAdmin', {
      userId: req.user._id,
    });

    res.status(200).json({
      status: 'success',
      message: 'All read notifications deleted',
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Admin: Get all notifications
exports.getAllNotifications = async (req, res) => {
  try {
    const page = parseInt(req.query.page, 10) || 1;
    const limit = parseInt(req.query.limit, 10) || 50;
    const skip = (page - 1) * limit;

    const notifications = await Notification.find()
      .populate('user', 'name email')
      .sort({ createdAt: -1 })
      .skip(skip)
      .limit(limit);

    const total = await Notification.countDocuments();

    res.status(200).json({
      status: 'success',
      results: notifications.length,
      data: {
        notifications,
        pagination: {
          page,
          limit,
          total,
          pages: Math.ceil(total / limit),
        },
      },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Admin: Create notification for specific user(s)
exports.createNotification = async (req, res) => {
  try {
    const {
      userId,
      title,
      message,
      type,
      priority,
      metadata,
      relatedId,
      relatedModel,
    } = req.body;

    if (!userId || !title || !message) {
      return res.status(400).json({
        status: 'fail',
        message: 'Please provide userId, title, and message',
      });
    }

    const {
      createNotification: createNotifService,
    } = require('../utils/notificationService');
    const notification = await createNotifService({
      userId,
      title,
      message,
      type: type || 'general',
      priority: priority || 'medium',
      metadata,
      relatedId: relatedId || undefined,
      relatedModel: relatedModel || undefined,
    });

    if (!notification) {
      return res.status(200).json({
        status: 'success',
        message: 'Notification skipped due to user preferences or error',
        data: null,
      });
    }

    res.status(201).json({
      status: 'success',
      data: { notification },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Admin: Broadcast notification to all users
exports.broadcastNotification = async (req, res) => {
  try {
    const {
      title,
      message,
      type,
      priority,
      metadata,
      userRole,
      relatedId,
      relatedModel,
    } = req.body;

    if (!title || !message) {
      return res.status(400).json({
        status: 'fail',
        message: 'Please provide title and message',
      });
    }

    const User = require('../models/userModel');

    let users;
    if (userRole === 'subscriber') {
      // Find all active newsletter emails
      const subscribers = await Newsletter.find({ isActive: true }).select(
        'email',
      );
      const emails = subscribers.map((s) => s.email);

      // Find users whose email is in the subscribers list
      users = await User.find({ email: { $in: emails } }).select('_id');
    } else {
      // Filter users by role if specified
      const filter = userRole && userRole !== 'all' ? { role: userRole } : {};
      users = await User.find(filter).select('_id');
    }

    const recipients = users.map((u) => u._id);
    const { createBulkNotifications } = require('../utils/notificationService');

    const results = await createBulkNotifications(recipients, {
      title,
      message,
      type: type || 'general',
      priority: priority || 'medium',
      metadata,
      relatedId: relatedId || undefined,
      relatedModel: relatedModel || undefined,
    });

    res.status(201).json({
      status: 'success',
      message: `Notification sent to ${results.length} recipients who opted in`,
      data: { count: results.length },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Admin: Delete any notification (no user ownership check)
exports.adminDeleteNotification = async (req, res) => {
  try {
    const notification = await Notification.findByIdAndDelete(req.params.id);

    if (!notification) {
      return res.status(404).json({
        status: 'fail',
        message: 'Notification not found',
      });
    }

    const io = getIO();
    // Notify the specific user that their notification was deleted
    io.to(notification.user.toString()).emit(
      'notificationDeleted',
      notification._id,
    );

    // Update the user's unread count after deletion
    await getAndEmitUnreadCount(notification.user);

    // Sync other admins
    io.emit('notificationDeletedAdmin', notification._id);

    res.status(200).json({
      status: 'success',
      message: 'Notification deleted successfully',
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Get user's notification preferences
exports.getMyPreferences = async (req, res) => {
  try {
    if (!req.user) {
      return res.status(401).json({
        status: 'fail',
        message: 'You must be logged in',
      });
    }

    res.status(200).json({
      status: 'success',
      data: {
        preferences: req.user.notificationPreferences,
      },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Update user's notification preferences
exports.updateMyPreferences = async (req, res) => {
  try {
    if (!req.user) {
      return res.status(401).json({
        status: 'fail',
        message: 'You must be logged in',
      });
    }

    const { preferences } = req.body;

    if (!preferences) {
      return res.status(400).json({
        status: 'fail',
        message: 'Please provide preferences to update',
      });
    }

    // Update user document
    const User = require('../models/userModel');
    const existingUser = await User.findById(req.user._id);

    // Guard: Force-enable notifications only for categories the user has permission for.
    // Admins always receive everything. Employees only receive what matches their permissions.
    if (req.user.role === 'admin') {
      if (preferences.orderUpdates) {
        preferences.orderUpdates.app = true;
        preferences.orderUpdates.email = true;
      }
      if (preferences.productUpdates) {
        preferences.productUpdates.app = true;
        preferences.productUpdates.email = true;
      }
      delete preferences.vendorOrderVisibility;
    } else if (req.user.role === 'employee') {
      const empPerms = req.user.permissions || [];
      // Only force-enable orderUpdates if the employee has manage_orders permission
      if (preferences.orderUpdates && empPerms.includes('manage_orders')) {
        preferences.orderUpdates.app = true;
        preferences.orderUpdates.email = true;
      }
      // Only force-enable productUpdates if the employee has manage_products permission
      if (preferences.productUpdates && empPerms.includes('manage_products')) {
        preferences.productUpdates.app = true;
        preferences.productUpdates.email = true;
      }
      delete preferences.vendorOrderVisibility;
    }

    // Logic to handle disabledAt and blackoutPeriods for vendorOrderVisibility
    if (preferences.vendorOrderVisibility) {
      const oldPref =
        (existingUser.notificationPreferences &&
          existingUser.notificationPreferences.vendorOrderVisibility) ||
        {};
      const wasEnabled = oldPref.app !== false;
      const isEnabled = preferences.vendorOrderVisibility.app !== false;

      const periods = oldPref.blackoutPeriods || [];

      if (wasEnabled && !isEnabled) {
        // Just turned off: set disabledAt (start of new blackout)
        preferences.vendorOrderVisibility.disabledAt = new Date();
        preferences.vendorOrderVisibility.blackoutPeriods = periods;
      } else if (!wasEnabled && isEnabled) {
        // Just turned on: close the current blackout period and clear disabledAt
        if (oldPref.disabledAt) {
          periods.push({
            start: oldPref.disabledAt,
            end: new Date(),
          });
        }
        preferences.vendorOrderVisibility.blackoutPeriods = periods;
        preferences.vendorOrderVisibility.disabledAt = null;
      } else if (!wasEnabled && !isEnabled) {
        // Stayed off: carry over state
        preferences.vendorOrderVisibility.disabledAt = oldPref.disabledAt;
        preferences.vendorOrderVisibility.blackoutPeriods = periods;
      } else {
        // Stayed on: carry over state
        preferences.vendorOrderVisibility.disabledAt = null;
        preferences.vendorOrderVisibility.blackoutPeriods = periods;
      }
    }

    const user = await User.findByIdAndUpdate(
      req.user._id,
      { notificationPreferences: preferences },
      { new: true, runValidators: true },
    );

    res.status(200).json({
      status: 'success',
      data: {
        preferences: user.notificationPreferences,
      },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

// Admin: Get current vendor preference state (reads first active vendor as representative)
exports.getVendorGlobalPreferences = async (req, res) => {
  try {
    const User = require('../models/userModel');
    const vendor = await User.findOne({ role: 'vendor', isActive: true })
      .select('notificationPreferences')
      .lean();

    const defaults = {
      orderUpdates: { app: true, email: true },
      productUpdates: { app: true, email: true },
      vendorOrderVisibility: { app: true, email: true },
    };

    if (!vendor || !vendor.notificationPreferences) {
      return res
        .status(200)
        .json({ status: 'success', data: { preferences: defaults } });
    }

    const p = vendor.notificationPreferences;
    return res.status(200).json({
      status: 'success',
      data: {
        preferences: {
          orderUpdates: {
            app: p.orderUpdates?.app !== false,
            email: p.orderUpdates?.email !== false,
          },
          productUpdates: {
            app: p.productUpdates?.app !== false,
            email: p.productUpdates?.email !== false,
          },
          vendorOrderVisibility: {
            app: p.vendorOrderVisibility?.app !== false,
            email: p.vendorOrderVisibility?.email !== false,
          },
        },
      },
    });
  } catch (err) {
    res.status(500).json({ status: 'error', message: err.message });
  }
};

// Admin: Bulk-update preferences for ALL active vendor users
// This lets admins globally control whether vendors receive notifications / see orders
exports.updateAllVendorPreferences = async (req, res) => {
  try {
    if (!req.user) {
      return res
        .status(401)
        .json({ status: 'fail', message: 'You must be logged in' });
    }

    const { preferences } = req.body;
    if (!preferences) {
      return res
        .status(400)
        .json({ status: 'fail', message: 'Please provide preferences' });
    }

    const User = require('../models/userModel');
    const now = new Date();

    // Find all active vendor users
    const vendors = await User.find({ role: 'vendor', isActive: true }).select(
      '_id notificationPreferences',
    );

    if (vendors.length === 0) {
      return res.status(200).json({
        status: 'success',
        message: 'No active vendors found',
        data: { updatedCount: 0 },
      });
    }

    const bulkOps = vendors.map((vendor) => {
      const existingPrefs = vendor.notificationPreferences || {};
      const updatedPrefs = { ...existingPrefs };

      // Apply orderUpdates preference — app and email are always kept in sync
      if (preferences.orderUpdates !== undefined) {
        const val =
          typeof preferences.orderUpdates.app === 'boolean'
            ? preferences.orderUpdates.app
            : true;
        updatedPrefs.orderUpdates = {
          ...(existingPrefs.orderUpdates || {}),
          app: val,
          email: val,
        };
      }

      // Apply productUpdates preference — app and email are always kept in sync
      if (preferences.productUpdates !== undefined) {
        const val =
          typeof preferences.productUpdates.app === 'boolean'
            ? preferences.productUpdates.app
            : true;
        updatedPrefs.productUpdates = {
          ...(existingPrefs.productUpdates || {}),
          app: val,
          email: val,
        };
      }

      // Apply vendorOrderVisibility preference with blackout tracking
      if (preferences.vendorOrderVisibility !== undefined) {
        const oldVis = existingPrefs.vendorOrderVisibility || {};
        const wasEnabled = oldVis.app !== false;
        const isEnabled = preferences.vendorOrderVisibility.app !== false;
        const periods = oldVis.blackoutPeriods || [];

        let disabledAt = oldVis.disabledAt || null;

        if (wasEnabled && !isEnabled) {
          // Turning OFF: record when it was disabled
          disabledAt = now;
        } else if (!wasEnabled && isEnabled) {
          // Turning ON: close the current blackout period
          if (oldVis.disabledAt) {
            periods.push({ start: oldVis.disabledAt, end: now });
          }
          disabledAt = null;
        } else if (!wasEnabled && !isEnabled) {
          // Stayed off: keep previous disabledAt
        } else {
          // Stayed on
          disabledAt = null;
        }

        // vendorOrderVisibility: app and email always in sync
        updatedPrefs.vendorOrderVisibility = {
          app: isEnabled,
          email: isEnabled,
          disabledAt,
          blackoutPeriods: periods,
        };
      }

      return {
        updateOne: {
          filter: { _id: vendor._id },
          update: { $set: { notificationPreferences: updatedPrefs } },
        },
      };
    });

    const result = await User.bulkWrite(bulkOps);

    // Emit a socket event so online vendors refresh their preferences
    const { getIO } = require('../utils/socket');
    try {
      const io = getIO();
      vendors.forEach((vendor) => {
        io.to(vendor._id.toString()).emit('preferencesUpdated', {
          preferences: bulkOps.find(
            (op) =>
              op.updateOne.filter._id.toString() === vendor._id.toString(),
          )?.updateOne?.update?.$set?.notificationPreferences,
        });
      });
    } catch (socketErr) {
      // Non-critical — socket might not be available
      console.error(
        'Socket emit error in updateAllVendorPreferences:',
        socketErr,
      );
    }

    res.status(200).json({
      status: 'success',
      message: `Updated preferences for ${result.modifiedCount} vendor(s)`,
      data: { updatedCount: result.modifiedCount },
    });
  } catch (err) {
    res.status(500).json({ status: 'error', message: err.message });
  }
};

// ─── Stock Subscription Handlers ─────────────────────────────────────────────

const StockSubscription = require('../models/stockSubscriptionModel');

// POST /notifications/stock-subscribe/:productId
exports.subscribeToStock = async (req, res) => {
  try {
    const { productId } = req.params;
    const userId = req.user._id;

    // Upsert: create if not exists, reset notifiedAt so they get notified again on next restock
    await StockSubscription.findOneAndUpdate(
      { user: userId, product: productId },
      { user: userId, product: productId, notifiedAt: null },
      { upsert: true, new: true, setDefaultsOnInsert: true },
    );

    res.status(200).json({
      status: 'success',
      data: { subscribed: true },
    });
  } catch (err) {
    res.status(500).json({ status: 'error', message: err.message });
  }
};

// DELETE /notifications/stock-subscribe/:productId
exports.unsubscribeFromStock = async (req, res) => {
  try {
    const { productId } = req.params;
    const userId = req.user._id;

    await StockSubscription.findOneAndDelete({
      user: userId,
      product: productId,
    });

    res.status(200).json({
      status: 'success',
      data: { subscribed: false },
    });
  } catch (err) {
    res.status(500).json({ status: 'error', message: err.message });
  }
};

// GET /notifications/stock-subscribe/:productId
exports.checkStockSubscription = async (req, res) => {
  try {
    const { productId } = req.params;
    const userId = req.user._id;

    const sub = await StockSubscription.findOne({
      user: userId,
      product: productId,
    });

    res.status(200).json({
      status: 'success',
      data: { subscribed: !!sub },
    });
  } catch (err) {
    res.status(500).json({ status: 'error', message: err.message });
  }
};