const Promo = require('../models/promoCodeModel');
const Order = require('../models/orderModel');

exports.createPromo = async (req, res) => {
  try {
    const data = req.body;
    if (data.code) data.code = String(data.code).trim().toUpperCase();
    if (data.categoryId === '') data.categoryId = null;
    const promo = await Promo.create(data);
    res.status(201).json({
      status: 'success',
      data: { promo },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

exports.getPromos = async (req, res) => {
  try {
    const promos = await Promo.find().sort({ createdAt: -1 }).limit(200);
    res.status(200).json({
      status: 'success',
      results: promos.length,
      data: { promos },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

exports.getPromo = async (req, res) => {
  try {
    const promo = await Promo.findById(req.params.id);
    if (!promo)
      return res
        .status(404)
        .json({ status: 'fail', message: 'Promo not found' });
    res.status(200).json({
      status: 'success',
      data: { promo },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

exports.updatePromo = async (req, res) => {
  try {
    const data = req.body;
    if (data.code) data.code = String(data.code).trim().toUpperCase();
    if (data.categoryId === '') data.categoryId = null;
    const promo = await Promo.findByIdAndUpdate(req.params.id, data, {
      new: true,
      runValidators: true,
    });
    if (!promo)
      return res
        .status(404)
        .json({ status: 'fail', message: 'Promo not found' });
    res.status(200).json({
      status: 'success',
      data: { promo },
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};

exports.deletePromo = async (req, res) => {
  try {
    const promo = await Promo.findByIdAndDelete(req.params.id);
    if (!promo)
      return res
        .status(404)
        .json({ status: 'fail', message: 'Promo not found' });
    res.status(204).json({
      status: 'success',
      data: null,
    });
  } catch (err) {
    res.status(500).json({
      status: 'error',
      message: err.message,
    });
  }
};
const computeDiscountAmount = (type, value, base) => {
  const numericBase = Number(base) || 0;
  const numericValue = Number(value) || 0;
  if (type === 'shipping') return 0; // Shipping discount doesn't affect subtotal
  if (type === 'percentage' || type === 'welcome')
    return Math.max(0, (numericBase * numericValue) / 100);
  return Math.max(0, numericValue);
};

exports.validatePromo = async (req, res) => {
  try {
    const { promoCode, subtotal, items } = req.body || {};
    const base = Number(subtotal) || 0;
    const cartItems = Array.isArray(items) ? items : [];
    if (!promoCode)
      return res.status(200).json({
        status: 'success',
        data: { code: null, discountedTotal: base },
      });

    const upper = String(promoCode).trim().toUpperCase();
    const now = new Date();

    const promo = await Promo.findOne({ code: upper });

    if (!promo) {
      return res.status(200).json({
        status: 'fail',
        message: 'كود الخصم غير موجود',
      });
    }

    if (!promo.active) {
      return res.status(200).json({
        status: 'fail',
        message: 'كود الخصم هذا غير مفعّل حالياً',
      });
    }

    if (promo.startsAt && promo.startsAt > now) {
      return res.status(200).json({
        status: 'fail',
        message: 'كود الخصم لم يبدأ مفعوله بعد',
      });
    }

    if (promo.expiresAt && promo.expiresAt < now) {
      return res.status(200).json({
        status: 'fail',
        message: 'انتهت صلاحية كود الخصم هذا',
      });
    }

    if (promo.minOrderValue > base) {
      return res.status(200).json({
        status: 'fail',
        message: `يجب أن تكون قيمة الطلب ${promo.minOrderValue} جنيه على الأقل لاستخدام هذا الكود`,
      });
    }

    // Check usage limits if needed
    if (promo.usageLimit !== null && promo.usedCount >= promo.usageLimit) {
      return res.status(200).json({
        status: 'fail',
        message: 'تم استهلاك الحد الأقصى لاستخدام كود الخصم هذا',
      });
    }

    // Check per-user limit
    if (req.user && promo.perUserLimit !== null) {
      const userUsageCount = await Order.countDocuments({
        user: req.user._id,
        promoCode: upper,
        orderStatus: { $ne: 'cancelled' }, // Count everything except cancelled
      });

      if (userUsageCount >= promo.perUserLimit) {
        return res.status(200).json({
          status: 'fail',
          message: `لقد استنفدت الحد الأقصى لاستخدام هذا الكود (${promo.perUserLimit} مرات)`,
        });
      }
    }

    // Determine eligible base for discount calculation
    let eligibleBase = base;
    if (promo.canBeUsedWithSaleItems === false && cartItems.length > 0) {
      eligibleBase = cartItems.reduce((sum, item) => {
        // If product is NOT on sale, it is eligible
        if (!item.isOnSale) {
          return sum + Number(item.price) * Number(item.quantity);
        }
        return sum;
      }, 0);

      // If no eligible items and it's not a shipping discount, return error
      if (eligibleBase <= 0 && promo.type !== 'shipping') {
        return res.status(200).json({
          status: 'fail',
          message: 'كود الخصم هذا لا يمكن استخدامه مع المنتجات المخفضة',
        });
      }
    }

    const discount = computeDiscountAmount(
      promo.type,
      promo.value,
      eligibleBase,
    );
    const discounted = Math.max(0, base - discount);

    return res.status(200).json({
      status: 'success',
      data: {
        code: promo.code,
        discountType: promo.type,
        discountValue: promo.value,
        discountedTotal: discounted,
        isFreeShipping: promo.type === 'shipping',
        expiresAt: promo.expiresAt,
      },
    });
  } catch (err) {
    res.status(500).json({ status: 'error', message: err.message });
  }
};