const Product = require('../models/Product');
const InventoryHistory = require('../models/InventoryHistory');
const { successResponse, errorResponse } = require('../utils/apiResponse');

// @desc    Get stock overview & alerts (Admin)
// @route   GET /api/inventory/overview
// @access  Private/Admin
const getStockOverview = async (req, res, next) => {
  try {
    const products = await Product.find({})
      .select('name sku stock lowStockThreshold price category brand images')
      .populate('category', 'name')
      .populate('brand', 'name');

    const lowStock = products.filter(p => p.stock > 0 && p.stock <= p.lowStockThreshold);
    const outOfStock = products.filter(p => p.stock === 0);

    return successResponse(res, 'Stock overview retrieved', {
      totalProducts: products.length,
      lowStockCount: lowStock.length,
      outOfStockCount: outOfStock.length,
      lowStock,
      outOfStock,
      products
    });
  } catch (error) {
    next(error);
  }
};

// @desc    Adjust inventory stock level (Admin)
// @route   POST /api/inventory/adjust
// @access  Private/Admin
const adjustStock = async (req, res, next) => {
  try {
    const { productId, newStock, reason, changeType = 'Manual Adjustment' } = req.body;

    const product = await Product.findById(productId);
    if (!product) {
      return errorResponse(res, 'Product not found', [], 404);
    }

    const previousStock = product.stock;
    const quantityChanged = Number(newStock) - previousStock;

    product.stock = Number(newStock);
    await product.save();

    // Log history
    const history = await InventoryHistory.create({
      product: product._id,
      sku: product.sku,
      changeType,
      quantityChanged,
      previousStock,
      newStock: product.stock,
      reason: reason || 'Manual admin inventory adjustment',
      performedBy: req.user._id
    });

    return successResponse(res, 'Stock adjusted successfully', { product, history });
  } catch (error) {
    next(error);
  }
};

// @desc    Get complete inventory change audit log (Admin)
// @route   GET /api/inventory/history
// @access  Private/Admin
const getInventoryHistory = async (req, res, next) => {
  try {
    const history = await InventoryHistory.find({})
      .populate('product', 'name images')
      .populate('performedBy', 'name email')
      .sort({ createdAt: -1 })
      .limit(100);

    return successResponse(res, 'Inventory history audit log retrieved', history);
  } catch (error) {
    next(error);
  }
};

module.exports = { getStockOverview, adjustStock, getInventoryHistory };