<?php
namespace App\Services;

use App\Models\Stock;
use App\Models\StockLog;
use Illuminate\Support\Facades\DB;

class StockService
{
    /**
     * 锁定库存（审核订单时调用）
     */
    public function lock($skuCode, $warehouseId, $quantity, $orderId)
    {
        if ($quantity <= 0) {
            throw new \InvalidArgumentException('占用数量必须为正数');
        }

        return DB::transaction(function () use ($skuCode, $warehouseId, $quantity, $orderId) {
            $stock = $this->getStock($skuCode, $warehouseId);
            $available = $this->getAvailableQuantity($stock);
            if ($available < $quantity) {
                throw new \Exception("商品 {$skuCode} 可用库存不足，当前可用{$available}，需占用{$quantity}");
            }

            $stock->increment('locked_quantity', $quantity);

            StockLog::create([
                'sku_code' => $skuCode,
                'warehouse_id' => $warehouseId,
                'change_quantity' => $quantity,
                'type' => 'lock',
                'order_id' => $orderId,
                'remark' => "锁定库存，订单ID {$orderId}",
            ]);

            return $stock;
        });
    }

    /**
     * 获取指定SKU在仓库的可用库存
     */
    public function checkStock($skuCode, $warehouseId)
    {
        $stock = Stock::where('sku_code', $skuCode)
            ->where('warehouse_id', $warehouseId)
            ->first();

        if (!$stock) {
            return 0; // 无记录表示库存为0
        }

        return $this->getAvailableQuantity($stock);
    }

    /**
     * 发货出库（扣减锁定库存）
     */
    public function ship($skuCode, $warehouseId, $quantity, $orderId, $trackingNo = null)
    {
        if ($quantity <= 0) {
            throw new \InvalidArgumentException('出库数量必须为正数');
        }

        return DB::transaction(function () use ($skuCode, $warehouseId, $quantity, $orderId, $trackingNo) {
            $stock = $this->getStock($skuCode, $warehouseId);

            // 检查锁定库存是否足够
            if ($stock->locked_quantity < $quantity) {
                throw new \Exception("商品 {$skuCode} 锁定库存不足，当前锁定{$stock->locked_quantity}，需出库{$quantity}");
            }

            // 扣减总库存和锁定库存
            $stock->decrement('quantity', $quantity);
            $stock->decrement('locked_quantity', $quantity);

            StockLog::create([
                'sku_code' => $skuCode,
                'warehouse_id' => $warehouseId,
                'change_quantity' => -$quantity,
                'type' => 'ship',
                'order_id' => $orderId,
                'remark' => "发货出库，订单ID {$orderId}，运单号 {$trackingNo}",
            ]);

            return $stock;
        });
    }

    /**
     * 获取或创建库存记录
     */
    protected function getStock($skuCode, $warehouseId)
    {
        return Stock::firstOrCreate(
            ['sku_code' => $skuCode, 'warehouse_id' => $warehouseId],
            [
                'quantity' => 0,
                'locked_quantity' => 0,
                'defective_quantity' => 0,
            ]
        );
    }

    /**
     * 计算可用库存
     */
    protected function getAvailableQuantity($stock)
    {
        return $stock->quantity - $stock->locked_quantity - $stock->defective_quantity;
    }
}