<?php

namespace App\Service\business;

/**
 * 套餐报价与补差价
 *
 * 后台存倍率=1 的基准分；小程序展示/下单再乘用户倍率。
 * 清单应付用「套餐价 + 当前明细合计 − 原价快照」，删行、换规格、加散件都落在这一条公式里。
 */
class PackageQuoteService
{
    private static mixed $_instance;

    public static function getInstance(): null|static
    {
        $name = get_called_class();
        if (!isset(self::$_instance[$name])) {
            self::$_instance[$name] = new static();
        }
        return self::$_instance[$name];
    }

    /**
     * 后台改搭配：原价变了就把差额补到套餐报价上，不允许报负价
     */
    public function applyOriginalDiff(int $oldOriginal, int $newOriginal, int $packageAmount): int
    {
        return max(0, $packageAmount + ($newOriginal - $oldOriginal));
    }

    /**
     * 基准价乘用户倍率，仍回整数分
     */
    public function applyMultiplier(int $cents, mixed $multiplier = 1): int
    {
        if ($cents <= 0) {
            return 0;
        }
        $price = PriceService::getInstance();
        $yuan = $price->centsToYuan($cents);
        return $price->yuanToCents($yuan, $multiplier);
    }

    /**
     * 套餐清单应付
     *
     * 未绑套餐：应付 = 当前明细合计。
     * 已绑套餐：应付 = 套餐价快照 + 当前合计 − 原价快照（删除的套餐行会从原价里扣掉）。
     *
     * @param array<int, array{unit_price?:int,quantity?:int}> $items
     * @return array{package_amount:int,original_amount:int,diff_amount:int,payable_amount:int,items_amount:int}
     */
    public function listPayable(int $packageId, int $packageAmount, int $originalAmount, array $items): array
    {
        $itemsAmount = 0;
        foreach ($items as $item) {
            $qty = max(1, (int) ($item['quantity'] ?? 1));
            $itemsAmount += (int) ($item['unit_price'] ?? 0) * $qty;
        }
        if ($packageId <= 0) {
            return [
                'package_amount' => 0,
                'original_amount' => $itemsAmount,
                'diff_amount' => 0,
                'payable_amount' => $itemsAmount,
                'items_amount' => $itemsAmount,
            ];
        }
        $payable = max(0, $packageAmount + $itemsAmount - $originalAmount);
        return [
            'package_amount' => $packageAmount,
            'original_amount' => $originalAmount,
            'diff_amount' => $payable - $packageAmount,
            'payable_amount' => $payable,
            'items_amount' => $itemsAmount,
        ];
    }

    /**
     * 给金额数组补 *_text 元字段，方便前端直接渲染
     *
     * @param array<string, int> $amounts
     * @return array<string, int|string>
     */
    public function withText(array $amounts, bool $showPrice = true): array
    {
        $price = PriceService::getInstance();
        foreach (['package_amount', 'original_amount', 'diff_amount', 'payable_amount', 'items_amount', 'discount_amount'] as $key) {
            if (!array_key_exists($key, $amounts)) {
                continue;
            }
            $cents = (int) $amounts[$key];
            $amounts[$key . '_text'] = $showPrice ? $price->centsToYuan($cents) : PriceService::MASK;
        }
        return $amounts;
    }
}