<?php
namespace app\api\library\mlbb;

/**
 * 抽奖服务
 * 规则：
 * 1. 总共12次抽奖机会；四个礼包+5个代金卷，共9个奖品；
 * 2. 前四次抽奖，必定包含3个不同的礼包和1个代金卷；
 * 3. 礼包在12次抽奖中不可重复获得；
 * 4. 抽奖概率：1元代金卷12%，其他所有奖品（包括礼包和其他代金卷）均为11%。
 */
class LotteryService
{
    /** @var array 原始奖品池 */
    private $prizePool = [];

    public function __construct(array $prizePool)
    {
        $this->prizePool = $prizePool;
    }

    /**
     * 单次抽奖
     * @param array $userHistory 用户已抽奖历史
     * @return array 中奖奖品
     */
    public function draw(array $userHistory): array
    {
        $drawCount = count($userHistory) + 1; // 当前是第几抽
        $pool = $this->preparePool($userHistory, $drawCount);

        $result = $this->weightedDraw($pool);

        return $result;
    }

    /**
     * 根据历史和规则准备奖品池
     */
    private function preparePool(array $userHistory, int $drawCount): array
    {
        $pool = [];

        // 已中过礼包
        $gotPacks = array_column(
            array_filter($userHistory, function ($h) {
                return $h['prize_type'] == 1;
            }),
            'prize_mark'
        );

        foreach ($this->prizePool as $item) {
            // 礼包已中过，权重清零
            if ($item['type'] === 'pack' && in_array($item['prize_mark'], $gotPacks)) {
                $item['weight'] = 0;
            }
            $pool[$item['prize_mark']] = $item;
        }

        // 规则：前 4 抽
        if ($drawCount <= 4) {
            $packCount = count(array_filter($userHistory, function ($h) {
                return $h['prize_type'] == 1;
            }));
            $couponCount = count(array_filter($userHistory, function ($h) {
                return $h['prize_type'] == 2;
            }));

            // 前 3 次必须保证能抽到礼包
            if ($packCount < 3 && $drawCount <= 4) {
                // 仅保留礼包
                $pool = array_filter($pool, function ($p) {
                    return $p['type'] === 'pack' && $p['weight'] > 0;
                });
            }
            // 第 4 次必须保证出代金券
            if ($drawCount == 4 && $couponCount < 1) {
                $pool = array_filter($pool, function ($p) {
                    return $p['type'] === 'coupon' && $p['weight'] > 0;
                });
            }
        }

        return $pool;
    }

    /**
     * 加权随机抽取
     */
    private function weightedDraw(array $pool): array
    {
        $total = array_sum(array_column($pool, 'weight'));
        if ($total <= 0) {
            throw new \Exception("奖品池权重总和为 0，无法抽取");
        }

        $r = mt_rand() / mt_getrandmax() * $total;
        $acc = 0.0;
        foreach ($pool as $item) {
            if ($item['weight'] <= 0) continue;
            $acc += $item['weight'];
            if ($r <= $acc) {
                return $item;
            }
        }
        // 兜底
        foreach (array_reverse($pool, true) as $item) {
            if ($item['weight'] > 0) return $item;
        }
        throw new \Exception("未能选出奖品");
    }
}


// // 奖品池（使用整数权重）
// $prizePool = [
//     ['prize_mark' => 1, 'prize_name' => '殿堂礼包',   'type' => 'pack',   'weight' => 11],
//     ['prize_mark' => 2, 'prize_name' => '勇者晋级礼包', 'type' => 'pack',   'weight' => 11],
//     ['prize_mark' => 3, 'prize_name' => '勇者冒险礼包', 'type' => 'pack',   'weight' => 11],
//     ['prize_mark' => 4, 'prize_name' => '勇者荣耀礼包', 'type' => 'pack',   'weight' => 11],
//     ['prize_mark' => 5, 'prize_name' => '1元代金券',  'type' => 'coupon', 'weight' => 12],
//     ['prize_mark' => 6, 'prize_name' => '25元代金券', 'type' => 'coupon', 'weight' => 11],
//     ['prize_mark' => 7, 'prize_name' => '40元代金券', 'type' => 'coupon', 'weight' => 11],
//     ['prize_mark' => 8, 'prize_name' => '65元代金券', 'type' => 'coupon', 'weight' => 11],
//     ['prize_mark' => 9, 'prize_name' => '100元代金券','type' => 'coupon', 'weight' => 11],
// ];
//
// $lottery = new LotteryService($prizePool);
//
// $totalRounds = 10000; // 模拟 1 万轮
// $counts = [];
//
// for ($round = 0; $round < $totalRounds; $round++) {
//     $userHistory = [];
//
//     // 每轮 12 抽
//     for ($i = 0; $i < 12; $i++) {
//         $result = $lottery->draw($userHistory);
//         $mark = $result['prize_mark'];
//
//         if (!isset($counts[$mark])) {
//             $counts[$mark] = 0;
//         }
//         $counts[$mark]++;
//
//         // 记录历史
//         $userHistory[] = [
//             'prize_mark' => $mark,
//             'prize_type' => $result['type'] === 'pack' ? 1 : 2,
//         ];
//     }
// }
//
// // 输出统计结果
// $totalDraws = $totalRounds * 12;
// echo "=== 模拟 {$totalRounds} 轮（共 {$totalDraws} 次抽奖）结果 ===\n";
// foreach ($prizePool as $p) {
//     $mark = $p['prize_mark'];
//     $count = $counts[$mark] ?? 0;
//     $ratio = $count / $totalDraws * 100;
//     echo "{$p['prize_name']} : {$count} 次, 占比 " . number_format($ratio, 2) . "%\n";
// }