<?php

namespace App\Services;

use App\Enums\DrawLogStatus;
use App\Enums\DrawPrizeType;
use App\Exceptions\BizException;
use App\Models\DrawActivity;
use App\Models\DrawActivityPrize;
use App\Models\DrawLog;
use App\Models\User;
use Illuminate\Support\Facades\DB;

class DrawActivityService
{
    /**
     * 活动抽奖
     *
     * @param \App\Models\DrawActivity $drawActivity
     * @param \App\Models\User $user
     * @return \App\Models\DrawLog
     */
    public function draw(DrawActivity $drawActivity, User $user): DrawLog
    {
        if (! $drawActivity->isPublished()) {
            throw new BizException('抽奖活动未发布');
        }

        if ($drawActivity->isUnstart()) {
            throw new BizException('抽奖活动未开始');
        }

        if ($drawActivity->isClosed()) {
            throw new BizException('抽奖活动已结束');
        }

        (new DrawTicketService())->change($user, $drawActivity, -1, '活动抽奖');

        $prize = $this->getDrawActivityPrize($drawActivity);

        // 如果限制了奖品数量，则需扣除奖品库存
        if ($prize->limited) {
            $prize->update([
                'stock' => DB::raw('stock-1'),
                'winnings' => DB::raw('winnings+1'),
            ]);
        } else {
            $prize->increment('winnings', 1);
        }

        $drawLog = DrawLog::create([
            'user_id' => $user->id,
            'draw_activity_id' => $drawActivity->id,
            'draw_activity_prize_id' => $prize->id,
            'status' => match ($prize->type) {
                DrawPrizeType::None => DrawLogStatus::Completed,
                default => DrawLogStatus::Pending,
            },
        ]);

        return $drawLog->setRelation('prize', $prize);
    }

    /**
     * @param \App\Models\DrawActivity $drawActivity
     * @return \App\Models\DrawActivityPrize
     */
    protected function getDrawActivityPrize(DrawActivity $drawActivity): DrawActivityPrize
    {
        $drawActivityPrizes = $drawActivity->prizes()->get();

        // 过滤权重为0或库存不足的奖品
        $prizes = $drawActivityPrizes->filter(function ($item) {
            if ($item->weight === 0 || ($item->limited && $item->stock === 0)) {
                return false;
            }

            return true;
        });

        $max = $prizes->sum('weight');

        if ($max > 0) {
            $rand = mt_rand($min = 1, $max);

            foreach ($prizes as $prize) {
                if ($rand <= $prize->weight + $min) {
                    return $prize;
                }

                $min += $prize->weight;
            }
        }

        throw new BizException('抽奖活动异常');
    }
}