<?php

declare(strict_types=1);

namespace app\common\service\qywx;

use InvalidArgumentException;

/** 获客方案成员的加权随机选择；数据库锁与持久化由调度服务负责。 */
class QywxPromotionWeightedRandom
{
    /**
     * @param list<array<string,mixed>> $members
     * @param int|null $draw 测试用固定抽签值；生产环境留空并使用 random_int。
     * @return array{selected_id:int,members:list<array<string,mixed>>,eligible_count:int,total_weight:int}
     */
    public static function select(array $members, string $today, int $now, ?int $draw = null): array
    {
        $eligibleIndexes = [];
        $totalWeight = 0;
        foreach ($members as $index => &$member) {
            if ((string) ($member['today_date'] ?? '') !== $today) {
                $member['today_date'] = $today;
                $member['today_count'] = 0;
            }
            // current_weight 是旧版平滑轮询游标；随机模式不再使用，统一归零。
            $member['current_weight'] = 0;
            if (!self::eligible($member, $now)) {
                continue;
            }
            $weight = max(1, (int) ($member['weight'] ?? 1));
            $eligibleIndexes[] = ['index' => $index, 'weight' => $weight];
            $totalWeight += $weight;
        }
        unset($member);

        if ($eligibleIndexes === []) {
            return [
                'selected_id' => 0,
                'members' => array_values($members),
                'eligible_count' => 0,
                'total_weight' => 0,
            ];
        }

        $ticket = $draw ?? random_int(1, $totalWeight);
        if ($ticket < 1 || $ticket > $totalWeight) {
            throw new InvalidArgumentException('加权随机抽签值超出有效范围');
        }
        $cursor = 0;
        $selectedIndex = (int) $eligibleIndexes[0]['index'];
        foreach ($eligibleIndexes as $candidate) {
            $cursor += (int) $candidate['weight'];
            if ($ticket <= $cursor) {
                $selectedIndex = (int) $candidate['index'];
                break;
            }
        }

        return [
            'selected_id' => (int) ($members[$selectedIndex]['id'] ?? 0),
            'members' => array_values($members),
            'eligible_count' => count($eligibleIndexes),
            'total_weight' => $totalWeight,
        ];
    }

    /** @param array<string,mixed> $member */
    public static function eligible(array $member, int $now): bool
    {
        if ((int) ($member['enabled'] ?? 0) !== 1 || (int) ($member['weight'] ?? 0) <= 0) {
            return false;
        }
        $start = max(0, (int) ($member['active_start'] ?? 0));
        $end = max(0, (int) ($member['active_end'] ?? 0));
        if (($start > 0 && $start > $now) || ($end > 0 && $end < $now)) {
            return false;
        }
        $limit = max(0, (int) ($member['daily_limit'] ?? 0));

        return $limit === 0 || (int) ($member['today_count'] ?? 0) < $limit;
    }
}