<?php

namespace App\Services;

use App\Models\ActivityReward;
use App\Models\ActivityRewardRecipient;
use Illuminate\Support\Facades\DB;

class ActivityQuotaService
{
    /** A preliminary check; award() always checks again under the activity lock. */
    public static function canAward(ActivityReward $activity, $memberId): bool
    {
        if ((int)$activity->type === 2) return true;
        if (!$activity->quota_enabled) {
            return $activity->budget === null || bccomp((string)($activity->budget_used ?? '0'), (string)$activity->budget, 2) < 0;
        }
        $member = static::memberKey($memberId);
        if ($member === null) return false;
        if (static::hasReceived($activity->id, $member)) return true;
        return $activity->reward_quota === null || (int)$activity->rewarded_count < (int)$activity->reward_quota;
    }

    /** Count a member only on their first successful positive reward for this activity. */
    public static function award(ActivityReward $activity, $memberId, $amount, callable $grant): bool
    {
        $member = static::memberKey($memberId);
        if ($member === null || !is_numeric($amount)
            || !preg_match('/^\d{1,12}(\.\d{1,2})?$/', (string)$amount)
            || bccomp((string)$amount, '0', 2) <= 0) {
            return false;
        }
        return DB::transaction(function () use ($activity, $member, $amount, $grant) {
            $locked = ActivityReward::where('id', $activity->id)->lockForUpdate()->first();
            if (!$locked) return false;
            if ((int)$locked->type === 2) {
                $grant();
                return true;
            }
            if (!$locked->quota_enabled) return ActivityBudgetService::award($locked, $amount, $grant);
            // Match the locked counter with a current read, even inside an older caller snapshot.
            $received = static::hasReceived($locked->id, $member, true);
            if (!$received && $locked->reward_quota !== null
                && (int)$locked->rewarded_count >= (int)$locked->reward_quota) {
                return false;
            }
            $grant();
            if (!$received) {
                ActivityRewardRecipient::create([
                    'activity_id' => $locked->id,
                    'member_id' => $member,
                    'created_at' => date('Y-m-d H:i:s'),
                ]);
                $locked->rewarded_count = (int)$locked->rewarded_count + 1;
                $locked->save();
            }
            return true;
        });
    }

    private static function hasReceived($activityId, string $memberId, bool $currentRead = false): bool
    {
        $query = ActivityRewardRecipient::where('activity_id', $activityId)->where('member_id', $memberId);
        return $currentRead ? $query->lockForUpdate()->first() !== null : $query->exists();
    }

    private static function memberKey($memberId): ?string
    {
        if (!is_int($memberId) && !is_string($memberId)) return null;
        $member = trim((string)$memberId);
        return $member === '' || $member === '0' || strlen($member) > 64 ? null : $member;
    }
}