<?php

namespace App\Services;

use App\Models\Venue;
use Illuminate\Support\Collection;

class RealtimeCrowdService
{
    /**
     * 第三方实时客流占位实现：
     * - 目前使用可复现的模拟数；
     * - 后续对接第三方接口时，只需替换本类方法。
     *
     * @param Collection<int, int> $venueIds
     * @return array{city_total: int, top_venues: array<int, array{venue_id:int, venue_name:string, current_count:int}>}
     */
    public function citySummary(Collection $venueIds): array
    {
        $ids = $venueIds->map(fn ($id) => (int) $id)->filter()->unique()->values();
        if ($ids->isEmpty()) {
            return ['city_total' => 0, 'top_venues' => []];
        }

        $map = $this->venueCurrentMap($ids);
        $top = collect($map)
            ->sortByDesc('current_count')
            ->take(3)
            ->values()
            ->all();
        $cityTotal = collect($map)->sum('current_count');

        return [
            'city_total' => (int) $cityTotal,
            'top_venues' => $top,
        ];
    }

    /**
     * @param Collection<int, int> $venueIds
     * @return array<int, array{venue_id:int, venue_name:string, current_count:int}>
     */
    public function venueCurrentMap(Collection $venueIds): array
    {
        $ids = $venueIds->map(fn ($id) => (int) $id)->filter()->unique()->values();
        if ($ids->isEmpty()) {
            return [];
        }

        $venues = Venue::query()->whereIn('id', $ids)->get(['id', 'name']);
        $seed = (int) now()->format('YmdHi'); // 分钟级动态变化

        return $venues->map(function (Venue $venue) use ($seed) {
            $base = abs(crc32((string) ($venue->id * 131 + $seed)));
            $current = 20 + ($base % 380); // 20~399
            return [
                'venue_id' => (int) $venue->id,
                'venue_name' => (string) $venue->name,
                'current_count' => (int) $current,
            ];
        })->values()->all();
    }
}