<?php

namespace App\Delivery;

use App\Channels\ChannelRegistry;
use App\Enums\DeliveryResult;
use App\Enums\EventState;
use App\Enums\Presence;
use App\Models\Channel;
use App\Models\Delivery;
use App\Models\Event;
use App\Models\User;
use App\Scheduling\DueResolver;
use App\Scheduling\StateResolver;
use App\Scheduling\Window;
use App\Scheduling\WindowResolver;
use Illuminate\Contracts\Cache\Repository as Cache;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Str;

/**
 * Один тик планировщика (раз в минуту): переходы состояний по датам и решение,
 * доставлять ли напоминание в открытое окно и куда.
 */
final class Tick
{
    public function __construct(
        private readonly DueResolver $due,
        private readonly StateResolver $states,
        private readonly WindowResolver $windows,
        private readonly ChannelRegistry $registry,
        private readonly Cache $cache,
        private readonly int $presenceTtl,
    ) {}

    public function run(): void
    {
        Event::query()
            ->whereIn('state', EventState::nonTerminalValues())
            ->with('user')
            ->chunkById(200, fn (Collection $events) => $events->each(fn (Event $e) => $this->process($e)));
    }

    private function process(Event $event): void
    {
        $user = $event->user;
        $now = $user->now();

        $state = $this->states->resolve($event, $user, $now);
        if ($state !== $event->state) {
            $event->state = $state;
            $event->save();
        }
        if (! $state->isActive() || $now->lt($event->quiet_until)) {
            return;
        }

        $window = $this->windows->current($state, $user, $this->due->resolve($event, $user), $now);
        if ($window === null) {
            return;
        }
        if (Delivery::where('event_id', $event->id)->where('window_start', $window->start->utc())->exists()) {
            return;
        }

        $channels = $user->channels()->where('enabled', true)->get();
        if ($channels->isEmpty()) {
            return;
        }

        $present = $channels->filter(fn (Channel $c) => $this->presence($c, $user) === Presence::Present);
        if ($present->isNotEmpty()) {
            $this->dispatch($event, $present, $window);

            return;
        }
        if ($window->fallbackAllowed && $now->gte($window->fallbackAt)) {
            $this->dispatch($event, $channels, $window);
        }
    }

    private function presence(Channel $channel, User $user): Presence
    {
        return $this->cache->remember(
            "presence:{$channel->id}",
            $this->presenceTtl,
            fn () => $this->registry->for($channel->type)->presence($user, $channel->config),
        );
    }

    /** Строка pending — в транзакции ДО постановки job-а: следующий тик её уже видит. */
    private function dispatch(Event $event, Collection $channels, Window $window): void
    {
        DB::transaction(function () use ($event, $channels, $window) {
            foreach ($channels as $channel) {
                $delivery = Delivery::create([
                    'event_id' => $event->id,
                    'channel_id' => $channel->id,
                    'window_start' => $window->start->utc(),
                    'action_token' => Str::random(48),
                    'result' => DeliveryResult::Pending,
                ]);
                DeliverJob::dispatch($delivery->id)->afterCommit();
            }
        });
    }
}