<?php

namespace App\Support\Readiness;

use App\Support\Settings;
use Illuminate\Support\Carbon;

/**
 * Whether anything is actually running this installation, right now — as
 * opposed to every other group in this file, which asks whether it is
 * CONFIGURED to run at all.
 *
 * Queue-driven delivery has no error path for "nobody is picking up the
 * queue": a paid order just sits there, forever, with nothing in the console
 * to tell an operator apart from a quiet afternoon. Two heartbeats because the
 * scheduler and the provisioning worker fail independently — the dangerous
 * case is the scheduler running and enqueueing jobs that nobody executes, and
 * a single heartbeat written by the scheduler alone would call that healthy.
 */
final class OperationChecks
{
    public const GROUP = 'operation';

    /**
     * A heartbeat older than this is as good as none: the process that was
     * writing it has gone quiet. Five minutes is generous slack against a
     * `->everyMinute()` schedule — a deploy restarting the container, a GC
     * pause, one skipped tick — without also covering up a worker that has
     * actually stopped.
     */
    private const STALE_AFTER_MINUTES = 5;

    /** @return array<int, Check> */
    public static function all(): array
    {
        return [
            new Check(
                key: 'operation.scheduler',
                group: self::GROUP,
                severity: Check::SEVERITY_BLOCKING,
                label: __('readiness.operation.scheduler'),
                breaks: __('readiness.operation.scheduler_breaks'),
                tab: 'integrations',
                satisfied: self::isFresh('heartbeat.scheduler'),
            ),
            new Check(
                key: 'operation.queue_provisioning',
                group: self::GROUP,
                severity: Check::SEVERITY_BLOCKING,
                label: __('readiness.operation.queue_provisioning'),
                breaks: __('readiness.operation.queue_provisioning_breaks'),
                tab: 'integrations',
                // Written by RecordProvisioningHeartbeat, which the scheduler
                // enqueues but only the worker actually runs. A fresh
                // timestamp here is proof of a running worker, not just of a
                // running scheduler.
                satisfied: self::isFresh('heartbeat.queue_provisioning'),
            ),
        ];
    }

    private static function isFresh(string $key): bool
    {
        $recordedAt = Settings::get($key);

        if (blank($recordedAt)) {
            return false;
        }

        // Not diffInMinutes(): App\Models\Incident::durationMinutes() already
        // documents that it is SIGNED, and `now()->diffInMinutes($recordedAt)`
        // with $recordedAt in the past returns a NEGATIVE number — which
        // would compare as "less than 5" for a heartbeat six hours stale, and
        // report a dead worker as healthy. A direct threshold comparison has
        // no sign to get backwards.
        return Carbon::parse($recordedAt)->greaterThan(now()->subMinutes(self::STALE_AFTER_MINUTES));
    }
}