<?php

namespace App\Services\Maintenance;

use App\Mail\MaintenanceAnnouncementMail;
use App\Mail\MaintenanceCancelledMail;
use App\Models\Customer;
use App\Models\MaintenanceNotification;
use App\Models\MaintenanceWindow;
use Illuminate\Mail\Mailable;
use Illuminate\Support\Facades\Mail;

/**
 * Ledger-guarded delivery of maintenance emails. Shared by the admin console and
 * the mail-event listeners so idempotency and the announcement/cancellation
 * pairing are enforced in exactly one place.
 */
class MaintenanceNotifier
{
    /** A pending notification is presumed failed (retryable) after this long. */
    public const RETRY_AFTER_MIN = 60;

    public function announce(MaintenanceWindow $window): void
    {
        foreach ($window->affectedCustomers() as $customer) {
            $this->deliver($window, $customer, 'announcement', new MaintenanceAnnouncementMail($window, $customer));
        }
    }

    /** Notify customers who actually received the announcement that it's cancelled. */
    public function notifyCancellation(MaintenanceWindow $window): void
    {
        $ids = MaintenanceNotification::query()
            ->where('maintenance_window_id', $window->id)
            ->where('event', 'announcement')
            ->whereNotNull('sent_at')
            ->pluck('customer_id');

        foreach (Customer::query()->whereIn('id', $ids)->get() as $customer) {
            $this->deliver($window, $customer, 'cancelled', new MaintenanceCancelledMail($window, $customer));
        }
    }

    /** Queue one mail per (window, customer, event), idempotently and retryably. */
    public function deliver(MaintenanceWindow $window, Customer $customer, string $event, Mailable $mail): void
    {
        $delivery = MaintenanceNotification::query()->firstOrCreate(
            ['maintenance_window_id' => $window->id, 'customer_id' => $customer->id, 'event' => $event],
            ['email' => $customer->email],
        );

        if ($delivery->sent_at !== null) {
            return; // already delivered — final
        }
        if (! $delivery->wasRecentlyCreated && $delivery->updated_at->gt(now()->subMinutes(self::RETRY_AFTER_MIN))) {
            return; // still pending/in-flight — don't duplicate
        }

        $wasNew = $delivery->wasRecentlyCreated;
        $priorUpdatedAt = $delivery->updated_at;
        $delivery->forceFill(['updated_at' => now()])->save();
        $mail->notificationId = $delivery->id;

        try {
            Mail::to($customer->email)
                ->locale($customer->locale ?: config('app.locale'))
                ->queue($mail);
        } catch (\Throwable $e) {
            $wasNew ? $delivery->delete() : $delivery->forceFill(['updated_at' => $priorUpdatedAt])->save();

            throw $e;
        }
    }
}