<?php

/**
 * TicketReferenceService.php
 *
 * Generates collision-resistant Helpdesk ticket references.
 */

declare(strict_types=1);

namespace Modules\Helpdesk\Services;

use Illuminate\Support\Facades\DB;
use Modules\Helpdesk\Models\Ticket;

final class TicketReferenceService
{
    /**
     * Build the next human-readable ticket reference for the current year.
     *
     * The lookup uses the highest numeric suffix, not the latest database id,
     * because imported, restored, or manually adjusted tickets may not be in
     * reference order. On PostgreSQL an advisory transaction lock is also used
     * so two users cannot generate the same reference at the same time.
     */
    public function next(): string
    {
        $year = now()->format('Y');
        $prefix = 'HD-'.$year.'-';

        $this->lockReferenceSeries($prefix);

        $lastReference = Ticket::query()
            ->where('reference', 'like', $prefix.'%')
            ->orderByDesc('reference')
            ->value('reference');

        $next = $lastReference === null
            ? 1
            : ((int) substr((string) $lastReference, -5)) + 1;

        return $prefix.str_pad((string) $next, 5, '0', STR_PAD_LEFT);
    }

    /**
     * Lock the current ticket reference series for the active transaction.
     */
    private function lockReferenceSeries(string $prefix): void
    {
        if (DB::connection()->getDriverName() !== 'pgsql') {
            return;
        }

        DB::select('select pg_advisory_xact_lock(hashtext(?))', [
            'helpdesk-ticket-reference:'.$prefix,
        ]);
    }
}