sachgiaokhoaorg/app/Controllers/Thumb.php

<?php

declare(strict_types=1);

namespace App\Controllers;

use App\Libraries\BookApi;
use App\Libraries\CoverArt;

/**
 * Thumbnail endpoint: /thumb/{W}x{H}/{id}.jpg
 * Lazily generates art-directed thumbnails from the cached original cover.
 */
class Thumb extends BaseController
{
    private BookApi $api;

    public function __construct()
    {
        $this->api = new BookApi();
    }

    public function serve(string $size, string $file)
    {
        // parse size + id
        if (! preg_match('/^(\d{2,4})x(\d{2,4})$/', $size, $m)) {
            return $this->response->setStatusCode(400);
        }
        [, $w, $h] = $m;
        $id = preg_replace('/\.jpg$/', '', $file);
        if (! $id || ! preg_match('/^[a-zA-Z0-9._-]+$/', $id)) {
            return $this->response->setStatusCode(400);
        }

        $book = $this->api->book($id);
        if (! $book || ! $book['coverEndpoint']) {
            return $this->response->setStatusCode(404);
        }

        // ensure the original is cached locally (fetch on demand)
        $dir  = WRITEPATH . 'cache/covers';
        $orig = $dir . '/' . preg_replace('/[^a-zA-Z0-9_-]/', '_', $id) . '.jpg';
        if (! is_file($orig)) {
            $tmp = $orig . '.tmp' . getmypid();
            if ($this->api->fetchToFile($book['coverEndpoint'], $tmp)) {
                if (! is_dir($dir)) {
                    mkdir($dir, 0775, true);
                }
                rename($tmp, $orig);
            } else {
                @unlink($tmp);
            }
        }
        if (! is_file($orig)) {
            return $this->response->setStatusCode(404);
        }

        $thumb = CoverArt::thumb($id, $orig, $book, (int) $w, (int) $h);
        if (! $thumb || ! is_file($thumb)) {
            return $this->response->setStatusCode(404);
        }

        header('Content-Type: image/jpeg');
        header('Content-Length: ' . (string) filesize($thumb));
        header('Cache-Control: public, max-age=604800');
        readfile($thumb);
        exit;
    }
}