<?php

namespace MingTsay\Akanyan;

abstract class FileViewer
{
    protected static bool $orderDesc = false;

    protected abstract static function directory(): string;

    protected abstract static function whitelist(): ?array;

    public static function list(): array
    {
        $directory = static::directory();
        $whitelist = static::whitelist();

        $list = array_values(array_filter(
            scandir($directory),
            fn($file) => ($whitelist === null || in_array($file, $whitelist)) && is_file("$directory/$file")
        ));

        if (static::$orderDesc) rsort($list);
        return $list;
    }

    public static function read($file): ?string
    {
        $directory = static::directory();
        $filename = "$directory/$file";

        if (!in_array($file, static::list()) || !file_exists($filename) || !is_file($filename)) return null;

        $extension = pathinfo($filename, PATHINFO_EXTENSION);
        $content = file_get_contents($filename);
        return $extension === 'gz' ? gzdecode($content) : $content;
    }
}