<?php
/**
 * Small, defensive helpers for reading ZIP archives.
 *
 * @package shouldcheck
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Archive helpers. Nothing here extracts files to disk.
 */
final class ShouldCheck_Zip {

	/**
	 * Whether an archive entry name is safe to read and report on.
	 *
	 * Rejects NUL bytes, backslashes, absolute paths, drive letters and "..", segments.
	 *
	 * @param string $name Entry name as stored in the archive.
	 * @return bool
	 */
	public static function is_safe_name( $name ) {
		if ( ! is_string( $name ) || '' === $name ) {
			return false;
		}
		if ( false !== strpos( $name, chr( 0 ) ) || false !== strpos( $name, chr( 92 ) ) ) {
			return false;
		}
		return 1 !== preg_match( '~(^/|(^|/)\.\.(/|$)|^[A-Za-z]:)~', $name );
	}

	/**
	 * Open an archive read-only.
	 *
	 * @param string $path Absolute file path.
	 * @return ZipArchive|WP_Error|string ZipArchive on success, otherwise an error code string.
	 */
	public static function open( $path ) {
		if ( ! class_exists( 'ZipArchive' ) ) {
			return 'zip_extension_missing';
		}
		if ( ! is_string( $path ) || '' === $path || ! is_file( $path ) ) {
			return 'file_missing';
		}
		$zip = new ZipArchive();
		if ( true !== $zip->open( $path ) ) {
			return 'zip_unreadable';
		}
		return $zip;
	}

	/**
	 * Human text for an error code returned by open().
	 *
	 * @param string $code Error code.
	 * @return string
	 */
	public static function error_message( $code ) {
		switch ( $code ) {
			case 'zip_extension_missing':
				return 'The PHP ZipArchive extension is unavailable.';
			case 'file_missing':
				return 'No plugin ZIP was uploaded.';
			default:
				return 'Cannot open the selected ZIP.';
		}
	}
}