From 087b4a128ed3b60dbec0f6008896c0ccefc3b942 Mon Sep 17 00:00:00 2001
From: Joshua Ramon Enslin <joshua@museum-digital.de>
Date: Wed, 30 Sep 2020 00:58:58 +0200
Subject: [PATCH] Add validation function for ISBN

---
 MD_STD_IN.php | 52 +++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 44 insertions(+), 8 deletions(-)

diff --git a/MD_STD_IN.php b/MD_STD_IN.php
index 6dd6b20..b3dc315 100644
--- a/MD_STD_IN.php
+++ b/MD_STD_IN.php
@@ -18,7 +18,7 @@ final class MD_STD_IN {
      *
      * @return integer
      */
-    final public static function sanitize_id($input):int {
+    public static function sanitize_id($input):int {
 
         $input = \filter_var($input, \FILTER_VALIDATE_INT, [
                 'options' => [
@@ -43,7 +43,7 @@ final class MD_STD_IN {
      *
      * @return integer
      */
-    final public static function sanitize_id_or_zero($input):int {
+    public static function sanitize_id_or_zero($input):int {
 
         if ($input === "") return 0;
 
@@ -71,7 +71,7 @@ final class MD_STD_IN {
      *
      * @return string
      */
-    final public static function sanitize_text($input):string {
+    public static function sanitize_text($input):string {
 
         $output = \filter_var($input,
             FILTER_SANITIZE_STRING,
@@ -96,7 +96,7 @@ final class MD_STD_IN {
      *
      * @return string
      */
-    final public static function get_http_input_text(string $var_name, string $default = "", array $allowed = []):string {
+    public static function get_http_input_text(string $var_name, string $default = "", array $allowed = []):string {
 
         if (isset($_GET[$var_name])) {
             $output = self::sanitize_text($_GET[$var_name]);
@@ -124,7 +124,7 @@ final class MD_STD_IN {
      *
      * @return string
      */
-    final public static function get_http_post_text(string $var_name, string $default = "", array $allowed = []):string {
+    public static function get_http_post_text(string $var_name, string $default = "", array $allowed = []):string {
 
         if (isset($_POST[$var_name])) {
             $output = self::sanitize_text($_POST[$var_name]);
@@ -146,7 +146,7 @@ final class MD_STD_IN {
      *
      * @return string
      */
-    final public static function sanitize_url($input):string {
+    public static function sanitize_url($input):string {
 
         if ($input === "") return "";
 
@@ -166,7 +166,7 @@ final class MD_STD_IN {
      *
      * @return string
      */
-    final public static function sanitize_email($input):string {
+    public static function sanitize_email($input):string {
 
         if ($input === "") return "";
 
@@ -186,7 +186,7 @@ final class MD_STD_IN {
      *
      * @return float
      */
-    final public static function sanitize_float(string $input):float {
+    public static function sanitize_float(string $input):float {
 
         $output = \str_replace(",", ".", $input);
         if (($output = \filter_var($output, FILTER_VALIDATE_FLOAT)) === false) {
@@ -196,4 +196,40 @@ final class MD_STD_IN {
 
     }
 
+    /**
+     * Validates ISBNs. Empty strings are accepted as well.
+     *
+     * @param string $input Input string.
+     *
+     * @return string
+     */
+    public static function validate_isbn(string $input):string {
+
+        if ($input === "") return "";
+
+        // Remove hyphens
+        $input = trim(strtr($input, ["-" => "", "–" => ""]));
+
+        // ISBN 10
+        if (\mb_strlen($input) === 10) {
+
+            if (\preg_match('/\d{9}[0-9xX]/i', $input)) {
+                return $input;
+            }
+
+        }
+
+        // ISBN 13
+        if (\mb_strlen($input) === 10) {
+
+            if (\preg_match('/\d{13}/i', $input)) {
+                return $input;
+            }
+
+        }
+
+        throw new MDgenericInvalidInputsException("ISBNs must be either 10 or 13 characters long.");
+
+    }
+
 }