Move Encoding class away from the Language namespace

Language\Encoding::__mbMimeEncode -> Convert\MimeEncode::__mbMimeEncode
Langauge\Encoding::checkConvertEncoding -> Check\Encoding::checkConvertEncoding
Langauge\Encoding::setErrorChar -> Check\Encoding::setErrorChar
Langauge\Encoding::getErrorChar -> Encoding::getErrorChar
Langauge\Encoding::convertEncoding -> Convert\Encoding::convertEncoding

Also fixed encoding check that not only a code point but a string can
also be used as a parameter.

Update phpunit tests and split them out for each class

Normal test page is still combined for all classes but updated to
correctly use each class

www/lib/CoreLibs/Check/Encoding.php

@@ -0,0 +1,117 @@
+<?php
+
+/*
+ * check if string is valid in target encoding
+ */
+
+declare(strict_types=1);
+
+namespace CoreLibs\Check;
+
+class Encoding
+{
+	/** @var int<min, -1>|int<1, max>|string */
+	private static $mb_error_char = '';
+
+	/**
+	 * set error char
+	 *
+	 * @param  string|int|null $string The character to use to represent
+	 *                                 error chars
+	 *                                 "long" for long, "none" for none
+	 *                                 or a valid code point in int
+	 *                                 like 0x2234 (8756, ∴)
+	 *                                 default character is ? (63)
+	 *                                 if null is set then "none"
+	 * @return void
+	 */
+	public static function setErrorChar($string): void
+	{
+		if (empty($string)) {
+			$string = 'none';
+		}
+		// if not special string or char but code point
+		if (in_array($string, ['none', 'long', 'entity'])) {
+			self::$mb_error_char = $string;
+		} else {
+			// always convert to char for internal use
+			self::$mb_error_char = \IntlChar::chr($string);
+			// if string convert to code point
+			if (is_string($string)) {
+				$string = \IntlChar::ord($string);
+			}
+		}
+		mb_substitute_character($string);
+	}
+
+	/**
+	 * get the current set error character
+	 *
+	 * @param  bool $return_substitute_func if set to true return the set
+	 *                                      character from the php function
+	 *                                      directly
+	 * @return string|int Set error character
+	 */
+	public static function getErrorChar(bool $return_substitute_func = false)
+	{
+		// return mb_substitute_character();
+		if ($return_substitute_func === true) {
+			return mb_substitute_character();
+		} else {
+			return self::$mb_error_char;
+		}
+	}
+
+	/**
+	 * test if a string can be safely convert between encodings.
+	 * mostly utf8 to shift jis
+	 * the default compare has a possibility of failure, especially with windows
+	 * it is recommended to the following in the script which uses this method:
+	 * mb_substitute_character(0x2234);
+	 * $class->mb_error_char = '∴';
+	 * if check to Shift JIS
+	 * if check to ISO-2022-JP
+	 * if check to ISO-2022-JP-MS
+	 * set three dots (∴) as wrong character for correct convert error detect
+	 * (this char is used, because it is one of the least used ones)
+	 *
+	 * @param  string     $string        string to test
+	 * @param  string     $from_encoding encoding of string to test
+	 * @param  string     $to_encoding   target encoding
+	 * @return bool|array<string>        false if no error or
+	 *                                   array with failed characters
+	 */
+	public static function checkConvertEncoding(
+		string $string,
+		string $from_encoding,
+		string $to_encoding
+	) {
+		// convert to target encoding and convert back
+		$temp = mb_convert_encoding($string, $to_encoding, $from_encoding);
+		$compare = mb_convert_encoding($temp, $from_encoding, $to_encoding);
+		// if string does not match anymore we have a convert problem
+		if ($string != $compare) {
+			$failed = [];
+			// go through each character and find the ones that do not match
+			for ($i = 0, $iMax = mb_strlen($string, $from_encoding); $i < $iMax; $i++) {
+				$char = mb_substr($string, $i, 1, $from_encoding);
+				$r_char = mb_substr($compare, $i, 1, $from_encoding);
+				// the ord 194 is a hack to fix the IE7/IE8
+				// bug with line break and illegal character
+				if (
+					(($char != $r_char && (!self::$mb_error_char ||
+					in_array(self::$mb_error_char, ['none', 'long', 'entity']))) ||
+					($char != $r_char && $r_char == self::$mb_error_char && self::$mb_error_char)) &&
+					ord($char) != 194
+				) {
+					$failed[] = $char;
+				}
+			}
+			return $failed;
+		} else {
+			return false;
+		}
+	}
+}
+
+// __END__