<?php
/**
 * ==============================================================================
 * File: internationalization_internal.lib.php
 * Main API extension library for Dokeos 1.8.7 LMS,
 * contains functions for internal use only.
 * License: GNU/GPL version 2 or later (Free Software Foundation)
 * @author Ivan Tcholakov, <ivantcholakov@gmail.com>, September 2009
 * @author More authors, mentioned in the correpsonding fragments of this source.
 * @package dokeos.library
 * ==============================================================================
 *
 * Note: All functions and data structures here are not to be used directly.
 * See the file internationalization.lib.php which contains the "public" API.
 */


/**
 * ----------------------------------------------------------------------------
 * Internal constants
 * ----------------------------------------------------------------------------
 */

// A regular expression for accessing declared encoding within xml-formatted text.
// Published by Steve Minutillo,
// http://minutillo.com/steve/weblog/2004/6/17/php-xml-and-character-encodings-a-tale-of-sadness-rage-and-data-loss/
define('_PCRE_XML_ENCODING', '/<?xml.*encoding=[\'"](.*?)[\'"].*?>/m');


/**
 * ----------------------------------------------------------------------------
 * Global variables used by some callback functions
 * ----------------------------------------------------------------------------
 */

$_api_encoding = null;
$_api_collator = null;


/**
 * ----------------------------------------------------------------------------
 * Appendix to "Language support"
 * ----------------------------------------------------------------------------
 */

/**
 * Upgrades the function get_lang() with the following logic:
 * 1. Checks whether the retrieved human language string is UTF-8 valid or not.
 * 2. If the system encoding is UTF-8 and the string is not UTF-8, the function
 * performs conversion from supposed non UTF-8 encodeng.
 * 3. If the system encoding is non UTF-8 but the string is valid UTF-8, then
 * conversion from UTF-8 is performed.
 * 4. At the end the string is purified from HTML entities.
 * @param string $string	This is the retrieved human language string.
 * @param string $language	A language identiticator.
 * @return string			Returns the human language string, checked for proper encoding and purified.
 */
function & _get_lang_purifier(& $string, & $language) {
	$system_encoding = api_get_system_encoding();
	if (api_is_utf8($system_encoding)) {
		if (!api_is_valid_utf8($string)) {
			$string = api_utf8_encode($string, api_get_non_utf8_encoding($language));
		}
	} else {
		if (api_is_valid_utf8($string)) {
			$string = api_utf8_decode($string, $system_encoding);
		}
	}
	return api_html_entity_decode($string, ENT_QUOTES, $system_encoding);
}

/**
 * This function returns an array of those languages that can use Latin 1 encoding.
 * @return array	The array of languages that can use Latin 1 encoding (ISO-8859-15, ISO-8859-1, WINDOWS-1252, ...).
 * Note: The returned language identificators are purified, without suffixes.
 */
function _api_get_latin1_compatible_languages() {
	static $latin1_languages;
	if (!isset($latin1_languages)) {
		$latin1_languages = array();
		$encodings = & _api_non_utf8_encodings();
		foreach ($encodings as $key => $value) {
			if (api_is_latin1($value[0])) {
				$latin1_languages[] = $key;
			}
		}
	}
	return $latin1_languages;
}


/**
 * ----------------------------------------------------------------------------
 * Appendix to "Date and time formats"
 * ----------------------------------------------------------------------------
 */

/**
 * Returns an array of translated week days and months, short and normal names.
 * @param string $language (optional)	Language indentificator. If it is omited, the current interface language is assumed.
 * @return array						Returns a multidimensional array with translated week days and months.
 */
function &_api_get_day_month_names($language = null) {
	static $date_parts = array();
	if (empty($language)) {
		$language = api_get_interface_language();
	}
	if (!isset($date_parts[$language])) {
		$week_day = array('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday');
		$month = array('January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December');
		for ($i = 0; $i < 7; $i++) {
			$date_parts[$language]['days_short'][] = get_lang($week_day[$i].'Short', '', $language);
			$date_parts[$language]['days_long'][] = get_lang($week_day[$i].'Long', '', $language);
		}
		for ($i = 0; $i < 12; $i++) {
			$date_parts[$language]['months_short'][] = get_lang($month[$i].'Short', '', $language);
			$date_parts[$language]['months_long'][] = get_lang($month[$i].'Long', '', $language);
		}
	}
	return $date_parts[$language];
}


/**
 * ----------------------------------------------------------------------------
 * Appendix to "Name order conventions"
 * ----------------------------------------------------------------------------
 */

/**
 * Returns returns person name convention for a given language.
 * @param string $language	The input language.
 * @param string $type		The type of the requested convention. It may be 'format' for name order convention or 'sort_by' for name sorting convention.
 * @return mixed			Depending of the requested type, the returned result may be string or boolean; null is returned on error;
 */
function _api_get_person_name_convention($language, $type) {
	static $conventions;
	$language = api_purify_language_id($language);
	if (!isset($conventions)) {
		$file = dirname(__FILE__).'/internationalization_database/name_order_conventions.php';
		if (file_exists($file)) {
			$conventions = include ($file);
		} else {
			$conventions = array('english' => array('format' => 'title first_name last_name', 'sort_by' => 'first_name'));
		}
		$search1 = array('FIRST_NAME', 'LAST_NAME', 'TITLE');
		$replacement1 = array('%F', '%L', '%T');
		$search2 = array('first_name', 'last_name', 'title');
		$replacement2 = array('%f', '%l', '%t');
		foreach (array_keys($conventions) as $key) {
			$conventions[$key]['format'] = str_replace($search1, $replacement1, $conventions[$key]['format']);
			$conventions[$key]['format'] = _api_validate_person_name_format(_api_clean_person_name(str_replace('%', ' %', str_ireplace($search2, $replacement2, $conventions[$key]['format']))));
			$conventions[$key]['sort_by'] = strtolower($conventions[$key]['sort_by']) != 'last_name' ? true : false;
		}
	}
	switch ($type) {
		case 'format':
			return is_string($conventions[$language]['format']) ? $conventions[$language]['format'] : '%t %f %l';
		case 'sort_by':
			return is_bool($conventions[$language]['sort_by']) ? $conventions[$language]['sort_by'] : true;
	}
	return null;
}

/**
 * Replaces non-valid formats for person names with the default (English) format.
 * @param string $format	The input format to be verified.
 * @return bool				Returns the same format if is is valid, otherwise returns a valid English format.
 */
function _api_validate_person_name_format($format) {
	if (empty($format) || stripos($format, '%f') === false || stripos($format, '%l') === false) {
		return '%t %f %l';
	}
	return $format;
}

/**
 * Removes leading, trailing and duplicate whitespace and/or commas in a full person name.
 * Cleaning is needed for the cases when not all parts of the name are available or when the name is constructed using a "dirty" pattern.
 * @param string $person_name	The input person name.
 * @return string				Returns cleaned person name.
 */
function _api_clean_person_name($person_name) {
	return preg_replace(array('/\s+/', '/, ,/', '/,+/', '/^[ ,]/', '/[ ,]$/'), array(' ', ', ', ',', '', ''), $person_name);
}


/**
 * ----------------------------------------------------------------------------
 * Appendix to "Multibyte string conversion functions"
 * ----------------------------------------------------------------------------
 */

/**
 * This is a php-implementation of a function that is similar to mb_convert_encoding() from mbstring extension.
 * The function converts a given string from one to another character encoding.
 * @param string $string					The string being converted.
 * @param string $to_encoding				The encoding that $string is being converted to.
 * @param string $from_encoding				The encoding that $string is being converted from.
 * @return string							Returns the converted string.
 */
function _api_convert_encoding($string, $to_encoding, $from_encoding) {
	static $character_map = array();
	static $utf8_compatible = array('UTF-8', 'US-ASCII');
	if (empty($string)) {
		return $string;
	}
	$to_encoding = api_refine_encoding_id($to_encoding);
	$from_encoding = api_refine_encoding_id($from_encoding);
	if (api_equal_encodings($to_encoding, $from_encoding)) {
		return $string;
	}
	if ($to_encoding == 'HTML-ENTITIES') {
		return api_htmlentities($string, ENT_QUOTES, $from_encoding);
	}
	if ($from_encoding == 'HTML-ENTITIES') {
		return api_html_entity_decode($string, ENT_QUOTES, $to_encoding);
	}
	$to = _api_get_character_map_name($to_encoding);
	$from = _api_get_character_map_name($from_encoding);
	if (empty($to) || empty($from) || $to == $from || (in_array($to, $utf8_compatible) && in_array($from, $utf8_compatible))) {
		return $string;
	}
	if (!isset($character_map[$to])) {
		$character_map[$to] = &_api_parse_character_map($to);
	}
	if ($character_map[$to] === false) {
		return $string;
	}
	if (!isset($character_map[$from])) {
		$character_map[$from] = &_api_parse_character_map($from);
	}
	if ($character_map[$from] === false) {
		return $string;
	}
	if ($from != 'UTF-8') {
		$len = api_byte_count($string);
		$codepoints = array();
		for ($i = 0; $i < $len; $i++) {
			$ord = ord($string[$i]);
			if ($ord > 127) {
				if (isset($character_map[$from]['local'][$ord])) {
					$codepoints[] = $character_map[$from]['local'][$ord];
				} else {
					$codepoints[] = 0xFFFD; // U+FFFD REPLACEMENT CHARACTER is the general substitute character in the Unicode Standard.
				}
			} else {
				$codepoints[] = $ord;
			}
		}
	} else {
		$codepoints = _api_utf8_to_unicode($string);
	}
	if ($to != 'UTF-8') {
		foreach ($codepoints as $i => &$codepoint) {
			if ($codepoint > 127) {
				if (isset($character_map[$to]['unicode'][$codepoint])) {
					$codepoint = chr($character_map[$to]['unicode'][$codepoint]);
				} else {
					$codepoint = '?'; // Unknown character.
				}
			} else {
				$codepoint = chr($codepoint);
			}
		}
		$string = implode($codepoints);
	} else {
		$string = _api_utf8_from_unicode($codepoints);
	}
	return $string;
}

/**
 * This function determines the name of corresponding to a given encoding conversion table.
 * It is able to deal with some aliases of the encoding.
 * @param string $encoding		The given encoding identificator, for example 'WINDOWS-1252'.
 * @return string				Returns the name of the corresponding conversion table, for the same example - 'CP1252'.
 */
function _api_get_character_map_name($encoding) {
	static $character_map_selector;
	if (!isset($character_map_selector)) {
		$file = dirname(__FILE__).'/internationalization_database/conversion/character_map_selector.php';
		if (file_exists($file)) {
			$character_map_selector = include ($file);
		} else {
			$character_map_selector = array();
		}
	}
	return isset($character_map_selector[$encoding]) ? $character_map_selector[$encoding] : '';
}

/**
 * This function parses a given conversion table (a text file) and creates in the memory
 * two tables for conversion - character set from/to Unicode codepoints.
 * @param string $name		The name of the thext file that contains the conversion table, for example 'CP1252' (file CP1252.TXT will be parsed).
 * @return array			Returns an array that contains forward and reverse tables (from/to Unicode).
 */
function &_api_parse_character_map($name) {
	$result = array();
	$file = dirname(__FILE__).'/internationalization_database/conversion/' . $name . '.TXT';
	if (file_exists($file)) {
		$text = @file_get_contents($file);
		if ($text !== false) {
			$text = explode(chr(10), $text);
			foreach ($text as $line) {
				if (empty($line)) {
					continue;
				}
				if (!empty($line) && trim($line) && $line[0] != '#') {
					$matches = array();
					preg_match('/[[:space:]]*0x([[:alnum:]]*)[[:space:]]+0x([[:alnum:]]*)[[:space:]]+/', $line, $matches);
					$ord = hexdec(trim($matches[1]));
					if ($ord > 127) {
						$codepoint =  hexdec(trim($matches[2]));
						$result['local'][$ord] = $codepoint;
						$result['unicode'][$codepoint] = $ord;
					}
				}
			}
		} else {
			return false ;
		}
	} else {
		return false;
	}
	return $result;
}

/**
 * Takes an UTF-8 string and returns an array of integer values representing the Unicode characters.
 * Astral planes are supported ie. the ints in the output can be > 0xFFFF. Occurrances of the BOM are ignored.
 * Surrogates are not allowed.
 * @param string $string				The UTF-8 encoded string.
 * @return array						Returns an array of unicode code points.
 * @author Henri Sivonen, mailto:hsivonen@iki.fi
 * @link http://hsivonen.iki.fi/php-utf8/
 * @author Ivan Tcholakov, August 2009, adaptation for the Dokeos LMS.
*/
function _api_utf8_to_unicode($string) {
	$state = 0;			// cached expected number of octets after the current octet
						// until the beginning of the next UTF8 character sequence
	$codepoint  = 0;	// cached Unicode character
	$bytes = 1;			// cached expected number of octets in the current sequence
	$result = array();
	$len = api_byte_count($string);
	for ($i = 0; $i < $len; $i++) {
		$byte = ord($string[$i]);
		if ($state == 0) {
			// When state is zero we expect either a US-ASCII character or a multi-octet sequence.
			if (0 == (0x80 & ($byte))) {
				// US-ASCII, pass straight through.
				$result[] = $byte;
				$bytes = 1;
			} else if (0xC0 == (0xE0 & ($byte))) {
				// First octet of 2 octet sequence
				$codepoint = ($byte);
				$codepoint = ($codepoint & 0x1F) << 6;
				$state = 1;
				$bytes = 2;
			} else if (0xE0 == (0xF0 & ($byte))) {
				// First octet of 3 octet sequence
				$codepoint = ($byte);
				$codepoint = ($codepoint & 0x0F) << 12;
				$state = 2;
				$bytes = 3;
			} else if (0xF0 == (0xF8 & ($byte))) {
				// First octet of 4 octet sequence
				$codepoint = ($byte);
				$codepoint = ($codepoint & 0x07) << 18;
				$state = 3;
				$bytes = 4;
            } else if (0xF8 == (0xFC & ($byte))) {
				// First octet of 5 octet sequence.
				// This is illegal because the encoded codepoint must be either
				// (a) not the shortest form or
				// (b) outside the Unicode range of 0-0x10FFFF.
				// Rather than trying to resynchronize, we will carry on until the end
				// of the sequence and let the later error handling code catch it.
                $codepoint = ($byte);
                $codepoint = ($codepoint & 0x03) << 24;
                $state = 4;
                $bytes = 5;
			} else if (0xFC == (0xFE & ($byte))) {
				// First octet of 6 octet sequence, see comments for 5 octet sequence.
				$codepoint = ($byte);
				$codepoint = ($codepoint & 1) << 30;
				$state = 5;
				$bytes = 6;
			} else {
				// Current octet is neither in the US-ASCII range nor a legal first octet of a multi-octet sequence.
				$state = 0;
				$codepoint = 0;
				$bytes = 1;
				$result[] = 0xFFFD; // U+FFFD REPLACEMENT CHARACTER is the general substitute character in the Unicode Standard.
				continue ;
			}
		} else {
			// When state is non-zero, we expect a continuation of the multi-octet sequence
			if (0x80 == (0xC0 & ($byte))) {
				// Legal continuation.
				$shift = ($state - 1) * 6;
				$tmp = $byte;
				$tmp = ($tmp & 0x0000003F) << $shift;
				$codepoint |= $tmp;
				// End of the multi-octet sequence. $codepoint now contains the final Unicode codepoint to be output
                if (0 == --$state) {
					// Check for illegal sequences and codepoints.
					// From Unicode 3.1, non-shortest form is illegal
					if (((2 == $bytes) && ($codepoint < 0x0080)) ||
						((3 == $bytes) && ($codepoint < 0x0800)) ||
						((4 == $bytes) && ($codepoint < 0x10000)) ||
						(4 < $bytes) ||
						// From Unicode 3.2, surrogate characters are illegal
						(($codepoint & 0xFFFFF800) == 0xD800) ||
						// Codepoints outside the Unicode range are illegal
						($codepoint > 0x10FFFF)) {
						$state = 0;
						$codepoint = 0;
						$bytes = 1;
						$result[] = 0xFFFD;
						continue ;
					}
					if (0xFEFF != $codepoint) {
						// BOM is legal but we don't want to output it
						$result[] = $codepoint;
					}
					// Initialize UTF8 cache
					$state = 0;
					$codepoint = 0;
					$bytes = 1;
				}
			} else {
				// ((0xC0 & (*in) != 0x80) && (state != 0))
				// Incomplete multi-octet sequence.
				$state = 0;
				$codepoint = 0;
				$bytes = 1;
				$result[] = 0xFFFD;
			}
		}
	}
	return $result;
}

/**
 * Takes an array of Unicode codepoints and returns a UTF-8 string.
 * @param array $codepoints				An array of Unicode codepoints representing a string.
 * @return string						Returns a UTF-8 string constructed using the given codepoints.
*/
function _api_utf8_from_unicode($codepoints) {
	return implode(array_map('_api_utf8_chr', $codepoints));
}

/**
 * Takes a codepoint and returns its correspondent UTF-8 encoded character.
 * Astral planes are supported, ie the intger input can be > 0xFFFF. Occurrances of the BOM are ignored.
 * Surrogates are not allowed.
 * @param int $codepoint				The Unicode codepoint.
 * @return string						Returns the corresponding UTF-8 character.
 * @author Henri Sivonen, mailto:hsivonen@iki.fi
 * @link http://hsivonen.iki.fi/php-utf8/
 * @author Ivan Tcholakov, 2009, modifications for the Dokeos LMS.
 * @see _api_utf8_from_unicode()
 * This is a UTF-8 aware version of the function chr().
 * @link http://php.net/manual/en/function.chr.php
 */
function _api_utf8_chr($codepoint) {
	// ASCII range (including control chars)
	if ( ($codepoint >= 0) && ($codepoint <= 0x007f) ) {
		$result = chr($codepoint);
	// 2 byte sequence
	} else if ($codepoint <= 0x07ff) {
		$result = chr(0xc0 | ($codepoint >> 6)) . chr(0x80 | ($codepoint & 0x003f));
	// Byte order mark (skip)
	} else if($codepoint == 0xFEFF) {
		// nop -- zap the BOM
		$result = '';
	// Test for illegal surrogates
	} else if ($codepoint >= 0xD800 && $codepoint <= 0xDFFF) {
		// found a surrogate
		$result = _api_utf8_chr(0xFFFD); // U+FFFD REPLACEMENT CHARACTER is the general substitute character in the Unicode Standard.
	// 3 byte sequence
	} else if ($codepoint <= 0xffff) {
		$result = chr(0xe0 | ($codepoint >> 12)) . chr(0x80 | (($codepoint >> 6) & 0x003f)) . chr(0x80 | ($codepoint & 0x003f));
	// 4 byte sequence
	} else if ($codepoint <= 0x10ffff) {
		$result = chr(0xf0 | ($codepoint >> 18)) . chr(0x80 | (($codepoint >> 12) & 0x3f)) . chr(0x80 | (($codepoint >> 6) & 0x3f)) . chr(0x80 | ($codepoint & 0x3f));
	} else {
 		// out of range
		$result = _api_utf8_chr(0xFFFD);
	}
	return $result;
}

/**
 * Takes the first UTF-8 character in a string and returns its Unicode codepoint.
 * @param string $utf8_character	The UTF-8 encoded character.
 * @return int						Returns: the codepoint; or 0xFFFD (unknown character) when the input string is empty.
 * This is a UTF-8 aware version of the function ord().
 * @link http://php.net/manual/en/function.ord.php
 * Note about a difference with the original funtion ord(): ord('') returns 0.
 */
function _api_utf8_ord($utf8_character) {
	if (empty($utf8_character)) {
		return 0xFFFD;
	}
	$codepoints = _api_utf8_to_unicode($utf8_character);
	return $codepoints[0];
}

/**
 * Makes a html-entity from Unicode codepoint.
 * @param int $codepoint			The Unicode codepoint.
 * @return string					Returns the corresponding html-entity; or ASCII character if $codepoint < 128.
 */
function _api_html_entity_from_unicode($codepoint) {
	if ($codepoint < 128) {
		return chr($codepoint);
	}
	return '&#'.$codepoint.';';
}

/**
 * Converts character encoding of a xml-formatted text. If inside the text the encoding is declared, it is modified accordingly.
 * @param string $string					The text being converted.
 * @param string $to_encoding				The encoding that text is being converted to.
 * @param string $from_encoding (optional)	The encoding that text is being converted from. If the value is empty, it is tried to be detected then.
 * @return string							Returns the converted xml-text.
 */
function _api_convert_encoding_xml(&$string, $to_encoding, $from_encoding) {
	if (empty($from_encoding)) {
		$from_encoding = api_detect_encoding_xml($string);
	}
	global $_api_encoding;
	$_api_encoding = api_refine_encoding_id($to_encoding);
	return api_convert_encoding(preg_replace_callback(_PCRE_XML_ENCODING, '_api_convert_encoding_xml_callback', $string), $to_encoding, $from_encoding);
}

/**
 * A callback for serving the function _api_convert_encoding_xml().
 * @param array $matches	Input array of matches corresponding to the xml-declaration.
 * @return string			Returns the xml-declaration with modified encoding.
 */
function _api_convert_encoding_xml_callback($matches) {
	global $_api_encoding;
	return str_replace($matches[1], $_api_encoding, $matches[0]);
}


/**
 * ----------------------------------------------------------------------------
 * Appendix to "Common multibyte string functions"
 * ----------------------------------------------------------------------------
 */

/**
 * The following function reads case folding properties about a given character from a file-based "database".
 * @param int $codepoint			The Unicode codepoint that represents a caharacter.
 * @param string $type (optional)	The type of initial case to be altered: 'lower' (default) or 'upper'.
 * @return array					Returns an array with properties used to change case of the character.
 */
function &_api_utf8_get_letter_case_properties($codepoint, $type = 'lower') {
	static $config = array();
	static $range = array();
	if (!isset($range[$codepoint])) {
		if ($codepoint > 128 && $codepoint < 256)  {
			$range[$codepoint] = '0080_00ff'; // Latin-1 Supplement
		} elseif ($codepoint < 384) {
			$range[$codepoint] = '0100_017f'; // Latin Extended-A
		} elseif ($codepoint < 592) {
			$range[$codepoint] = '0180_024F'; // Latin Extended-B
		} elseif ($codepoint < 688) {
			$range[$codepoint] = '0250_02af'; // IPA Extensions
		} elseif ($codepoint >= 880 && $codepoint < 1024) {
			$range[$codepoint] = '0370_03ff'; // Greek and Coptic
		} elseif ($codepoint < 1280) {
			$range[$codepoint] = '0400_04ff'; // Cyrillic
		} elseif ($codepoint < 1328) {
			$range[$codepoint] = '0500_052f'; // Cyrillic Supplement
		} elseif ($codepoint < 1424) {
			$range[$codepoint] = '0530_058f'; // Armenian
		} elseif ($codepoint >= 7680 && $codepoint < 7936) {
			$range[$codepoint] = '1e00_1eff'; // Latin Extended Additional
		} elseif ($codepoint < 8192) {
			$range[$codepoint] = '1f00_1fff'; // Greek Extended
		} elseif ($codepoint >= 8448 && $codepoint < 8528) {
			$range[$codepoint] = '2100_214f'; // Letterlike Symbols
		} elseif ($codepoint < 8592) {
			$range[$codepoint] = '2150_218f'; // Number Forms
		} elseif ($codepoint >= 9312 && $codepoint < 9472) {
			$range[$codepoint] = '2460_24ff'; // Enclosed Alphanumerics
		} elseif ($codepoint >= 11264 && $codepoint < 11360) {
			$range[$codepoint] = '2c00_2c5f'; // Glagolitic
		} elseif ($codepoint < 11392) {
			$range[$codepoint] = '2c60_2c7f'; // Latin Extended-C
		} elseif ($codepoint < 11520) {
			$range[$codepoint] = '2c80_2cff'; // Coptic
		} elseif ($codepoint >= 65280 && $codepoint < 65520) {
			$range[$codepoint] = 'ff00_ffef'; // Halfwidth and Fullwidth Forms
		} else {
			$range[$codepoint] = false;
		}
		if ($range[$codepoint] === false) {
			return null;
		}
		if (!isset($config[$range[$codepoint]])) {
			$file = dirname(__FILE__).'/internationalization_database/casefolding/' . $range[$codepoint] . '.php';
			if (file_exists($file)) {
				include $file;
			}
		}
	}
	if ($range[$codepoint] === false || !isset($config[$range[$codepoint]])) {
		return null;
	}
	$result = array();
	$count = count($config[$range[$codepoint]]);
	for ($i = 0; $i < $count; $i++) {
		if ($type === 'lower' && $config[$range[$codepoint]][$i][$type][0] === $codepoint) {
			$result[] = $config[$range[$codepoint]][$i];
		} elseif ($type === 'upper' && $config[$range[$codepoint]][$i][$type] === $codepoint) {
			$result[] = $config[$range[$codepoint]][$i];
		}
	}
	return $result;
}

/**
 * A callback for serving the function api_ucwords().
 * @param array $matches	Input array of matches corresponding to a single word
 * @return string			Returns a with first char of the word in uppercase
 */
function _api_utf8_ucwords_callback($matches) {
	return $matches[2] . api_ucfirst(ltrim($matches[0]), 'UTF-8');
}


/**
 * ----------------------------------------------------------------------------
 * Appendix to "Common sting operations with arrays"
 * ----------------------------------------------------------------------------
 */

/**
 * This callback function converts from UTF-8 to other encoding. It works with strings or arrays of strings.
 * @param mixed $variable	The variable to be converted, a string or an array.
 * @return mixed			Returns the converted form UTF-8 $variable with the same type, string or array.
 */
function _api_array_utf8_decode($variable) {
	global $_api_encoding;
	if (is_array($variable)) {
		return array_map('_api_array_utf8_decode', $variable);
	}
    if (is_string($var)) {
    	return api_utf8_decode($variable, $_api_encoding);
    }
    return $variable;
}


/**
 * ----------------------------------------------------------------------------
 * Appendix to "String comparison"
 * ----------------------------------------------------------------------------
 */

/**
 * Returns an instance of Collator class (ICU) created for a specified language.
 * @param string $language (optional)	Language indentificator: 'english', 'french' ... If it is omited, the current interface language is assumed.
 * @return object						Returns a instance of Collator class that is suitable for common string comparisons.
 */
function _api_get_collator($language = null) {
	static $collator = array();
	if (empty($language)) {
		$language = api_get_interface_language();
	}
	if (!isset($collator[$language])) {
		$locale = _api_get_locale_from_language($language);
		$collator[$language] = collator_create($locale);
		if (is_object($collator[$language])) {
			collator_set_attribute($collator[$language], Collator::CASE_FIRST, Collator::UPPER_FIRST);
		}
	}
	return $collator[$language];
}

/**
 * Returns an instance of Collator class (ICU) created for a specified language. This collator treats substrings of digits as numbers.
 * @param string $language (optional)	Language indentificator. If it is omited, the current interface language is assumed.
 * @return object						Returns a instance of Collator class that is suitable for alpha-numerical comparisons.
 */
function _api_get_alpha_numerical_collator($language = null) {
	static $collator = array();
	if (empty($language)) {
		$language = api_get_interface_language();
	}
	if (!isset($collator[$language])) {
		$locale = _api_get_locale_from_language($language);
		$collator[$language] = collator_create($locale);
		if (is_object($collator[$language])) {
			collator_set_attribute($collator[$language], Collator::CASE_FIRST, Collator::UPPER_FIRST);
			collator_set_attribute($collator[$language], Collator::NUMERIC_COLLATION, Collator::ON);
		}
	}
	return $collator[$language];
}

/**
 * A string comparison callback function for sorting.
 * @param string $string1		The first string.
 * @param string $string2		The second string.
 * @return int					Returns 0 if $string1 = $string2 or if there is an error; 1 if $string1 > $string2; -1 if $string1 < $string2.
 */
function _api_cmp($string1, $string2) {
	global $_api_collator, $_api_encoding;
	$result = collator_compare($_api_collator, api_utf8_encode($string1, $_api_encoding), api_utf8_encode($string2, $_api_encoding));
	return $result === false ? 0 : $result;
}

/**
 * A reverse string comparison callback function for sorting.
 * @param string $string1		The first string.
 * @param string $string2		The second string.
 * @return int					Returns 0 if $string1 = $string2 or if there is an error; 1 if $string1 < $string2; -1 if $string1 > $string2.
 */
function _api_rcmp($string1, $string2) {
	global $_api_collator, $_api_encoding;
	$result = collator_compare($_api_collator, api_utf8_encode($string2, $_api_encoding), api_utf8_encode($string1, $_api_encoding));
	return $result === false ? 0 : $result;
}

/**
 * A case-insensitive string comparison callback function for sorting.
 * @param string $string1		The first string.
 * @param string $string2		The second string.
 * @return int					Returns 0 if $string1 = $string2 or if there is an error; 1 if $string1 > $string2; -1 if $string1 < $string2.
 */
function _api_casecmp($string1, $string2) {
	global $_api_collator, $_api_encoding;
	$result = collator_compare($_api_collator, api_strtolower(api_utf8_encode($string1, $_api_encoding), 'UTF-8'), api_strtolower(api_utf8_encode($string2, $_api_encoding), 'UTF-8'));
	return $result === false ? 0 : $result;
}

/**
 * A reverse case-insensitive string comparison callback function for sorting.
 * @param string $string1		The first string.
 * @param string $string2		The second string.
 * @return int					Returns 0 if $string1 = $string2 or if there is an error; 1 if $string1 < $string2; -1 if $string1 > $string2.
 */
function _api_casercmp($string1, $string2) {
	global $_api_collator, $_api_encoding;
	$result = collator_compare($_api_collator, api_strtolower(api_utf8_encode($string2, $_api_encoding), 'UTF-8'), api_strtolower(api_utf8_encode($string1, $_api_encoding), 'UTF-8'));
	return $result === false ? 0 : $result;
}

/**
 * A reverse function from php-core function strnatcmp(), performs string comparison in reverse natural (alpha-numerical) order.
 * @param string $string1		The first string.
 * @param string $string2		The second string.
 * @return int					Returns 0 if $string1 = $string2; >0 if $string1 < $string2; <0 if $string1 > $string2.
 */
function _api_strnatrcmp($string1, $string2) {
	return strnatcmp($string2, $string1);
}

/**
 * A reverse function from php-core function strnatcasecmp(), performs string comparison in reverse case-insensitive natural (alpha-numerical) order.
 * @param string $string1		The first string.
 * @param string $string2		The second string.
 * @return int					Returns 0 if $string1 = $string2; >0 if $string1 < $string2; <0 if $string1 > $string2.
 */
function _api_strnatcasercmp($string1, $string2) {
	return strnatcasecmp($string2, $string1);
}

/**
 * A fuction that translates sorting flag constants from php core to correspondent constants from intl extension.
 * @param int $sort_flag (optional)		Sorting modifier flag as it is defined for php core. The default value is SORT_REGULAR.
 * @return int							Retturns the corresponding sorting modifier flag as it is defined in intl php-extension.
 */
function _api_get_collator_sort_flag($sort_flag = SORT_REGULAR) {
	switch ($sort_flag) {
		case SORT_STRING:
		case SORT_SORT_LOCALE_STRING:
			return Collator::SORT_STRING;
		case SORT_NUMERIC:
			return Collator::SORT_NUMERIC;
	}
	return Collator::SORT_REGULAR;
}


/**
 * ----------------------------------------------------------------------------
 * ICU locales (accessible through intl extension).
 * ----------------------------------------------------------------------------
 */

/**
 * Returns isocode (see api_get_language_isocode()) which is purified accordingly to
 * be used by the php intl extension (ICU library).
 * @param string $language (optional)	This is the name of the folder containing translations for the corresponding language.
 * If $language is omitted, interface language is assumed then.
 * @return string						The found language locale id or null on error. Examples: bg, en, pt_BR, ...
 */
function _api_get_locale_from_language($language = null) {
	static $locale = array();
	if (empty($language)) {
		$language = api_get_interface_language();
	}
	if (!isset($locale[$language])) {
		$locale[$language] = api_get_language_isocode($language);
		$locale[$language] = empty($locale[$language]) ? 'en' : str_replace('-', '_', $locale[$language]);
	}
	return $locale[$language];
}

/**
 * Sets/gets the default internal value of the locale id (for the intl extension, ICU).
 * @param string $locale (optional)	The locale id to be set. When it is omitted, the function returns (gets, reads) the default internal value.
 * @return mixed						When the function sets the default value, it returns TRUE on success or FALSE on error. Otherwise the function returns as string the current default value.
 */
function _api_set_default_locale($locale = null) {
	static $default_locale = 'en';
	if (!empty($locale)) {
		$default_locale = $locale;
		if (INTL_INSTALLED) {
			return @locale_set_default($locale);
		}
		return true;
	} else {
		if (INTL_INSTALLED) {
			$default_locale = @locale_get_default();
		}
	}
	return $default_locale;
}

/**
 * Gets the default internal value of the locale id (for the intl extension, ICU).
 * @return string		Returns as string the current default value.
 */
function api_get_default_locale() {
	return _api_set_default_locale();
}


/**
 * ----------------------------------------------------------------------------
 * Appendix to "Encoding management functions"
 * ----------------------------------------------------------------------------
 */

/**
 * Returns a table with non-UTF-8 encodings for all system languages.
 * @return array		Returns an array in the form array('language1' => array('encoding1', encoding2', ...), ...)
 * Note: The function api_get_non_utf8_encoding() returns the first encoding from this array that is correspondent to the given language.
 */
function & _api_non_utf8_encodings() {
	static $encodings;
	if (!isset($encodings)) {
		$file = dirname(__FILE__).'/internationalization_database/non_utf8_encodings.php';
		if (file_exists($file)) {
			$encodings = include ($file);
		} else {
			$encodings = array('english' => array('ISO-8859-15'));
		}
	}
	return $encodings;
}

/**
 * Sets/Gets internal character encoding of the common string functions within the PHP mbstring extension.
 * @param string $encoding (optional)	When this parameter is given, the function sets the internal encoding.
 * @return string						When $encoding parameter is not given, the function returns the internal encoding.
 * Note: This function is used in the global initialization script for setting the internal encoding to the platform's character set.
 * @link http://php.net/manual/en/function.mb-internal-encoding
 */
function _api_mb_internal_encoding($encoding = null) {
	static $mb_internal_encoding = null;
	if (empty($encoding)) {
		if (is_null($mb_internal_encoding)) {
			if (MBSTRING_INSTALLED) {
				$mb_internal_encoding = @mb_internal_encoding();
			} else {
				$mb_internal_encoding = 'ISO-8859-15';
			}
		}
		return $mb_internal_encoding;
	}
	$mb_internal_encoding = $encoding;
	if (_api_mb_supports($encoding)) {
		return @mb_internal_encoding($encoding);
	}
	return false;
}

/**
 * Sets/Gets internal character encoding of the regular expression functions (ereg-like) within the PHP mbstring extension.
 * @param string $encoding (optional)	When this parameter is given, the function sets the internal encoding.
 * @return string						When $encoding parameter is not given, the function returns the internal encoding.
 * Note: This function is used in the global initialization script for setting the internal encoding to the platform's character set.
 * @link http://php.net/manual/en/function.mb-regex-encoding
 */
function _api_mb_regex_encoding($encoding = null) {
	static $mb_regex_encoding = null;
	if (empty($encoding)) {
		if (is_null($mb_regex_encoding)) {
			if (MBSTRING_INSTALLED) {
				$mb_regex_encoding = @mb_regex_encoding();
			} else {
				$mb_regex_encoding = 'ISO-8859-15';
			}
		}
		return $mb_regex_encoding;
	}
	$mb_regex_encoding = $encoding;
	if (_api_mb_supports($encoding)) {
		return @mb_regex_encoding($encoding);
	}
	return false;
}

/**
 * Retrieves specified internal encoding configuration variable within the PHP iconv extension.
 * @param string $type	The parameter $type could be: 'iconv_internal_encoding', 'iconv_input_encoding', or 'iconv_output_encoding'.
 * @return mixed		The function returns the requested encoding or FALSE on error.
 * @link http://php.net/manual/en/function.iconv-get-encoding
 */
function _api_iconv_get_encoding($type) {
	return _api_iconv_set_encoding($type);
}

/**
 * Sets specified internal encoding configuration variables within the PHP iconv extension.
 * @param string $type					The parameter $type could be: 'iconv_internal_encoding', 'iconv_input_encoding', or 'iconv_output_encoding'.
 * @param string $encoding (optional)	The desired encoding to be set.
 * @return bool							Returns TRUE on success, FALSE on error.
 * Note: This function is used in the global initialization script for setting these three internal encodings to the platform's character set.
 * @link http://php.net/manual/en/function.iconv-set-encoding
 */
function _api_iconv_set_encoding($type, $encoding = null) {
	static $iconv_internal_encoding = null;
	static $iconv_input_encoding = null;
	static $iconv_output_encoding = null;
	if (!ICONV_INSTALLED) {
		return false;
	}
	switch ($type) {
		case 'iconv_internal_encoding':
			if (empty($encoding)) {
				if (is_null($iconv_internal_encoding)) {
					$iconv_internal_encoding = @iconv_get_encoding($type);
				}
				return $iconv_internal_encoding;
			}
			if (_api_iconv_supports($encoding)) {
				if(@iconv_set_encoding($type, $encoding)) {
					$iconv_internal_encoding = $encoding;
					return true;
				}
				return false;
			}
			return false;
		case 'iconv_input_encoding':
			if (empty($encoding)) {
				if (is_null($iconv_input_encoding)) {
					$iconv_input_encoding = @iconv_get_encoding($type);
				}
				return $iconv_input_encoding;
			}
			if (_api_iconv_supports($encoding)) {
				if(@iconv_set_encoding($type, $encoding)) {
					$iconv_input_encoding = $encoding;
					return true;
				}
				return false;
			}
			return false;
		case 'iconv_output_encoding':
			if (empty($encoding)) {
				if (is_null($iconv_output_encoding)) {
					$iconv_output_encoding = @iconv_get_encoding($type);
				}
				return $iconv_output_encoding;
			}
			if (_api_iconv_supports($encoding)) {
				if(@iconv_set_encoding($type, $encoding)) {
					$iconv_output_encoding = $encoding;
					return true;
				}
				return false;
			}
			return false;
	}
	return false;
}

/**
 * Ckecks whether a given encoding is known to define single-byte characters only.
 * The result might be not accurate for unknown by this library encodings. This is not fatal,
 * then the library picks up conversions plus Unicode related internal algorithms.
 * @param string $encoding		A given encoding identificator.
 * @return bool					TRUE if the encoding is known as single-byte (for ISO-8859-15, WINDOWS-1251, etc.), FALSE otherwise.
 */
function _api_is_single_byte_encoding($encoding) {
	static $checked = array();
	if (!isset($checked[$encoding])) {
		$character_map = _api_get_character_map_name(api_refine_encoding_id($encoding));
		$checked[$encoding] = (!empty($character_map)
			&& !in_array($character_map, array('UTF-8', 'HTML-ENTITIES')));
	}
	return $checked[$encoding];
}

/**
 * Checks whether the specified encoding is supported by the PHP mbstring extension.
 * @param string $encoding	The specified encoding.
 * @return bool				Returns TRUE when the specified encoding is supported, FALSE othewise.
 */
function _api_mb_supports($encoding) {
	static $supported = array();
	if (!isset($supported[$encoding])) {
		if (MBSTRING_INSTALLED) {
			$supported[$encoding] = api_equal_encodings($encoding, mb_list_encodings(), true);
		} else {
			$supported[$encoding] = false;
		}
	}
	return $supported[$encoding];
}

/**
 * Checks whether the specified encoding is supported by the PHP iconv extension.
 * @param string $encoding	The specified encoding.
 * @return bool				Returns TRUE when the specified encoding is supported, FALSE othewise.
 */
function _api_iconv_supports($encoding) {
	static $supported = array();
	if (!isset($supported[$encoding])) {
		if (ICONV_INSTALLED) {
			$enc = api_refine_encoding_id($encoding);
			if ($enc != 'HTML-ENTITIES') {
				$test_string = '';
				for ($i = 32; $i < 128; $i++) {
					$test_string .= chr($i);
				}
				$supported[$encoding] = (@iconv_strlen($test_string, $enc)) ? true : false;
			} else {
				$supported[$encoding] = false;
			}
		} else {
			$supported[$encoding] = false;
		}
	}
	return $supported[$encoding];
}

// This function checks whether the function _api_convert_encoding() (the php-
// implementation) is able to convert from/to a given encoding.
function _api_convert_encoding_supports($encoding) {
	static $supports = array();
	if (!isset($supports[$encoding])) {
		$supports[$encoding] = _api_get_character_map_name(api_refine_encoding_id($encoding)) != '';
	}
	return $supports[$encoding];
}

/**
 * Checks whether the specified encoding is supported by the html-entitiy related functions.
 * @param string $encoding	The specified encoding.
 * @return bool				Returns TRUE when the specified encoding is supported, FALSE othewise.
 */
function _api_html_entity_supports($encoding) {
	static $supports = array();
	if (!isset($supports[$encoding])) {
		// See http://php.net/manual/en/function.htmlentities.php
		$html_entity_encodings = array(
			'ISO-8859-1',
			'ISO-8859-15',
			'UTF-8',
			'CP866',
			'CP1251',
			'CP1252',
			'KOI8-R',
			'BIG5', '950',
			'GB2312', '936',
			'BIG5-HKSCS',
			'Shift_JIS', 'SJIS', '932',
			'EUC-JP', 'EUCJP'
		);
		$supports[$encoding] = api_equal_encodings($encoding, $html_entity_encodings);
	}
	return $supports[$encoding];
}


/**
 * ----------------------------------------------------------------------------
 * Upgrading the PHP5 mbstring extension
 * ----------------------------------------------------------------------------
 */

// A multibyte replacement of strchr(). This function exists in PHP 5 >= 5.2.0
// See http://php.net/manual/en/function.mb-strrchr
if (MBSTRING_INSTALLED && !function_exists('mb_strchr')) {
	function mb_strchr($haystack, $needle, $part = false, $encoding = null) {
		if (empty($encoding)) {
			$encoding = mb_internal_encoding();
		}
		return mb_strstr($haystack, $needle, $part, $encoding);
	}
}

// A multibyte replacement of stripos(). This function exists in PHP 5 >= 5.2.0
// See http://php.net/manual/en/function.mb-stripos
if (MBSTRING_INSTALLED && !function_exists('mb_stripos')) {
	function mb_stripos($haystack, $needle, $offset = 0, $encoding = null) {
		if (empty($encoding)) {
			$encoding = mb_internal_encoding();
		}
		return mb_strpos(mb_strtolower($haystack, $encoding), mb_strtolower($needle, $encoding), $offset, $encoding);
	}
}

// A multibyte replacement of stristr(). This function exists in PHP 5 >= 5.2.0
// See http://php.net/manual/en/function.mb-stristr
if (MBSTRING_INSTALLED && !function_exists('mb_stristr')) {
	function mb_stristr($haystack, $needle, $part = false, $encoding = null) {
		if (empty($encoding)) {
			$encoding = mb_internal_encoding();
		}
		$pos = mb_strpos(mb_strtolower($haystack, $encoding), mb_strtolower($needle, $encoding), 0, $encoding);
		if ($pos === false) {
			return false;
		}
		if ($part) {
			return mb_substr($haystack, 0, $pos + 1, $encoding);
		}
		return mb_substr($haystack, $pos, mb_strlen($haystack, $encoding), $encoding);
	}
}

// A multibyte replacement of strrchr(). This function exists in PHP 5 >= 5.2.0
// See http://php.net/manual/en/function.mb-strrchr
if (MBSTRING_INSTALLED && !function_exists('mb_strrchr')) {
	function mb_strrchr($haystack, $needle, $part = false, $encoding = null) {
		if (empty($encoding)) {
			$encoding = mb_internal_encoding();
		}
		$needle = mb_substr($needle, 0, 1, $encoding);
		$pos = mb_strrpos($haystack, $needle, mb_strlen($haystack, $encoding) - 1, $encoding);
		if ($pos === false) {
			return false;
		}
		if ($part) {
			return mb_substr($haystack, 0, $pos + 1, $encoding);
		}
		return mb_substr($haystack, $pos, mb_strlen($haystack, $encoding), $encoding);
	}
}

// A multibyte replacement of strstr(). This function exists in PHP 5 >= 5.2.0
// See http://php.net/manual/en/function.mb-strstr
if (MBSTRING_INSTALLED && !function_exists('mb_strstr')) {
	function mb_strstr($haystack, $needle, $part = false, $encoding = null) {
		if (empty($encoding)) {
			$encoding = mb_internal_encoding();
		}
		$pos = mb_strpos($haystack, $needle, 0, $encoding);
		if ($pos === false) {
			return false;
		}
		if ($part) {
			return mb_substr($haystack, 0, $pos + 1, $encoding);
		}
		return mb_substr($haystack, $pos, mb_strlen($haystack, $encoding), $encoding);
	}
}
