<?php
/*
Copyright (c) 2003, 2009 Danilo Segan <danilo@kvota.net>.
Copyright (c) 2005 Nico Kaiser <nico@siriux.net>

This file is part of PHP-gettext.

PHP-gettext is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

PHP-gettext is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with PHP-gettext; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

*/
/**
 * Provides a simple gettext replacement that works independently from
 * the system's gettext abilities.
 * It can read MO files and use them for translating strings.
 * The files are passed to gettext_reader as a Stream (see streams.php)
 *
 * This version has the ability to cache all strings and translations to
 * speed up the string lookup.
 * While the cache is enabled by default, it can be switched off with the
 * second parameter in the constructor (e.g. whenusing very large MO files
 * that you don't want to keep in memory)
 */
class gettext_reader

{

	// public:

	var $error = 0; // public variable that holds error code (0 if no error)

	// private:

	var $BYTEORDER = 0; // 0: low endian, 1: big endian
	var $STREAM = NULL;
	var $short_circuit = false;
	var $enable_cache = false;
	var $originals = NULL; // offset of original table
	var $translations = NULL; // offset of translation table
	var $pluralheader = NULL; // cache header field for plural forms
	var $total = 0; // total string count
	var $table_originals = NULL; // table for original strings (offsets)
	var $table_translations = NULL; // table for translated strings (offsets)
	var $cache_translations = NULL; // original -> translation mapping
	/* Methods */
	/**
	 * Reads a 32bit Integer from the Stream
	 *
	 * @access private
	 * @return Integer from the Stream
	 */
	function readint()
	{
		if ($this->BYTEORDER == 0) {

			// low endian

			$input = unpack('V', $this->STREAM->read(4));
			return array_shift($input);
		}
		else {

			// big endian

			$input = unpack('N', $this->STREAM->read(4));
			return array_shift($input);
		}
	}

	function read($bytes)
	{
		return $this->STREAM->read($bytes);
	}

	/**
	 * Reads an array of Integers from the Stream
	 *
	 * @param int count How many elements should be read
	 * @return Array of Integers
	 */
	function readintarray($count)
	{
		if ($this->BYTEORDER == 0) {

			// low endian

			return unpack('V' . $count, $this->STREAM->read(4 * $count));
		}
		else {

			// big endian

			return unpack('N' . $count, $this->STREAM->read(4 * $count));
		}
	}

	/**
	 * Constructor
	 *
	 * @param object Reader the StreamReader object
	 * @param boolean enable_cache Enable or disable caching of strings (default on)
	 */
	function __construct($Reader, $enable_cache = true)
	{

		// If there isn't a StreamReader, turn on short circuit mode.

		if (!$Reader || isset($Reader->error)) {
			$this->short_circuit = true;
			return;
		}

		// Caching can be turned off

		$this->enable_cache = $enable_cache;
		$MAGIC1 = "\x95\x04\x12\xde";
		$MAGIC2 = "\xde\x12\x04\x95";
		$this->STREAM = $Reader;
		$magic = $this->read(4);
		if ($magic == $MAGIC1) {
			$this->BYTEORDER = 1;
		}
		elseif ($magic == $MAGIC2) {
			$this->BYTEORDER = 0;
		}
		else {
			$this->error = 1; // not MO file
			return false;
		}

		// FIXME: Do we care about revision? We should.

		$revision = $this->readint();
		$this->total = $this->readint();
		$this->originals = $this->readint();
		$this->translations = $this->readint();
	}

	/**
	 * Loads the translation tables from the MO file into the cache
	 * If caching is enabled, also loads all strings into a cache
	 * to speed up translation lookups
	 *
	 * @access private
	 */
	function load_tables()
	{
		if (is_array($this->cache_translations) && is_array($this->table_originals) && is_array($this->table_translations)) return;
		/* get original and translations tables */
		if (!is_array($this->table_originals)) {
			$this->STREAM->seekto($this->originals);
			$this->table_originals = $this->readintarray($this->total * 2);
		}

		if (!is_array($this->table_translations)) {
			$this->STREAM->seekto($this->translations);
			$this->table_translations = $this->readintarray($this->total * 2);
		}

		if ($this->enable_cache) {
			$this->cache_translations = array();
			/* read all strings in the cache */
			for ($i = 0; $i < $this->total; $i++) {
				$this->STREAM->seekto($this->table_originals[$i * 2 + 2]);
				$original = $this->STREAM->read($this->table_originals[$i * 2 + 1]);
				$this->STREAM->seekto($this->table_translations[$i * 2 + 2]);
				$translation = $this->STREAM->read($this->table_translations[$i * 2 + 1]);
				$this->cache_translations[$original] = $translation;
			}
		}
	}

	/**
	 * Returns a string from the "originals" table
	 *
	 * @access private
	 * @param int num Offset number of original string
	 * @return string Requested string if found, otherwise ''
	 */
	function get_original_string($num)
	{
		$length = $this->table_originals[$num * 2 + 1];
		$offset = $this->table_originals[$num * 2 + 2];
		if (!$length) return '';
		$this->STREAM->seekto($offset);
		$data = $this->STREAM->read($length);
		return (string)$data;
	}

	/**
	 * Returns a string from the "translations" table
	 *
	 * @access private
	 * @param int num Offset number of original string
	 * @return string Requested string if found, otherwise ''
	 */
	function get_translation_string($num)
	{
		$length = $this->table_translations[$num * 2 + 1];
		$offset = $this->table_translations[$num * 2 + 2];
		if (!$length) return '';
		$this->STREAM->seekto($offset);
		$data = $this->STREAM->read($length);
		return (string)$data;
	}

	/**
	 * Binary search for string
	 *
	 * @access private
	 * @param string string
	 * @param int start (internally used in recursive function)
	 * @param int end (internally used in recursive function)
	 * @return int string number (offset in originals table)
	 */
	function find_string($string, $start = - 1, $end = - 1)
	{
		if (($start == - 1) or ($end == - 1)) {

			// find_string is called with only one parameter, set start end end

			$start = 0;
			$end = $this->total;
		}

		if (abs($start - $end) <= 1) {

			// We're done, now we either found the string, or it doesn't exist

			$txt = $this->get_original_string($start);
			if ($string == $txt) return $start;
			else return -1;
		}
		else
		if ($start > $end) {

			// start > end -> turn around and start over

			return $this->find_string($string, $end, $start);
		}
		else {

			// Divide table in two parts

			$half = (int)(($start + $end) / 2);
			$cmp = strcmp($string, $this->get_original_string($half));
			if ($cmp == 0)

			// string is exactly in the middle => return it

			return $half;
			else
			if ($cmp < 0)

			// The string is in the upper half

			return $this->find_string($string, $start, $half);
			else

			// The string is in the lower half

			return $this->find_string($string, $half, $end);
		}
	}

	/**
	 * Translates a string
	 *
	 * @access public
	 * @param string string to be translated
	 * @return string translated string (or original, if not found)
	 */
	function translate($string)
	{
		if ($this->short_circuit) return $string;
		$this->load_tables();
		if ($this->enable_cache) {

			// Caching enabled, get translated string from cache

			if (array_key_exists($string, $this->cache_translations)) return $this->cache_translations[$string];
			else return $string;
		}
		else {

			// Caching not enabled, try to find string

			$num = $this->find_string($string);
			if ($num == - 1) return $string;
			else return $this->get_translation_string($num);
		}
	}

	/**
	 * Sanitize plural form expression for use in PHP eval call.
	 *
	 * @access private
	 * @return string sanitized plural form expression
	 */
	function sanitize_plural_expression($expr)
	{

		// Get rid of disallowed characters.

		$expr = preg_replace('@[^a-zA-Z0-9_:;\(\)\?\|\&=!<>+*/\%-]@', '', $expr);

		// Add parenthesis for tertiary '?' operator.

		$expr.= ';';
		$res = '';
		$p = 0;
		for ($i = 0; $i < strlen($expr); $i++) {
			$ch = $expr[$i];
			switch ($ch) {
			case '?':
				$res.= ' ? (';
				$p++;
				break;

			case ':':
				$res.= ') : (';
				break;

			case ';':
				$res.= str_repeat(')', $p) . ';';
				$p = 0;
				break;

			default:
				$res.= $ch;
			}
		}

		return $res;
	}

	/**
	 * Parse full PO header and extract only plural forms line.
	 *
	 * @access private
	 * @return string verbatim plural form header field
	 */
	function extract_plural_forms_header_from_po_header($header)
	{
		if (preg_match("/(^|\n)plural-forms: ([^\n]*)\n/i", $header, $regs)) $expr = $regs[2];
		else $expr = "nplurals=2; plural=n == 1 ? 0 : 1;";
		return $expr;
	}

	/**
	 * Get possible plural forms from MO header
	 *
	 * @access private
	 * @return string plural form header
	 */
	function get_plural_forms()
	{

		// lets assume message number 0 is header
		// this is true, right?

		$this->load_tables();

		// cache header field for plural forms

		if (!is_string($this->pluralheader)) {
			if ($this->enable_cache) {
				$header = $this->cache_translations[""];
			}
			else {
				$header = $this->get_translation_string(0);
			}

			$expr = $this->extract_plural_forms_header_from_po_header($header);
			$this->pluralheader = $this->sanitize_plural_expression($expr);
		}

		return $this->pluralheader;
	}

	/**
	 * Detects which plural form to take
	 *
	 * @access private
	 * @param n count
	 * @return int array index of the right plural form
	 */
	function select_string($n)
	{
		if (!is_int($n)) {
			throw new InvalidArgumentException("Select_string only accepts integers: " . $n);
		}

		$string = $this->get_plural_forms();
		$string = str_replace('nplurals', "\$total", $string);
		$string = str_replace("n", $n, $string);
		$string = str_replace('plural', "\$plural", $string);
		$total = 0;
		$plural = 0;
		eval("$string");
		if ($plural >= $total) $plural = $total - 1;
		return $plural;
	}

	/**
	 * Plural version of gettext
	 *
	 * @access public
	 * @param string single
	 * @param string plural
	 * @param string number
	 * @return translated plural form
	 */
	function ngettext($single, $plural, $number)
	{
		if ($this->short_circuit) {
			if ($number != 1) return $plural;
			else return $single;
		}

		// find out the appropriate form

		$select = $this->select_string($number);

		// this should contains all strings separated by NULLs

		$key = $single . chr(0) . $plural;
		if ($this->enable_cache) {
			if (!array_key_exists($key, $this->cache_translations)) {
				return ($number != 1) ? $plural : $single;
			}
			else {
				$result = $this->cache_translations[$key];
				$list = explode(chr(0) , $result);
				return $list[$select];
			}
		}
		else {
			$num = $this->find_string($key);
			if ($num == - 1) {
				return ($number != 1) ? $plural : $single;
			}
			else {
				$result = $this->get_translation_string($num);
				$list = explode(chr(0) , $result);
				return $list[$select];
			}
		}
	}

	function pgettext($context, $msgid)
	{
		$key = $context . chr(4) . $msgid;
		$ret = $this->translate($key);
		if (strpos($ret, "\004") !== FALSE) {
			return $msgid;
		}
		else {
			return $ret;
		}
	}

	function npgettext($context, $singular, $plural, $number)
	{
		$key = $context . chr(4) . $singular;
		$ret = $this->ngettext($key, $plural, $number);
		if (strpos($ret, "\004") !== FALSE) {
			return $singular;
		}
		else {
			return $ret;
		}
	}
}
