<?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:
    public $error = 0; // public variable that holds error code (0 if no error)

    //private:
    public $BYTEORDER = 0;        // 0: low endian, 1: big endian

    public $STREAM = null;

    public $short_circuit = false;

    public $enable_cache = false;

    public $originals = null;      // offset of original table

    public $translations = null;    // offset of translation table

    public $pluralheader = null;    // cache header field for plural forms

    public $total = 0;          // total string count

    public $table_originals = null;  // table for original strings (offsets)

    public $table_translations = null;  // table for translated strings (offsets)

    public $cache_translations = null;  // original -> translation mapping

    /* Methods */

    /**
     * Reads a 32bit Integer from the Stream.
     *
     * @return int from the Stream
     */
    public 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);
        }
    }

    public 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
     */
    public 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 bool enable_cache Enable or disable caching of strings (default on)
     */
    public 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.
     */
    public 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) {
            $this->cache_translations = [];
            /* read all strings in the cache */
            for ($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.
     *
     * @param int num Offset number of original string
     * @return string Requested string if found, otherwise ''
     */
    public 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.
     *
     * @param int num Offset number of original string
     * @return string Requested string if found, otherwise ''
     */
    public 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.
     *
     * @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)
     */
    public 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 $start;
            } else {
                return -1;
            }
        } elseif ($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 $half;
            } elseif ($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.
     *
     * @param string string to be translated
     * @return string translated string (or original, if not found)
     */
    public 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.
     *
     * @return string sanitized plural form expression
     */
    public 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.
     *
     * @return string verbatim plural form header field
     */
    public 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.
     *
     * @return string plural form header
     */
    public 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['']; // edited by vinod 5 jan 2020
                $header = isset($this->cache_translations['']) ? $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.
     *
     * @param n count
     * @return int array index of the right plural form
     */
    public 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.
     *
     * @param string single
     * @param string plural
     * @param string number
     * @return translated plural form
     */
    public 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];
            }
        }
    }

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

    public 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;
        }
    }
}
