<?php

class Qs_Gettext_PoFile
{
    protected static $headers = [
        'Project-Id-Version'            => '',
        'Report-Msgid-Bugs-To'          => '',
        'POT-Creation-Date'             => '',
        'PO-Revision-Date'              => '',
        'Last-Translator'               => '',
        'Language-Team'                 => '',
        'Content-Type'                  => '',
        'Content-Transfer-Encoding'     => '',
        'Plural-Forms'                  => '',
    ];

    public static function load($file, $context = null)
    {
        $pattern = '/(msgctxt\s+"(.*?(?<!\\\\))"\s+)?'
                 . 'msgid\s+((?:".*(?<!\\\\)"\s*)+)\s+'
                 . 'msgstr\s+((?:".*(?<!\\\\)"\s*)+)/';

        $content = file_get_contents($file);
        // parse headers
        $lines = preg_split('/\r?\n/', $content);
        $headers = self::$headers;
        $i = 2;
        while ($line = $lines[$i++]) {
            $line = substr($line, 1, -1);
            $colonIndex = strpos($line, ':');
            if ($colonIndex === false) {
                continue;
            }
            $headerName = substr($line, 0, $colonIndex);
            if (!isset($headers[$headerName])) {
                continue;
            }
            $headers[$headerName] = substr($line, $colonIndex + 1, -2);
        }
        // end parse headers

        $matches = [];
        $matchCount = preg_match_all($pattern, $content, $matches);

        $messages = [];
        for ($i = 0; $i < $matchCount; ++$i) {
            if ($matches[2][$i] == $context) {
                $id = self::decode($matches[3][$i]);
                $message = self::decode($matches[4][$i]);
                $messages[$id] = $message;
            }
        }
        return $messages;
    }

    public static function save($file, array $messages)
    {
        $content = '';

        foreach ($messages as $id => $message) {
            $separatorPosition = strpos($id, chr(4));
            if ($separatorPosition !== false) {
                $content .= 'msgctxt "' . substr($id, 0, $separatorPosition) . "\"\n";
                $id = substr($id, $separatorPosition + 1);
            }
            $content .= 'msgid "' . self::encode($id) . "\"\n";

            $lines = preg_split('/\r?\n/', $message);
            if (count($lines) > 1) {
                $content .= 'msgstr ""' . "\n";
                foreach ($lines as $line) {
                    $line = trim($line);
                    if ($line) {
                        $content .= '"' . self::encode($line) . '\n"' . "\n";
                    }
                }
                $content .= "\n";
            } else {
                $content .= 'msgstr "' . self::encode($message) . "\"\n\n";
            }

        }
        return file_put_contents($file, $content);
    }

    protected static function encode($string)
    {
        return str_replace(['"', "\n", "\t", "\r"], ['\\"', '\\n', '\\t', '\\r'], $string);
    }

    protected static function decode($string)
    {
        $string = preg_replace(
            ['/"\s+"/', '/\\\\n/', '/\\\\r/', '/\\\\t/', '/\\\\"/'],
            ['', "\n", "\r", "\t", '"'],
            $string
        );
        return substr(rtrim($string), 1, -1);
    }
}