<?php

namespace AOP\App;

/**
 * The translations that ship with the plugin (languages/) fill the gaps of a language pack of translate.wordpress.org.
 *
 * WordPress takes one file per text domain: the language pack when there is one, otherwise the bundled file. A pack
 * that was made for an older release lacks the new texts, and those would show in English until the translators
 * approve them. So the pack still wins for every text it has, and the bundled file answers for the rest: for PHP a
 * second file for the same text domain (WordPress looks through the files in the order they were loaded), for
 * scripts the missing keys of the bundled JSON file.
 */
class Translations
{
    /**
     * On init: tell WordPress where the bundled files are, and add them behind the language pack.
     */
    public static function load(): void
    {
        load_plugin_textdomain(Plugin::NAME, false, dirname(plugin_basename(Plugin::baseFile())) . '/languages');

        self::addBundled(determine_locale());
    }

    /**
     * Action `change_locale`: WordPress loaded the language pack again for the other locale.
     *
     * @param string $locale
     */
    public static function changeLocale($locale): void
    {
        self::addBundled((string) $locale);
    }

    /**
     * The bundled file of this locale, behind whatever WordPress loads first (the language pack, or the same file).
     */
    public static function addBundled(string $locale): void
    {
        $file = Plugin::languagesDir() . '/' . Plugin::NAME . '-' . $locale . '.mo';

        if (!is_readable($file) && !is_readable(substr($file, 0, -3) . '.l10n.php')) {
            return;
        }

        // The file WordPress chooses (just in time) comes first, so a language pack keeps priority.
        get_translations_for_domain(Plugin::NAME);

        load_textdomain(Plugin::NAME, $file, $locale);
    }

    /**
     * Filter `load_script_translations`: a JSON file of a language pack gets the texts it lacks from the bundled JSON
     * file of the same script (same file name: the md5 of the path of the script).
     *
     * @param string|false $translations The JSON WordPress read.
     * @param string       $file         The file it was read from.
     * @param string       $handle
     * @param string       $domain
     *
     * @return string|false
     */
    public static function fillScriptTranslations($translations, $file, $handle, $domain)
    {
        if ($domain !== Plugin::NAME || !is_string($translations) || !is_string($file)) {
            return $translations;
        }

        $bundled = Plugin::languagesDir() . '/' . basename($file);

        if (wp_normalize_path($bundled) === wp_normalize_path($file) || !is_readable($bundled)) {
            return $translations;
        }

        return self::mergeJson($translations, (string) file_get_contents($bundled));
    }

    /**
     * The messages of $first, with the messages of $second that $first does not have.
     *
     * @param string $first  JED JSON as `wp i18n make-json` writes it (the language pack).
     * @param string $second The same for the bundled file.
     */
    public static function mergeJson(string $first, string $second): string
    {
        $a = json_decode($first, true);
        $b = json_decode($second, true);

        if (!is_array($a) || !is_array($b) || !isset($a['locale_data']) || !is_array($a['locale_data'])) {
            return $first;
        }

        foreach ($a['locale_data'] as $key => $messages) {
            if (!is_array($messages) || !isset($b['locale_data'][$key]) || !is_array($b['locale_data'][$key])) {
                continue;
            }

            // Keys of $a stay, keys only in $b are added; the header entry ("") stays the one of $a.
            $a['locale_data'][$key] = $messages + $b['locale_data'][$key];
        }

        return (string) wp_json_encode($a);
    }
}