<?php
/*
 * Name: Language Filter
 * Version: 0.1
 * Description: Filters out postings in languages not spoken by the users
 * Author: Tobias Diekershoff <https://f.diekershoff.de/u/tobias>
 * License: MIT
 */

require_once('library/langdet/Text/LanguageDetect.php');

/* Define the hooks we want to use
 * that is, we have settings, we need to save the settings and we want
 * to modify the content of a posting when friendica prepares it.
 */
function langfilter_install() {
	register_hook('prepare_body',         'addon/langfilter/langfilter.php', 'langfilter_prepare_body', 10);
	register_hook('plugin_settings',      'addon/langfilter/langfilter.php', 'langfilter_addon_settings');
	register_hook('plugin_settings_post', 'addon/langfilter/langfilter.php', 'langfilter_addon_settings_post');
}
function langfilter_uninstall() {
	unregister_hook('prepare_body',         'addon/langfilter/langfilter.php', 'langfilter_prepare_body');
	unregister_hook('plugin_settings',      'addon/langfilter/langfilter.php', 'langfilter_addon_settings');
	unregister_hook('plugin_settings_post', 'addon/langfilter/langfilter.php', 'langfilter_addon_settings_post');
}

/* The settings
 * 1st check if somebody logged in is calling
 * 2nd get the current settings
 * 3rd parse a SMARTY3 template, replacing some translateable strings for the form
 */
function langfilter_addon_settings(&$a,&$s) {
	if(! local_user())
		return;

	$enable_checked = (intval(get_pconfig(local_user(),'langfilter','disable')) ? '' : ' checked="checked" ');
	$languages = get_pconfig(local_user(),'langfilter','languages');
	if(! $languages)
		$languages = 'en,de,fr,it,es';

	$t = get_markup_template("settings.tpl", "addon/langfilter/" );
	$s .= replace_macros ($t, array(
	    '$title' => t("Language Filter"),
	    '$intro' => t ('This addon tries to identify the language of a postings. If it does not match any language spoken by you (see below) the posting will be collapsed. Remember detecting the language is not perfect, especially with short postings.'),
	    '$enabled' => array('langfilter_enable', t('Use the language filter'), $enable_checked, ''),
	    '$regex' => t('Use /expression/ to provide regular expressions'),
	    '$languages' => array('langfilter_languages', t('I speak'), $languages, t('List of abbreviations for languages you speak, comma seperated. For excample "de,it".') ),
	    '$submit' => t('Save Settings'),
	));

	return;
}
/* Save the settings
 * 1st check it's a logged in user calling
 * 2nd check the langfilter form is to be saved
 * 3rd save the settings to the DB for later usage
 */
function langfilter_addon_settings_post(&$a,&$b) {
	if(! local_user())
		return;

	if($_POST['langfilter-settings-submit']) {
		set_pconfig(local_user(),'langfilter','languages',trim($_POST['langfilter_languages']));
		$enable = ((x($_POST,'langfilter_enable')) ? intval($_POST['langfilter_enable']) : 0);
		$disable = 1-$enable;
		set_pconfig(local_user(),'langfilter','disable', $disable);
		info( t('Language Filter Settings saved.') . EOL);
	}
}
/* Actually filter postings by their language
 * 1st check if the user wants to filter postings
 * 2nd get the user settings which languages shall be not filtered out
 * 3rd determine the language of a posting
 * 4th if the determined language does not fit to the spoken languages
 *     of the user, then collapse the posting, but provide a link to
 *     expand it again.
 */
function langfilter_prepare_body(&$a,&$b) {
	if(get_pconfig(local_user(),'langfilter','disable'))
		return;

	if(local_user()) {
		$langs = get_pconfig(local_user(),'langfilter','languages');
	}
	if($langs) {
		$arr = explode(',',$langs);
	} else {
		return;
	}

	$found = false;
    $l = new Text_LanguageDetect;
    $l->_name_mode = 2;   // two letter codes
    $l->_threshold = 600; // make it a bit harder to be confident with a lng
                          // IOW make it more possible that lng is correct
    $lng = $l->detectSimple($b['html']);
    if ($lng==null)
		return;
    if (! in_array($lng, $arr))
		$found = true;
	if ($lng==null)
		$found = false;

	if($found) {
		$rnd = random_string(8);
		$b['html'] = '<div id="langfilter-wrap-' . $rnd . '" class="fakelink" onclick=openClose(\'langfilter-' . $rnd . '\'); >' . sprintf( t('unspoken language %s - Click to open/close'),$lng ) . '</div><div id="langfilter-' . $rnd . '" style="display: none; " >' . $b['html'] . '</div>';  
	}
}
?>