<?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');
	$minconfidence = get_pconfig(local_user(),'langfilter','minconfidence')*100;
	$minlength = get_pconfig(local_user(),'langfilter','minlength');
	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'), $enable_checked, ''),
	    '$languages' => array('langfilter_languages', t('I speak'), $languages, t('List of abbreviations (iso2 codes) for languages you speak, comma separated. For example "de,it".') ),
	    '$minconfidence' => array('langfilter_minconfidence', t('Minimum confidence in language detection'), $minconfidence, t('Minimum confidence in language detection being correct, from 0 to 100. Posts will not be filtered when the confidence of language detection is below this percent value.') ),
	    '$minlength' => array('langfilter_minlength', t('Minimum length of message body'), $minlength, t('Minimum length of message body for language filter to be used. Posts shorter than this number of characters will not be filtered.') ),
	    '$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);
		$minconfidence = 0+$_POST['langfilter_minconfidence'];
		if ( ! $minconfidence ) $minconfidence = 0;
		else if ( $minconfidence < 0 ) $minconfidence = 0;
		else if ( $minconfidence > 100 ) $minconfidence = 100;
		set_pconfig(local_user(),'langfilter','minconfidence', $minconfidence/100.0);

		$minlength = 0+$_POST['langfilter_minlength'];
		if ( ! $minlength ) $minlength = 32;
		else if ( $minlength < 0 ) $minlength = 32;
		set_pconfig(local_user(),'langfilter','minlength', $minlength);

		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 extract 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) {

    $logged_user = local_user();
    if ( ! $logged_user ) return;

    # Never filter own messages
    # TODO: find a better way to extract this
    $logged_user_profile = $a->config['system']['url'] . '/profile/' . $a->user['nickname'];
    if ( $logged_user_profile == $b['item']['author-link'] ) return;

    # Don't filter if language filter is disabled
    if( get_pconfig($logged_user,'langfilter','disable') ) return;

    # Don't filter if body lenght is below minimum
    $minlen = get_pconfig(local_user(),'langfilter','minlength');
    if ( ! $minlen ) $minlen = 32;
    if ( strlen($b['item']['body']) < $minlen ) return;

    $spoken_config = get_pconfig(local_user(),'langfilter','languages');
    $minconfidence = get_pconfig(local_user(),'langfilter','minconfidence');

    # Don't filter if no spoken languages are configured 
    if ( ! $spoken_config ) return;
    $spoken_languages = explode(',', $spoken_config);

    # Extract the language of the post
    $opts = $b['item']['postopts'];
    if ( ! $opts ) return; # no options associated to post
    if ( ! preg_match('/\blang=([^;]*);([^:]*)/', $opts, $matches ) )
            return; # no lang options associated to post

    $lang = $matches[1];
    $confidence = $matches[2];

    # Do not filter if language detection confidence is too low
    if ( $minconfidence && $confidence < $minconfidence ) return;

    $iso2 = Text_LanguageDetect_ISO639::nameToCode2($lang);

    if ( ! $iso2 ) return;
    $spoken = in_array($iso2, $spoken_languages);

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