MDNodaHelpers/src/NodaWikidataFetcher.php

<?PHP
/**
 * This file contains tools for fetching data from Wikidata.
 *
 * @file
 * @author Joshua Ramon Enslin <joshua@museum-digital.de>
 */
declare(strict_types = 1);

/**
 * Helps fetching information from Wikidata.
 */
final class NodaWikidataFetcher {

    private const WIKIDATA_FETCH_HEADERS = [
        'User-Agent: museum-digital-bot GND-to-Wikidata PHP/' . PHP_VERSION,
        'Accept: application/sparql-results+json',
    ];

    public const LANGUAGES_MAIN_DESC = ['de', 'da', 'en', 'es', 'fr', 'hu', 'it', 'jp', 'nl', 'pt', 'ru', 'sv', 'sk', 'uk', 'zh'];
    public const LANGUAGES_TO_CHECK = ['ar', 'bg', 'bn', 'cs', 'da', 'de', 'el', 'en', 'es', 'fa', 'fi', 'fr', 'ha', 'he', 'hi', 'hu', 'id', 'it', 'ja', 'ka', 'ko', 'nl', 'pl', 'pt', 'ro', 'ru', 'sv', 'sk', 'sw', 'ta', 'th', 'tl', 'tr', 'uk', 'ur', 'vi', 'zh'];

    public const LANGUAGES_TO_CAPITALIZE = ["cs", "da", "de", "en", "es", "fr", "fi", "id", "it", "nl", "pl", "pt", "ru", "sv", 'sk', "tl", "tr"];

    public const P_IDS_NODA_TAGS = [
        'gnd' => 'P227',
        'lcsh' => 'P244',
        'aat' => 'P1014',
        'iconclass' => 'P1256',
        'osm' => 'P402',
        'loc' => 'P244',
        'nomisma' => 'P2950',
        'cona' => 'P1669',

        "rkd"  => "P650",
        "ulan" => "P245",
        "viaf" => "P214",
        "bnf"  => "P268",
        "pim"  => "P3973",
        "ndl"  => "P349",    // National Diet Library (Japan)
        "npg"  => "P1816",   // "National" portrait gallery
        "bne"  => "P950",  // Espana National Library
        "orcid" => "P496",
    ];

    private const WIKIPEDIA_REMOVE_LITERALS = [
        "<p>Si vous disposez d'ouvrages ou d'articles de référence ou si vous ",
        '<p><b>En pratique&#160;:</b> <a href="/wiki/Wikip%C3%A9dia:Citez_vos_sources#Qualité_des_sources" title="Wikipédia:Citez vos sources">Quelles sources sont attendu',
        '<pVous pouvez partager vos connaissances en l’améliorant (',
        '<p class="mw-empty-elt">',
        '<p><small>Géolocalisation sur la carte',
        '<p><b>Koordinaatit:</b>',
        '<p><span class="executeJS" data-gadgetname="ImgToggle"></span',
        '<p><span class="imgtoggleboxTitle">',
        //'<div class="mw-parser-output"><p>',
        '<p><span style="font-size: small;"><span id="coordinates">',
        '<p><span></span></p>',
        '<p><a rel="nofollow" class="external text" href="https://maps.gs',
        '<p><span class="plainlinks nourlexpansion"><a class="external text" href="//tools.wmflabs.org/geohack/geohack.php?langu',
        '<p><span style="display:none">',
        '<p>&#32;</p>',
        '<p><span class="geo noexcerpt"',
    ];

    public const RETRIEVAL_MODES_ACCEPTED = [
        'list',
        'add',
        'keep',
        'replace',
    ];

    public const RETRIEVAL_MODES_DEFAULT = 'list';

    /** @var 'list'|'add'|'keep'|'replace' */
    private string $_retrievalMode = self::RETRIEVAL_MODES_DEFAULT;

    /** @var MDMysqli */
    private MDMysqli $_mysqli_noda;

    /**
     * Returns the API link to Wikipedia's API for getting information on a page.
     *
     * @param string $lang       Language / wikipedia version to fetch.
     * @param string $searchTerm Search term.
     *
     * @return non-empty-string
     */
    private static function _getWikipediaApiLink(string $lang, string $searchTerm):string {

        return "https://" . urlencode($lang) . ".wikipedia.org/w/api.php?action=parse&page=" . urlencode($searchTerm) . "&prop=text&section=0&format=json";

    }

    /**
     * Returns Wikipedia links from Wikidata's API output.
     *
     * @param array<mixed> $data Wikidata API output.
     *
     * @return array<string, array{url: string, title: string}>
     */
    private static function _getWikipediaLinksFromWikidataOutput(array $data):array {

        $wikilinks = [];

        foreach (self::LANGUAGES_MAIN_DESC as $tLang) {
            if (!isset($data['sitelinks'][$tLang . 'wiki']['url']) || !isset($data['sitelinks'][$tLang . 'wiki']['title']))   continue;
            if (!is_string($data['sitelinks'][$tLang . 'wiki']['url']) || !is_string($data['sitelinks'][$tLang . 'wiki']['title']))   continue;
            $wikilinks[$tLang] = [
                'url' => $data['sitelinks'][$tLang . 'wiki']['url'],
                'title' => str_replace(' ', '_', $data['sitelinks'][$tLang . 'wiki']['title']),
            ];
        }

        return $wikilinks;

    }

    /**
     * Parses coordinates from Wikidata API output.
     *
     * @param array<mixed> $data Wikidata API output.
     *
     * @return array{}|array{longitude: float, latitude: float}
     */
    private static function _getPlaceCoordinatesFromWikidata(array $data):array {

        if (!isset($data['claims']['P625'])) {
            return [];
        }

        $latitude_wd = \filter_var($data['claims']['P625'][0]['mainsnak']['datavalue']['value']['latitude'], FILTER_VALIDATE_FLOAT);
        $longitude_wd = \filter_var($data['claims']['P625'][0]['mainsnak']['datavalue']['value']['longitude'], FILTER_VALIDATE_FLOAT);

        if ($latitude_wd === false || $longitude_wd === false) return [];

        return [
            'longitude' => $longitude_wd,
            'latitude' => $latitude_wd,
        ];

    }

    /**
     * Loads Wikipedia page and cleans output.
     *
     * @param string $lang  Language to load in.
     * @param string $title Title to load from.
     *
     * @return string
     */
    private static function _getCleanedWikipediaSnippet(string $lang, string $title):string {

        $datafromwiki = MD_STD::runCurl(self::_getWikipediaApiLink($lang, $title), 10000);
        $json_decoded = json_decode($datafromwiki, true);
        if (empty($json_decoded) || !isset($json_decoded['parse'])) {
            return '';
        }
        $datafromwiki = strval($json_decoded['parse']['text']['*']);

        return self::_cleanWikidataInput($datafromwiki);

    }

    /**
     * Loads data for a single entity from Wikidata.
     *
     * @param string $wikidata_id Wikidata Q-ID.
     *
     * @return array<mixed>
     */
    private static function _getWikidataEntity(string $wikidata_id):array {

        $data = json_decode(MD_STD::runCurl("https://www.wikidata.org/wiki/Special:EntityData/" . urlencode($wikidata_id) . ".json", 10000), true);
        if ($data === null) {
            throw new MDhttpFailedException("Failed fetching from Wikidata. Try again later.");
        }
        if (empty($data['entities'][$wikidata_id])) {
            throw new MDhttpFailedException("Failed fetching from Wikidata. Try again later.");
        }
        return $data['entities'][$wikidata_id];

    }

    /**
     * Parses wikidata results to MDNodaLink entries.
     *
     * @param 'tag'|'persinst'|'place' $target      Target vocabulary type.
     * @param string                   $wikidata_id Wikidata ID.
     * @param array<mixed>             $data        Wikidata result.
     *
     * @return list<MDNodaLink>
     */
    public function _getNodaLinksFromWikidataResult(string $target, string $wikidata_id, array $data):array {

        $linkableVocabularies = match($target) {
            'tag' => MDNodaRepositoriesSet::REPOSITORIES_TAG,
            'persinst' => MDNodaRepositoriesSet::REPOSITORIES_ACTOR,
            'place' => MDNodaRepositoriesSet::REPOSITORIES_PLACE,
        };

        $output = [
            new MDNodaLink(MDNodaRepository::wikidata, $wikidata_id)
        ];
        foreach (self::P_IDS_NODA_TAGS as $vocabName => $pId) {

            if (!isset($data['claims'][$pId])) {
                continue;
            }
            if (empty($data['claims'][$pId][0]['mainsnak']['datavalue'])) {
                continue;
            }

            $url = $data['claims'][$pId][0]['mainsnak']['datavalue']['value'];

            if ($vocabName === 'loc' || ($vocabName === 'lcsh')) {
                $vocabName = $this->_determineLocRefMode($url);
                if (empty($vocabName)) continue;
            }

            if (!in_array($vocabName, $linkableVocabularies, true)) continue;

            $output[] = new MDNodaLink(MDNodaRepository::fromString($vocabName), $url);

        }

        return $output;

    }

    /**
     * Checks if a vocabulary link to the library
     * of congress is a valid LCSH or LOC link or
     * something else completely.
     * This is necessary, since Wikidata only knows
     * one type of link to the LOC authority files,
     * while museum-digital knows two.
     *
     * @param string $url LOC ID to check.
     *
     * @return 'loc'|'lcsh'|''
     */
    private function _determineLocRefMode(string $url):string {

        try {
            if (MDNodaRepository::loc->validateId($url) !== false) {
                return 'loc';
            }
        }
        catch (MDgenericInvalidInputsException | MDInvalidNodaLinkException | MDInvalidNodaLink $e) {
        }

        try {
            if (MDNodaRepository::lcsh->validateId($url) !== false) {
                return 'lcsh';
            }
        }
        catch (MDgenericInvalidInputsException | MDInvalidNodaLinkException | MDInvalidNodaLink $e) {
        }

        return '';

    }

    /**
     * Cleans basic tags off Wikidata input.
     *
     * @param string $input Input string.
     *
     * @return string
     */
    private static function _cleanWikidataInputHtml(string $input):string {

        // Clean off anything before first <p>
        if ($pStartPos = strpos($input, '<p')) {
            $input = substr($input, $pStartPos);
        }
        if ($pEndPos = strrpos($input, '</p>')) {
            $input = substr($input, 0, $pEndPos + 4);
        }

        $doc = new DOMDocument();
        try {
            $doc->loadXML('<section>' . trim($input) . '</section>');
        }
        catch (Exception $e) {
            throw new Exception("Failed to load DOMDocument." . PHP_EOL . $e->getMessage() . PHP_EOL . PHP_EOL . '---' . $input . '---');
        }

        $list = $doc->getElementsByTagName("style");
        while ($list->length > 0) {
            $p = $list->item(0);
            if ($p === null || $p->parentNode === null) break;
            $p->parentNode->removeChild($p);
        }

        $list = $doc->getElementsByTagName("table");
        while ($list->length > 0) {
            $p = $list->item(0);
            if ($p === null || $p->parentNode === null) break;
            $p->parentNode->removeChild($p);
        }

        $list = $doc->getElementsByTagName("ol");
        while ($list->length > 0) {
            $p = $list->item(0);
            if ($p === null || $p->parentNode === null) break;
            $p->parentNode->removeChild($p);
        }

        if (($firstP = $doc->getElementsByTagName("p")->item(0)) !== null) {
            if (($firstPhtml = $doc->saveHTML($firstP)) !== false) {
                if (strpos($firstPhtml, 'geohack') !== false) {
                    if ($firstP->parentNode !== null) $firstP->parentNode->removeChild($firstP);
                }
            }
        }

        $output = [];
        foreach ($doc->getElementsByTagName("p") as $p) {
            $output[] = trim($p->textContent);
        }

        /*
        if (strpos($doc->saveHTML(), 'Coordinates:') !== false) {
            echo $doc->saveHTML();
            exit;
        }
         */
        return str_replace(PHP_EOL, PHP_EOL . PHP_EOL, trim(implode(PHP_EOL, $output)));

    }

    /**
     * Cleans brackets ([1], [2]) off description text.
     *
     * @param string $input Input string.
     *
     * @return string
     */
    private static function _cleanSourceBracketsOffTranslation(string $input):string {

        $bracketsToRemove = [];
        for ($i = 0; $i < 100; $i++) {
            $bracketsToRemove["[$i]"] = "";
        }
        return strtr($input, $bracketsToRemove);

    }

    /**
     * Cleans contents parsed from Wikipedia.
     *
     * @param string $input Input string.
     *
     * @return string
     */
    private static function _cleanWikidataInput(string $input):string {

        $input = trim($input, '"');
        foreach (self::WIKIPEDIA_REMOVE_LITERALS as $tToRemove) $input = str_replace($tToRemove, "", $input);

        if (substr($input, 0, strlen('<')) === '<') {

            $input = self::_cleanWikidataInputHtml($input);

            if (mb_strlen($input) > 600) {
                if (strpos($input, PHP_EOL . PHP_EOL, 600) !== false) {
                    $input = substr($input, 0, strpos($input, PHP_EOL . PHP_EOL, 600));
                }
            }

            $input = self::_cleanSourceBracketsOffTranslation($input);

            $input = str_replace("\t", " ", $input);

            // Remove newlines with ensuing spaces
            while (strpos($input, PHP_EOL . " ") !== false) {
                $input = str_replace(PHP_EOL . " ", PHP_EOL, $input);
            }

            // Remove double newlines
            while (strpos($input, PHP_EOL . PHP_EOL . PHP_EOL) !== false) {
                $input = str_replace(PHP_EOL . PHP_EOL . PHP_EOL, PHP_EOL . PHP_EOL, $input);
            }
            return MD_STD_IN::sanitize_text($input);

        }

        $input = str_replace(PHP_EOL, '', $input);

        if (empty($input)) return "";

        // Remove infobox tables specifically
        $firstParagraphPosition = strpos($input, '<p', 1);
        $currentSearchPos = strpos($input, "<table>");
        if ($currentSearchPos !== false && $currentSearchPos < $firstParagraphPosition) {
            if (($tableEndPos = strpos($input, "</table>")) !== false) {
                if (($pStartPos = strpos($input, '<p', $tableEndPos + 6)) !== false) {
                    $input = substr($input, $pStartPos);
                }
            }
        }

        // Remove leftover unnecessary paragraphs before actual content

        $removeFirstParagraph = false;
        $firstParagraphPosition = strpos($input, '<p', 1);

        foreach (["</table>", "<img"] as $tagPart) {
            $currentSearchPos = strpos($input, $tagPart);
            if ($currentSearchPos !== false && $currentSearchPos < $firstParagraphPosition) {
                $removeFirstParagraph = true;
                break;
            }
        }

        if ($removeFirstParagraph === true) {
            $input = substr($input, $firstParagraphPosition ?: 0);
        }

        $input = str_replace('</p>', '</p>' . PHP_EOL . PHP_EOL . PHP_EOL, $input);
        # $input = str_replace('?/i', '', $input);
        $input = strip_tags($input);

        # for ($i = 150; $i < 1000; $i++) $input = str_replace("&#$i;", " ", $input);
        $i = 0;
        while (strpos($input, ".mw-parser-output") !== false and strpos($input, "}", strpos($input, ".mw-parser-output")) !== false) {
            $part1 = substr($input, 0, strpos($input, ".mw-parser-output"));
            $part2 = substr($input, strpos($input, "}", strpos($input, ".mw-parser-output")) + 1);
            $input = $part1 . $part2;
            ++$i;
            if ($i === 30) break;
        }

        $input = self::_cleanSourceBracketsOffTranslation($input);

        $input = str_replace("\t", " ", $input);

        // Remove double whitespaces
        while (strpos($input, "  ") !== false) {
            $input = str_replace("  ", " ", $input);
        }

        // Remove newlines with ensuing spaces
        while (strpos($input, PHP_EOL . " ") !== false) {
            $input = str_replace(PHP_EOL . " ", PHP_EOL, $input);
        }

        // Remove double newlines
        while (strpos($input, PHP_EOL . PHP_EOL . PHP_EOL) !== false) {
            $input = str_replace(PHP_EOL . PHP_EOL . PHP_EOL, PHP_EOL . PHP_EOL, $input);
        }

        $stableToRemove = [
            "Vous pouvez partager vos connaissances en l’améliorant (comment ?) selon les recommandations des projets correspondants.",
        ];
        foreach ($stableToRemove as $tToRemove) $input = str_replace($tToRemove, "", $input);

        $endings = [
            "StubDenne artikel om et vandløb ",
        ];
        foreach ($endings as $ending) {
            if (strpos($input, $ending) !== false) $input = substr($input, 0, strpos($input, $ending));
        }

        $input = trim($input);

        // Cut off overly long articles
        if (mb_strlen($input) > 600) {
            if (strpos($input, PHP_EOL . PHP_EOL, 600) !== false) {
                $input = trim(substr($input, 0, strpos($input, PHP_EOL . PHP_EOL, 600)));
            }
        }

        if (empty($input)) return '';

        $input = str_replace("'", "´", MD_STD::preg_replace_str("/\&\#91\;[0-9]\&\#93\;/", '', $input));

        $input = html_entity_decode($input);

        return MD_STD_IN::sanitize_text($input);

    }

    /**
     * Wrapper around _cleanWikidataInput for testing.
     *
     * @param string $input Input string.
     *
     * @return string
     */
    public static function cleanWikidataInput(string $input):string {

        if (PHP_SAPI !== 'cli') throw new Exception("Use this function only for testing");
        return self::_cleanWikidataInput($input);

    }

    /**
     * Sets the retrieval mode.
     *
     * @param string $retrievalMode New retrieval mode to set.
     *
     * @return void
     */
    public function setRetrievalMode(string $retrievalMode):void {

        if (!in_array($retrievalMode, self::RETRIEVAL_MODES_ACCEPTED, true)) {
            throw new Exception("Retrieval mode not in list of accepted retrieval modes: " . implode(',', self::RETRIEVAL_MODES_ACCEPTED));
        }

        $this->_retrievalMode = $retrievalMode;

    }

    /**
     * Validates a Wikidata ID. A Wikidata ID must start with a capital Q and be
     * numeric otherwise.
     *
     * @param string $wikidata_id Input ID to validate.
     *
     * @return void
     */
    public static function validateWikidataId(string $wikidata_id):void {

        if (substr($wikidata_id, 0, 1) !== 'Q') {
            throw new MDgenericInvalidInputsException("Wikidata IDs start with Q");
        }

        if (!is_numeric(substr($wikidata_id, 1))) {
            throw new MDgenericInvalidInputsException("Wikidata IDs are numeric following the Q");
        }

    }

    /**
     * Attempts to fetch a Wikidata ID from a provided URL.
     *
     * @param non-empty-string $linkUrl Link to a page.
     *
     * @return string
     */
    public static function getWikidataIdFromLink(string $linkUrl):string {

        if (!filter_var($linkUrl, FILTER_VALIDATE_URL)) {
            throw new MDExpectedException("Invalid URL");
        }

        if (strpos($linkUrl, "http://www.wikidata.org/entity/") !== false) {
            if ($output = self::getWikidataIdFromWikidataLink($linkUrl)) {
                return $output;
            }
        }
        if (strpos($linkUrl, "https://www.wikidata.org/entity/") !== false) {
            if ($output = self::getWikidataIdFromWikidataLink($linkUrl)) {
                return $output;
            }
        }

        if (strpos($linkUrl, "https://www.wikidata.org/wiki/") !== false) {
            if ($output = self::getWikidataIdFromWikidataLink($linkUrl)) {
                return $output;
            }
        }

        if (strpos($linkUrl, ".wikipedia.org/") !== false) {
            if ($output = self::getWikidataIdFromWikipedia($linkUrl)) {
                return $output;
            }
        }

        return '';

    }

    /**
     * Attempts to fetch a Wikidata ID from a provided URL.
     *
     * @param string $linkUrl Link to a Wikidata page.
     *
     * @return string
     */
    public static function getWikidataIdFromWikidataLink(string $linkUrl):string {

        if (str_contains($linkUrl, "https://www.wikidata.org/wiki/") === false
            && str_contains($linkUrl, "https://www.wikidata.org/entity/") === false
            && str_contains($linkUrl, "http://www.wikidata.org/entity/") === false
        ) {
            return '';
        }

        $linkUrl = trim($linkUrl, '/ ');
        $parts = explode('/', $linkUrl);
        return end($parts);

    }

    /**
     * Attempts to fetch a Wikidata ID from a provided URL.
     *
     * @param non-empty-string $linkUrl Link to a Wikipedia page.
     *
     * @return string
     */
    public static function getWikidataIdFromWikipedia(string $linkUrl):string {

        if (strpos($linkUrl, ".wikipedia.org/") === false) {
            return '';
        }

        if (empty($wikipedia_cont = MD_STD::runCurl($linkUrl))) return '';

        libxml_use_internal_errors(true);
        $doc = new DOMDocument();
        if (!$doc->loadHTML($wikipedia_cont)) {
            return '';
        }
        libxml_use_internal_errors(false);

        if (!($wikidataLinkLi = $doc->getElementById("t-wikibase"))) {
            return '';
        }
        if (!($wikidataLink = $wikidataLinkLi->firstChild)) {
            return '';
        }

        if (!($t_wikibase_href = $wikidataLink->getAttribute('href'))) {
            return '';
        }
        $t_wikibase = (string)$t_wikibase_href;

        // if (!empty($t_wikibase)) {
        if (($wikidata_id_end = strrpos($t_wikibase, '/')) !== false) {
            $wikidata_id = trim(substr($t_wikibase, $wikidata_id_end + 1), '/');

            if (substr($wikidata_id, 0, 1) === 'Q') {
                return $wikidata_id;
            }
        }
        // }

        return '';

    }

    /**
     * Runs a SPARQL query against the Wikidata SPARQL endpoint.
     *
     * @param string $sparqlQuery Query string.
     *
     * @return array<mixed>
     */
    public static function sparqlQuery(string $sparqlQuery):array {

        $url = 'https://query.wikidata.org/sparql?query=' . urlencode($sparqlQuery);
        $result = MD_STD::runCurl($url, 100000000, self::WIKIDATA_FETCH_HEADERS);

        return json_decode($result, true);

    }

    /**
     * Formulates a SPARQL query string for fetching from Wikidata based on an external ID.
     *
     * @param string $repoName   Name of the repository.
     * @param string $externalId ID in the external repository.
     * @param string $repoPId    Optional P-ID of the external repository. Needed for
     *                           Geonames and TGN, obsolete otherwise.
     *
     * @return string
     */
    public static function formulateWikidataQueryByExtId(string $repoName, string $externalId, string $repoPId = ''):string {

        if (empty($repoPId)) {

            if (empty(NodaWikidataFetcher::P_IDS_NODA_TAGS[$repoName])) {
                throw new MDmainEntityNotExistentException("Unknown external repository. The following repositories are known with their Wikidata ID: " . implode(', ', array_keys(NodaWikidataFetcher::P_IDS_NODA_TAGS)));
            }

            $repoPId = NodaWikidataFetcher::P_IDS_NODA_TAGS[$repoName];

        }

        return 'SELECT ?id ?idLabel WHERE {
            ?id wdt:' . $repoPId . ' "' . $externalId . '".
            SERVICE wikibase:label {
                bd:serviceParam wikibase:language "en" .
            }
        }';

    }

    /**
     * Gets the Wikidata ID based on a result from Wikidata's SPARQL endpoint.
     *
     * @param array<mixed> $queryResult Query result.
     *
     * @return string
     */
    public static function readWikidataIdFromSparqlResult(array $queryResult):string {

        if (count($queryResult['results']['bindings']) !== 1) return '';

        if (!empty($wikidataLink = $queryResult['results']['bindings'][0]['id']['value'])) {
            if (($endSlashPos = strrpos($wikidataLink, '/')) !== false) {
                return substr($wikidataLink, $endSlashPos + 1);
            }
        }

        return '';

    }

    /**
     * Queries Wikidata by an external repository's ID and returns the matching Q-ID
     * if there is any.
     *
     * @param string $repoName   Name of the repository.
     * @param string $externalId ID in the external repository.
     * @param string $repoPId    Optional P-ID of the external repository. Needed for
     *                           Geonames and TGN, obsolete otherwise.
     *
     * @return string
     */
    public static function getWikidataIdByExternalId(string $repoName, string $externalId, string $repoPId = ''):string {

        $sparqlQueryString = self::formulateWikidataQueryByExtId($repoName, $externalId, $repoPId = '');

        $queryResult = self::sparqlQuery($sparqlQueryString);
        return self::readWikidataIdFromSparqlResult($queryResult);

    }

    /**
     * Gets translation source Wikipedia pages from Wikidata.
     *
     * @param array<string> $checkagainstLanguage The language to check against.
     * @param array<mixed>  $data                 Data fetched from Wikidata.
     *
     * @return array{0: array<string, non-empty-string>, 1: array<string, string>}
     */
    public static function getWikidataWikipediaTranslationSources(array $checkagainstLanguage, array $data) {

        $languagesToFetch = $wikilinks = [];
        foreach ($checkagainstLanguage as $lang) {

            if (empty($data['labels'][$lang])) {
                continue;
            }

            if (!empty($data['sitelinks'][$lang . 'wiki'])) {

                $wikilink = $data['sitelinks'][$lang . 'wiki']['url'];
                $wikilinkterm = str_replace(' ', '_', $data['sitelinks'][$lang . 'wiki']['title']);

                if (isset($wikilink)) {

                    $languagesToFetch[$lang] = self::_getWikipediaApiLink($lang, $wikilinkterm);
                    $wikilinks[$lang] = $wikilink;

                }
            }
        }

        return [$languagesToFetch, $wikilinks];

    }

    /**
     * Loads translations from Wikipedia pages through wikidata and then merges
     * them with Wikidata's own translations into a usable array.
     *
     * @param array<string> $checkagainstLanguage The language to check against.
     * @param array<mixed>  $data                 Data fetched from Wikidata.
     *
     * @return array<string, array{label: string, description: string, link: string}>
     */
    public static function listTranslationsFromWikidataWikipedia(array $checkagainstLanguage, array $data):array {

        list($languagesToFetch, $wikilinks) = self::getWikidataWikipediaTranslationSources($checkagainstLanguage, $data);
        if (empty($languagesToFetch)) {
            return [];
        }

        try {
            $contents = MD_STD::runCurlMulti($languagesToFetch, 10000);
        }
        catch (TypeError $e) {
            throw new MDExpectedException("Failed to initialize a request. Try pressing F5 to run the requests again.");
        }

        $output = [];

        # $descs = [];
        foreach ($checkagainstLanguage as $lang) {

            if (!empty($languagesToFetch[$lang]) && !empty($data['sitelinks'][$lang . 'wiki']) && !empty($wikilinks[$lang])) {

                $wikilink = $wikilinks[$lang];
                if (!empty($contents[$lang])) {

                    $descFromWiki = json_decode($contents[$lang], true)['parse']['text']['*'];

                    # Process data retrieved from wikipedia

                    if ($descFromWiki !== null) $tDescription = (string)$descFromWiki;
                    else $tDescription = "";

                }
                else {
                    $tDescription = "";
                }

                if ($tDescription !== '' && !empty($desc_cleaned = self::_cleanWikidataInput($tDescription))) {
                    # $descs[$lang] = $tDescription;
                    $output[$lang] = [
                        'label' => self::_cleanWikidataInput((string)$data['labels'][$lang]['value']),
                        'description' => '"' . $desc_cleaned . '" - (' . $data['labels'][$lang]['language'] . '.wikipedia.org ' . date('d.m.Y') . ')',
                        'link' => $wikilink,
                    ];
                }
                // Fallback: Use Wikidata description
                else if (!empty($data['labels'][$lang]['value']) and !empty($data['descriptions'][$lang])) {

                    $output[$lang] = [
                        'label' => self::_cleanWikidataInput($data['labels'][$lang]['value']),
                        'description' => self::_cleanWikidataInput($data['descriptions'][$lang]['value']),
                        'link' => "",
                    ];

                }

            }
                // echo '<br><b style="color: cc0000;">Wikipedia Links fehlen</b>';
            else if (!empty($data['labels'][$lang]['value']) and !empty($data['descriptions'][$lang])) {

                $output[$lang] = [
                    'label' => self::_cleanWikidataInput($data['labels'][$lang]['value']),
                    'description' => self::_cleanWikidataInput($data['descriptions'][$lang]['value']),
                    'link' => "",
                ];

            }

        }

        return $output;

    }

    /**
     * Function for fetching description from Wikipedia
     *
     * @param integer $persinst_id  Person ID.
     * @param string  $wikidata_id  Wikidata ID.
     * @param string  $datafromwiki Data fetched from Wikipedia.
     * @param string  $preflang     The user's currently used language.
     * @param string  $lang         Currently queried language.
     * @param string  $erfasst_von  User who adds the info.
     *
     * @return boolean
     */
    public function retrievePersinstDescFromWikipedia(int $persinst_id, string $wikidata_id, string $datafromwiki, string $preflang, string $lang, string $erfasst_von):bool {

        $output = false;

        $datafromwiki = '"' . $datafromwiki . '" - (Wikipedia (' . $lang . ') ' . date('d.m.Y') . ')';

        $cergebnis = $this->_mysqli_noda->query_by_stmt("SELECT `persinst_kurzinfo`, `persinst_anzeigename` AS `display_name`
            FROM `persinst`
            WHERE `persinst_id` = ?", "i", $persinst_id);

        if (!($cinfo = $cergebnis->fetch_row())) {
            throw new Exception("There is no actor of ID #" . $persinst_id);
        }
        $cergebnis->close();

        $persinst_kurzinfo = $cinfo[0];
        $display_name = $cinfo[1];

        // Update persinst table
        $updatePersinstStmt = $this->_mysqli_noda->do_prepare("UPDATE `persinst`
            SET `persinst_kurzinfo` = ?
            WHERE `persinst_id` = ?");

        if (!empty($persinst_kurzinfo) and substr($persinst_kurzinfo, 0, 3) !== 'GND') {

            switch ($this->_retrievalMode) {
            case "add":

                $newDesc = $persinst_kurzinfo . PHP_EOL . PHP_EOL . $datafromwiki;

                $updatePersinstStmt->bind_param("si", $newDesc, $persinst_id);
                $updatePersinstStmt->execute();
                $output = true;
                break;

            case "keep":
                break;

            case "replace":

                $updatePersinstStmt->bind_param("si", $datafromwiki, $persinst_id);
                $updatePersinstStmt->execute();
                $output = true;
                break;

            default:

                $tlLoader = new MDTlLoader("wiki_getter_persinst", $preflang);
                echo self::generateHTMLHeadForWikidataFetcher($lang);
                echo self::generateWikidataFetcherHeader($tlLoader, "", $display_name);
                echo '
        <p class="alert icons iconsAlert">Es gibt schon einen Eintrag im Beschreibungsfeld</p>
        <div class="wikiReplaceTTile">
            <h3>Bisher vorhanden</h3>
            <p>' . nl2br($persinst_kurzinfo) . '</p>
        </div>
        <div class="wikiReplaceTTile">
            <h3>Jetzt gefunden</h3><p>' . $datafromwiki . '</p>
        </div>
            <a href="get_wikidata_for_persinst.php?wikidata_id=' . $wikidata_id . write_get_vars(['suchbegriff', 'lang', 'persinst_id']) . '&keep=keep" class="buttonLike icons iconsPin">Keep old entry</a>';
                echo '<br><a href="get_wikidata_for_persinst.php?wikidata_id=' . $wikidata_id . write_get_vars(['suchbegriff', 'lang', 'persinst_id']) . '&keep=replace" class="buttonLike icons iconsPinOff">Replace with new entry</a>';
                echo '<br><a href="get_wikidata_for_persinst.php?wikidata_id=' . $wikidata_id . write_get_vars(['suchbegriff', 'lang', 'persinst_id']) . '&keep=add" class="buttonLike icons iconsPlusOne">Keep old and add new entry</a><br><br><br>';

                exit;

            }

        }
        else {

            $updatePersinstStmt->bind_param("si", $datafromwiki, $persinst_id);
            $updatePersinstStmt->execute();

            $output = true;

        }
        $updatePersinstStmt->close();

        // Update edit metadata
        $updatePersinstEditInfoStmt = $this->_mysqli_noda->do_prepare("UPDATE `persinst`
            SET `persinst_erfasst_am` = NOW(),
                `persinst_erfasst_von` = ?
            WHERE `persinst_id` = ?");
        $updatePersinstEditInfoStmt->bind_param("si", $erfasst_von, $persinst_id);
        $updatePersinstEditInfoStmt->execute();
        $updatePersinstEditInfoStmt->close();

        return $output;

    }

    /**
     * Function for updating birth and death times based on Wikidata information.
     *
     * @param array<mixed> $data        Data loaded from Wikidata.
     * @param integer      $persinst_id Actor ID.
     *
     * @return void
     */
    public function enterPersinstBirthDeathDatesFromWikidata(array $data, int $persinst_id):void {

        $result = $this->_mysqli_noda->query_by_stmt("SELECT `persinst_geburtsjahr`,
                `persinst_sterbejahr`, `persinst_gender`
            FROM `persinst`
            WHERE `persinst_id` = ?", "i", $persinst_id);
        if (!($actor_dates = $result->fetch_assoc())) {
            throw new MDmainEntityNotExistentException("Failed to fetch actor information");
        }
        $result->close();

        if ($actor_dates['persinst_geburtsjahr'] === '') {

            // Try to get birth date
            if (!empty($data['claims']['P569'])
                and !empty($data['claims']['P569']['0']['mainsnak']['datavalue']['value']['time'])
                // Ignore entries with century / very inprecise birth dates
                and (empty($data['claims']['P569']['0']['mainsnak']['datavalue']['value']['precision']) || (int)$data['claims']['P569']['0']['mainsnak']['datavalue']['value']['precision'] !== 7)
            ) {
                $birth_date = self::wikidataBirthDeathToYear($data['claims']['P569']['0']['mainsnak']['datavalue']['value']['time']);
            }

            if (!empty($birth_date)) {
                $updateStmt = $this->_mysqli_noda->do_prepare("UPDATE `persinst`
                    SET `persinst_geburtsjahr` = ?
                    WHERE `persinst_id` = ?
                    LIMIT 1");
                $updateStmt->bind_param("ii", $birth_date, $persinst_id);
                $updateStmt->execute();
                $updateStmt->close();
            }

        }

        if ($actor_dates['persinst_sterbejahr'] === '') {

            // Try to get birth date
            if (!empty($data['claims']['P570']) and !empty($data['claims']['P570']['0']['mainsnak']['datavalue']['value']['time'])) {
                $death_date = self::wikidataBirthDeathToYear($data['claims']['P570']['0']['mainsnak']['datavalue']['value']['time']);
            }

            if (!empty($death_date)) {
                $updateStmt = $this->_mysqli_noda->do_prepare("UPDATE `persinst`
                    SET `persinst_sterbejahr` = ?
                    WHERE `persinst_id` = ?
                    LIMIT 1");
                $updateStmt->bind_param("ii", $death_date, $persinst_id);
                $updateStmt->execute();
                $updateStmt->close();
            }

        }

        if ($actor_dates['persinst_gender'] === '') {

            // Try to get birth date
            if (!empty($data['claims']['P21']) and !empty($data['claims']['P21']['0']['mainsnak']['datavalue']['value']['id'])) {
                $wikidata_gender_id = $data['claims']['P21']['0']['mainsnak']['datavalue']['value']['id'];

                switch ($wikidata_gender_id) {
                case "Q6581097":    // male
                case "Q44148":      // male organism
                case "Q2449503":    // transgender man
                    $wikidata_gender = "male";
                    break;
                case "Q6581072":
                case "Q1052281":    // transgender female
                case "Q43445":      // female organism
                    $wikidata_gender = "female";
                    break;
                case "Q48270":
                    $wikidata_gender = "other";
                    break;
                default:
                    throw new Exception("Unknown gender: Q-ID is " . $wikidata_gender_id);
                }
            }

            if (!empty($wikidata_gender)) {
                $updateStmt = $this->_mysqli_noda->do_prepare("UPDATE `persinst`
                    SET `persinst_gender` = ?
                    WHERE `persinst_id` = ?
                    LIMIT 1");
                $updateStmt->bind_param("si", $wikidata_gender, $persinst_id);
                $updateStmt->execute();
                $updateStmt->close();
            }

        }

    }

    /**
     * Function for retrieving information.
     *
     * @param string  $lang        The user's selected used language.
     * @param string  $wikidata_id Wikidata ID.
     * @param integer $persinst_id Actor ID.
     * @param string  $erfasst_von User name who's currently editing.
     *
     * @return void
     */
    public function retrievePersinstInfoFromWikidataID(string $lang, string $wikidata_id, int $persinst_id, string $erfasst_von) {

        self::validateWikidataId($wikidata_id);
        $data = self::_getWikidataEntity($wikidata_id);

        // Get links to wikipedia

        $wikilinks = self::_getWikipediaLinksFromWikidataOutput($data);
        $alreadyEntered = false;

        if (isset($wikilinks[$lang])) {
            # Process data retrieved from wikipedia
            if (!empty($datafromwiki = self::_getCleanedWikipediaSnippet($lang, $wikilinks[$lang]['title']))) {
                $alreadyEntered = $this->retrievePersinstDescFromWikipedia($persinst_id, $wikidata_id, $datafromwiki, $lang, $lang, $erfasst_von);
            }

        }

        foreach (self::LANGUAGES_MAIN_DESC as $cur_lang) {

            if ($alreadyEntered === true || !isset($wikilinks[$cur_lang])) continue;

            if ($datafromwiki = self::_getCleanedWikipediaSnippet($lang, $wikilinks[$cur_lang]['title'])) {
                $alreadyEntered = $this->retrievePersinstDescFromWikipedia($persinst_id, $wikidata_id, $datafromwiki, $lang, "$cur_lang", $erfasst_von);
            }

        }

        $this->enterPersinstBirthDeathDatesFromWikidata($data, $persinst_id);

        // Get links to other norm data sources

        if (!empty($nodaLinks = $this->_getNodaLinksFromWikidataResult('persinst', $wikidata_id, $data))) {
            NodaBatchInserter::linkNodaForPersinst($this->_mysqli_noda, $persinst_id, $nodaLinks, $erfasst_von);
        }

        $this->getWikidataTranslationsForPersinst($data, $persinst_id);

        NodaLogEdit::logPersinstEdit($this->_mysqli_noda, $persinst_id, "wikidata-fetcher", $erfasst_von, 'update', 'synchronize');

    }

    /**
     * Function for retrieving information.
     *
     * @param string  $wikidata_id Wikidata ID.
     * @param integer $persinst_id Actor ID.
     * @param string  $erfasst_von User name who's currently editing.
     *
     * @return void
     */
    public function retrievePersinstNormDataLinksFromWikidataID(string $wikidata_id, int $persinst_id, string $erfasst_von) {

        self::validateWikidataId($wikidata_id);
        $data = self::_getWikidataEntity($wikidata_id);
        if (!empty($nodaLinks = $this->_getNodaLinksFromWikidataResult('persinst', $wikidata_id, $data))) {
            NodaBatchInserter::linkNodaForPersinst($this->_mysqli_noda, $persinst_id, $nodaLinks, $erfasst_von);
        }

    }

    /**
     * Retrieves only norm data links from Wikidata.
     *
     * @param string  $wikidata_id Wikidata Q-ID.
     * @param integer $onum        Place ID.
     * @param string  $erfasst_von User name of the current user.
     *
     * @return void
     */
    public function retrievePlaceNormDataLinksFromWikidataID(string $wikidata_id, int $onum, string $erfasst_von) {

        self::validateWikidataId($wikidata_id);
        $data = self::_getWikidataEntity($wikidata_id);
        if (!empty($nodaLinks = $this->_getNodaLinksFromWikidataResult('place', $wikidata_id, $data))) {
            NodaBatchInserter::linkNodaForPlace($this->_mysqli_noda, $onum, $nodaLinks, $erfasst_von);
        }

    }

    /**
     * Function for fetching translations from Wikipedia, based on Wikidata information.
     *
     * @param array<mixed> $data          Entity fetched from wikidata.
     * @param integer      $persinst_id   Actor ID.
     * @param string[]     $checkForLangs Languages to check for. Defaults to all
     *                                    languages generally loaded by the wikidata fetcher.
     *
     * @return void
     */
    public function getWikidataTranslationsForPersinst(array $data, int $persinst_id, array $checkForLangs = self::LANGUAGES_TO_CHECK):void {

        if (empty($translations = self::listTranslationsFromWikidataWikipedia($checkForLangs, $data))) {
            return;
        }

        $toInsert = [];

        foreach ($translations as $lang => $values) {

            $toInsert[] = [
                'persinst_id' => $persinst_id,
                'lang' => $lang,
                'name' => $values['label'],
                'description' => $values['description'],
                'link' => $values['link'],
            ];

        }

        NodaBatchInserter::insertPersinstTranslations($this->_mysqli_noda, $toInsert);

    }

    /**
     * Returns the current description of a place.
     *
     * @param integer $onum Place ID.
     *
     * @return string
     */
    private function getPlaceDescription(int $onum):string {

        $currentPlaceResult = $this->_mysqli_noda->query_by_stmt("SELECT `ort_anmerkung`
            FROM `orte`
            WHERE `ort_id` = ?", "i", $onum);

        if (!($curPlaceInfo = $currentPlaceResult->fetch_row())) {
            $currentPlaceResult->close();
            throw new Exception("This place does not exist");
        }
        $currentPlaceResult->close();

        return $curPlaceInfo[0];

    }

    /**
     * Returns the current description of a tag.
     *
     * @param integer $tag_id Tag ID.
     *
     * @return string
     */
    private function getTagDescription(int $tag_id):string {

        $result = $this->_mysqli_noda->query_by_stmt("SELECT `tag_anmerkung`
            FROM `tag`
            WHERE `tag_id` = ?", "i", $tag_id);

        if (!($cur = $result->fetch_row())) {
            $result->close();
            return '';
        }
        $result->close();

        return $cur[0];

    }

    /**
     * Function for entering base information about a place from wikidata.
     *
     * @param string  $cur_place_desc Mysqli result pointing to the current place.
     * @param string  $datafromwiki   Data parsed from wikidata.
     * @param string  $preflang       Language of the user interface in general.
     * @param string  $lang           Language of the main entry.
     * @param integer $placeID        ID of the place.
     * @param string  $erfasst_von    User name.
     *
     * @return boolean
     */
    public function enterPlaceDescFromWikidata(string $cur_place_desc, string $datafromwiki, string $preflang, string $lang, int $placeID, string $erfasst_von):bool {

        $datafromwiki = '"' . $datafromwiki . '" - (Wikipedia (' . $lang . ') ' . date("d.m.Y") . ')';

        if (!empty(trim($cur_place_desc)) and substr($cur_place_desc, 0, 3) !== 'GND') {

            switch ($this->_retrievalMode) {
            case "add":
                $datafromwiki = $cur_place_desc . PHP_EOL . PHP_EOL . $datafromwiki;
                break;
            case "keep":
                $datafromwiki = $cur_place_desc;
                break;
            case "replace":
                break;
            default:
                $tlLoader = new MDTlLoader("wiki_getter_place", $preflang);
                echo self::generateHTMLHeadForWikidataFetcher($lang);
                echo self::generateWikidataFetcherHeader($tlLoader);
                echo '
                <p class="alert icons iconsAlert">There is already an entry for description ...</p>
                <div class="wikiReplaceTTile">
                    <h3>Actual entry</h3><p>' . nl2br($cur_place_desc) . '</p>
                </div>
                <div class="wikiReplaceTTile">
                    <h3>Now found</h3>
                    <p>' . $datafromwiki . '</p>
                </div>
                <a href="get_wikidata_for_ort.php?keep=keep' . write_get_vars(['suchbegriff', 'lang', 'wikidata_id', 'ort_id']) . '" class="buttonLike icons iconsPin">Keep old entry</a>
                <br><a href="get_wikidata_for_ort.php?keep=replace' . write_get_vars(['suchbegriff', 'lang', 'wikidata_id', 'ort_id']) . '" class="buttonLike icons iconsPinOff">Replace with new entry</a>
                <br><a href="get_wikidata_for_ort.php?keep=add' . write_get_vars(['suchbegriff', 'lang', 'wikidata_id', 'ort_id']) . '" class="buttonLike icons iconsPlusOne">Keep old and add new entry</a><br><br><br>
                ';

                exit;

            }

        }

        // Write description to DB
        $updateStmt = $this->_mysqli_noda->do_prepare("UPDATE `orte`
            SET `ort_anmerkung` = ?,
                `ort_erfasst_am` = NOW(),
                `ort_erfasst_von` = ?
            WHERE ort_id = ?");
        try {
            $updateStmt->bind_param("ssi", $datafromwiki, $erfasst_von, $placeID);
            $updateStmt->execute();
        }
        catch (MDMysqliInvalidEncodingError $e) {
        }
        $updateStmt->close();
        unset($updateStmt);

        return true;

    }

    /**
     * Function for retrieving a superordinate place relation from Wikidata information
     * for places
     *
     * @param integer      $onum Place ID.
     * @param array<mixed> $data Wikidata information (P131 claim).
     *
     * @return void
     */
    public function retrieveSuperordinateAdministrativePlace(int $onum, array $data):void {

        if (!empty($data[0]["mainsnak"]["datavalue"]["value"]["id"])) {

            // Check if there already is a superordinate of the current place
            $result = $this->_mysqli_noda->query_by_stmt("SELECT 1
                FROM `ort_relation`
                WHERE `ort_menor_id` = ?
                LIMIT 1", "i", $onum);
            if ($result->num_rows !== 0) {
                $result->close();
                return;
            }
            $result->close();

            // If there is no superordinate, check if the identified superordinate
            // is known in the noda DB.

            $superordinateId = $data[0]["mainsnak"]["datavalue"]["value"]["id"];

            $result = $this->_mysqli_noda->query_by_stmt("SELECT `ort_id`
                FROM `noda_orte`
                WHERE `noda_source` = 'wikidata'
                AND `noda_nrinsource` = ?", "s", $superordinateId);

            if (!($superordinateData = $result->fetch_row())) {
                $result->close();
                return;
            }
            $result->close();

            $topPlaceId = $superordinateData[0];

            // Enter superordinate place by Wikidata
            $insertStmt = $this->_mysqli_noda->do_prepare("INSERT INTO `ort_relation`
                (`ort_mayor_id`, `ort_menor_id`, `ort_relation`)
                VALUES
                (?, ?, 1)");
            $insertStmt->bind_param("ii", $topPlaceId, $onum);
            $insertStmt->execute();
            $insertStmt->close();

        }

    }

    /**
     * Function for retrieving place information based on a Wikidata ID.
     *
     * @param string  $lang        Language.
     * @param string  $wikidata_id Wikidata Q-ID.
     * @param integer $onum        Place ID.
     * @param string  $erfasst_von User name of the current user.
     *
     * @return void
     */
    public function retrievePlaceInfoFromWikidataID(string $lang, string $wikidata_id, int $onum, string $erfasst_von) {

        self::validateWikidataId($wikidata_id);
        $data = self::_getWikidataEntity($wikidata_id);

        $wikilinks = self::_getWikipediaLinksFromWikidataOutput($data);

        // Get current description for overwriting

        // P131: Located in administrative unit
        if (isset($data['claims']['P131'])) {
            $this->retrieveSuperordinateAdministrativePlace($onum, $data['claims']['P131']);
        }

        $cur_place_desc = $this->getPlaceDescription($onum);
        $alreadyEntered = false;

        if (!empty($wikilinks[$lang])) {

            $datafromwiki = MD_STD::runCurl(self::_getWikipediaApiLink($lang, $wikilinks[$lang]['title']), 10000);
            $datafromwiki = json_decode($datafromwiki, true)['parse']['text']['*'];

            if (!empty($datafromwiki) and !empty($datafromwiki = self::_cleanWikidataInput((string)$datafromwiki))) {
                $alreadyEntered = $this->enterPlaceDescFromWikidata($cur_place_desc, $datafromwiki, $lang, $lang, $onum, $erfasst_von);
            }
        }

        foreach (self::LANGUAGES_MAIN_DESC as $cur_lang) {

            //if ($alreadyEntered === true) break;
            if ($alreadyEntered === true) break;
            if (!isset($wikilinks[$cur_lang]['url'])) continue;

            $datafromwiki = MD_STD::runCurl(self::_getWikipediaApiLink($cur_lang, $wikilinks[$cur_lang]['title']), 10000);
            $datafromwiki = json_decode($datafromwiki, true)['parse']['text']['*'];
            if (!empty($datafromwiki) and !empty($datafromwiki = self::_cleanWikidataInput((string)$datafromwiki))) {
                $alreadyEntered = $this->enterPlaceDescFromWikidata($cur_place_desc, $datafromwiki, $lang, $cur_lang, $onum, $erfasst_von);
            }

        }

        if (isset($data['claims']['P1566'])) $geonames_id = filter_var($data['claims']['P1566'][0]['mainsnak']['datavalue']['value'], FILTER_VALIDATE_INT);
        if (isset($data['claims']['P1667'])) $tgn_id = filter_var($data['claims']['P1667'][0]['mainsnak']['datavalue']['value'], FILTER_VALIDATE_INT);

        if (!empty($nodaLinks = $this->_getNodaLinksFromWikidataResult('place', $wikidata_id, $data))) {
            NodaBatchInserter::linkNodaForPlace($this->_mysqli_noda, $onum, $nodaLinks, $erfasst_von);
        }

        $coordinates_wd = self::_getPlaceCoordinatesFromWikidata($data);

        $this->_mysqli_noda->autocommit(false);
        if (!empty($tgn_id)) {

            $updateStmt = $this->_mysqli_noda->do_prepare("UPDATE `orte`
                SET `ort_land` = ?
                WHERE `ort_id` = ?");
            $updateStmt->bind_param("ii", $tgn_id, $onum);
            $updateStmt->execute();
            $updateStmt->close();
            unset($updateStmt);

        }
        if (!empty($geonames_id)) {

            $updateStmt = $this->_mysqli_noda->do_prepare("UPDATE `orte`
                SET `ort_geonames` = ?
                WHERE `ort_id` = ?");
            $updateStmt->bind_param("ii", $geonames_id, $onum);
            $updateStmt->execute();
            $updateStmt->close();
            unset($updateStmt);

        }

        if (!empty($coordinates_wd)) {

            $updateStmt = $this->_mysqli_noda->do_prepare("UPDATE `orte`
                SET `ort_nord_sued` = ?, `ort_west_ost` = ?
                WHERE `ort_id` = ?");
            $updateStmt->bind_param("ddi", $coordinates_wd['latitude'], $coordinates_wd['longitude'], $onum);
            $updateStmt->execute();
            $updateStmt->close();
            unset($updateStmt);

        }

        $this->_mysqli_noda->commit();
        $this->_mysqli_noda->autocommit(true);

        $this->getWikidataTranslationsForPlace($data, $onum);

        NodaLogEdit::logPlaceEdit($this->_mysqli_noda, $onum, "wikidata-fetcher", $erfasst_von, 'update', 'synchronize');

    }

    /**
     * Function for fetching translations from wikidata.
     *
     * @param array<mixed> $data          Entity data fetched from wikidata.
     * @param integer      $ort_id        Place ID.
     * @param string[]     $checkForLangs Languages to check for. Defaults to all
     *                                    languages generally loaded by the wikidata fetcher.
     *
     * @return void
     */
    public function getWikidataTranslationsForPlace(array $data, int $ort_id, array $checkForLangs = self::LANGUAGES_TO_CHECK):void {

        if (empty($translations = self::listTranslationsFromWikidataWikipedia($checkForLangs, $data))) {
            return;
        }

        $toInsert = [];

        foreach ($translations as $lang => $values) {

            $toInsert[] = [
                'ort_id' => $ort_id,
                'lang' => $lang,
                'name' => $values['label'],
                'description' => $values['description'],
                'link' => $values['link'],
            ];

        }

        NodaBatchInserter::insertPlaceTranslations($this->_mysqli_noda, $toInsert);

    }

    /**
     * Function for fetching description from Wikipedia
     *
     * @param integer $tag_id       Tag ID.
     * @param string  $datafromwiki Data fetched from Wikipedia.
     * @param string  $preflang     The user's currently used language.
     * @param string  $lang         Currently queried language.
     * @param string  $erfasst_von  User who adds the info.
     *
     * @return boolean
     */
    public function retrieveTagDescFromWikipedia(int $tag_id, string $datafromwiki, string $preflang, string $lang, string $erfasst_von):bool {

        $output = false;

        $datafromwiki = '"' . $datafromwiki . '" - (Wikipedia (' . $lang . ') ' . date("d.m.Y") . ')';
        $datafromwiki = str_replace("'", "´", MD_STD::preg_replace_str("/\&\#91\;[0-9]\&\#93\;/", '', $datafromwiki));

        $tag_anmerkung = $this->getTagDescription($tag_id);

        $this->_mysqli_noda->autocommit(false);

        $updateTagDescStmt = $this->_mysqli_noda->do_prepare("UPDATE `tag`
            SET `tag_anmerkung` = ?
            WHERE `tag_id` = ?");

        if (!empty($tag_anmerkung) and substr($tag_anmerkung, 0, 3) !== 'GND') {

            switch ($this->_retrievalMode) {
            case "add":

                $newDesc = $tag_anmerkung . PHP_EOL . PHP_EOL . $datafromwiki;

                $updateTagDescStmt->bind_param("si", $newDesc, $tag_id);
                $updateTagDescStmt->execute();
                $output = true;
                break;

            case "keep":
                break;

            case "replace":

                $updateTagDescStmt->bind_param("si", $datafromwiki, $tag_id);
                $updateTagDescStmt->execute();
                $output = true;
                break;

            default:

                $tlLoader = new MDTlLoader("wiki_getter_tag", $preflang);
                echo self::generateHTMLHeadForWikidataFetcher($lang);
                echo self::generateWikidataFetcherHeader($tlLoader);
                echo '
                <p class="alert icons iconsAlert">Es gibt schon einen Eintrag im Beschreibungsfeld</b>
                <div class="wikiReplaceTTile">
                    <h3>Bisher vorhanden</h3><p>' . nl2br($tag_anmerkung) . '</p>
                </div>
                <div class="wikiReplaceTTile">
                    <h3>Jetzt gefunden</h3><p>' . $datafromwiki . '<p>
                </div>

                <a href="get_wikidata_for_tag.php?keep=keep' . write_get_vars(['suchbegriff', 'lang', 'wikidata_id', 'tag_id']) . '" class="buttonLike icons iconsPin">Keep old entry</a>';
                echo '<br><a href="get_wikidata_for_tag.php?keep=replace' . write_get_vars(['suchbegriff', 'lang', 'wikidata_id', 'tag_id']) . '" class="buttonLike icons iconsPinOff">Replace with new entry</a>';
                echo '<br><a href="get_wikidata_for_tag.php?keep=add' . write_get_vars(['suchbegriff', 'lang', 'wikidata_id', 'tag_id']) . '" class="buttonLike icons iconsPlusOne">Keep old and add new entry</a><br><br><br>';

                exit;

            }

        }
        else {

            $updateTagDescStmt->bind_param("si", $datafromwiki, $tag_id);
            $updateTagDescStmt->execute();
        }

        $updateTagDescStmt->close();

        $this->_mysqli_noda->commit();
        $this->_mysqli_noda->autocommit(true);

        // Update tag editing metadata
        $updateTagEditInfoStmt = $this->_mysqli_noda->do_prepare("UPDATE `tag`
            SET `tag_erfasst_am` = NOW(),
                `tag_erfasst_von` = ?
            WHERE `tag_id` = ?");
        $updateTagEditInfoStmt->bind_param("si", $erfasst_von, $tag_id);
        $updateTagEditInfoStmt->execute();
        $updateTagEditInfoStmt->close();

        return true;

    }

    /**
     * Function for retrieving information.
     *
     * @param string  $lang        The user's selected used language.
     * @param string  $wikidata_id Wikidata ID.
     * @param integer $tag_id      Tag ID.
     * @param string  $erfasst_von User name who's currently editing.
     *
     * @return void
     */
    public function retrieveTagInfoFromWikidataID(string $lang, string $wikidata_id, int $tag_id, string $erfasst_von) {

        self::validateWikidataId($wikidata_id);
        $data = self::_getWikidataEntity($wikidata_id);

        $wikilinks = self::_getWikipediaLinksFromWikidataOutput($data);

        $alreadyEntered = false;

        if (isset($wikilinks[$lang])) {

            $datafromwiki = MD_STD::runCurl(self::_getWikipediaApiLink($lang, $wikilinks[$lang]['title']), 10000);
            $datafromwiki = json_decode($datafromwiki, true)['parse']['text']['*'];

            # Process data retrieved from wikipedia
            if (!empty($datafromwiki = self::_cleanWikidataInput((string)$datafromwiki))) {
                $alreadyEntered = $this->retrieveTagDescFromWikipedia($tag_id, $datafromwiki, $lang, $lang, $erfasst_von);
            }

        }

        foreach (self::LANGUAGES_MAIN_DESC as $cur_lang) {

            if ($alreadyEntered === true || !isset($wikilinks[$cur_lang])) continue;

            $datafromwiki = MD_STD::runCurl(self::_getWikipediaApiLink($cur_lang, $wikilinks[$cur_lang]['title']), 10000);
            $datafromwiki = json_decode($datafromwiki, true)['parse']['text']['*'];

            # Process data retrieved from wikipedia
            if ($datafromwiki = self::_cleanWikidataInput((string)$datafromwiki)) {
                $alreadyEntered = $this->retrieveTagDescFromWikipedia($tag_id, $datafromwiki, $lang, $cur_lang, $erfasst_von);
            }

        }

        if (!empty($nodaLinks = $this->_getNodaLinksFromWikidataResult('tag', $wikidata_id, $data))) {
            NodaBatchInserter::linkNodaForTag($this->_mysqli_noda, $tag_id, $nodaLinks, $erfasst_von);
        }

        // Get translations
        if (!empty($data)) $this->getWikidataTranslationsForTag($data, $tag_id);

        NodaLogEdit::logTagEdit($this->_mysqli_noda, $tag_id, "wikidata-fetcher", $erfasst_von, 'update', 'synchronize');

    }

    /**
     * Function for fetching translations from wikidata.
     *
     * @param array<mixed> $data          Entity data fetched from wikidata.
     * @param integer      $tag_id        Tag ID.
     * @param string[]     $checkForLangs Languages to check for. Defaults to all
     *                                    languages generally loaded by the wikidata fetcher.
     *
     * @return void
     */
    public function getWikidataTranslationsForTag(array $data, int $tag_id, array $checkForLangs = self::LANGUAGES_TO_CHECK):void {

        if (empty($translations = self::listTranslationsFromWikidataWikipedia($checkForLangs, $data))) {
            return;
        }

        $toInsert = [];

        foreach ($translations as $lang => $values) {

            if (in_array($lang, self::LANGUAGES_TO_CAPITALIZE, true)) {
                $label = ucfirst($values['label']);
                $description = ucfirst($values['description']);
            }
            else {
                $label = $values['label'];
                $description = $values['description'];
            }

            $toInsert[] = [
                'tag_id' => $tag_id,
                'lang' => $lang,
                'name' => $label,
                'description' => $description,
                'link' => $values['link'],
            ];

        }

        NodaBatchInserter::insertTagTranslations($this->_mysqli_noda, $toInsert);

    }

    /**
     * Searches Wikidata for a string.
     *
     * @param string $searchTerm Search string.
     * @param string $lang       Searched language. Defaults to German.
     *
     * @return array<mixed>
     */
    public static function searchWikidataForString(string $searchTerm, string $lang = "de"):array {

        $wikidata_data = MD_STD::runCurl("https://www.wikidata.org/w/api.php?action=wbsearchentities&format=json&search=" . urlencode($searchTerm) . "&language=" . urlencode($lang) . "&limit=20", 10000);
        if (($wikidata_data = json_decode($wikidata_data, true)) === false) {
            return [];
        }

        if (empty($wikidata_data['search'])) {
            return [];
        }

        $output = [];

        foreach ($wikidata_data['search'] as $result) {

            if (empty($result['label'])
                or (!empty($result['description']) and $result['description'] === 'Wikipedia disambiguation page')
                or (!empty($result['description']) and $result['description'] === 'Wikimedia disambiguation page')
            ) continue;

            $cur = [
                'id' => $result['id'],
                'label' => $result['label'],
                'label_ext' => '',
                'description' => '',
            ];

            if (!empty($result['match'])) {
                $cur['label_ext'] = "{$result['match']['language']}: {$result['match']['text']}";
            }
            if (!empty($result['description'])) {
                $cur['description'] = $result['description'];
            }

            $output[] = $cur;

        }

        return $output;

    }

    /**
     * Generates the HTML for an entry in the general wikidata search results list.
     *
     * @param string       $link       Links.
     * @param string       $searchTerm Search term.
     * @param string       $lang       Language.
     * @param array<mixed> $result     Single result to display.
     *
     * @return string
     */
    public static function generateWikidataResultsListEntry(string $link, string $searchTerm, string $lang, array $result):string {

        if (empty($result['label']) or (isset($result['description']) and in_array($result['description'], ['Wikipedia disambiguation page', 'Wikimedia disambiguation page'], true))) {
            return '';
        }

        $output = '<div><a href="' . $link . 'suchbegriff=' . htmlspecialchars($searchTerm) . '&wikidata_id=' . htmlspecialchars((string)$result['id']) . '&lang=' . htmlspecialchars($lang) . '">
            <h4 class="icons iconsTag">' . $result['id'] . '</h4>';
        $output .= '<p class="wikidataSummary">' . $result['label'];
        if (!empty($result['label_ext'])) $output .= " (<span class='icons iconsTranslate'>{$result['label_ext']}</span>)";
        $output .= '</p>';
        if (!empty($result['description'])) $output .= '<p>' . $result['description'] . '</p>';
        $output .= '</a><a class="icons iconsEye" target="_blank" href="https://www.wikidata.org/wiki/' . $result['id'] . '">Wikidata page</a></div>';
        return $output;

    }

    /**
     * Function for generating a wikidata results list.
     *
     * @param string $link       Links.
     * @param string $searchTerm Search term.
     * @param string $lang       Language.
     *
     * @return string
     */
    public static function generateWikidataResultsList(string $link, string $searchTerm, string $lang):string {

        if (empty($wikidata_data = self::searchWikidataForString($searchTerm))) {
            return '<p class="icons iconsAlert alert"><b>' . ucfirst($searchTerm) . '</b>  not found in Wikidata</p>';
        }

        $output = '
        <main id="wikidataResultsList">';
        foreach ($wikidata_data as $result) {
            $output .= self::generateWikidataResultsListEntry($link, $searchTerm, $lang, $result);
        }
        $output .= '
        </main>';

        return $output;

    }

    /**
     * Attempts to parse birth or death years from the data returned by wikidata.
     *
     * @param string $inputTime Input time in the format delivered by wikidata.
     *
     * @return string
     */
    public static function wikidataBirthDeathToYear(string $inputTime):string {

        $birth_date_int = strtotime(substr($inputTime, 1, 4));
        if ($birth_date_int) {
            $birth_date = date("Y", $birth_date_int);
            if ($birth_date === date("Y") and ($tTime = strtotime($inputTime)) !== false) {
                $birth_date = date("Y", $tTime);
            }

            return $birth_date;
        }

        return '';

    }

    /**
     * Function for generating a wikidata results list for actors, keeping track of life dates.
     *
     * @param string  $link        Links.
     * @param string  $searchTerm  Search term.
     * @param string  $lang        Language.
     * @param integer $yearOfBirth Year of birth.
     * @param integer $yearOfDeath Year of death.
     *
     * @return string
     */
    public static function generateWikidataResultsListForActors(string $link, string $searchTerm, string $lang, int $yearOfBirth, int $yearOfDeath):string {

        if (empty($wikidata_data = self::searchWikidataForString($searchTerm))) {
            return '<p class="icons iconsAlert alert"><b>' . ucfirst($searchTerm) . '</b>  not found in Wikidata</p>';
        }

        $qLinksToCheck = [];
        foreach ($wikidata_data as $entry) {
            $qLinksToCheck[$entry['id']] = "https://www.wikidata.org/wiki/Special:EntityData/" . $entry['id'] . ".json";
        }
        $fetched = MD_STD::runCurlMulti($qLinksToCheck, 10000);

        $yearsOfBirthList = $yearsOfDeathList = [];
        foreach ($fetched as $qId => $data) {
            if (!($jsonData = json_decode($data, true))) {
                continue;
            }
            if (empty($jsonData['entities'][$qId])) {
                continue;
            }
            $data = $jsonData['entities'][$qId];

            if (!empty($data['claims']['P569']) and !empty($data['claims']['P569']['0']['mainsnak']['datavalue']['value']['time'])) {
                $yearsOfBirthList[$qId] = (int)self::wikidataBirthDeathToYear($data['claims']['P569']['0']['mainsnak']['datavalue']['value']['time']);
            }

            if (!empty($data['claims']['P570']) and !empty($data['claims']['P570']['0']['mainsnak']['datavalue']['value']['time'])) {
                $yearsOfDeathList[$qId] = (int)self::wikidataBirthDeathToYear($data['claims']['P570']['0']['mainsnak']['datavalue']['value']['time']);
            }
        }

        $output = '
        <main id="wikidataResultsList">';
        foreach ($wikidata_data as $result) {
            if (empty($result['id'])) continue;

            if (!empty($yearsOfBirthList[$result['id']])) {
                if (empty($result['description'])) {
                    $result['description'] = 'Born: ' . $yearsOfBirthList[$result['id']];
                }
                else $result['description'] .= '<br/>Born: ' . $yearsOfBirthList[$result['id']];
            }

            if (!empty($yearsOfDeathList[$result['id']])) {
                if (empty($result['description'])) {
                    $result['description'] = 'Death: ' . $yearsOfDeathList[$result['id']];
                }
                else $result['description'] .= '<br/>Death: ' . $yearsOfDeathList[$result['id']];
            }

            if (!empty($yearsOfBirthList[$result['id']]) && !empty($yearsOfDeathList[$result['id']])) {
                if ($yearsOfBirthList[$result['id']] === $yearOfBirth
                    && $yearsOfDeathList[$result['id']] === $yearOfDeath
                ) {
                    $result['description'] .= '<br/><span class="buttonLike">Suggestion!</span>';
                }
            }

            $output .= self::generateWikidataResultsListEntry($link, $searchTerm, $lang, $result);
        }
        $output .= '
        </main>';

        return $output;

    }

    /**
     * Function generates HTML head for wikidata fetchers.
     *
     * @param string  $lang     User language.
     * @param boolean $implyEnd If set to true, the end string will be echoed at the end of the script execution.
     *
     * @return string
     */
    public static function generateHTMLHeadForWikidataFetcher(string $lang, bool $implyEnd = true):string {
        $output = "<!DOCTYPE html><html class=\"getWikidata\" lang=\"{$lang}\">
    <head>
        <title>Get Wikidata</title>
        <meta name=\"viewport\" content=\"width=device-width, initial-scale=1\" />
        <link rel=\"manifest\" href=\"../manifest.webmanifest\" />
        <meta name=\"theme-color\" content=\"#0b1728\" />
        <link rel=\"shortcut icon\" sizes=\"16x16 32x32\" href=\"../img/mdlogo-nodac.svg.png\" />
        <link rel=\"apple-touch-icon\" sizes=\"256x256\" href=\"../img/mdterm-256px.png\" />
        <script type=\"text/javascript\" src=\"../js/wikidataGetter.min.js\" async></script>
        <meta http-equiv=\"content-type\" content=\"text/html; charset=UTF-8\"/>";
        if (defined("MAIN_CSS_FILE")) {
            $output .= "<link rel=\"stylesheet\" type=\"text/css\" href=\"" . htmlspecialchars(MAIN_CSS_FILE) . "\">";
        }
        $output .= "
        <meta name=\"description\" content=\"Fetch information from Wikidata.\" />
    </head>
    <body>";

        if ($implyEnd === true) {
            register_shutdown_function(function() :void {
                echo printHTMLEnd();
            });
        }

        return MD_STD::minimizeHTMLString($output);

    }

    /**
     * Function generate header for wikidata fetcher pages.
     *
     * @param MDTlLoader $tlLoader   Translation variable.
     * @param string     $additional Additional info.
     * @param string     $searchTerm Search term.
     *
     * @return string
     */
    public static function generateWikidataFetcherHeader(MDTlLoader $tlLoader, string $additional = "", string $searchTerm = ""):string {

        if (empty($searchTerm) and !empty($_GET['suchbegriff'])) {
            $searchTerm = (string)$_GET['suchbegriff'];
        }

        $output = '
        <header>
            <h1><img src="../img/wikidata.png" alt="Logo: Wikidata" />' . $tlLoader->tl("wiki", "wiki", "fetch_from_wikidata");
        $output .= ': ' . htmlspecialchars($searchTerm);
        $output .= '</h1>';
        $output .= $additional;
        $output .= '</header>';
        return $output;

    }

    /**
     * Constructor.
     *
     * @param MDMysqli $mysqli_noda DB connection.
     *
     * @return void
     */
    public function __construct(MDMysqli $mysqli_noda) {

        $this->_mysqli_noda = $mysqli_noda;

    }
}