Implement regex data gathering magic

}

wp_embed_register_handler('umap', '#^https://umap.openstreetmap.de/[a-z]{2}/map/[^/]*#', 'fscoli_embed_umap');

/**

 * Helper function: Matches the given regex against the given string and

 * returns the $group-th match group of the match. Returns null if there is

 * no such group or there was no match.

 */

function fscoli_regex_match_group($regex, $str, $group) {

    preg_match($regex, $str, $matches);

    /* 

     * Q: Wait, where did $matches suddenly come from?

     * A: We passed it by reference (https://www.php.net/manual/en/language.references.pass.php). This means

     * we told the function it should store its results in a variable we can later access as $matches.

     * Yes, that's a thing in some programming languages.

     */ 

    if(array_key_exists($group, $matches)) {

        return $matches[$group];

    } else {

        return null;

    }

}

/*

 * Add privacy protection for embed elements: You have to click a button of a consent prompt

 * before the content is loaded.

 */

function fscoli_show_embed_privacy_consent_prompt($embed_html) {

    // Extract this from the embed_html string with regular expressions and heuristics

    $width              = null;  // TODO

    $height             = null;  // TODO

    $provider_url       = null;  // TODO

    $provider_domain    = null;  // TODO

    $privacy_policy_url = null;  // TODO

    // Try to guess width and height of the consent prompt to match the dimensions of the embedded content

    $width              = fscoli_regex_match_group('/width ?(:|= ?["\']) ?(\d+ ?px)/', $embed_html, 2);

    $height             = fscoli_regex_match_group('/height ?(:|= ?["\']) ?(\d+ ?px)/', $embed_html, 2);

    if($width === null) {

        $width = "auto";

    }

    if($height === null) {

        $height = "auto";

    }

    $provider_url       = fscoli_regex_match_group('/src ?= ?["\'](https?://(.*?))/.*?["\']/', $embed_html, 1);

    $provider_domain    = fscoli_regex_match_group('/src ?= ?["\'](https?://(.*?))/.*?["\']/', $embed_html, 2);

    $privacy_policy_url = null;

    if($provider_domain === "umap.openstreetmap.de") {

        $privacy_policy_url = "https://www.fossgis.de/datenschutzerkl%C3%A4rung";

    }

    if($privacy_policy_url !== null) {

        $privacy_policy_link = <<<HTML

        <a href="${esc_url(privacy_policy_url)}">dort verlinkte Datenschutzerklärung</a>

        HTML;

    } else {

        $privacy_policy_link = "dort verlinkte Datenschutzerklärung";

    }

    /* 

     * We use the heredoc syntax (https://www.php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc)

        <section class="privacy-consent-prompt">

            <button onclick="givePrivacyConsent(this.parentElement)">Inhalt anzeigen</button>

            <p>Dabei werden Daten an <a href="${esc_url(provider_url)}">${esc_html(provider_domain)}</a> (und ggfs. weitere Anbieter) übertragen. Es gilt die <a href="${esc_url(privacy_policy_url)}">dort verlinkte Datenschutzerklärung</a>.</p>

            <p>Dabei werden Daten an <a href="${esc_url(provider_url)}">${esc_html(provider_domain)}</a> (und ggfs. weitere Anbieter) übertragen. Es gilt die $privacy_policy_link.</p>

        </section>

    </div>