(function () {
  'use strict';

  var forumOrigin = window.location.origin;

  function showTarget(targetValue) {
    var targetUrl;
    var forumLink;
    var targetUrlLabel;
    var postPanel;
    var fallbackPanel;

    if (!targetValue) {
      return false;
    }

    try {
      targetUrl = new URL(targetValue);

      if (targetUrl.origin !== forumOrigin) {
        console.warn(
          'Rejected forum target with unexpected origin:',
          targetUrl.origin
        );

        return false;
      }

      if (targetUrl.pathname.indexOf('/d/') !== 0) {
        console.warn(
          'Rejected forum target with unexpected path:',
          targetUrl.pathname
        );

        return false;
      }

      forumLink = document.getElementById('forum-link');
      targetUrlLabel = document.getElementById('target-url');
      postPanel = document.getElementById('post-panel');
      fallbackPanel = document.getElementById('fallback-panel');

      if (
        !forumLink ||
        !targetUrlLabel ||
        !postPanel ||
        !fallbackPanel
      ) {
        console.warn(
          'Required landing-page elements were not found.'
        );

        return false;
      }

      forumLink.href = targetUrl.href;
      targetUrlLabel.textContent = targetUrl.href;

      postPanel.hidden = false;
      fallbackPanel.hidden = true;

      return true;
    } catch (error) {
      console.warn(
        'The forum target URL is invalid.',
        error
      );

      return false;
    }
  }

  async function initialize() {
    var parameters;
    var queryTarget;
    var context;
    var subPageId;

    parameters = new URLSearchParams(
      window.location.search
    );

    queryTarget = parameters.get('target');

    /*
     * Allow direct browser tests with ?target=...
     */
    if (showTarget(queryTarget)) {
      return;
    }

    /*
     * In Microsoft Teams the target is passed as subEntityId.
     * TeamsJS v2 exposes that value as context.page.subPageId.
     */
    if (
      !window.microsoftTeams ||
      !window.microsoftTeams.app
    ) {
      console.info(
        'TeamsJS is unavailable; showing the notifications fallback.'
      );

      return;
    }

    try {
      await window.microsoftTeams.app.initialize();

      context =
        await window.microsoftTeams.app.getContext();

      subPageId =
        context &&
        context.page &&
        context.page.subPageId
          ? context.page.subPageId
          : null;

      console.info(
        'Teams page.subPageId:',
        subPageId || '[none]'
      );

      showTarget(subPageId);
    } catch (error) {
      console.warn(
        'Could not read the Microsoft Teams context.',
        error
      );
    }
  }

  initialize();
})();