/*
 * Hide Header on scroll down
 */

$(function() {
  const $searchInput = $("#search-input");
  const delta = ScrollHelper.getTopbarHeight();

  let didScroll;
  let lastScrollTop = 0;

  function hasScrolled() {
    let st = $(this).scrollTop();

    /* Make sure they scroll more than delta */
    if (Math.abs(lastScrollTop - st) <= delta) {
      return;
    }

    if (st > lastScrollTop ) { // Scroll Down
      ScrollHelper.hideTopbar();

      if ($searchInput.is(":focus")) {
        $searchInput.blur(); /* remove focus */
      }

    } else  { // Scroll up
      // has not yet scrolled to the bottom of the screen, that is, there is still space for scrolling
      if (st + $(window).height() < $(document).height()) {

        if (ScrollHelper.hasScrollUpTask()) {
          return;
        }

        if (ScrollHelper.topbarLocked()) { // avoid redundant scroll up event from smooth scrolling
          ScrollHelper.unlockTopbar();
        } else {
          if (ScrollHelper.orientationLocked()) { // avoid device auto scroll up on orientation change
            ScrollHelper.unLockOrientation();
          } else {
            ScrollHelper.showTopbar();
          }
        }
      }
    }

    lastScrollTop = st;

  } // hasScrolled()

  function handleLandscape() {
    if ($(window).scrollTop() === 0) {
      return;
    }
    ScrollHelper.lockOrientation();
    ScrollHelper.hideTopbar();
  }

  if (screen.orientation) {
    screen.orientation.onchange = () => {
      const type = screen.orientation.type;
      if (type ===  "landscape-primary" || type === "landscape-secondary") {
        handleLandscape();
      }
    };

  } else {
    // for the browsers that not support `window.screen.orientation` API
    $(window).on("orientationchange",() => {
      if ($(window).width() < $(window).height()) { // before rotating, it is still in portrait mode.
        handleLandscape();
      }
    });
  }

  $(window).scroll(() => {
    if (didScroll) {
      return;
    }
    didScroll = true;
  });

  setInterval(() => {
    if (didScroll) {
      hasScrolled();
      didScroll = false;
    }
  }, 250);

});