import { zx, Component, stream } from "../src";
import "./header.scss";

export const Header = () => {
  let scroll$ = stream();
  window.addEventListener("scroll", scroll$);

  let headerHidden$ = stream(false);
  let header = zx`
    <div
      class=${headerHidden$.map(
        hidden =>
          "row big-header highlight-background " + (hidden ? "hidden" : "")
      )}
      onclick=${e => e.target.tagName !== "A" && scrollUp()}
    >
      <div class="container">
        <div class="row">
          <div class="col s12 center">
            <img src="./icon.png" />
          </div>
          <h1 class="col s12 center highlight">ZLIQ</h1>
        </div>
        <h3 class="center highlight-less">
          The web-framework-force you want your Padawan to learn.
        </h3>
      </div>
      <div class="link-list center">
        <a href="#motivation">Motivation</a>
        <a href="#tutorial">Tutorial</a>
        <a href="#streams">Streams</a>
        <a href="#state">State</a>
        <a href="#helpers">Helpers</a>
        <a href="#routing">Routing</a>
        <a href="#lifecycle">Lifecycle</a>
        <a href="#testing">Testing</a>
      </div>
    </div>
  `;

  scroll$
    .map(() => {
      if (!headerHidden$.value && document.body.scrollHeight < 900)
        return false;
      let scrollTop = window.scrollY;
      return scrollTop > 100;
    })
    .map(headerHidden$);

  return header;
};

function scrollUp() {
  scrollTo(document.body, 0, 0.5);
}

function scrollTo(element, to, duration) {
  if (duration <= 0) return;
  var difference = to - element.scrollTop;
  var perTick = (difference / duration) * 10;

  setTimeout(function() {
    element.scrollTop = element.scrollTop + perTick;
    if (element.scrollTop === to) return;
    scrollTo(element, to, duration - 10);
  }, 10);
}