<!DOCTYPE html>
<meta charset="utf-8">
<title>ScrollTimeline constructor</title>
  <link rel="help" href="https://wicg.github.io/scroll-animations/#scrolltimeline-interface">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<style>
.scroller {
  height: 100px;
  width: 100px;
  overflow: scroll;
}

.content {
  height: 500px;
  width: 500px;
}
</style>

<div class="scroller">
  <div class="content"></div>
</div>

<script>
'use strict';

function formatOffset(v) {
  if (typeof(v) == 'object')
    return `${v.constructor.name}(${v.toString()})`;
  return `'${v.toString()}'`;
}

function assert_offsets_equal(a, b) {
  assert_equals(formatOffset(a), formatOffset(b));
}

// source

test(t => {
  const scroller = document.querySelector('.scroller');
  assert_equals(
      new ScrollTimeline({source: scroller}).source, scroller);
}, 'A ScrollTimeline can be created with a source');

test(t => {
  const div = document.createElement('div');
  assert_equals(new ScrollTimeline({source: div}).source, div);
}, 'A ScrollTimeline can be created with a non-scrolling source');

test(t => {
  assert_equals(new ScrollTimeline({source: null}).source, null);
}, 'A ScrollTimeline created with a null source should have no source');

test(t => {
  assert_equals(new ScrollTimeline().source, document.scrollingElement);
}, 'A ScrollTimeline created without a source should use the ' +
   'document.scrollingElement');

// axis

test(t => {
  assert_equals(new ScrollTimeline().axis, 'block');
}, 'A ScrollTimeline created with the default axis should default to ' +
   `'block'`);

const gValidAxisValues = [
  'block',
  'inline',
  'x',
  'y',
];

for (let axis of gValidAxisValues) {
  test(function() {
    const scrollTimeline =
        new ScrollTimeline({axis: axis});
    assert_equals(scrollTimeline.axis, axis);
  }, `'${axis}' is a valid axis value`);
}

test(t => {
  let constructorFunc = function() {
    new ScrollTimeline({axis: 'nonsense'})
  };
  assert_throws_js(TypeError, constructorFunc);

  // 'auto' for axis was previously in the spec, but was removed. Make
  // sure that implementations do not support it.
  constructorFunc = function() {
    new ScrollTimeline({axis: 'auto'})
  };
  assert_throws_js(TypeError, constructorFunc);
}, 'Creating a ScrollTimeline with an invalid axis value should throw');
</script>
