<!doctype html>
<meta charset=utf-8>
<title>KeyframeEffect.setKeyframes() for CSS transitions</title>
<!-- TODO: Add a more specific link for this once it is specified. -->
<link rel="help" href="https://drafts.csswg.org/css-transitions-2/#csstransition">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/helper.js"></script>
<div id="log"></div>
<script>
'use strict';

test(t => {
  const div = addDiv(t);

  div.style.left = '0px';
  getComputedStyle(div).transitionProperty;
  div.style.transition = 'left 100s';
  div.style.left = '100px';

  const transition = div.getAnimations()[0];
  transition.effect.setKeyframes({ left: ['200px', '300px', '100px'] });

  assert_equals(getComputedStyle(div).left, '200px');
}, 'Keyframes set using setKeyframes() are reflected in computed style for'
   + ' a running transition');

test(t => {
  const div = addDiv(t);

  div.style.left = '0px';
  getComputedStyle(div).transitionProperty;
  div.style.transition = 'left 100s';
  div.style.left = '100px';

  const transition = div.getAnimations()[0];
  transition.effect.setKeyframes({ top: ['0px', '100px', '300px'] });

  assert_equals(transition.transitionProperty, 'left');
}, 'A transition with replaced keyframes still returns the original'
   + ' transitionProperty');

test(t => {
  const div = addDiv(t);

  div.style.left = '0px';
  getComputedStyle(div).transitionProperty;
  div.style.transition = 'left 100s';
  div.style.left = '100px';

  const transition = div.getAnimations()[0];
  transition.effect.setKeyframes({ });

  assert_equals(transition.transitionProperty, 'left');
}, 'A transition with no keyframes still returns the original'
   + ' transitionProperty');

function retarget_test(description, newKeyframes, reversed_start) {
  test(t => {
    const div = addDiv(t);

    div.style.left = '0px';
    getComputedStyle(div).transitionProperty;
    div.style.transition = 'left 100s linear';
    div.style.left = '100px';

    const transition = div.getAnimations()[0];
    transition.currentTime = 50 * MS_PER_SEC;
    transition.effect.setKeyframes(newKeyframes);

    // Reverse transition
    div.style.left = '0px';
    const reversedTransition = div.getAnimations()[0];

    assert_approx_equals(
      reversedTransition.effect.getComputedTiming().activeDuration,
      50 * MS_PER_SEC, 1,
      "The reversed transition has correctly reduced duration"
    );
    assert_equals(reversedTransition.effect.getKeyframes()[0].left, reversed_start,
        "The reversed transition starts at the expected point");
  },  description);
}

retarget_test("A transition with replaced keyframes animating the same property " +
    "still exhibits normal reversing behavior.",
    {left: ['200px', '300px', '100px']}, '300px');

retarget_test("A transition with replaced keyframes animating a different property " +
    "still exhibits normal reversing behavior  (reversing from the base value).",
    {top: ['200px', '300px', '100px']}, '100px');

retarget_test("A transition with replaced keyframes animating nothing " +
    "still exhibits normal reversing behavior (reversing from the base value).",
    {}, '100px');

test(t => {
  const div = addDiv(t);

  // Initialize the style.
  div.style.left = '100px';
  div.style.top = '100px';
  div.style.transition = 'left 100s linear, top 100s linear';
  getComputedStyle(div).left;

  // Start some transitions.
  div.style.left ='200px';
  div.style.top = '200px';
  const transitions = div.getAnimations();

  // Hand control of the left property over to top's transition. The composite
  // ordering of the animations is 'left' then 'top' since the transitions were
  // generated in the same transition generation and follow Unicode ordering.
  assert_equals(transitions[0].transitionProperty, 'left');
  transitions[0].effect.setKeyframes({});
  transitions[1].effect.setKeyframes([
    {left: '100px', top: '100px'},
    {left: '400px', top: '200px'}])
  getComputedStyle(div).left;

  // These updates form a single style change, equivalent to setting times and
  // then setting left.
  transitions[0].currentTime = 50 * MS_PER_SEC;
  div.style.left ='100px';
  transitions[1].currentTime = 60 * MS_PER_SEC;

  // As there was a style change event, the new 'left' transition now has a
  // higher value for the transition generation than the 'top' transition,
  // reversing the order of the transitions returned by getAnimations.
  const reversedTransition = div.getAnimations()[1];
  assert_equals(reversedTransition.transitionProperty, 'left',
      "A reversed transition on left is produced");

  assert_approx_equals(
      reversedTransition.effect.getComputedTiming().activeDuration,
      50 * MS_PER_SEC, 1,
      "The reversed transition has correctly reduced duration (based on the " +
      "original left transition).");

  assert_equals(reversedTransition.effect.getKeyframes()[0].left, '280px',
      "The reversed transition gets its start value from the other " +
      "transition controlling left");

},  "A transition with replaced keyframes animating nothing on a property " +
    "being controlled by another modified transition exhibits normal " +
    "reversing behavior and reverses from the other transition's current " +
    "value.");

test(t => {
  const div = addDiv(t);

  // Initialize the style.
  div.style.left = '100px';
  div.style.transition = 'left 100s linear';
  getComputedStyle(div).left;

  // Start the transtion.
  div.style.left ='200px';
  const transition = div.getAnimations()[0];

  // Update the keyframes and advance to the midpoint of the animation.
  transition.effect.setKeyframes([
    { offset: 0, left: '-50px', composite: 'add', easing: 'linear'}]);
  transition.currentTime = 50 * MS_PER_SEC;
  assert_equals(getComputedStyle(div).left, '175px',
                'The computed style is based on the updated keyframes');

  div.style.left = '100px';
  const reversedTransition = div.getAnimations()[0];
  assert_equals(reversedTransition.effect.getKeyframes()[0].left, '175px',
                'The start value matches the \'before change\' value');

}, 'A transition with replaced kefyrames and composite \'add\' exhibits ' +
   'normal reversing behavior, and the effect is not double counted when ' +
   'calculating the before change style');

</script>