<!DOCTYPE html>
<script src="helper-functions.js"></script>
<div style="height: 200px; width: 100px;"></div>
<div id="target" style="background-color: green; width:100px; height:100px"></div>
<div style="height: 200px; width: 100px;"></div>
<script>
var port;
var entries = [];
var target = document.getElementById('target');
var scroller = document.scrollingElement;
var nextStep;

// Note that we never use RAF in this code, because this frame might get render-throttled.
// Instead of RAF-ing, we just post an empty message to the parent window, which will
// RAF when it is received, and then send us a message to cause the next step to run.

// Use a rootMargin here, and verify it does NOT get applied for the cross-origin case.
var observer = new IntersectionObserver(
    changes => { entries = entries.concat(changes) },
    { rootMargin: "7px" }
);
observer.observe(target);

function step0() {
  entries = entries.concat(observer.takeRecords());
  nextStep = step1;
  port.postMessage({actual: entries.map(entryToJson), expected: []}, "*");
  entries = [];
  port.postMessage({scrollTo: 200}, "*");
}

function step1() {
  entries = entries.concat(observer.takeRecords());
  port.postMessage({actual: entries.map(entryToJson), expected: []}, "*");
  entries = [];
  scroller.scrollTop = 250;
  nextStep = step2;
  port.postMessage({}, "*");
}

function step2() {
  entries = entries.concat(observer.takeRecords());
  var expected = [{
    boundingClientRect: coordinatesToClientRectJson(-42, 108, 58, 8),
    intersectionRect: coordinatesToClientRectJson(0, 108, 58, 8),
    rootBounds: "null",
    target: target.id
  }];
  port.postMessage({actual: entries.map(entryToJson), expected: expected}, "*");
  entries = [];
  nextStep = step3;
  port.postMessage({scrollTo: 100}, "*");
}

function step3() {
  entries = entries.concat(observer.takeRecords());
  var expected = [{
    boundingClientRect: coordinatesToClientRectJson(-42, 108, 58, 8),
    intersectionRect: coordinatesToClientRectJson(0, 0, 0, 0),
    rootBounds: "null",
    target: target.id
  }];
  port.postMessage({actual: entries.map(entryToJson), expected: expected}, "*");
  port.postMessage({DONE: 1}, "*");
}

function handleMessage(event)
{
  port = event.source;
  nextStep();
}

nextStep = step0;
window.addEventListener("message", handleMessage);
</script>