function ok(a, msg) {
  postMessage({ type: "status", status: !!a, msg });
}

function is(a, b, msg) {
  ok(a === b, msg);
}

function finish() {
  postMessage({ type: "finish" });
}

let isRounded = (x, expectedPrecision) => {
  let rounded = Math.floor(x / expectedPrecision) * expectedPrecision;
  // First we do the perfectly normal check that should work just fine
  if (rounded === x || x === 0) {
    return true;
  }

  // When we're diving by non-whole numbers, we may not get perfect
  // multiplication/division because of floating points.
  // When dealing with ms since epoch, a double's precision is on the order
  // of 1/5 of a microsecond, so we use a value a little higher than that as
  // our epsilon.
  // To be clear, this error is introduced in our re-calculation of 'rounded'
  // above in JavaScript.
  if (Math.abs(rounded - x + expectedPrecision) < 0.0005) {
    return true;
  } else if (Math.abs(rounded - x) < 0.0005) {
    return true;
  }

  // Then we handle the case where you're sub-millisecond and the timer is not
  // We check that the timer is not sub-millisecond by assuming it is not if it
  // returns an even number of milliseconds
  if (expectedPrecision < 1 && Math.round(x) == x) {
    if (Math.round(rounded) == x) {
      return true;
    }
  }

  ok(
    false,
    "Looming Test Failure, Additional Debugging Info: Expected Precision: " +
      expectedPrecision +
      " Measured Value: " +
      x +
      " Rounded Vaue: " +
      rounded +
      " Fuzzy1: " +
      Math.abs(rounded - x + expectedPrecision) +
      " Fuzzy 2: " +
      Math.abs(rounded - x)
  );

  return false;
};

function runTimerTests(expectedPrecision) {
  ok(
    isRounded(performance.timeOrigin, expectedPrecision),
    `In a worker, for reduceTimerPrecision, performance.timeOrigin is not correctly rounded: ` +
      performance.timeOrigin
  );

  // Try to add some entries.
  performance.mark("Test");
  performance.mark("Test-End");
  performance.measure("Test-Measure", "Test", "Test-End");

  // Check the entries in performance.getEntries/getEntriesByType/getEntriesByName.
  is(
    performance.getEntries().length,
    3,
    "In a worker, for reduceTimerPrecision: Incorrect number of entries for performance.getEntries() for workers: " +
      performance.getEntries().length
  );
  for (var i = 0; i < 3; i++) {
    let startTime = performance.getEntries()[i].startTime;
    let duration = performance.getEntries()[i].duration;
    ok(
      isRounded(startTime, expectedPrecision),
      "In a worker, for reduceTimerPrecision(" +
        expectedPrecision +
        "), performance.getEntries(" +
        i.toString() +
        ").startTime is not rounded: " +
        startTime.toString()
    );
    ok(
      isRounded(duration, expectedPrecision),
      "In a worker, for reduceTimerPrecision(" +
        expectedPrecision +
        "), performance.getEntries(" +
        i.toString() +
        ").duration is not rounded: " +
        duration.toString()
    );
  }
  is(
    performance.getEntriesByType("mark").length,
    2,
    "In a worker, for reduceTimerPrecision: Incorrect number of entries for performance.getEntriesByType() for workers: " +
      performance.getEntriesByType("resource").length
  );
  is(
    performance.getEntriesByName("Test", "mark").length,
    1,
    "In a worker, for reduceTimerPrecision: Incorrect number of entries for performance.getEntriesByName() for workers: " +
      performance.getEntriesByName("Test", "mark").length
  );

  finish();
}

self.onmessage = function (e) {
  if (e.data.type === "runTimerTests") {
    runTimerTests(e.data.precision);
  } else {
    ok(false, "Unknown message type");
  }
};