"use strict";

var session = ChromeUtils.import("resource://gre/modules/TelemetrySession.jsm", {});

const DUMMY_PAGE_DATA_URI = `data:text/html,
    <html>
      <head>
        <meta charset="utf-8"/>
        <title>Dummy</title>
      </head>
      <body>
        <h1 id='header'>Just a regular everyday normal page.</h1>
      </body>
    </html>`;

/**
 * Tests the MEMORY_DISTRIBUTION_AMONG_CONTENT probe by opening a few tabs, then triggering
 * the memory probes and waiting for the "gather-memory-telemetry-finished" notification.
 */
add_task(async function test_memory_distribution() {
  waitForExplicitFinish();

  if (SpecialPowers.getIntPref("dom.ipc.processCount", 1) < 2) {
    ok(true, "Skip this test if e10s-multi is disabled.");
    finish();
    return;
  }

  Services.telemetry.canRecordExtended = true;

  let histogram = Services.telemetry.getKeyedHistogramById("MEMORY_DISTRIBUTION_AMONG_CONTENT");
  histogram.clear();

  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, DUMMY_PAGE_DATA_URI);
  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, DUMMY_PAGE_DATA_URI);
  let tab3 = await BrowserTestUtils.openNewForegroundTab(gBrowser, DUMMY_PAGE_DATA_URI);

  let finishedGathering = new Promise(resolve => {
    let obs = function () {
      Services.obs.removeObserver(obs, "gather-memory-telemetry-finished");
      resolve();
    }
    Services.obs.addObserver(obs, "gather-memory-telemetry-finished");
  });

  session.TelemetrySession.getPayload();

  await finishedGathering;

  let s = histogram.snapshot();
  ok("0 - 10 tabs" in s, "We should have some samples by now in this bucket.")
  for (var key in s) {
    is(key, "0 - 10 tabs");
    let fewTabsSnapshot = s[key];
    ok(fewTabsSnapshot.sum > 0, "Zero difference between all the content processes is unlikely, what happened?");
    ok(fewTabsSnapshot.sum < 80, "20 percentage difference on average is unlikely, what happened?");
    let c = fewTabsSnapshot.counts;
    for (let i = 10; i < c.length; i++) {
      // If this check fails it means that one of the content processes uses at least 20% more or 20% less than the mean.
      is(c[i], 0, "All the buckets above 10 should be empty");
    }
  }

  histogram.clear();

  await BrowserTestUtils.removeTab(tab3);
  await BrowserTestUtils.removeTab(tab2);
  await BrowserTestUtils.removeTab(tab1);
  finish();
});
