// ownerGlobal isn't defined in content privileged windows.
/* eslint-disable mozilla/use-ownerGlobal */

// Utilities for synthesizing of native events.

function getResolution() {
  let resolution = -1; // bogus value in case DWU fails us
  // Use window.top to get the root content window which is what has
  // the resolution.
  resolution = SpecialPowers.getDOMWindowUtils(window.top).getResolution();
  return resolution;
}

function getPlatform() {
  if (navigator.platform.indexOf("Win") == 0) {
    return "windows";
  }
  if (navigator.platform.indexOf("Mac") == 0) {
    return "mac";
  }
  // Check for Android before Linux
  if (navigator.appVersion.includes("Android")) {
    return "android";
  }
  if (navigator.platform.indexOf("Linux") == 0) {
    return "linux";
  }
  return "unknown";
}

function nativeVerticalWheelEventMsg() {
  switch (getPlatform()) {
    case "windows":
      return 0x020a; // WM_MOUSEWHEEL
    case "mac":
      var useWheelCodepath = SpecialPowers.getBoolPref(
        "apz.test.mac.synth_wheel_input",
        false
      );
      // Default to 1 (kCGScrollPhaseBegan) to trigger PanGestureInput events
      // from widget code. Allow setting a pref to override this behaviour and
      // trigger ScrollWheelInput events instead.
      return useWheelCodepath ? 0 : 1;
    case "linux":
      return 4; // value is unused, pass GDK_SCROLL_SMOOTH anyway
  }
  throw new Error(
    "Native wheel events not supported on platform " + getPlatform()
  );
}

function nativeHorizontalWheelEventMsg() {
  switch (getPlatform()) {
    case "windows":
      return 0x020e; // WM_MOUSEHWHEEL
    case "mac":
      return 0; // value is unused, can be anything
    case "linux":
      return 4; // value is unused, pass GDK_SCROLL_SMOOTH anyway
  }
  throw new Error(
    "Native wheel events not supported on platform " + getPlatform()
  );
}

// Given an event target which may be a window or an element, get the associated window.
function windowForTarget(aTarget) {
  if (aTarget instanceof Window) {
    return aTarget;
  }
  return aTarget.ownerDocument.defaultView;
}

// Given an event target which may be a window or an element, get the associated element.
function elementForTarget(aTarget) {
  if (aTarget instanceof Window) {
    return aTarget.document.documentElement;
  }
  return aTarget;
}

// Given an event target which may be a window or an element, get the associatd nsIDOMWindowUtils.
function utilsForTarget(aTarget) {
  return SpecialPowers.getDOMWindowUtils(windowForTarget(aTarget));
}

// Given a pixel scrolling delta, converts it to the platform's native units.
function nativeScrollUnits(aTarget, aDimen) {
  switch (getPlatform()) {
    case "linux": {
      // GTK deltas are treated as line height divided by 3 by gecko.
      var targetWindow = windowForTarget(aTarget);
      var targetElement = elementForTarget(aTarget);
      var lineHeight = targetWindow.getComputedStyle(targetElement)[
        "font-size"
      ];
      return aDimen / (parseInt(lineHeight) * 3);
    }
  }
  return aDimen;
}

function nativeMouseDownEventMsg() {
  switch (getPlatform()) {
    case "windows":
      return 2; // MOUSEEVENTF_LEFTDOWN
    case "mac":
      return 1; // NSEventTypeLeftMouseDown
    case "linux":
      return 4; // GDK_BUTTON_PRESS
    case "android":
      return 5; // ACTION_POINTER_DOWN
  }
  throw new Error(
    "Native mouse-down events not supported on platform " + getPlatform()
  );
}

function nativeMouseMoveEventMsg() {
  switch (getPlatform()) {
    case "windows":
      return 1; // MOUSEEVENTF_MOVE
    case "mac":
      return 5; // NSEventTypeMouseMoved
    case "linux":
      return 3; // GDK_MOTION_NOTIFY
    case "android":
      return 7; // ACTION_HOVER_MOVE
  }
  throw new Error(
    "Native mouse-move events not supported on platform " + getPlatform()
  );
}

function nativeMouseUpEventMsg() {
  switch (getPlatform()) {
    case "windows":
      return 4; // MOUSEEVENTF_LEFTUP
    case "mac":
      return 2; // NSEventTypeLeftMouseUp
    case "linux":
      return 7; // GDK_BUTTON_RELEASE
    case "android":
      return 6; // ACTION_POINTER_UP
  }
  throw new Error(
    "Native mouse-up events not supported on platform " + getPlatform()
  );
}

function getBoundingClientRectRelativeToVisualViewport(aElement) {
  let utils = SpecialPowers.getDOMWindowUtils(window);
  var rect = aElement.getBoundingClientRect();
  var offsetX = {},
    offsetY = {};
  // TODO: Audit whether these offset values are correct or not for
  // position:fixed elements especially in the case where the visual viewport
  // offset is not 0.
  utils.getVisualViewportOffsetRelativeToLayoutViewport(offsetX, offsetY);
  rect.x -= offsetX.value;
  rect.y -= offsetY.value;
  return rect;
}

// Several event sythesization functions below (and their helpers) take a "target"
// parameter which may be either an element or a window. For such functions,
// the target's "bounding rect" refers to the bounding client rect for an element,
// and the window's origin for a window.
// Not all functions have been "upgraded" to allow a window argument yet; feel
// free to upgrade others as necessary.

// Get the origin of |aTarget| relative to the root content document's
// visual viewport in CSS coordinates.
// |aTarget| may be an element (contained in the root content document or
// a subdocument) or, as a special case, the root content window.
// FIXME: Support iframe windows as targets.
function getTargetOrigin(aTarget) {
  let origin = { left: 0, top: 0 };

  // If the target is the root content window, its origin relative
  // to the visual viewport is (0, 0).
  if (aTarget instanceof Window) {
    // FIXME: Assert that it's not an iframe window.
    return origin;
  }

  // Otherwise, we have an element. Start with the origin of
  // its bounding client rect which is relative to the enclosing
  // document's layout viewport. Note that for iframes, the
  // layout viewport is also the visual viewport.
  let rect = aTarget.getBoundingClientRect();
  origin.left += rect.left;
  origin.top += rect.top;

  // Iterate up the window hierarchy until we reach the root
  // content window, adding the offsets of any iframe windows
  // relative to their parent window.
  while (aTarget.ownerDocument.defaultView.frameElement) {
    let iframe = aTarget.ownerDocument.defaultView.frameElement;
    // The offset of the iframe window relative to the parent window
    // includes the iframe's border, and the iframe's origin in its
    // containing document.
    let style = iframe.ownerDocument.defaultView.getComputedStyle(iframe);
    let borderLeft = parseFloat(style.borderLeftWidth) || 0;
    let borderTop = parseFloat(style.borderTopWidth) || 0;
    let paddingLeft = parseFloat(style.paddingLeft) || 0;
    let paddingTop = parseFloat(style.paddingTop) || 0;
    rect = iframe.getBoundingClientRect();
    origin.left += rect.left + borderLeft + paddingLeft;
    origin.top += rect.top + borderTop + paddingTop;
    aTarget = iframe;
  }

  // Now we have coordinates relative to the root content document's
  // layout viewport. Subtract the offset of the visual viewport
  // relative to the layout viewport, to get coordinates relative to
  // the visual viewport.
  var offsetX = {},
    offsetY = {};
  let rootUtils = SpecialPowers.getDOMWindowUtils(window.top);
  rootUtils.getVisualViewportOffsetRelativeToLayoutViewport(offsetX, offsetY);
  origin.left -= offsetX.value;
  origin.top -= offsetY.value;
  return origin;
}

// Convert (aX, aY), in CSS pixels relative to aTarget's bounding rect
// to device pixels relative to the screen.
// TODO: this function currently does not incorporate some CSS transforms on
// elements enclosing aTarget, e.g. scale transforms.
function coordinatesRelativeToScreen(aX, aY, aTarget) {
  // Note that |window| might not be the root content window, for two
  // possible reasons:
  //  1. The mochitest that's calling into this function is not using a mechanism
  //     like runSubtestsSeriallyInFreshWindows() to load the test page in
  //     a top-level context, so it's loaded into an iframe by the mochitest
  //     harness.
  //  2. The mochitest itself creates an iframe and calls this function from
  //     script running in the context of the iframe.
  // Since the resolution applies to the root content document, below we use
  // the mozInnerScreen{X,Y} of the root content window (window.top) only,
  // and factor any offsets between iframe windows and the root content window
  // into |origin|.
  var utils = SpecialPowers.getDOMWindowUtils(window);
  var deviceScale = utils.screenPixelsPerCSSPixel;
  var deviceScaleNoOverride = utils.screenPixelsPerCSSPixelNoOverride;
  var resolution = getResolution();
  var origin = getTargetOrigin(aTarget);
  // moxInnerScreen{X,Y} are in CSS coordinates of the browser chrome.
  // The device scale applies to them, but the resolution only zooms the content.
  // In addition, if we're inside RDM, RDM overrides the device scale;
  // the overridden scale only applies to the content inside the RDM
  // document, not to mozInnerScreen{X,Y}.
  return {
    x:
      window.top.mozInnerScreenX * deviceScaleNoOverride +
      (origin.left + aX) * resolution * deviceScale,
    y:
      window.top.mozInnerScreenY * deviceScaleNoOverride +
      (origin.top + aY) * resolution * deviceScale,
  };
}

// Get the bounding box of aElement, and return it in device pixels
// relative to the screen.
// TODO: This function should probably take into account the resolution
//       and use getBoundingClientRectRelativeToVisualViewport()
//       like coordinatesRelativeToScreen() does.
function rectRelativeToScreen(aElement) {
  var targetWindow = aElement.ownerDocument.defaultView;
  var scale = targetWindow.devicePixelRatio;
  var rect = aElement.getBoundingClientRect();
  return {
    x: (targetWindow.mozInnerScreenX + rect.left) * scale,
    y: (targetWindow.mozInnerScreenY + rect.top) * scale,
    w: rect.width * scale,
    h: rect.height * scale,
  };
}

// Synthesizes a native mousewheel event and returns immediately. This does not
// guarantee anything; you probably want to use one of the other functions below
// which actually wait for results.
// aX and aY are relative to the top-left of |aTarget|'s bounding rect.
// aDeltaX and aDeltaY are pixel deltas, and aObserver can be left undefined
// if not needed.
function synthesizeNativeWheel(aTarget, aX, aY, aDeltaX, aDeltaY, aObserver) {
  var pt = coordinatesRelativeToScreen(aX, aY, aTarget);
  if (aDeltaX && aDeltaY) {
    throw new Error(
      "Simultaneous wheeling of horizontal and vertical is not supported on all platforms."
    );
  }
  aDeltaX = nativeScrollUnits(aTarget, aDeltaX);
  aDeltaY = nativeScrollUnits(aTarget, aDeltaY);
  var msg = aDeltaX
    ? nativeHorizontalWheelEventMsg()
    : nativeVerticalWheelEventMsg();
  var utils = utilsForTarget(aTarget);
  var element = elementForTarget(aTarget);
  utils.sendNativeMouseScrollEvent(
    pt.x,
    pt.y,
    msg,
    aDeltaX,
    aDeltaY,
    0,
    0,
    0,
    element,
    aObserver
  );
  return true;
}

// Synthesizes a native mousewheel event and invokes the callback once the
// request has been successfully made to the OS. This does not necessarily
// guarantee that the OS generates the event we requested. See
// synthesizeNativeWheel for details on the parameters.
function synthesizeNativeWheelAndWaitForObserver(
  aElement,
  aX,
  aY,
  aDeltaX,
  aDeltaY,
  aCallback
) {
  var observer = {
    observe(aSubject, aTopic, aData) {
      if (aCallback && aTopic == "mousescrollevent") {
        setTimeout(aCallback, 0);
      }
    },
  };
  return synthesizeNativeWheel(aElement, aX, aY, aDeltaX, aDeltaY, observer);
}

// Synthesizes a native mousewheel event and invokes the callback once the
// wheel event is dispatched to |aTarget|'s containing window. If the event
// targets content in a subdocument, |aTarget| should be inside the
// subdocument (or the subdocument's window). See synthesizeNativeWheel for
// details on the other parameters.
function synthesizeNativeWheelAndWaitForWheelEvent(
  aTarget,
  aX,
  aY,
  aDeltaX,
  aDeltaY,
  aCallback
) {
  let p = promiseNativeWheelAndWaitForWheelEvent(
    aTarget,
    aX,
    aY,
    aDeltaX,
    aDeltaY
  );
  if (aCallback) {
    p.then(aCallback);
  }
  return true;
}

// Same as synthesizeNativeWheelAndWaitForWheelEvent, except returns a promise
// instead of taking a callback
function promiseNativeWheelAndWaitForWheelEvent(
  aTarget,
  aX,
  aY,
  aDeltaX,
  aDeltaY
) {
  return new Promise((resolve, reject) => {
    var targetWindow = windowForTarget(aTarget);
    targetWindow.addEventListener(
      "wheel",
      function(e) {
        setTimeout(resolve, 0);
      },
      { once: true }
    );
    try {
      synthesizeNativeWheel(aTarget, aX, aY, aDeltaX, aDeltaY);
    } catch (e) {
      reject();
    }
  });
}

// Synthesizes a native mousewheel event and invokes the callback once the
// first resulting scroll event is dispatched to |aTarget|'s containing window.
// If the event targets content in a subdocument, |aTarget| should be inside
// the subdocument (or the subdocument's window).  See synthesizeNativeWheel
// for details on the other parameters.
function synthesizeNativeWheelAndWaitForScrollEvent(
  aTarget,
  aX,
  aY,
  aDeltaX,
  aDeltaY,
  aCallback
) {
  promiseNativeWheelAndWaitForScrollEvent(
    aTarget,
    aX,
    aY,
    aDeltaX,
    aDeltaY
  ).then(aCallback);
  return true;
}

// Same as synthesizeNativeWheelAndWaitForScrollEvent, but returns a promise
// instead of taking a callback
function promiseNativeWheelAndWaitForScrollEvent(
  aTarget,
  aX,
  aY,
  aDeltaX,
  aDeltaY
) {
  return new Promise((resolve, reject) => {
    var targetWindow = windowForTarget(aTarget);
    targetWindow.addEventListener(
      "scroll",
      function() {
        setTimeout(resolve, 0);
      },
      { capture: true, once: true }
    ); // scroll events don't always bubble
    try {
      synthesizeNativeWheel(aTarget, aX, aY, aDeltaX, aDeltaY);
    } catch (e) {
      reject();
    }
  });
}

// Synthesizes a native mouse move event and returns immediately.
// aX and aY are relative to the top-left of |aTarget|'s bounding rect.
function synthesizeNativeMouseMove(aTarget, aX, aY) {
  var pt = coordinatesRelativeToScreen(aX, aY, aTarget);
  var utils = utilsForTarget(aTarget);
  var element = elementForTarget(aTarget);
  utils.sendNativeMouseEvent(pt.x, pt.y, nativeMouseMoveEventMsg(), 0, element);
  return true;
}

// Synthesizes a native mouse move event and invokes the callback once the
// mouse move event is dispatched to |aTarget|'s containing window. If the event
// targets content in a subdocument, |aTarget| should be inside the
// subdocument (or the subdocument window). See synthesizeNativeMouseMove for
// details on the other parameters.
function synthesizeNativeMouseMoveAndWaitForMoveEvent(
  aTarget,
  aX,
  aY,
  aCallback
) {
  promiseNativeMouseMoveAndWaitForMoveEvent(aTarget, aX, aY).then(aCallback);
  return true;
}

// Same as synthesizeNativeMouseMoveAndWaitForMoveEvent but returns a promise
// instead of taking a callback.
function promiseNativeMouseMoveAndWaitForMoveEvent(aTarget, aX, aY) {
  return new Promise((resolve, reject) => {
    var targetWindow = windowForTarget(aTarget);
    targetWindow.addEventListener(
      "mousemove",
      function(e) {
        setTimeout(resolve, 0);
      },
      { once: true }
    );
    try {
      synthesizeNativeMouseMove(aTarget, aX, aY);
    } catch (e) {
      reject();
    }
  });
}

// Synthesizes a native touch event and dispatches it. aX and aY in CSS pixels
// relative to the top-left of |aTarget|'s bounding rect.
function synthesizeNativeTouch(
  aTarget,
  aX,
  aY,
  aType,
  aObserver = null,
  aTouchId = 0
) {
  var pt = coordinatesRelativeToScreen(aX, aY, aTarget);
  var utils = utilsForTarget(aTarget);
  utils.sendNativeTouchPoint(aTouchId, aType, pt.x, pt.y, 1, 90, aObserver);
  return true;
}

// Function to generate native touch events for a multi-touch sequence.
// aTarget is the element or window whose bounding rect the coordinates are relative to.
// aPositions is a 2D array of position data. It is indexed as [row][column],
//   where advancing the row counter moves forward in time, and each column
//   represents a single "finger" (or touch input). Each row must have exactly
//   the same number of columns, and the number of columns must match the length
//   of the aTouchIds parameter.
//   For each row, each entry is either an object with x and y fields,
//   or a null. A null value indicates that the "finger" should be "lifted"
//   (i.e. send a touchend for that touch input). A non-null value therefore
//   indicates the position of the touch input.
//   This function takes care of the state tracking necessary to send
//   touchstart/touchend inputs as necessary as the fingers go up and down.
// aObserver is the observer that will get registered on the very last
//   synthesizeNativeTouch call this function makes.
// aTouchIds is an array holding the touch ID values of each "finger".
function synthesizeNativeTouchSequences(
  aTarget,
  aPositions,
  aObserver = null,
  aTouchIds = [0]
) {
  // We use lastNonNullValue to figure out which synthesizeNativeTouch call
  // will be the last one we make, so that we can register aObserver on it.
  var lastNonNullValue = -1;
  for (let i = 0; i < aPositions.length; i++) {
    if (aPositions[i] == null) {
      throw new Error(`aPositions[${i}] was unexpectedly null`);
    }
    if (aPositions[i].length != aTouchIds.length) {
      throw new Error(
        `aPositions[${i}] did not have the expected number of positions; ` +
          `expected ${aTouchIds.length} touch points but found ${aPositions[i].length}`
      );
    }
    for (let j = 0; j < aTouchIds.length; j++) {
      if (aPositions[i][j] != null) {
        lastNonNullValue = i * aTouchIds.length + j;
        // Do the conversion to screen space before actually synthesizing
        // the events, otherwise the screen space may change as a result of
        // the touch inputs and the conversion may not work as intended.
        aPositions[i][j] = coordinatesRelativeToScreen(
          aPositions[i][j].x,
          aPositions[i][j].y,
          aTarget
        );
      }
    }
  }
  if (lastNonNullValue < 0) {
    throw new Error("All values in positions array were null!");
  }

  // Insert a row of nulls at the end of aPositions, to ensure that all
  // touches get removed. If the touches have already been removed this will
  // just add an extra no-op iteration in the aPositions loop below.
  var allNullRow = new Array(aTouchIds.length);
  allNullRow.fill(null);
  aPositions.push(allNullRow);

  // The last sendNativeTouchPoint call will be the TOUCH_REMOVE which happens
  // one iteration of aPosition after the last non-null value.
  var lastSynthesizeCall = lastNonNullValue + aTouchIds.length;

  // track which touches are down and which are up. start with all up
  var currentPositions = new Array(aTouchIds.length);
  currentPositions.fill(null);

  var utils = utilsForTarget(aTarget);
  // Iterate over the position data now, and generate the touches requested
  for (let i = 0; i < aPositions.length; i++) {
    for (let j = 0; j < aTouchIds.length; j++) {
      if (aPositions[i][j] == null) {
        // null means lift the finger
        if (currentPositions[j] == null) {
          // it's already lifted, do nothing
        } else {
          // synthesize the touch-up. If this is the last call we're going to
          // make, pass the observer as well
          var thisIndex = i * aTouchIds.length + j;
          var observer = lastSynthesizeCall == thisIndex ? aObserver : null;
          utils.sendNativeTouchPoint(
            aTouchIds[j],
            SpecialPowers.DOMWindowUtils.TOUCH_REMOVE,
            currentPositions[j].x,
            currentPositions[j].y,
            1,
            90,
            observer
          );
          currentPositions[j] = null;
        }
      } else {
        utils.sendNativeTouchPoint(
          aTouchIds[j],
          SpecialPowers.DOMWindowUtils.TOUCH_CONTACT,
          aPositions[i][j].x,
          aPositions[i][j].y,
          1,
          90,
          null
        );
        currentPositions[j] = aPositions[i][j];
      }
    }
  }
  return true;
}

// Note that when calling this function you'll want to make sure that the pref
// "apz.touch_start_tolerance" is set to 0, or some of the touchmove will get
// consumed to overcome the panning threshold.
function synthesizeNativeTouchDrag(
  aTarget,
  aX,
  aY,
  aDeltaX,
  aDeltaY,
  aObserver = null,
  aTouchId = 0
) {
  var steps = Math.max(Math.abs(aDeltaX), Math.abs(aDeltaY));
  var positions = [[{ x: aX, y: aY }]];
  for (var i = 1; i < steps; i++) {
    var dx = i * (aDeltaX / steps);
    var dy = i * (aDeltaY / steps);
    var pos = { x: aX + dx, y: aY + dy };
    positions.push([pos]);
  }
  positions.push([{ x: aX + aDeltaX, y: aY + aDeltaY }]);
  return synthesizeNativeTouchSequences(aTarget, positions, aObserver, [
    aTouchId,
  ]);
}

// Promise-returning variant of synthesizeNativeTouchDrag
function promiseNativeTouchDrag(
  aTarget,
  aX,
  aY,
  aDeltaX,
  aDeltaY,
  aTouchId = 0
) {
  return new Promise(resolve => {
    synthesizeNativeTouchDrag(
      aTarget,
      aX,
      aY,
      aDeltaX,
      aDeltaY,
      resolve,
      aTouchId
    );
  });
}

function synthesizeNativeTap(aElement, aX, aY, aObserver = null) {
  var pt = coordinatesRelativeToScreen(aX, aY, aElement);
  var utils = SpecialPowers.getDOMWindowUtils(
    aElement.ownerDocument.defaultView
  );
  utils.sendNativeTouchTap(pt.x, pt.y, false, aObserver);
  return true;
}

function synthesizeNativeMouseEvent(aTarget, aX, aY, aType, aObserver = null) {
  var pt = coordinatesRelativeToScreen(aX, aY, aTarget);
  var utils = utilsForTarget(aTarget);
  var element = elementForTarget(aTarget);
  utils.sendNativeMouseEvent(pt.x, pt.y, aType, 0, element, aObserver);
  return true;
}

// Promise-returning variant of synthesizeNativeMouseEvent
function promiseNativeMouseEvent(aTarget, aX, aY, aType) {
  return new Promise(resolve => {
    synthesizeNativeMouseEvent(aTarget, aX, aY, aType, resolve);
  });
}

function synthesizeNativeClick(aElement, aX, aY, aObserver = null) {
  var pt = coordinatesRelativeToScreen(aX, aY, aElement);
  var utils = SpecialPowers.getDOMWindowUtils(
    aElement.ownerDocument.defaultView
  );
  utils.sendNativeMouseEvent(
    pt.x,
    pt.y,
    nativeMouseDownEventMsg(),
    0,
    aElement,
    function() {
      utils.sendNativeMouseEvent(
        pt.x,
        pt.y,
        nativeMouseUpEventMsg(),
        0,
        aElement,
        aObserver
      );
    }
  );
  return true;
}

// Promise-returning variant of synthesizeNativeClick.
function promiseNativeClick(aElement, aX, aY) {
  return new Promise(resolve => {
    synthesizeNativeClick(aElement, aX, aY, resolve);
  });
}

function synthesizeNativeClickAndWaitForClickEvent(
  aElement,
  aX,
  aY,
  aCallback
) {
  var targetWindow = windowForTarget(aElement);
  targetWindow.addEventListener(
    "click",
    function(e) {
      setTimeout(aCallback, 0);
    },
    { capture: true, once: true }
  );
  return synthesizeNativeClick(aElement, aX, aY);
}

// Promise-returning variant of synthesizeNativeClickAndWaitForClickEvent
function promiseNativeClickAndClickEvent(aElement, aX, aY) {
  return new Promise(resolve => {
    synthesizeNativeClickAndWaitForClickEvent(aElement, aX, aY, resolve);
  });
}

// Move the mouse to (dx, dy) relative to |target|, and scroll the wheel
// at that location.
// Moving the mouse is necessary to avoid wheel events from two consecutive
// moveMouseAndScrollWheelOver() calls on different elements being incorrectly
// considered as part of the same wheel transaction.
// We also wait for the mouse move event to be processed before sending the
// wheel event, otherwise there is a chance they might get reordered, and
// we have the transaction problem again.
function moveMouseAndScrollWheelOver(
  target,
  dx,
  dy,
  testDriver,
  waitForScroll = true,
  scrollDelta = 10
) {
  promiseMoveMouseAndScrollWheelOver(
    target,
    dx,
    dy,
    waitForScroll,
    scrollDelta
  ).then(testDriver);
  return true;
}

// Same as moveMouseAndScrollWheelOver, but returns a promise instead of taking
// a callback function.
function promiseMoveMouseAndScrollWheelOver(
  target,
  dx,
  dy,
  waitForScroll = true,
  scrollDelta = 10
) {
  let p = promiseNativeMouseMoveAndWaitForMoveEvent(target, dx, dy);
  if (waitForScroll) {
    p = p.then(() =>
      promiseNativeWheelAndWaitForScrollEvent(target, dx, dy, 0, -scrollDelta)
    );
  } else {
    p = p.then(() =>
      promiseNativeWheelAndWaitForWheelEvent(target, dx, dy, 0, -scrollDelta)
    );
  }
  return p;
}

// Synthesizes events to drag |target|'s vertical scrollbar by the distance
// specified, synthesizing a mousemove for each increment as specified.
// Returns null if the element doesn't have a vertical scrollbar. Otherwise,
// returns an async function that should be invoked after the mousemoves have been
// processed by the widget code, to end the scrollbar drag. Mousemoves being
// processed by the widget code can be detected by listening for the mousemove
// events in the caller, or for some other event that is triggered by the
// mousemove, such as the scroll event resulting from the scrollbar drag.
// The scaleFactor argument should be provided if the scrollframe has been
// scaled by an enclosing CSS transform. (TODO: this is a workaround for the
// fact that coordinatesRelativeToScreen is supposed to do this automatically
// but it currently does not).
// Note: helper_scrollbar_snap_bug1501062.html contains a copy of this code
// with modifications. Fixes here should be copied there if appropriate.
// |target| can be an element (for subframes) or a window (for root frames).
async function promiseVerticalScrollbarDrag(
  target,
  distance = 20,
  increment = 5,
  scaleFactor = 1
) {
  var targetElement = elementForTarget(target);
  var w = {},
    h = {};
  utilsForTarget(target).getScrollbarSizes(targetElement, w, h);
  var verticalScrollbarWidth = w.value;
  if (verticalScrollbarWidth == 0) {
    return null;
  }

  var upArrowHeight = verticalScrollbarWidth; // assume square scrollbar buttons
  var mouseX = targetElement.clientWidth + verticalScrollbarWidth / 2;
  var mouseY = upArrowHeight + 5; // start dragging somewhere in the thumb
  mouseX *= scaleFactor;
  mouseY *= scaleFactor;

  dump(
    "Starting drag at " +
      mouseX +
      ", " +
      mouseY +
      " from top-left of #" +
      targetElement.id +
      "\n"
  );

  // Move the mouse to the scrollbar thumb and drag it down
  await promiseNativeMouseEvent(
    target,
    mouseX,
    mouseY,
    nativeMouseMoveEventMsg()
  );
  // mouse down
  await promiseNativeMouseEvent(
    target,
    mouseX,
    mouseY,
    nativeMouseDownEventMsg()
  );
  // drag vertically by |increment| until we reach the specified distance
  for (var y = increment; y < distance; y += increment) {
    await promiseNativeMouseEvent(
      target,
      mouseX,
      mouseY + y,
      nativeMouseMoveEventMsg()
    );
  }
  await promiseNativeMouseEvent(
    target,
    mouseX,
    mouseY + distance,
    nativeMouseMoveEventMsg()
  );

  // and return an async function to call afterwards to finish up the drag
  return async function() {
    dump("Finishing drag of #" + targetElement.id + "\n");
    await promiseNativeMouseEvent(
      target,
      mouseX,
      mouseY + distance,
      nativeMouseUpEventMsg()
    );
  };
}

// Synthesizes a native mouse drag, starting at offset (mouseX, mouseY) from
// the given target. The drag occurs in the given number of steps, to a final
// destination of (mouseX + distanceX, mouseY + distanceY) from the target.
// Returns a promise (wrapped in a function, so it doesn't execute immediately)
// that should be awaited after the mousemoves have been processed by the widget
// code, to end the drag. This is important otherwise the OS can sometimes
// reorder the events and the drag doesn't have the intended effect (see
// bug 1368603).
// Example usage:
//   let dragFinisher = await promiseNativeMouseDrag(myElement, 0, 0);
//   await myIndicationThatDragHadAnEffect;
//   await dragFinisher();
async function promiseNativeMouseDrag(
  target,
  mouseX,
  mouseY,
  distanceX = 20,
  distanceY = 20,
  steps = 20
) {
  var targetElement = elementForTarget(target);
  dump(
    "Starting drag at " +
      mouseX +
      ", " +
      mouseY +
      " from top-left of #" +
      targetElement.id +
      "\n"
  );

  // Move the mouse to the target position
  await promiseNativeMouseEvent(
    target,
    mouseX,
    mouseY,
    nativeMouseMoveEventMsg()
  );
  // mouse down
  await promiseNativeMouseEvent(
    target,
    mouseX,
    mouseY,
    nativeMouseDownEventMsg()
  );
  // drag vertically by |increment| until we reach the specified distance
  for (var s = 1; s <= steps; s++) {
    let dx = distanceX * (s / steps);
    let dy = distanceY * (s / steps);
    dump(`Dragging to ${mouseX + dx}, ${mouseY + dy} from target\n`);
    await promiseNativeMouseEvent(
      target,
      mouseX + dx,
      mouseY + dy,
      nativeMouseMoveEventMsg()
    );
  }

  // and return a function-wrapped promise to call afterwards to finish the drag
  return function() {
    return promiseNativeMouseEvent(
      target,
      mouseX + distanceX,
      mouseY + distanceY,
      nativeMouseUpEventMsg()
    );
  };
}

// Synthesizes a native touch sequence of events corresponding to a pinch-zoom-in
// at the given focus point. The focus point must be specified in CSS coordinates
// relative to the document body.
function pinchZoomInTouchSequence(focusX, focusY) {
  // prettier-ignore
  var zoom_in = [
      [ { x: focusX - 25, y: focusY - 50 }, { x: focusX + 25, y: focusY + 50 } ],
      [ { x: focusX - 30, y: focusY - 80 }, { x: focusX + 30, y: focusY + 80 } ],
      [ { x: focusX - 35, y: focusY - 110 }, { x: focusX + 40, y: focusY + 110 } ],
      [ { x: focusX - 40, y: focusY - 140 }, { x: focusX + 45, y: focusY + 140 } ],
      [ { x: focusX - 45, y: focusY - 170 }, { x: focusX + 50, y: focusY + 170 } ],
      [ { x: focusX - 50, y: focusY - 200 }, { x: focusX + 55, y: focusY + 200 } ],
  ];

  var touchIds = [0, 1];
  return synthesizeNativeTouchSequences(document.body, zoom_in, null, touchIds);
}

// Returns a promise that is resolved when the observer service dispatches a
// message with the given topic.
function promiseTopic(aTopic) {
  return new Promise((resolve, reject) => {
    SpecialPowers.Services.obs.addObserver(function observer(
      subject,
      topic,
      data
    ) {
      try {
        SpecialPowers.Services.obs.removeObserver(observer, topic);
        resolve([subject, data]);
      } catch (ex) {
        SpecialPowers.Services.obs.removeObserver(observer, topic);
        reject(ex);
      }
    },
    aTopic);
  });
}

// Returns a promise that is resolved when a APZ transform ends.
function promiseTransformEnd() {
  return promiseTopic("APZ:TransformEnd");
}

// Returns a promise that resolves after the indicated number
// of touchend events have fired on the given target element.
function promiseTouchEnd(element, count = 1) {
  return new Promise(resolve => {
    var eventCount = 0;
    var counterFunction = function(e) {
      eventCount++;
      if (eventCount == count) {
        element.removeEventListener("touchend", counterFunction, {
          passive: true,
        });
        resolve();
      }
    };
    element.addEventListener("touchend", counterFunction, { passive: true });
  });
}

// This generates a touch-based pinch zoom-in gesture that is expected
// to succeed. It returns after APZ has completed the zoom and reaches the end
// of the transform. The focus point is expected to be in CSS coordinates
// relative to the document body.
async function pinchZoomInWithTouch(focusX, focusY) {
  // Register the listener for the TransformEnd observer topic
  let transformEndPromise = promiseTopic("APZ:TransformEnd");

  // Dispatch all the touch events
  pinchZoomInTouchSequence(focusX, focusY);

  // Wait for TransformEnd to fire.
  await transformEndPromise;
}

// This generates a touch-based pinch gesture that is expected to succeed
// and trigger an APZ:TransformEnd observer notification.
// It returns after that notification has been dispatched.
// The coordinates of touch events in `touchSequence` are expected to be
// in CSS coordinates relative to the document body.
async function synthesizeNativeTouchAndWaitForTransformEnd(
  touchSequence,
  touchIds
) {
  // Register the listener for the TransformEnd observer topic
  let transformEndPromise = promiseTopic("APZ:TransformEnd");

  // Dispatch all the touch events
  synthesizeNativeTouchSequences(document.body, touchSequence, null, touchIds);

  // Wait for TransformEnd to fire.
  await transformEndPromise;
}

// Returns a touch sequence for a pinch-zoom-out operation in the center
// of the visual viewport. The touch sequence returned is in CSS coordinates
// relative to the document body.
function pinchZoomOutTouchSequenceAtCenter() {
  // Divide the half of visual viewport size by 8, then cause touch events
  // starting from the 7th furthest away from the center towards the center.
  const deltaX = window.visualViewport.width / 16;
  const deltaY = window.visualViewport.height / 16;
  const centerX =
    window.visualViewport.pageLeft + window.visualViewport.width / 2;
  const centerY =
    window.visualViewport.pageTop + window.visualViewport.height / 2;
  // prettier-ignore
  var zoom_out = [
      [ { x: centerX - (deltaX * 6), y: centerY - (deltaY * 6) },
        { x: centerX + (deltaX * 6), y: centerY + (deltaY * 6) } ],
      [ { x: centerX - (deltaX * 5), y: centerY - (deltaY * 5) },
        { x: centerX + (deltaX * 5), y: centerY + (deltaY * 5) } ],
      [ { x: centerX - (deltaX * 4), y: centerY - (deltaY * 4) },
        { x: centerX + (deltaX * 4), y: centerY + (deltaY * 4) } ],
      [ { x: centerX - (deltaX * 3), y: centerY - (deltaY * 3) },
        { x: centerX + (deltaX * 3), y: centerY + (deltaY * 3) } ],
      [ { x: centerX - (deltaX * 2), y: centerY - (deltaY * 2) },
        { x: centerX + (deltaX * 2), y: centerY + (deltaY * 2) } ],
      [ { x: centerX - (deltaX * 1), y: centerY - (deltaY * 1) },
        { x: centerX + (deltaX * 1), y: centerY + (deltaY * 1) } ],
  ];
  return zoom_out;
}

// This generates a touch-based pinch zoom-out gesture that is expected
// to succeed. It returns after APZ has completed the zoom and reaches the end
// of the transform. The touch inputs are directed to the center of the
// current visual viewport.
async function pinchZoomOutWithTouchAtCenter() {
  var zoom_out = pinchZoomOutTouchSequenceAtCenter();
  var touchIds = [0, 1];
  await synthesizeNativeTouchAndWaitForTransformEnd(zoom_out, touchIds);
}