/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "TouchActionHelper.h"

#include "mozilla/layers/IAPZCTreeManager.h"
#include "nsContainerFrame.h"
#include "nsIFrameInlines.h"
#include "nsIScrollableFrame.h"
#include "nsLayoutUtils.h"

namespace mozilla {
namespace layers {

static void UpdateAllowedBehavior(StyleTouchAction aTouchActionValue,
                                  bool aConsiderPanning,
                                  TouchBehaviorFlags& aOutBehavior) {
  if (aTouchActionValue != StyleTouchAction::AUTO) {
    // Double-tap-zooming need property value AUTO
    aOutBehavior &= ~AllowedTouchBehavior::DOUBLE_TAP_ZOOM;
    if (aTouchActionValue != StyleTouchAction::MANIPULATION &&
        !(aTouchActionValue & StyleTouchAction::PINCH_ZOOM)) {
      // Pinch-zooming needs value AUTO or MANIPULATION, or the PINCH_ZOOM bit
      // set
      aOutBehavior &= ~AllowedTouchBehavior::PINCH_ZOOM;
    }
  }

  if (aConsiderPanning) {
    if (aTouchActionValue == StyleTouchAction::NONE) {
      aOutBehavior &= ~AllowedTouchBehavior::VERTICAL_PAN;
      aOutBehavior &= ~AllowedTouchBehavior::HORIZONTAL_PAN;
    }

    // Values pan-x and pan-y set at the same time to the same element do not
    // affect panning constraints. Therefore we need to check whether pan-x is
    // set without pan-y and the same for pan-y.
    if ((aTouchActionValue & StyleTouchAction::PAN_X) &&
        !(aTouchActionValue & StyleTouchAction::PAN_Y)) {
      aOutBehavior &= ~AllowedTouchBehavior::VERTICAL_PAN;
    } else if ((aTouchActionValue & StyleTouchAction::PAN_Y) &&
               !(aTouchActionValue & StyleTouchAction::PAN_X)) {
      aOutBehavior &= ~AllowedTouchBehavior::HORIZONTAL_PAN;
    }
  }
}

TouchBehaviorFlags TouchActionHelper::GetAllowedTouchBehavior(
    nsIWidget* aWidget, RelativeTo aRootFrame,
    const LayoutDeviceIntPoint& aPoint) {
  TouchBehaviorFlags behavior = AllowedTouchBehavior::VERTICAL_PAN |
                                AllowedTouchBehavior::HORIZONTAL_PAN |
                                AllowedTouchBehavior::PINCH_ZOOM |
                                AllowedTouchBehavior::DOUBLE_TAP_ZOOM;

  nsPoint relativePoint =
      nsLayoutUtils::GetEventCoordinatesRelativeTo(aWidget, aPoint, aRootFrame);

  nsIFrame* target = nsLayoutUtils::GetFrameForPoint(aRootFrame, relativePoint);
  if (!target) {
    return behavior;
  }
  nsIScrollableFrame* nearestScrollableParent =
      nsLayoutUtils::GetNearestScrollableFrame(target, 0);
  nsIFrame* nearestScrollableFrame = do_QueryFrame(nearestScrollableParent);

  // We're walking up the DOM tree until we meet the element with touch behavior
  // and accumulating touch-action restrictions of all elements in this chain.
  // The exact quote from the spec, that clarifies more:
  // To determine the effect of a touch, find the nearest ancestor (starting
  // from the element itself) that has a default touch behavior. Then examine
  // the touch-action property of each element between the hit tested element
  // and the element with the default touch behavior (including both the hit
  // tested element and the element with the default touch behavior). If the
  // touch-action property of any of those elements disallows the default touch
  // behavior, do nothing. Otherwise allow the element to start considering the
  // touch for the purposes of executing a default touch behavior.

  // Currently we support only two touch behaviors: panning and zooming.
  // For panning we walk up until we meet the first scrollable element (the
  // element that supports panning) or root element. For zooming we walk up
  // until the root element since Firefox currently supports only zooming of the
  // root frame but not the subframes.

  bool considerPanning = true;

  for (nsIFrame* frame = target; frame && frame->GetContent() && behavior;
       frame = frame->GetInFlowParent()) {
    UpdateAllowedBehavior(nsLayoutUtils::GetTouchActionFromFrame(frame),
                          considerPanning, behavior);

    if (frame == nearestScrollableFrame) {
      // We met the scrollable element, after it we shouldn't consider
      // touch-action values for the purpose of panning but only for zooming.
      considerPanning = false;
    }
  }

  return behavior;
}

}  // namespace layers
}  // namespace mozilla