# Copyright 2014 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

from telemetry.internal.actions import page_action
from telemetry.internal.actions import utils
from telemetry.util import js_template


class ScrollBounceAction(page_action.ElementPageAction):

  def __init__(self,
               selector=None,
               text=None,
               element_function=None,
               left_start_ratio=0.5,
               top_start_ratio=0.5,
               direction='down',
               distance=100,
               overscroll=10,
               repeat_count=10,
               speed_in_pixels_per_second=400,
               synthetic_gesture_source=page_action.GESTURE_SOURCE_DEFAULT,
               timeout=page_action.DEFAULT_TIMEOUT):
    super(ScrollBounceAction, self).__init__(
        selector, text, element_function, timeout=timeout)
    if direction not in ['down', 'up', 'left', 'right']:
      raise page_action.PageActionNotSupported(
          'Invalid scroll direction: %s' % self.direction)
    self._left_start_ratio = left_start_ratio
    self._top_start_ratio = top_start_ratio
    # Should be big enough to do more than just hide the URL bar.
    self._distance = distance
    self._direction = direction
    # This needs to be < height / repeat_count so we don't walk off the screen.
    # We also probably don't want to spend more than a couple frames in
    # overscroll since it may mask any synthetic delays.
    self._overscroll = overscroll
    # It's the transitions we really want to stress, make this big.
    self._repeat_count = repeat_count
    # 7 pixels per frame should be plenty of frames.
    self._speed = speed_in_pixels_per_second
    self._synthetic_gesture_source = (
        'chrome.gpuBenchmarking.%s_INPUT' % synthetic_gesture_source)

    if (self._selector is None and self._text is None and
        self._element_function is None):
      self._element_function = '(document.scrollingElement || document.body)'

  def WillRunAction(self, tab):
    utils.InjectJavaScript(tab, 'gesture_common.js')
    utils.InjectJavaScript(tab, 'scroll_bounce.js')

    # Fail if browser doesn't support synthetic scroll bounce gestures.
    if not tab.EvaluateJavaScript(
        'window.__ScrollBounceAction_SupportedByBrowser()'):
      raise page_action.PageActionNotSupported(
          'Synthetic scroll bounce not supported for this browser')

    # Fail if we can't send touch events (bouncing is really only
    # interesting for touch)
    if not page_action.IsGestureSourceTypeSupported(tab, 'touch'):
      raise page_action.PageActionNotSupported(
          'Touch scroll not supported for this browser')

    if self._synthetic_gesture_source == 'chrome.gpuBenchmarking.MOUSE_INPUT':
      raise page_action.PageActionNotSupported(
          'ScrollBounce page action does not support mouse input')

    tab.ExecuteJavaScript("""
        window.__scrollBounceActionDone = false;
        window.__scrollBounceAction = new __ScrollBounceAction(
            function() { window.__scrollBounceActionDone = true; });""")

  def RunAction(self, tab):
    code = js_template.Render(
        """
        function(element, info) {
          if (!element) {
            throw Error('Cannot find element: ' + info);
          }
          window.__scrollBounceAction.start({
            element: element,
            left_start_ratio: {{ left_start_ratio }},
            top_start_ratio: {{ top_start_ratio }},
            direction: {{ direction }},
            distance: {{ distance }},
            overscroll: {{ overscroll }},
            repeat_count: {{ repeat_count }},
            speed: {{ speed }}
          });
        }""",
        left_start_ratio=self._left_start_ratio,
        top_start_ratio=self._top_start_ratio,
        direction=self._direction,
        distance=self._distance,
        overscroll=self._overscroll,
        repeat_count=self._repeat_count,
        speed=self._speed)
    self.EvaluateCallback(tab, code)
    tab.WaitForJavaScriptCondition(
        'window.__scrollBounceActionDone', timeout=self.timeout)
