// 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.

#include "athena/wm/split_view_controller.h"

#include <cmath>

#include "athena/wm/public/window_list_provider.h"
#include "athena/wm/public/window_manager.h"
#include "base/bind.h"
#include "ui/aura/window.h"
#include "ui/compositor/closure_animation_observer.h"
#include "ui/compositor/layer_animation_observer.h"
#include "ui/compositor/scoped_layer_animation_settings.h"
#include "ui/events/event_handler.h"
#include "ui/gfx/display.h"
#include "ui/gfx/screen.h"
#include "ui/wm/core/window_util.h"

namespace athena {

SplitViewController::SplitViewController(
    aura::Window* container,
    WindowListProvider* window_list_provider)
    : state_(INACTIVE),
      container_(container),
      window_list_provider_(window_list_provider),
      left_window_(NULL),
      right_window_(NULL),
      separator_position_(0),
      weak_factory_(this) {
}

SplitViewController::~SplitViewController() {
}

bool SplitViewController::IsSplitViewModeActive() const {
  return state_ == ACTIVE;
}

void SplitViewController::ActivateSplitMode(aura::Window* left,
                                            aura::Window* right) {
  aura::Window::Windows windows = window_list_provider_->GetWindowList();
  aura::Window::Windows::reverse_iterator iter = windows.rbegin();
  if (state_ == ACTIVE) {
    if (left_window_ == right)
      left_window_ = left;
    if (right_window_ == left)
      right_window_ = right;

    if (!left)
      left = left_window_;
    if (!right)
      right = right_window_;
  }

  if (!left && iter != windows.rend()) {
    left = *iter;
    iter++;
    if (left == right && iter != windows.rend()) {
      left = *iter;
      iter++;
    }
  }

  if (!right && iter != windows.rend()) {
    right = *iter;
    iter++;
    if (right == left && iter != windows.rend()) {
      right = *iter;
      iter++;
    }
  }

  state_ = ACTIVE;
  if (right_window_ != right) {
    right_window_ = right;
    container_->StackChildAtTop(right_window_);
  }
  if (left_window_ != left) {
    left_window_ = left;
    container_->StackChildAtTop(left_window_);
  }
  UpdateLayout(true);
}

void SplitViewController::ReplaceWindow(aura::Window* window,
                                        aura::Window* replace_with) {
  CHECK(IsSplitViewModeActive());
  CHECK(replace_with);
  CHECK(window == left_window_ || window == right_window_);
  CHECK(replace_with != left_window_ && replace_with != right_window_);
#if !defined(NDEBUG)
  aura::Window::Windows windows = window_list_provider_->GetWindowList();
  DCHECK(std::find(windows.begin(), windows.end(), replace_with) !=
         windows.end());
#endif

  replace_with->SetBounds(window->bounds());
  replace_with->SetTransform(gfx::Transform());
  if (window == left_window_)
    left_window_ = replace_with;
  else
    right_window_ = replace_with;
  wm::ActivateWindow(replace_with);
  window->SetTransform(gfx::Transform());
}

void SplitViewController::DeactivateSplitMode() {
  CHECK_NE(SCROLLING, state_);
  state_ = INACTIVE;
  left_window_ = right_window_ = NULL;
}

void SplitViewController::UpdateLayout(bool animate) {
  if  (!left_window_)
    return;
  CHECK(right_window_);
  gfx::Transform left_transform;
  gfx::Transform right_transform;
  int container_width = container_->GetBoundsInScreen().width();
  if (state_ == ACTIVE) {
    // This method should only be called once in ACTIVE state when
    // the left and rightwindows are still full screen and need to be resized.
    CHECK_EQ(left_window_->bounds().width(), container_width);
    CHECK_EQ(right_window_->bounds().width(), container_width);
    // Windows should be resized via an animation when entering the ACTIVE
    // state.
    CHECK(animate);
    // We scale the windows here, but when the animation finishes, we reset
    // the scaling and update the window bounds to the proper size - see
    // OnAnimationCompleted().
    left_transform.Scale(.5, 1);
    right_transform.Scale(.5, 1);
    right_transform.Translate(container_width, 0);
  } else {
    left_transform.Translate(separator_position_ - container_width, 0);
    right_transform.Translate(separator_position_, 0);
  }
  left_window_->Show();
  right_window_->Show();
  SetWindowTransform(left_window_, left_transform, animate);
  SetWindowTransform(right_window_, right_transform, animate);
}

void SplitViewController::SetWindowTransform(aura::Window* window,
                                             const gfx::Transform& transform,
                                             bool animate) {
  if (animate) {
    scoped_refptr<ui::LayerAnimator> animator = window->layer()->GetAnimator();
    ui::ScopedLayerAnimationSettings settings(animator);
    settings.SetPreemptionStrategy(
        ui::LayerAnimator::IMMEDIATELY_ANIMATE_TO_NEW_TARGET);
    settings.AddObserver(new ui::ClosureAnimationObserver(
        base::Bind(&SplitViewController::OnAnimationCompleted,
                   weak_factory_.GetWeakPtr(),
                   window)));
    window->SetTransform(transform);
  } else {
    window->SetTransform(transform);
  }
}

void SplitViewController::OnAnimationCompleted(aura::Window* window) {
  DCHECK(window == left_window_ || window == right_window_);
  if (state_ == ACTIVE) {
    gfx::Rect window_bounds = gfx::Rect(container_->bounds().size());
    int container_width = window_bounds.width();
    window_bounds.set_width(container_width / 2);
    window->SetTransform(gfx::Transform());
    if (window == left_window_) {
      left_window_->SetBounds(window_bounds);
    } else {
      window_bounds.set_x(container_width / 2);
      right_window_->SetBounds(window_bounds);
    }
  } else {
    int container_width = container_->bounds().width();
    window->SetTransform(gfx::Transform());
    if (window == left_window_) {
      if (separator_position_ == 0)
        left_window_->Hide();
      if (state_ == INACTIVE)
        left_window_ = NULL;
    } else {
      if (separator_position_ == container_width)
        right_window_->Hide();
      if (state_ == INACTIVE)
        right_window_ = NULL;
    }
  }
}

void SplitViewController::UpdateSeparatorPositionFromScrollDelta(float delta) {
  gfx::Screen* screen = gfx::Screen::GetScreenFor(container_);
  const gfx::Rect& display_bounds =
      screen->GetDisplayNearestWindow(container_).bounds();
  gfx::Rect container_bounds = container_->GetBoundsInScreen();
  separator_position_ =
      delta > 0 ? ((int)delta) + display_bounds.x() - container_bounds.x()
                : display_bounds.right() - container_bounds.x() + delta;
}

///////////////////////////////////////////////////////////////////////////////
// BezelController::ScrollDelegate:

void SplitViewController::ScrollBegin(BezelController::Bezel bezel,
                                      float delta) {
  if (!CanScroll())
    return;
  state_ = SCROLLING;

  aura::Window::Windows windows = window_list_provider_->GetWindowList();
  CHECK(windows.size() >= 2);
  aura::Window::Windows::const_reverse_iterator iter = windows.rbegin();
  aura::Window* current_window = *(iter);
  CHECK(wm::IsActiveWindow(current_window));

  if (delta > 0) {
    right_window_ = current_window;
    left_window_ = *(iter + 1);
  } else {
    left_window_ = current_window;
    right_window_ = *(iter + 1);
  }

  CHECK(left_window_);
  CHECK(right_window_);

  UpdateSeparatorPositionFromScrollDelta(delta);
  UpdateLayout(false);
}

void SplitViewController::ScrollEnd() {
  if (state_ != SCROLLING)
    return;

  // Max distance from the scroll end position to the middle of the screen where
  // we would go into the split view mode.
  const int kMaxDistanceFromMiddle = 120;
  int container_width = container_->GetBoundsInScreen().width();
  if (std::abs(container_width / 2 - separator_position_) <=
      kMaxDistanceFromMiddle) {
    state_ = ACTIVE;
    separator_position_ = container_width / 2;
  } else if (separator_position_ < container_width / 2) {
    separator_position_ = 0;
    state_ = INACTIVE;
    wm::ActivateWindow(right_window_);
  } else {
    separator_position_ = container_width;
    state_ = INACTIVE;
    wm::ActivateWindow(left_window_);
  }
  UpdateLayout(true);
}

void SplitViewController::ScrollUpdate(float delta) {
  if (state_ != SCROLLING)
    return;
  UpdateSeparatorPositionFromScrollDelta(delta);
  UpdateLayout(false);
}

bool SplitViewController::CanScroll() {
  // TODO(mfomitchev): return false in vertical orientation, in full screen.
  bool result = (!IsSplitViewModeActive() &&
                 window_list_provider_->GetWindowList().size() >= 2);
  return result;
}

}  // namespace athena