// 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 "ash/accessibility/accessibility_focus_ring.h"

#include <stddef.h>
#include <algorithm>

#include "ash/shell.h"
#include "base/check.h"
#include "ui/display/display.h"
#include "ui/display/screen.h"
#include "ui/wm/core/coordinate_conversion.h"

namespace ash {
namespace {

bool IsFocusRingOffscreen(const gfx::Rect& top,
                          const gfx::Rect& middle,
                          const gfx::Rect& bottom,
                          const gfx::Rect& screen_bounds) {
  if (top.y() > screen_bounds.bottom())
    return true;
  if (middle.right() < screen_bounds.x())
    return true;
  if (middle.x() > screen_bounds.right())
    return true;
  if (bottom.bottom() < screen_bounds.y())
    return true;
  return false;
}

AccessibilityFocusRing CreateFromThreeRects(const gfx::Rect& top,
                                            const gfx::Rect& middle,
                                            const gfx::Rect& bottom,
                                            int margin) {
  AccessibilityFocusRing ring;
  ring.points[0] = gfx::Point(top.x(), top.bottom() - margin);
  ring.points[1] = gfx::Point(top.x(), top.y() + margin);
  ring.points[2] = gfx::Point(top.x(), top.y());
  ring.points[3] = gfx::Point(top.x() + margin, top.y());
  ring.points[4] = gfx::Point(top.right() - margin, top.y());
  ring.points[5] = gfx::Point(top.right(), top.y());
  ring.points[6] = gfx::Point(top.right(), top.y() + margin);
  ring.points[7] = gfx::Point(top.right(), top.bottom() - margin);
  ring.points[8] = gfx::Point(top.right(), top.bottom());
  if (top.right() < middle.right()) {
    ring.points[9] = gfx::Point(top.right() + margin, middle.y());
    ring.points[10] = gfx::Point(middle.right() - margin, middle.y());
  } else {
    ring.points[9] = gfx::Point(top.right(), middle.y());
    ring.points[10] = gfx::Point(middle.right(), middle.y());
  }
  ring.points[11] = gfx::Point(middle.right(), middle.y());
  ring.points[12] = gfx::Point(middle.right(), middle.y() + margin);
  ring.points[13] = gfx::Point(middle.right(), middle.bottom() - margin);
  ring.points[14] = gfx::Point(middle.right(), middle.bottom());
  if (bottom.right() < middle.right()) {
    ring.points[15] = gfx::Point(middle.right() - margin, bottom.y());
    ring.points[16] = gfx::Point(bottom.right() + margin, bottom.y());
  } else {
    ring.points[15] = gfx::Point(middle.right(), bottom.y());
    ring.points[16] = gfx::Point(bottom.right(), bottom.y());
  }
  ring.points[17] = gfx::Point(bottom.right(), bottom.y());
  ring.points[18] = gfx::Point(bottom.right(), bottom.y() + margin);
  ring.points[19] = gfx::Point(bottom.right(), bottom.bottom() - margin);
  ring.points[20] = gfx::Point(bottom.right(), bottom.bottom());
  ring.points[21] = gfx::Point(bottom.right() - margin, bottom.bottom());
  ring.points[22] = gfx::Point(bottom.x() + margin, bottom.bottom());
  ring.points[23] = gfx::Point(bottom.x(), bottom.bottom());
  ring.points[24] = gfx::Point(bottom.x(), bottom.bottom() - margin);
  ring.points[25] = gfx::Point(bottom.x(), bottom.y() + margin);
  ring.points[26] = gfx::Point(bottom.x(), bottom.y());
  if (bottom.x() > middle.x()) {
    ring.points[27] = gfx::Point(bottom.x() - margin, bottom.y());
    ring.points[28] = gfx::Point(middle.x() + margin, middle.bottom());
  } else {
    ring.points[27] = gfx::Point(bottom.x(), bottom.y());
    ring.points[28] = gfx::Point(middle.x(), middle.bottom());
  }
  ring.points[29] = gfx::Point(middle.x(), middle.bottom());
  ring.points[30] = gfx::Point(middle.x(), middle.bottom() - margin);
  ring.points[31] = gfx::Point(middle.x(), middle.y() + margin);
  ring.points[32] = gfx::Point(middle.x(), middle.y());
  if (top.x() > middle.x()) {
    ring.points[33] = gfx::Point(middle.x() + margin, middle.y());
    ring.points[34] = gfx::Point(top.x() - margin, top.bottom());
  } else {
    ring.points[33] = gfx::Point(middle.x(), middle.y());
    ring.points[34] = gfx::Point(top.x(), top.bottom());
  }
  ring.points[35] = gfx::Point(top.x(), top.bottom());

  int left = std::min(ring.points[1].x(),
                      std::min(ring.points[31].x(), ring.points[25].x()));
  int right = std::max(ring.points[6].x(),
                       std::max(ring.points[12].x(), ring.points[18].x()));
  ring.bounds_in_screen = gfx::Rect(left, ring.points[3].y(), right - left,
                                    ring.points[22].y() - ring.points[3].y());

  // Now ensure all the points are on the correct display.
  gfx::Rect bounds_in_display = gfx::Rect(ring.bounds_in_screen);
  display::Display display =
      display::Screen::GetScreen()->GetDisplayMatching(bounds_in_display);
  aura::Window* root_window = Shell::GetRootWindowForDisplayId(display.id());
  ::wm::ConvertRectFromScreen(root_window, &bounds_in_display);

  if (bounds_in_display != ring.bounds_in_screen) {
    // If they aren't on the right display, shift them all so they will be
    // drawn on-screen.
    for (size_t i = 0; i < 36; i++) {
      ::wm::ConvertPointFromScreen(root_window, &ring.points[i]);
    }
  }

  return ring;
}

int InterpolateInt(int i1, int i2, double fraction) {
  return i1 * (1 - fraction) + i2 * fraction;
}

gfx::Point InterpolatePoint(gfx::Point p1, gfx::Point p2, double fraction) {
  return gfx::Point(InterpolateInt(p1.x(), p2.x(), fraction),
                    InterpolateInt(p1.y(), p2.y(), fraction));
}

constexpr int kScreenPaddingDip = 2;
}  // namespace

int AccessibilityFocusRing::GetScreenPaddingForTesting() {
  return kScreenPaddingDip;
}

// static
gfx::Rect AccessibilityFocusRing::screen_bounds_for_testing_;

// static
AccessibilityFocusRing AccessibilityFocusRing::CreateWithRect(
    const gfx::Rect& bounds,
    int margin) {
  // Compute the height of the top and bottom cap.
  int cap_height = std::min(bounds.height() / 2, margin * 2);

  gfx::Rect top(bounds.x(), bounds.y(), bounds.width(), cap_height);
  gfx::Rect bottom(bounds.x(), bounds.bottom() - cap_height, bounds.width(),
                   cap_height);
  gfx::Rect body(bounds.x(), top.bottom(), bounds.width(),
                 bottom.y() - top.bottom());

  return CreateWithParagraphShape(top, body, bottom, margin);
}

// static
AccessibilityFocusRing AccessibilityFocusRing::Interpolate(
    const AccessibilityFocusRing& r1,
    const AccessibilityFocusRing& r2,
    double fraction) {
  AccessibilityFocusRing dst;
  for (int i = 0; i < 36; ++i) {
    dst.points[i] = InterpolatePoint(r1.points[i], r2.points[i], fraction);
  }
  dst.bounds_in_screen = gfx::Rect(
      InterpolatePoint(r1.bounds_in_screen.origin(),
                       r2.bounds_in_screen.origin(), fraction),
      gfx::Size(InterpolateInt(r1.bounds_in_screen.width(),
                               r2.bounds_in_screen.width(), fraction),
                InterpolateInt(r1.bounds_in_screen.height(),
                               r2.bounds_in_screen.height(), fraction)));
  return dst;
}

// static
void AccessibilityFocusRing::ClipToBounds(gfx::Rect* rect,
                                          const gfx::Rect& bounds) {
  if (rect->x() < bounds.x()) {
    rect->set_width(rect->width() + rect->x() - bounds.x());
    rect->set_x(bounds.x());
  }
  if (rect->x() > bounds.right()) {
    rect->set_width(0);
    rect->set_x(bounds.right());
  } else if (rect->right() > bounds.right()) {
    rect->set_width(rect->width() - rect->right() + bounds.right());
  }

  if (rect->y() < bounds.y()) {
    rect->set_height(rect->height() + rect->y() - bounds.y());
    rect->set_y(bounds.y());
  }
  if (rect->y() > bounds.bottom()) {
    rect->set_height(0);
    rect->set_y(bounds.bottom());
  } else if (rect->bottom() > bounds.bottom()) {
    rect->set_height(rect->height() - rect->bottom() + bounds.bottom());
  }
}

// static
AccessibilityFocusRing AccessibilityFocusRing::CreateWithParagraphShape(
    const gfx::Rect& orig_top_line,
    const gfx::Rect& orig_body,
    const gfx::Rect& orig_bottom_line,
    int margin) {
  gfx::Rect top = orig_top_line;
  gfx::Rect middle = orig_body;
  gfx::Rect bottom = orig_bottom_line;

  gfx::Rect screen_bounds = GetScreenBoundsForRect(middle);
  screen_bounds.Inset(kScreenPaddingDip, kScreenPaddingDip);

  // Don't force a focus ring that is entirely offscreen to display.
  if (IsFocusRingOffscreen(top, middle, bottom, screen_bounds))
    return CreateFromThreeRects(top, middle, bottom, margin);

  if (top.Intersects(screen_bounds))
    top.Intersect(screen_bounds);
  else
    ClipToBounds(&top, screen_bounds);

  if (middle.Intersects(screen_bounds))
    middle.Intersect(screen_bounds);
  else
    ClipToBounds(&middle, screen_bounds);

  if (bottom.Intersects(screen_bounds))
    bottom.Intersect(screen_bounds);
  else
    ClipToBounds(&bottom, screen_bounds);

  int min_height = std::min(top.height(), bottom.height());
  margin = std::min(margin, min_height / 2);

  // Add space around top/bottom, if necessary, to allow focus ring to draw
  // properly.
  if (top.x() <= middle.x() + 2 * margin) {
    top.set_width(top.width() + top.x() - middle.x());
    top.set_x(middle.x());
  }
  if (top.right() >= middle.right() - 2 * margin) {
    top.set_width(middle.right() - top.x());
  }

  if (bottom.x() <= middle.x() + 2 * margin) {
    bottom.set_width(bottom.width() + bottom.x() - middle.x());
    bottom.set_x(middle.x());
  }
  if (bottom.right() >= middle.right() - 2 * margin) {
    bottom.set_width(middle.right() - bottom.x());
  }

  return CreateFromThreeRects(top, middle, bottom, margin);
}

gfx::Rect AccessibilityFocusRing::GetBounds() const {
  return bounds_in_screen;
}

// static
gfx::Rect AccessibilityFocusRing::GetScreenBoundsForRect(
    const gfx::Rect& rect) {
  if (!screen_bounds_for_testing_.IsEmpty())
    return screen_bounds_for_testing_;

  DCHECK(display::Screen::GetScreen());
  return display::Screen::GetScreen()->GetDisplayMatching(rect).bounds();
}

}  // namespace ash
