// Copyright (c) 2012 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.

#ifndef UI_GFX_RENDER_TEXT_H_
#define UI_GFX_RENDER_TEXT_H_
#pragma once

#include <algorithm>
#include <vector>

#include "base/gtest_prod_util.h"
#include "base/i18n/rtl.h"
#include "base/string16.h"
#include "third_party/skia/include/core/SkColor.h"
#include "third_party/skia/include/core/SkPaint.h"
#include "ui/base/range/range.h"
#include "ui/gfx/font_list.h"
#include "ui/gfx/point.h"
#include "ui/gfx/rect.h"
#include "ui/gfx/selection_model.h"

class SkCanvas;
struct SkPoint;

namespace gfx {

class Canvas;
class RenderTextTest;

namespace internal {

// Internal helper class used by derived classes to draw text through Skia.
class SkiaTextRenderer {
 public:
  explicit SkiaTextRenderer(Canvas* canvas);
  ~SkiaTextRenderer();

  void SetTypeface(SkTypeface* typeface);
  void SetTextSize(int size);
  void SetFont(const gfx::Font& font);
  void SetFontStyle(int font_style);
  void SetForegroundColor(SkColor foreground);
  void SetShader(SkShader* shader);
  void DrawSelection(const std::vector<Rect>& selection, SkColor color);
  void DrawPosText(const SkPoint* pos,
                   const uint16* glyphs,
                   size_t glyph_count);
  void DrawDecorations(int x, int y, int width, bool underline, bool strike);

 private:
  SkCanvas* canvas_skia_;
  SkPaint paint_;

  DISALLOW_COPY_AND_ASSIGN(SkiaTextRenderer);
};

}  // namespace internal

// Color settings for text, backgrounds and cursor.
// These are tentative, and should be derived from theme, system
// settings and current settings.
// TODO(oshima): Change this to match the standard chrome
// before dogfooding textfield views.
const SkColor kSelectedTextColor = SK_ColorWHITE;
const SkColor kFocusedSelectionColor = SkColorSetRGB(30, 144, 255);
const SkColor kUnfocusedSelectionColor = SK_ColorLTGRAY;
const SkColor kCursorColor = SK_ColorBLACK;

// A visual style applicable to a range of text.
struct UI_EXPORT StyleRange {
  StyleRange();

  SkColor foreground;
  // A gfx::Font::FontStyle flag to specify bold and italic styles.
  int font_style;
  bool strike;
  bool underline;
  ui::Range range;
};

typedef std::vector<StyleRange> StyleRanges;

// TODO(msw): Distinguish between logical character stops and glyph stops?
// CHARACTER_BREAK cursor movements should stop at neighboring characters.
// WORD_BREAK cursor movements should stop at the nearest word boundaries.
// LINE_BREAK cursor movements should stop at the text ends as shown on screen.
enum BreakType {
  CHARACTER_BREAK,
  WORD_BREAK,
  LINE_BREAK,
};

// TODO(msw): Implement RenderText[Win|Linux] for Uniscribe/Pango BiDi...

// RenderText represents an abstract model of styled text and its corresponding
// visual layout. Support is built in for a cursor, a selection, simple styling,
// complex scripts, and bi-directional text. Implementations provide mechanisms
// for rendering and translation between logical and visual data.
class UI_EXPORT RenderText {
 public:
  virtual ~RenderText();

  // Creates a platform-specific RenderText instance.
  static RenderText* CreateRenderText();

  const string16& text() const { return text_; }
  void SetText(const string16& text);

  const FontList& font_list() const { return font_list_; }
  void SetFontList(const FontList& font_list);
  // Get the first font in |font_list_|.
  const Font& GetFont() const;

  const SelectionModel& selection_model() const { return selection_model_; }

  bool cursor_visible() const { return cursor_visible_; }
  void set_cursor_visible(bool visible) { cursor_visible_ = visible; }

  bool insert_mode() const { return insert_mode_; }
  void ToggleInsertMode();

  bool focused() const { return focused_; }
  void set_focused(bool focused) { focused_ = focused; }

  const StyleRange& default_style() const { return default_style_; }
  void set_default_style(const StyleRange& style) { default_style_ = style; }

  const Rect& display_rect() const { return display_rect_; }
  void SetDisplayRect(const Rect& r);

  void set_fade_head(bool fade_head) { fade_head_ = fade_head; }
  bool fade_head() const { return fade_head_; }
  void set_fade_tail(bool fade_tail) { fade_tail_ = fade_tail; }
  bool fade_tail() const { return fade_tail_; }

  // This cursor position corresponds to SelectionModel::selection_end. In
  // addition to representing the selection end, it's also where logical text
  // edits take place, and doesn't necessarily correspond to
  // SelectionModel::caret_pos.
  size_t GetCursorPosition() const;
  void SetCursorPosition(size_t position);

  // Moves the cursor left or right. Cursor movement is visual, meaning that
  // left and right are relative to screen, not the directionality of the text.
  // If |select| is false, the selection start is moved to the same position.
  void MoveCursorLeft(BreakType break_type, bool select);
  void MoveCursorRight(BreakType break_type, bool select);

  // Set the selection_model_ to the value of |selection|.
  // The selection model components are modified if invalid.
  // Returns true if the cursor position or selection range changed.
  // If |selectin_start_| or |selection_end_| or |caret_pos_| in
  // |selection_model| is not a cursorable position (not on grapheme boundary),
  // it is a NO-OP and returns false.
  bool MoveCursorTo(const SelectionModel& selection_model);

  // Move the cursor to the position associated with the clicked point.
  // If |select| is false, the selection start is moved to the same position.
  // Returns true if the cursor position or selection range changed.
  bool MoveCursorTo(const Point& point, bool select);

  // Set the selection_model_ based on |range|.
  // If the |range| start or end is greater than text length, it is modified
  // to be the text length.
  // If the |range| start or end is not a cursorable position (not on grapheme
  // boundary), it is a NO-OP and returns false. Otherwise, returns true.
  bool SelectRange(const ui::Range& range);

  size_t GetSelectionStart() const {
    return selection_model_.selection_start();
  }
  size_t MinOfSelection() const {
    return std::min(GetSelectionStart(), GetCursorPosition());
  }
  size_t MaxOfSelection() const {
    return std::max(GetSelectionStart(), GetCursorPosition());
  }
  bool EmptySelection() const {
    return GetSelectionStart() == GetCursorPosition();
  }

  // Returns true if the local point is over selected text.
  bool IsPointInSelection(const Point& point);

  // Selects no text, all text, or the word at the current cursor position.
  void ClearSelection();
  void SelectAll();
  void SelectWord();

  const ui::Range& GetCompositionRange() const;
  void SetCompositionRange(const ui::Range& composition_range);

  // Apply |style_range| to the internal style model.
  void ApplyStyleRange(const StyleRange& style_range);

  // Apply |default_style_| over the entire text range.
  void ApplyDefaultStyle();

  virtual base::i18n::TextDirection GetTextDirection();

  // Get the width of the entire string.
  virtual int GetStringWidth() = 0;

  void Draw(Canvas* canvas);

  // Gets the SelectionModel from a visual point in local coordinates.
  virtual SelectionModel FindCursorPosition(const Point& point) = 0;

  // Get the visual bounds of a cursor at |selection|. These bounds typically
  // represent a vertical line, but if |insert_mode| is true they contain the
  // bounds of the associated glyph. These bounds are in local coordinates, but
  // may be outside the visible region if the text is longer than the textfield.
  // Subsequent text, cursor, or bounds changes may invalidate returned values.
  virtual Rect GetCursorBounds(const SelectionModel& selection,
                               bool insert_mode) = 0;

  // Compute the current cursor bounds, panning the text to show the cursor in
  // the display rect if necessary. These bounds are in local coordinates.
  // Subsequent text, cursor, or bounds changes may invalidate returned values.
  const Rect& GetUpdatedCursorBounds();

  // Get the logical index of the grapheme following the argument |position|.
  size_t GetIndexOfNextGrapheme(size_t position);

  // Return a SelectionModel with the cursor at the current selection's start.
  // The returned value represents a cursor/caret position without a selection.
  SelectionModel GetSelectionModelForSelectionStart();

 protected:
  RenderText();

  const Point& GetUpdatedDisplayOffset();

  void set_cached_bounds_and_offset_valid(bool valid) {
    cached_bounds_and_offset_valid_ = valid;
  }

  const StyleRanges& style_ranges() const { return style_ranges_; }

  // Get the selection model that visually neighbors |position| by |break_type|.
  // The returned value represents a cursor/caret position without a selection.
  virtual SelectionModel GetLeftSelectionModel(const SelectionModel& current,
                                               BreakType break_type);
  virtual SelectionModel GetRightSelectionModel(const SelectionModel& current,
                                                BreakType break_type);

  // Get the SelectionModels corresponding to visual text ends.
  // The returned value represents a cursor/caret position without a selection.
  virtual SelectionModel LeftEndSelectionModel();
  virtual SelectionModel RightEndSelectionModel();

  // Sets the selection model, the argument is assumed to be valid.
  virtual void SetSelectionModel(const SelectionModel& model);

  // Get the visual bounds containing the logical substring within |from| to
  // |to| into |bounds|. If |from| equals to |to|, |bounds| is set as empty.
  // These bounds could be visually discontinuous if the substring is split by a
  // LTR/RTL level change. These bounds are in local coordinates, but may be
  // outside the visible region if the text is longer than the textfield.
  // Subsequent text, cursor, or bounds changes may invalidate returned values.
  virtual void GetSubstringBounds(size_t from,
                                  size_t to,
                                  std::vector<Rect>* bounds) = 0;

  // Return true if cursor can appear in front of the character at |position|,
  // which means it is a grapheme boundary or the first character in the text.
  virtual bool IsCursorablePosition(size_t position) = 0;

  // Update the layout so that the next draw request can correctly
  // render the text and its attributes.
  virtual void UpdateLayout() = 0;

  // Ensure the text is laid out.
  virtual void EnsureLayout() = 0;

  // Draw the text.
  virtual void DrawVisualText(Canvas* canvas) = 0;

  // Get the logical index of the grapheme preceding the argument |position|.
  // If |IsCursorablePosition(position)| is true, the result will be the start
  // of the previous grapheme, if any. Otherwise, the result will be the start
  // of the grapheme containing |position|.
  size_t GetIndexOfPreviousGrapheme(size_t position);

  // Apply composition style (underline) to composition range and selection
  // style (foreground) to selection range.
  void ApplyCompositionAndSelectionStyles(StyleRanges* style_ranges) const;

  // Convert points from the text space to the view space and back.
  // Handles the display area, display offset, and the application LTR/RTL mode.
  Point ToTextPoint(const Point& point);
  Point ToViewPoint(const Point& point);

  // Returns the origin point for drawing text via Skia.
  Point GetOriginForSkiaDrawing();

  // Applies fade effects to |renderer| and returns a text drawing offset when
  // fading the head would cause the text to change alignment.
  // TODO(asvitkine): Applying right-alignment in this way doesn't work well
  //                  with drawing the text selection and cursor. Instead, we
  //                  should make RenderText support horizontal alignment
  //                  explicitly.
  int ApplyFadeEffects(internal::SkiaTextRenderer* renderer);

 private:
  friend class RenderTextTest;

  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, DefaultStyle);
  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, CustomDefaultStyle);
  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, ApplyStyleRange);
  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, StyleRangesAdjust);
  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, GraphemePositions);
  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, SelectionModels);
  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, OriginForSkiaDrawing);

  // Return an index belonging to the |next| or previous logical grapheme.
  // If |next| is false and |IsCursorablePosition(index)| is true, the result
  // will be the start of the previous grapheme, if any. Otherwise, the result
  // will be the start of the grapheme containing |index|.
  // The return value is bounded by 0 and the text length, inclusive.
  virtual size_t IndexOfAdjacentGrapheme(size_t index, bool next) = 0;

  // Set the cursor to |position|, with the caret trailing the previous
  // grapheme, or if there is no previous grapheme, leading the cursor position.
  // If |select| is false, the selection start is moved to the same position.
  // If the |position| is not a cursorable position (not on grapheme boundary),
  // it is a NO-OP.
  void MoveCursorTo(size_t position, bool select);

  // Update the cached bounds and display offset to ensure that the current
  // cursor is within the visible display area.
  void UpdateCachedBoundsAndOffset();

  // Draw the selection and cursor.
  void DrawSelection(Canvas* canvas);
  void DrawCursor(Canvas* canvas);

  // Logical UTF-16 string data to be drawn.
  string16 text_;

  // A list of fonts used to render |text_|.
  FontList font_list_;

  // Logical selection range and visual cursor position.
  SelectionModel selection_model_;

  // The cached cursor bounds; get these bounds with GetUpdatedCursorBounds.
  Rect cursor_bounds_;

  // The cursor visibility and insert mode.
  bool cursor_visible_;
  bool insert_mode_;

  // The focus state of the text.
  bool focused_;

  // Composition text range.
  ui::Range composition_range_;

  // List of style ranges. Elements in the list never overlap each other.
  StyleRanges style_ranges_;
  // The default text style.
  StyleRange default_style_;

  // Fade text head and/or tail, if text doesn't fit into |display_rect_|.
  bool fade_head_;
  bool fade_tail_;

  // The local display area for rendering the text.
  Rect display_rect_;

  // The offset for the text to be drawn, relative to the display area.
  // Get this point with GetUpdatedDisplayOffset (or risk using a stale value).
  Point display_offset_;

  // The cached bounds and offset are invalidated by changes to the cursor,
  // selection, font, and other operations that adjust the visible text bounds.
  bool cached_bounds_and_offset_valid_;

  DISALLOW_COPY_AND_ASSIGN(RenderText);
};

}  // namespace gfx

#endif  // UI_GFX_RENDER_TEXT_H_