// Copyright (c) 2011 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 "ui/gfx/render_text.h"

#include <algorithm>

#include "base/i18n/break_iterator.h"
#include "base/logging.h"
#include "base/stl_util.h"
#include "ui/gfx/canvas.h"
#include "ui/gfx/canvas_skia.h"

namespace {

#ifndef NDEBUG
// Check StyleRanges invariant conditions: sorted and non-overlapping ranges.
void CheckStyleRanges(const gfx::StyleRanges& style_ranges, size_t length) {
  if (length == 0) {
    DCHECK(style_ranges.empty()) << "Style ranges exist for empty text.";
    return;
  }
  for (gfx::StyleRanges::size_type i = 0; i < style_ranges.size() - 1; i++) {
    const ui::Range& former = style_ranges[i].range;
    const ui::Range& latter = style_ranges[i + 1].range;
    DCHECK(!former.is_empty()) << "Empty range at " << i << ":" << former;
    DCHECK(former.IsValid()) << "Invalid range at " << i << ":" << former;
    DCHECK(!former.is_reversed()) << "Reversed range at " << i << ":" << former;
    DCHECK(former.end() == latter.start()) << "Ranges gap/overlap/unsorted." <<
        "former:" << former << ", latter:" << latter;
  }
  const gfx::StyleRange& end_style = *style_ranges.rbegin();
  DCHECK(!end_style.range.is_empty()) << "Empty range at end.";
  DCHECK(end_style.range.IsValid()) << "Invalid range at end.";
  DCHECK(!end_style.range.is_reversed()) << "Reversed range at end.";
  DCHECK(end_style.range.end() == length) << "Style and text length mismatch.";
}
#endif

void ApplyStyleRangeImpl(gfx::StyleRanges& style_ranges,
                         gfx::StyleRange style_range) {
  const ui::Range& new_range = style_range.range;
  // Follow StyleRanges invariant conditions: sorted and non-overlapping ranges.
  gfx::StyleRanges::iterator i;
  for (i = style_ranges.begin(); i != style_ranges.end();) {
    if (i->range.end() < new_range.start()) {
      i++;
    } else if (i->range.start() == new_range.end()) {
      break;
    } else if (new_range.Contains(i->range)) {
      i = style_ranges.erase(i);
      if (i == style_ranges.end())
        break;
    } else if (i->range.start() < new_range.start() &&
               i->range.end() > new_range.end()) {
      // Split the current style into two styles.
      gfx::StyleRange split_style = gfx::StyleRange(*i);
      split_style.range.set_end(new_range.start());
      i = style_ranges.insert(i, split_style) + 1;
      i->range.set_start(new_range.end());
      break;
    } else if (i->range.start() < new_range.start()) {
      i->range.set_end(new_range.start());
      i++;
    } else if (i->range.end() > new_range.end()) {
      i->range.set_start(new_range.end());
      break;
    } else
      NOTREACHED();
  }
  // Add the new range in its sorted location.
  style_ranges.insert(i, style_range);
}

}  // namespace

namespace gfx {

StyleRange::StyleRange()
    : font(),
      foreground(SK_ColorBLACK),
      strike(false),
      underline(false),
      range() {
}

void RenderText::SetText(const string16& text) {
  size_t old_text_length = text_.length();
  text_ = text;

  // Update the style ranges as needed.
  if (text_.empty()) {
    style_ranges_.clear();
  } else if (style_ranges_.empty()) {
    ApplyDefaultStyle();
  } else if (text_.length() > old_text_length) {
    style_ranges_.back().range.set_end(text_.length());
  } else if (text_.length() < old_text_length) {
    StyleRanges::iterator i;
    for (i = style_ranges_.begin(); i != style_ranges_.end(); i++) {
      if (i->range.start() >= text_.length()) {
        i = style_ranges_.erase(i);
        if (i == style_ranges_.end())
          break;
      } else if (i->range.end() > text_.length()) {
        i->range.set_end(text_.length());
      }
    }
    style_ranges_.back().range.set_end(text_.length());
  }
#ifndef NDEBUG
  CheckStyleRanges(style_ranges_, text_.length());
#endif
}

size_t RenderText::GetCursorPosition() const {
  return GetSelection().end();
}

void RenderText::SetCursorPosition(const size_t position) {
  SetSelection(ui::Range(position, position));
}

void RenderText::MoveCursorLeft(BreakType break_type, bool select) {
  if (break_type == LINE_BREAK) {
    MoveCursorTo(0, select);
    return;
  }
  size_t position = GetCursorPosition();
  // Cancelling a selection moves to the edge of the selection.
  if (!GetSelection().is_empty() && !select) {
    // Use the selection start if it is left of the selection end.
    if (GetCursorBounds(GetSelection().start(), false).x() <
        GetCursorBounds(position, false).x())
      position = GetSelection().start();
    // If |move_by_word|, use the nearest word boundary left of the selection.
    if (break_type == WORD_BREAK)
      position = GetLeftCursorPosition(position, true);
  } else {
    position = GetLeftCursorPosition(position, break_type == WORD_BREAK);
  }
  MoveCursorTo(position, select);
}

void RenderText::MoveCursorRight(BreakType break_type, bool select) {
  if (break_type == LINE_BREAK) {
    MoveCursorTo(text().length(), select);
    return;
  }
  size_t position = GetCursorPosition();
  // Cancelling a selection moves to the edge of the selection.
  if (!GetSelection().is_empty() && !select) {
    // Use the selection start if it is right of the selection end.
    if (GetCursorBounds(GetSelection().start(), false).x() >
        GetCursorBounds(position, false).x())
      position = GetSelection().start();
    // If |move_by_word|, use the nearest word boundary right of the selection.
    if (break_type == WORD_BREAK)
      position = GetRightCursorPosition(position, true);
  } else {
    position = GetRightCursorPosition(position, break_type == WORD_BREAK);
  }
  MoveCursorTo(position, select);
}

bool RenderText::MoveCursorTo(size_t position, bool select) {
  bool changed = GetCursorPosition() != position ||
                 select == GetSelection().is_empty();
  if (select)
    SetSelection(ui::Range(GetSelection().start(), position));
  else
    SetSelection(ui::Range(position, position));
  return changed;
}

bool RenderText::MoveCursorTo(const gfx::Point& point, bool select) {
  // TODO(msw): Make this function support cursor placement via mouse near BiDi
  //  level changes. The visual cursor appearance will depend on the location
  //  clicked, not solely the resulting logical cursor position. See the TODO
  //  note pertaining to selection_range_ for more information.
  return MoveCursorTo(FindCursorPosition(point), select);
}

const ui::Range& RenderText::GetSelection() const {
  return selection_range_;
}

void RenderText::SetSelection(const ui::Range& range) {
  selection_range_.set_end(std::min(range.end(), text().length()));
  selection_range_.set_start(std::min(range.start(), text().length()));

  // Update |display_offset_| to ensure the current cursor is visible.
  gfx::Rect cursor_bounds(GetCursorBounds(GetCursorPosition(), insert_mode()));
  int display_width = display_rect_.width();
  int string_width = GetStringWidth();
  if (string_width < display_width) {
    // Show all text whenever the text fits to the size.
    display_offset_.set_x(0);
  } else if ((display_offset_.x() + cursor_bounds.right()) > display_width) {
    // Pan to show the cursor when it overflows to the right,
     display_offset_.set_x(display_width - cursor_bounds.right());
  } else if ((display_offset_.x() + cursor_bounds.x()) < 0) {
    // Pan to show the cursor when it overflows to the left.
    display_offset_.set_x(-cursor_bounds.x());
  }
}

bool RenderText::IsPointInSelection(const gfx::Point& point) const {
  size_t pos = FindCursorPosition(point);
  return (pos >= GetSelection().GetMin() && pos < GetSelection().GetMax());
}

void RenderText::ClearSelection() {
  SetCursorPosition(GetCursorPosition());
}

void RenderText::SelectAll() {
  SetSelection(ui::Range(0, text().length()));
}

void RenderText::SelectWord() {
  size_t selection_start = GetSelection().start();
  size_t cursor_position = GetCursorPosition();
  // First we setup selection_start_ and cursor_pos_. There are so many cases
  // because we try to emulate what select-word looks like in a gtk textfield.
  // See associated testcase for different cases.
  if (cursor_position > 0 && cursor_position < text().length()) {
    if (isalnum(text()[cursor_position])) {
      selection_start = cursor_position;
      cursor_position++;
    } else
      selection_start = cursor_position - 1;
  } else if (cursor_position == 0) {
    selection_start = cursor_position;
    if (text().length() > 0)
      cursor_position++;
  } else {
    selection_start = cursor_position - 1;
  }

  // Now we move selection_start_ to beginning of selection. Selection boundary
  // is defined as the position where we have alpha-num character on one side
  // and non-alpha-num char on the other side.
  for (; selection_start > 0; selection_start--) {
    if (IsPositionAtWordSelectionBoundary(selection_start))
      break;
  }

  // Now we move cursor_pos_ to end of selection. Selection boundary
  // is defined as the position where we have alpha-num character on one side
  // and non-alpha-num char on the other side.
  for (; cursor_position < text().length(); cursor_position++) {
    if (IsPositionAtWordSelectionBoundary(cursor_position))
      break;
  }

  SetSelection(ui::Range(selection_start, cursor_position));
}

const ui::Range& RenderText::GetCompositionRange() const {
  return composition_range_;
}

void RenderText::SetCompositionRange(const ui::Range& composition_range) {
  CHECK(!composition_range.IsValid() ||
        ui::Range(0, text_.length()).Contains(composition_range));
  composition_range_.set_end(composition_range.end());
  composition_range_.set_start(composition_range.start());
}

void RenderText::ApplyStyleRange(StyleRange style_range) {
  const ui::Range& new_range = style_range.range;
  if (!new_range.IsValid() || new_range.is_empty())
    return;
  CHECK(!new_range.is_reversed());
  CHECK(ui::Range(0, text_.length()).Contains(new_range));
  ApplyStyleRangeImpl(style_ranges_, style_range);
#ifndef NDEBUG
  CheckStyleRanges(style_ranges_, text_.length());
#endif
}

void RenderText::ApplyDefaultStyle() {
  style_ranges_.clear();
  StyleRange style = StyleRange(default_style_);
  style.range.set_end(text_.length());
  style_ranges_.push_back(style);
}

base::i18n::TextDirection RenderText::GetTextDirection() const {
  // TODO(msw): Bidi implementation, intended to replace the functionality added
  //  in crrev.com/91881 (discussed in codereview.chromium.org/7324011).
  return base::i18n::LEFT_TO_RIGHT;
}

int RenderText::GetStringWidth() const {
  return GetSubstringBounds(ui::Range(0, text_.length()))[0].width();
}

void RenderText::Draw(gfx::Canvas* canvas) {
  // Clip the canvas to the text display area.
  canvas->ClipRectInt(display_rect_.x(), display_rect_.y(),
                      display_rect_.width(), display_rect_.height());

  // Draw the selection.
  std::vector<gfx::Rect> selection(GetSubstringBounds(GetSelection()));
  SkColor selection_color =
      focused() ? kFocusedSelectionColor : kUnfocusedSelectionColor;
  for (std::vector<gfx::Rect>::const_iterator i = selection.begin();
       i < selection.end(); ++i) {
    gfx::Rect r(*i);
    r.Offset(display_offset_);
    canvas->FillRectInt(selection_color, r.x(), r.y(), r.width(), r.height());
  }

  // Create a temporary copy of the style ranges for composition and selection.
  // TODO(msw): This pattern ought to be reconsidered; what about composition
  //            and selection overlaps, retain existing local style features?
  StyleRanges style_ranges(style_ranges_);
  // Apply a composition style override to a copy of the style ranges.
  if (composition_range_.IsValid() && !composition_range_.is_empty()) {
    StyleRange composition_style(default_style_);
    composition_style.underline = true;
    composition_style.range.set_start(composition_range_.start());
    composition_style.range.set_end(composition_range_.end());
    ApplyStyleRangeImpl(style_ranges, composition_style);
  }
  // Apply a selection style override to a copy of the style ranges.
  if (selection_range_.IsValid() && !selection_range_.is_empty()) {
    StyleRange selection_style(default_style_);
    selection_style.foreground = kSelectedTextColor;
    selection_style.range.set_start(selection_range_.GetMin());
    selection_style.range.set_end(selection_range_.GetMax());
    ApplyStyleRangeImpl(style_ranges, selection_style);
  }

  // Draw the text.
  gfx::Rect bounds(display_rect_);
  bounds.Offset(display_offset_);
  for (StyleRanges::const_iterator i = style_ranges.begin();
       i < style_ranges.end(); ++i) {
    Font font = !i->underline ? i->font :
        i->font.DeriveFont(0, i->font.GetStyle() | Font::UNDERLINED);
    string16 text = text_.substr(i->range.start(), i->range.length());
    bounds.set_width(font.GetStringWidth(text));
    canvas->DrawStringInt(text, font, i->foreground, bounds);

    // Draw the strikethrough.
    if (i->strike) {
      SkPaint paint;
      paint.setAntiAlias(true);
      paint.setStyle(SkPaint::kFill_Style);
      paint.setColor(i->foreground);
      paint.setStrokeWidth(kStrikeWidth);
      canvas->AsCanvasSkia()->drawLine(SkIntToScalar(bounds.x()),
                                       SkIntToScalar(bounds.bottom()),
                                       SkIntToScalar(bounds.right()),
                                       SkIntToScalar(bounds.y()),
                                       paint);
    }

    bounds.set_x(bounds.x() + bounds.width());
  }

  // Paint cursor. Replace cursor is drawn as rectangle for now.
  if (cursor_visible() && focused()) {
    bounds = GetCursorBounds(GetCursorPosition(), insert_mode());
    bounds.Offset(display_offset_);
    if (!bounds.IsEmpty())
      canvas->DrawRectInt(kCursorColor,
                          bounds.x(),
                          bounds.y(),
                          bounds.width(),
                          bounds.height());
  }
}

size_t RenderText::FindCursorPosition(const gfx::Point& point) const {
  const gfx::Font& font = Font();
  int left = 0;
  int left_pos = 0;
  int right = font.GetStringWidth(text());
  int right_pos = text().length();

  int x = point.x();
  if (x <= left) return left_pos;
  if (x >= right) return right_pos;
  // binary searching the cursor position.
  // TODO(oshima): use the center of character instead of edge.
  // Binary search may not work for language like arabic.
  while (std::abs(static_cast<long>(right_pos - left_pos) > 1)) {
    int pivot_pos = left_pos + (right_pos - left_pos) / 2;
    int pivot = font.GetStringWidth(text().substr(0, pivot_pos));
    if (pivot < x) {
      left = pivot;
      left_pos = pivot_pos;
    } else if (pivot == x) {
      return pivot_pos;
    } else {
      right = pivot;
      right_pos = pivot_pos;
    }
  }
  return left_pos;
}

std::vector<gfx::Rect> RenderText::GetSubstringBounds(
    const ui::Range& range) const {
  size_t start = range.GetMin();
  size_t end = range.GetMax();
  gfx::Font font;
  int start_x = font.GetStringWidth(text().substr(0, start));
  int end_x = font.GetStringWidth(text().substr(0, end));
  std::vector<gfx::Rect> bounds;
  bounds.push_back(gfx::Rect(start_x, 0, end_x - start_x, font.GetHeight()));
  return bounds;
}

gfx::Rect RenderText::GetCursorBounds(size_t cursor_pos,
                                      bool insert_mode) const {
  gfx::Font font;
  int x = font.GetStringWidth(text_.substr(0U, cursor_pos));
  DCHECK_GE(x, 0);
  int h = std::min(display_rect_.height(), font.GetHeight());
  gfx::Rect bounds(x, (display_rect_.height() - h) / 2, 1, h);
  if (!insert_mode && text_.length() != cursor_pos)
    bounds.set_width(font.GetStringWidth(text_.substr(0, cursor_pos + 1)) - x);
  return bounds;
}

size_t RenderText::GetLeftCursorPosition(size_t position,
                                         bool move_by_word) const {
  if (!move_by_word)
    return position == 0? position : position - 1;
  // Notes: We always iterate words from the begining.
  // This is probably fast enough for our usage, but we may
  // want to modify WordIterator so that it can start from the
  // middle of string and advance backwards.
  base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
  bool success = iter.Init();
  DCHECK(success);
  if (!success)
    return position;
  int last = 0;
  while (iter.Advance()) {
    if (iter.IsWord()) {
      size_t begin = iter.pos() - iter.GetString().length();
      if (begin == position) {
        // The cursor is at the beginning of a word.
        // Move to previous word.
        break;
      } else if(iter.pos() >= position) {
        // The cursor is in the middle or at the end of a word.
        // Move to the top of current word.
        last = begin;
        break;
      } else {
        last = iter.pos() - iter.GetString().length();
      }
    }
  }

  return last;
}

size_t RenderText::GetRightCursorPosition(size_t position,
                                          bool move_by_word) const {
  if (!move_by_word)
    return std::min(position + 1, text().length());
  base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
  bool success = iter.Init();
  DCHECK(success);
  if (!success)
    return position;
  size_t pos = 0;
  while (iter.Advance()) {
    pos = iter.pos();
    if (iter.IsWord() && pos > position) {
      break;
    }
  }
  return pos;
}

RenderText::RenderText()
    : text_(),
      selection_range_(),
      cursor_visible_(false),
      insert_mode_(true),
      composition_range_(),
      style_ranges_(),
      default_style_(),
      display_rect_(),
      display_offset_() {
}

RenderText::~RenderText() {
}

bool RenderText::IsPositionAtWordSelectionBoundary(size_t pos) {
  return pos == 0 || (isalnum(text()[pos - 1]) && !isalnum(text()[pos])) ||
      (!isalnum(text()[pos - 1]) && isalnum(text()[pos]));
}

}  // namespace gfx