text: /*
   * Copyright (c) 2021, the SerenityOS developers.
   *
   * SPDX-License-Identifier: BSD-2-Clause
   */
  
  #include <LibGUI/EditingEngine.h>
  #include <LibGUI/Event.h>
  #include <LibGUI/TextEditor.h>
  
  namespace GUI {
  
  EditingEngine::~EditingEngine()
  {
  }
  
  void EditingEngine::attach(TextEditor& editor)
  {
      VERIFY(!m_editor);
      m_editor = editor;
  }
  
  void EditingEngine::detach()
  {
      VERIFY(m_editor);
      m_editor = nullptr;
  }
  
  bool EditingEngine::on_key(const KeyEvent& event)
  {
      if (event.key() == KeyCode::Key_Left) {
          if (!event.shift() && m_editor->selection()->is_valid()) {
              m_editor->set_cursor(m_editor->selection()->normalized().start());
              m_editor->selection()->clear();
              m_editor->did_update_selection();
              if (!event.ctrl()) {
                  m_editor->update();
                  return true;
              }
          }
          if (event.ctrl()) {
              move_to_previous_span(event);
              if (event.shift() && m_editor->selection()->start().is_valid()) {
                  m_editor->selection()->set_end(m_editor->cursor());
                  m_editor->did_update_selection();
              }
              return true;
          }
          move_one_left(event);
          if (event.shift() && m_editor->selection()->start().is_valid()) {
              m_editor->selection()->set_end(m_editor->cursor());
              m_editor->did_update_selection();
          }
          return true;
      }
  
      if (event.key() == KeyCode::Key_Right) {
          if (!event.shift() && m_editor->selection()->is_valid()) {
              m_editor->set_cursor(m_editor->selection()->normalized().end());
              m_editor->selection()->clear();
              m_editor->did_update_selection();
              if (!event.ctrl()) {
                  m_editor->update();
                  return true;
              }
          }
          if (event.ctrl()) {
              move_to_next_span(event);
              return true;
          }
          move_one_right(event);
          if (event.shift() && m_editor->selection()->start().is_valid()) {
              m_editor->selection()->set_end(m_editor->cursor());
              m_editor->did_update_selection();
          }
          return true;
      }
  
      if (event.key() == KeyCode::Key_Up) {
          move_one_up(event);
          if (event.shift() && m_editor->selection()->start().is_valid()) {
              m_editor->selection()->set_end(m_editor->cursor());
              m_editor->did_update_selection();
          }
          return true;
      }
  
      if (event.key() == KeyCode::Key_Down) {
          move_one_down(event);
          if (event.shift() && m_editor->selection()->start().is_valid()) {
              m_editor->selection()->set_end(m_editor->cursor());
              m_editor->did_update_selection();
          }
          return true;
      }
  
      if (event.key() == KeyCode::Key_Home) {
          if (event.ctrl()) {
              m_editor->toggle_selection_if_needed_for_event(event.shift());
              move_to_first_line();
              if (event.shift() && m_editor->selection()->start().is_valid()) {
                  m_editor->selection()->set_end(m_editor->cursor());
                  m_editor->did_update_selection();
              }
          } else {
              move_to_line_beginning(event);
              if (event.shift() && m_editor->selection()->start().is_valid()) {
                  m_editor->selection()->set_end(m_editor->cursor());
                  m_editor->did_update_selection();
              }
          }
          return true;
      }
  
      if (event.key() == KeyCode::Key_End) {
          if (event.ctrl()) {
              m_editor->toggle_selection_if_needed_for_event(event.shift());
              move_to_last_line();
              if (event.shift() && m_editor->selection()->start().is_valid()) {
                  m_editor->selection()->set_end(m_editor->cursor());
                  m_editor->did_update_selection();
              }
          } else {
              move_to_line_end(event);
              if (event.shift() && m_editor->selection()->start().is_valid()) {
                  m_editor->selection()->set_end(m_editor->cursor());
                  m_editor->did_update_selection();
              }
          }
          return true;
      }
  
      if (event.key() == KeyCode::Key_PageUp) {
          move_page_up(event);
          if (event.shift() && m_editor->selection()->start().is_valid()) {
              m_editor->selection()->set_end(m_editor->cursor());
              m_editor->did_update_selection();
          }
          return true;
      }
  
      if (event.key() == KeyCode::Key_PageDown) {
          move_page_down(event);
          if (event.shift() && m_editor->selection()->start().is_valid()) {
              m_editor->selection()->set_end(m_editor->cursor());
              m_editor->did_update_selection();
          }
          return true;
      }
  
      return false;
  }
  
  void EditingEngine::move_one_left(const KeyEvent& event)
  {
      if (m_editor->cursor().column() > 0) {
          int new_column = m_editor->cursor().column() - 1;
          m_editor->toggle_selection_if_needed_for_event(event.shift());
          m_editor->set_cursor(m_editor->cursor().line(), new_column);
      } else if (m_editor->cursor().line() > 0) {
          int new_line = m_editor->cursor().line() - 1;
          int new_column = m_editor->lines()[new_line].length();
          m_editor->toggle_selection_if_needed_for_event(event.shift());
          m_editor->set_cursor(new_line, new_column);
      }
  }
  
  void EditingEngine::move_one_right(const KeyEvent& event)
  {
      int new_line = m_editor->cursor().line();
      int new_column = m_editor->cursor().column();
      if (m_editor->cursor().column() < m_editor->current_line().length()) {
          new_line = m_editor->cursor().line();
          new_column = m_editor->cursor().column() + 1;
      } else if (m_editor->cursor().line() != m_editor->line_count() - 1) {
          new_line = m_editor->cursor().line() + 1;
          new_column = 0;
      }
      m_editor->toggle_selection_if_needed_for_event(event.shift());
      m_editor->set_cursor(new_line, new_column);
  }
  
  void EditingEngine::move_to_previous_span(const KeyEvent& event)
  {
      TextPosition new_cursor;
      if (m_editor->document().has_spans()) {
          auto span = m_editor->document().first_non_skippable_span_before(m_editor->cursor());
          if (span.has_value()) {
              new_cursor = span.value().range.start();
          } else {
              // No remaining spans, just use word break calculation
              new_cursor = m_editor->document().first_word_break_before(m_editor->cursor(), true);
          }
      } else {
          new_cursor = m_editor->document().first_word_break_before(m_editor->cursor(), true);
      }
      m_editor->toggle_selection_if_needed_for_event(event.shift());
      m_editor->set_cursor(new_cursor);
  }
  
  void EditingEngine::move_to_next_span(const KeyEvent& event)
  {
      TextPosition new_cursor;
      if (m_editor->document().has_spans()) {
          auto span = m_editor->document().first_non_skippable_span_after(m_editor->cursor());
          if (span.has_value()) {
              new_cursor = span.value().range.start();
          } else {
              // No remaining spans, just use word break calculation
              new_cursor = m_editor->document().first_word_break_after(m_editor->cursor());
          }
      } else {
          new_cursor = m_editor->document().first_word_break_after(m_editor->cursor());
      }
      m_editor->toggle_selection_if_needed_for_event(event.shift());
      m_editor->set_cursor(new_cursor);
      if (event.shift() && m_editor->selection()->start().is_valid()) {
          m_editor->selection()->set_end(m_editor->cursor());
          m_editor->did_update_selection();
      }
  }
  
  void EditingEngine::move_to_line_beginning(const KeyEvent& event)
  {
      TextPosition new_cursor;
      m_editor->toggle_selection_if_needed_for_event(event.shift());
      if (m_editor->is_wrapping_enabled()) {
          // FIXME: Replicate the first_nonspace_column behavior in wrapping mode.
          auto home_position = m_editor->cursor_content_rect().location().translated(-m_editor->width(), 0);
          new_cursor = m_editor->text_position_at_content_position(home_position);
      } else {
          size_t first_nonspace_column = m_editor->current_line().first_non_whitespace_column();
          if (m_editor->cursor().column() == first_nonspace_column) {
              new_cursor = { m_editor->cursor().line(), 0 };
          } else {
              new_cursor = { m_editor->cursor().line(), first_nonspace_column };
          }
      }
      m_editor->set_cursor(new_cursor);
  }
  
  void EditingEngine::move_to_line_end(const KeyEvent& event)
  {
      TextPosition new_cursor;
      if (m_editor->is_wrapping_enabled()) {
          auto end_position = m_editor->cursor_content_rect().location().translated(m_editor->width(), 0);
          new_cursor = m_editor->text_position_at_content_position(end_position);
      } else {
          new_cursor = { m_editor->cursor().line(), m_editor->current_line().length() };
      }
      m_editor->toggle_selection_if_needed_for_event(event.shift());
      m_editor->set_cursor(new_cursor);
  }
  
  void EditingEngine::move_one_up(const KeyEvent& event)
  {
      if (m_editor->cursor().line() > 0 || m_editor->is_wrapping_enabled()) {
          if (event.ctrl() && event.shift()) {
              move_selected_lines_up();
              return;
          }
          TextPosition new_cursor;
          if (m_editor->is_wrapping_enabled()) {
              auto position_above = m_editor->cursor_content_rect().location().translated(0, -m_editor->line_height());
              new_cursor = m_editor->text_position_at_content_position(position_above);
          } else {
              size_t new_line = m_editor->cursor().line() - 1;
              size_t new_column = min(m_editor->cursor().column(), m_editor->line(new_line).length());
              new_cursor = { new_line, new_column };
          }
          m_editor->toggle_selection_if_needed_for_event(event.shift());
          m_editor->set_cursor(new_cursor);
      }
  };
  
  void EditingEngine::move_one_down(const KeyEvent& event)
  {
      if (m_editor->cursor().line() < (m_editor->line_count() - 1) || m_editor->is_wrapping_enabled()) {
          if (event.ctrl() && event.shift()) {
              move_selected_lines_down();
              return;
          }
          TextPosition new_cursor;
          if (m_editor->is_wrapping_enabled()) {
              auto position_below = m_editor->cursor_content_rect().location().translated(0, m_editor->line_height());
              new_cursor = m_editor->text_position_at_content_position(position_below);
          } else {
              size_t new_line = m_editor->cursor().line() + 1;
              size_t new_column = min(m_editor->cursor().column(), m_editor->line(new_line).length());
              new_cursor = { new_line, new_column };
          }
          m_editor->toggle_selection_if_needed_for_event(event.shift());
          m_editor->set_cursor(new_cursor);
      }
  };
  
  void EditingEngine::move_up(const KeyEvent& event, double page_height_factor)
  {
      if (m_editor->cursor().line() > 0 || m_editor->is_wrapping_enabled()) {
          int pixels = (int)(m_editor->visible_content_rect().height() * page_height_factor);
  
          TextPosition new_cursor;
          if (m_editor->is_wrapping_enabled()) {
              auto position_above = m_editor->cursor_content_rect().location().translated(0, -pixels);
              new_cursor = m_editor->text_position_at_content_position(position_above);
          } else {
              size_t page_step = (size_t)pixels / (size_t)m_editor->line_height();
              size_t new_line = m_editor->cursor().line() < page_step ? 0 : m_editor->cursor().line() - page_step;
              size_t new_column = min(m_editor->cursor().column(), m_editor->line(new_line).length());
              new_cursor = { new_line, new_column };
          }
          m_editor->toggle_selection_if_needed_for_event(event.shift());
          m_editor->set_cursor(new_cursor);
      }
  };
  
  void EditingEngine::move_down(const KeyEvent& event, double page_height_factor)
  {
      if (m_editor->cursor().line() < (m_editor->line_count() - 1) || m_editor->is_wrapping_enabled()) {
          int pixels = (int)(m_editor->visible_content_rect().height() * page_height_factor);
          TextPosition new_cursor;
          if (m_editor->is_wrapping_enabled()) {
              auto position_below = m_editor->cursor_content_rect().location().translated(0, pixels);
              new_cursor = m_editor->text_position_at_content_position(position_below);
          } else {
              size_t new_line = min(m_editor->line_count() - 1, m_editor->cursor().line() + pixels / m_editor->line_height());
              size_t new_column = min(m_editor->cursor().column(), m_editor->lines()[new_line].length());
              new_cursor = { new_line, new_column };
          }
          m_editor->toggle_selection_if_needed_for_event(event.shift());
          m_editor->set_cursor(new_cursor);
      };
  }
  
  void EditingEngine::move_page_up(const KeyEvent& event)
  {
      move_up(event, 1);
  };
  
  void EditingEngine::move_page_down(const KeyEvent& event)
  {
      move_down(event, 1);
  };
  
  void EditingEngine::move_to_first_line()
  {
      m_editor->set_cursor(0, 0);
  };
  
  void EditingEngine::move_to_last_line()
  {
      m_editor->set_cursor(m_editor->line_count() - 1, m_editor->lines()[m_editor->line_count() - 1].length());
  };
  
  void EditingEngine::get_selection_line_boundaries(size_t& first_line, size_t& last_line)
  {
      auto selection = m_editor->normalized_selection();
      if (!selection.is_valid()) {
          first_line = m_editor->cursor().line();
          last_line = m_editor->cursor().line();
          return;
      }
      first_line = selection.start().line();
      last_line = selection.end().line();
      if (first_line != last_line && selection.end().column() == 0)
          last_line -= 1;
  }
  
  TextPosition EditingEngine::find_beginning_of_next_word()
  {
      /* The rules that have been coded in:
       * Jump to the next punct or alnum after any whitespace
       * Jump to the next non-consecutive punct regardless of whitespace
       * Jump to the next alnum if started on punct regardless of whitespace
       * If the end of the input is reached, jump there
       */
  
      auto vim_isalnum = [](int c) {
          return c == '_' || isalnum(c);
      };
  
      auto vim_ispunct = [](int c) {
          return c != '_' && ispunct(c);
      };
  
      bool started_on_punct = vim_ispunct(m_editor->current_line().to_utf8().characters()[m_editor->cursor().column()]);
      bool has_seen_whitespace = false;
      bool is_first_line = true;
      auto& lines = m_editor->lines();
      auto cursor = m_editor->cursor();
      for (size_t line_index = cursor.line(); line_index < lines.size(); line_index++) {
          auto& line = lines.at(line_index);
  
          if (line.is_empty() && !is_first_line) {
              return { line_index, 0 };
          } else if (line.is_empty()) {
              has_seen_whitespace = true;
          }
  
          is_first_line = false;
  
          for (size_t column_index = 0; column_index < lines.at(line_index).length(); column_index++) {
              if (line_index == cursor.line() && column_index < cursor.column())
                  continue;
              const u32* line_chars = line.view().code_points();
              const u32 current_char = line_chars[column_index];
  
              if (started_on_punct && vim_isalnum(current_char)) {
                  return { line_index, column_index };
              }
  
              if (vim_ispunct(current_char) && !started_on_punct) {
                  return { line_index, column_index };
              }
  
              if (isspace(current_char))
                  has_seen_whitespace = true;
  
              if (has_seen_whitespace && (vim_isalnum(current_char) || vim_ispunct(current_char))) {
                  return { line_index, column_index };
              }
  
              if (line_index == lines.size() - 1 && column_index == line.length() - 1) {
                  return { line_index, column_index };
              }
  
              // Implicit newline
              if (column_index == line.length() - 1)
                  has_seen_whitespace = true;
          }
      }
      VERIFY_NOT_REACHED();
  }
  
  void EditingEngine::move_to_beginning_of_next_word()
  {
      m_editor->set_cursor(find_beginning_of_next_word());
  }
  
  TextPosition EditingEngine::find_end_of_next_word()
  {
      /* The rules that have been coded in:
       * If the current_char is alnum and the next is whitespace or punct
       * If the current_char is punct and the next is whitespace or alnum
       * If the end of the input is reached, jump there
       */
  
      auto vim_isalnum = [](int c) {
          return c == '_' || isalnum(c);
      };
  
      auto vim_ispunct = [](int c) {
          return c != '_' && ispunct(c);
      };
  
      bool is_first_line = true;
      bool is_first_iteration = true;
      auto& lines = m_editor->lines();
      auto cursor = m_editor->cursor();
  
      if ((lines.at(cursor.line()).length() - cursor.column()) <= 1)
          return { cursor.line(), cursor.column() };
  
      for (size_t line_index = cursor.line(); line_index < lines.size(); line_index++) {
          auto& line = lines.at(line_index);
  
          if (line.is_empty() && !is_first_line) {
              return { line_index, 0 };
          }
  
          is_first_line = false;
  
          for (size_t column_index = 0; column_index < lines.at(line_index).length(); column_index++) {
              if (line_index == cursor.line() && column_index < cursor.column())
                  continue;
  
              const u32* line_chars = line.view().code_points();
              const u32 current_char = line_chars[column_index];
  
              if (column_index == lines.at(line_index).length() - 1 && !is_first_iteration && (vim_isalnum(current_char) || vim_ispunct(current_char)))
                  return { line_index, column_index };
              else if (column_index == lines.at(line_index).length() - 1) {
                  is_first_iteration = false;
                  continue;
              }
  
              const u32 next_char = line_chars[column_index + 1];
  
              if (!is_first_iteration && vim_isalnum(current_char) && (isspace(next_char) || vim_ispunct(next_char)))
                  return { line_index, column_index };
  
              if (!is_first_iteration && vim_ispunct(current_char) && (isspace(next_char) || vim_isalnum(next_char)))
                  return { line_index, column_index };
  
              if (line_index == lines.size() - 1 && column_index == line.length() - 1) {
                  return { line_index, column_index };
              }
  
              is_first_iteration = false;
          }
      }
      VERIFY_NOT_REACHED();
  }
  
  void EditingEngine::move_to_end_of_next_word()
  {
  
      m_editor->set_cursor(find_end_of_next_word());
  }
  
  TextPosition EditingEngine::find_end_of_previous_word()
  {
      auto vim_isalnum = [](int c) {
          return c == '_' || isalnum(c);
      };
  
      auto vim_ispunct = [](int c) {
          return c != '_' && ispunct(c);
      };
  
      bool started_on_punct = vim_ispunct(m_editor->current_line().to_utf8().characters()[m_editor->cursor().column()]);
      bool is_first_line = true;
      bool has_seen_whitespace = false;
      auto& lines = m_editor->lines();
      auto cursor = m_editor->cursor();
      for (size_t line_index = cursor.line(); (int)line_index >= 0; line_index--) {
          auto& line = lines.at(line_index);
  
          if (line.is_empty() && !is_first_line) {
              return { line_index, 0 };
          } else if (line.is_empty()) {
              has_seen_whitespace = true;
          }
  
          is_first_line = false;
  
          size_t line_length = lines.at(line_index).length();
          for (size_t column_index = line_length - 1; (int)column_index >= 0; column_index--) {
              if (line_index == cursor.line() && column_index > cursor.column())
                  continue;
  
              const u32* line_chars = line.view().code_points();
              const u32 current_char = line_chars[column_index];
  
              if (started_on_punct && vim_isalnum(current_char)) {
                  return { line_index, column_index };
              }
  
              if (vim_ispunct(current_char) && !started_on_punct) {
                  return { line_index, column_index };
              }
  
              if (isspace(current_char)) {
                  has_seen_whitespace = true;
              }
  
              if (has_seen_whitespace && (vim_isalnum(current_char) || vim_ispunct(current_char))) {
                  return { line_index, column_index };
              }
  
              if (line_index == 0 && column_index == 0) {
                  return { line_index, column_index };
              }
  
              // Implicit newline when wrapping back up to the end of the previous line.
              if (column_index == 0)
                  has_seen_whitespace = true;
          }
      }
      VERIFY_NOT_REACHED();
  }
  
  void EditingEngine::move_to_end_of_previous_word()
  {
      m_editor->set_cursor(find_end_of_previous_word());
  }
  
  TextPosition EditingEngine::find_beginning_of_previous_word()
  {
      auto vim_isalnum = [](int c) {
          return c == '_' || isalnum(c);
      };
  
      auto vim_ispunct = [](int c) {
          return c != '_' && ispunct(c);
      };
  
      bool is_first_iterated_line = true;
      bool is_first_iteration = true;
      auto& lines = m_editor->lines();
      auto cursor = m_editor->cursor();
  
      if ((lines.at(cursor.line()).length() - cursor.column()) <= 1)
          return { cursor.line(), cursor.column() };
  
      for (size_t line_index = cursor.line(); (int)line_index >= 0; line_index--) {
          auto& line = lines.at(line_index);
  
          if (line.is_empty() && !is_first_iterated_line) {
              return { line_index, 0 };
          }
  
          is_first_iterated_line = false;
  
          size_t line_length = lines.at(line_index).length();
          for (size_t column_index = line_length; (int)column_index >= 0; column_index--) {
              if (line_index == cursor.line() && column_index > cursor.column())
                  continue;
  
              if (column_index == line_length) {
                  is_first_iteration = false;
                  continue;
              }
  
              const u32* line_chars = line.view().code_points();
              const u32 current_char = line_chars[column_index];
  
              if (column_index == 0 && !is_first_iteration && (vim_isalnum(current_char) || vim_ispunct(current_char))) {
                  return { line_index, column_index };
              } else if (line_index == 0 && column_index == 0) {
                  return { line_index, column_index };
              } else if (column_index == 0 && is_first_iteration) {
                  is_first_iteration = false;
                  continue;
              }
  
              const u32 next_char = line_chars[column_index - 1];
  
              if (!is_first_iteration && vim_isalnum(current_char) && (isspace(next_char) || vim_ispunct(next_char)))
                  return { line_index, column_index };
  
              if (!is_first_iteration && vim_ispunct(current_char) && (isspace(next_char) || vim_isalnum(next_char)))
                  return { line_index, column_index };
  
              is_first_iteration = false;
          }
      }
      VERIFY_NOT_REACHED();
  }
  
  void EditingEngine::move_to_beginning_of_previous_word()
  {
      m_editor->set_cursor(find_beginning_of_previous_word());
  }
  
  void EditingEngine::move_selected_lines_up()
  {
      if (!m_editor->is_editable())
          return;
      size_t first_line;
      size_t last_line;
      get_selection_line_boundaries(first_line, last_line);
  
      if (first_line == 0)
          return;
  
      auto& lines = m_editor->document().lines();
      lines.insert((int)last_line, lines.take((int)first_line - 1));
      m_editor->set_cursor({ first_line - 1, 0 });
  
      if (m_editor->has_selection()) {
          m_editor->selection()->set_start({ first_line - 1, 0 });
          m_editor->selection()->set_end({ last_line - 1, m_editor->line(last_line - 1).length() });
      }
  
      m_editor->did_change();
      m_editor->update();
  }
  
  void EditingEngine::move_selected_lines_down()
  {
      if (!m_editor->is_editable())
          return;
      size_t first_line;
      size_t last_line;
      get_selection_line_boundaries(first_line, last_line);
  
      auto& lines = m_editor->document().lines();
      VERIFY(lines.size() != 0);
      if (last_line >= lines.size() - 1)
          return;
  
      lines.insert((int)first_line, lines.take((int)last_line + 1));
      m_editor->set_cursor({ first_line + 1, 0 });
  
      if (m_editor->has_selection()) {
          m_editor->selection()->set_start({ first_line + 1, 0 });
          m_editor->selection()->set_end({ last_line + 1, m_editor->line(last_line + 1).length() });
      }
  
      m_editor->did_change();
      m_editor->update();
  }
  
  void EditingEngine::delete_char()
  {
      if (!m_editor->is_editable())
          return;
      m_editor->do_delete();
  };
  
  void EditingEngine::delete_line()
  {
      if (!m_editor->is_editable())
          return;
      m_editor->delete_current_line();
  };
  
  }
  