content: /*
   * Copyright (C) 2006 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package android.text;
  
  import android.annotation.TestApi;
  import android.annotation.UnsupportedAppUsage;
  
  import java.text.BreakIterator;
  
  
  /**
   * Utility class for manipulating cursors and selections in CharSequences.
   * A cursor is a selection where the start and end are at the same offset.
   */
  public class Selection {
      private Selection() { /* cannot be instantiated */ }
  
      /*
       * Retrieving the selection
       */
  
      /**
       * Return the offset of the selection anchor or cursor, or -1 if
       * there is no selection or cursor.
       */
      public static final int getSelectionStart(CharSequence text) {
          if (text instanceof Spanned) {
              return ((Spanned) text).getSpanStart(SELECTION_START);
          }
          return -1;
      }
  
      /**
       * Return the offset of the selection edge or cursor, or -1 if
       * there is no selection or cursor.
       */
      public static final int getSelectionEnd(CharSequence text) {
          if (text instanceof Spanned) {
              return ((Spanned) text).getSpanStart(SELECTION_END);
          }
          return -1;
      }
  
      private static int getSelectionMemory(CharSequence text) {
          if (text instanceof Spanned) {
              return ((Spanned) text).getSpanStart(SELECTION_MEMORY);
          }
          return -1;
      }
  
      /*
       * Setting the selection
       */
  
      // private static int pin(int value, int min, int max) {
      //     return value < min ? 0 : (value > max ? max : value);
      // }
  
      /**
       * Set the selection anchor to <code>start</code> and the selection edge
       * to <code>stop</code>.
       */
      public static void setSelection(Spannable text, int start, int stop) {
          setSelection(text, start, stop, -1);
      }
  
      /**
       * Set the selection anchor to <code>start</code>, the selection edge
       * to <code>stop</code> and the memory horizontal to <code>memory</code>.
       */
      private static void setSelection(Spannable text, int start, int stop, int memory) {
          // int len = text.length();
          // start = pin(start, 0, len);  XXX remove unless we really need it
          // stop = pin(stop, 0, len);
  
          int ostart = getSelectionStart(text);
          int oend = getSelectionEnd(text);
  
          if (ostart != start || oend != stop) {
              text.setSpan(SELECTION_START, start, start,
                      Spanned.SPAN_POINT_POINT | Spanned.SPAN_INTERMEDIATE);
              text.setSpan(SELECTION_END, stop, stop, Spanned.SPAN_POINT_POINT);
              updateMemory(text, memory);
          }
      }
  
      /**
       * Update the memory position for text. This is used to ensure vertical navigation of lines
       * with different lengths behaves as expected and remembers the longest horizontal position
       * seen during a vertical traversal.
       */
      private static void updateMemory(Spannable text, int memory) {
          if (memory > -1) {
              int currentMemory = getSelectionMemory(text);
              if (memory != currentMemory) {
                  text.setSpan(SELECTION_MEMORY, memory, memory, Spanned.SPAN_POINT_POINT);
                  if (currentMemory == -1) {
                      // This is the first value, create a watcher.
                      final TextWatcher watcher = new MemoryTextWatcher();
                      text.setSpan(watcher, 0, text.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
                  }
              }
          } else {
              removeMemory(text);
          }
      }
  
      private static void removeMemory(Spannable text) {
          text.removeSpan(SELECTION_MEMORY);
          MemoryTextWatcher[] watchers = text.getSpans(0, text.length(), MemoryTextWatcher.class);
          for (MemoryTextWatcher watcher : watchers) {
              text.removeSpan(watcher);
          }
      }
  
      /**
       * @hide
       */
      @TestApi
      public static final class MemoryTextWatcher implements TextWatcher {
  
          @Override
          public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
  
          @Override
          public void onTextChanged(CharSequence s, int start, int before, int count) {}
  
          @Override
          public void afterTextChanged(Editable s) {
              s.removeSpan(SELECTION_MEMORY);
              s.removeSpan(this);
          }
      }
  
      /**
       * Move the cursor to offset <code>index</code>.
       */
      public static final void setSelection(Spannable text, int index) {
          setSelection(text, index, index);
      }
  
      /**
       * Select the entire text.
       */
      public static final void selectAll(Spannable text) {
          setSelection(text, 0, text.length());
      }
  
      /**
       * Move the selection edge to offset <code>index</code>.
       */
      public static final void extendSelection(Spannable text, int index) {
          extendSelection(text, index, -1);
      }
  
      /**
       * Move the selection edge to offset <code>index</code> and update the memory horizontal.
       */
      private static void extendSelection(Spannable text, int index, int memory) {
          if (text.getSpanStart(SELECTION_END) != index) {
              text.setSpan(SELECTION_END, index, index, Spanned.SPAN_POINT_POINT);
          }
          updateMemory(text, memory);
      }
  
      /**
       * Remove the selection or cursor, if any, from the text.
       */
      public static final void removeSelection(Spannable text) {
          text.removeSpan(SELECTION_START, Spanned.SPAN_INTERMEDIATE);
          text.removeSpan(SELECTION_END);
          removeMemory(text);
      }
  
      /*
       * Moving the selection within the layout
       */
  
      /**
       * Move the cursor to the buffer offset physically above the current
       * offset, to the beginning if it is on the top line but not at the
       * start, or return false if the cursor is already on the top line.
       */
      public static boolean moveUp(Spannable text, Layout layout) {
          int start = getSelectionStart(text);
          int end = getSelectionEnd(text);
  
          if (start != end) {
              int min = Math.min(start, end);
              int max = Math.max(start, end);
  
              setSelection(text, min);
  
              if (min == 0 && max == text.length()) {
                  return false;
              }
  
              return true;
          } else {
              int line = layout.getLineForOffset(end);
  
              if (line > 0) {
                  setSelectionAndMemory(
                          text, layout, line, end, -1 /* direction */, false /* extend */);
                  return true;
              } else if (end != 0) {
                  setSelection(text, 0);
                  return true;
              }
          }
  
          return false;
      }
  
      /**
       * Calculate the movement and memory positions needed, and set or extend the selection.
       */
      private static void setSelectionAndMemory(Spannable text, Layout layout, int line, int end,
              int direction, boolean extend) {
          int move;
          int newMemory;
  
          if (layout.getParagraphDirection(line)
                  == layout.getParagraphDirection(line + direction)) {
              int memory = getSelectionMemory(text);
              if (memory > -1) {
                  // We have a memory position
                  float h = layout.getPrimaryHorizontal(memory);
                  move = layout.getOffsetForHorizontal(line + direction, h);
                  newMemory = memory;
              } else {
                  // Create a new memory position
                  float h = layout.getPrimaryHorizontal(end);
                  move = layout.getOffsetForHorizontal(line + direction, h);
                  newMemory = end;
              }
          } else {
              move = layout.getLineStart(line + direction);
              newMemory = -1;
          }
  
          if (extend) {
              extendSelection(text, move, newMemory);
          } else {
              setSelection(text, move, move, newMemory);
          }
      }
  
      /**
       * Move the cursor to the buffer offset physically below the current
       * offset, to the end of the buffer if it is on the bottom line but
       * not at the end, or return false if the cursor is already at the
       * end of the buffer.
       */
      public static boolean moveDown(Spannable text, Layout layout) {
          int start = getSelectionStart(text);
          int end = getSelectionEnd(text);
  
          if (start != end) {
              int min = Math.min(start, end);
              int max = Math.max(start, end);
  
              setSelection(text, max);
  
              if (min == 0 && max == text.length()) {
                  return false;
              }
  
              return true;
          } else {
              int line = layout.getLineForOffset(end);
  
              if (line < layout.getLineCount() - 1) {
                  setSelectionAndMemory(
                          text, layout, line, end, 1 /* direction */, false /* extend */);
                  return true;
              } else if (end != text.length()) {
                  setSelection(text, text.length());
                  return true;
              }
          }
  
          return false;
      }
  
      /**
       * Move the cursor to the buffer offset physically to the left of
       * the current offset, or return false if the cursor is already
       * at the left edge of the line and there is not another line to move it to.
       */
      public static boolean moveLeft(Spannable text, Layout layout) {
          int start = getSelectionStart(text);
          int end = getSelectionEnd(text);
  
          if (start != end) {
              setSelection(text, chooseHorizontal(layout, -1, start, end));
              return true;
          } else {
              int to = layout.getOffsetToLeftOf(end);
  
              if (to != end) {
                  setSelection(text, to);
                  return true;
              }
          }
  
          return false;
      }
  
      /**
       * Move the cursor to the buffer offset physically to the right of
       * the current offset, or return false if the cursor is already at
       * at the right edge of the line and there is not another line
       * to move it to.
       */
      public static boolean moveRight(Spannable text, Layout layout) {
          int start = getSelectionStart(text);
          int end = getSelectionEnd(text);
  
          if (start != end) {
              setSelection(text, chooseHorizontal(layout, 1, start, end));
              return true;
          } else {
              int to = layout.getOffsetToRightOf(end);
  
              if (to != end) {
                  setSelection(text, to);
                  return true;
              }
          }
  
          return false;
      }
  
      /**
       * Move the selection end to the buffer offset physically above
       * the current selection end.
       */
      public static boolean extendUp(Spannable text, Layout layout) {
          int end = getSelectionEnd(text);
          int line = layout.getLineForOffset(end);
  
          if (line > 0) {
              setSelectionAndMemory(text, layout, line, end, -1 /* direction */, true /* extend */);
              return true;
          } else if (end != 0) {
              extendSelection(text, 0);
              return true;
          }
  
          return true;
      }
  
      /**
       * Move the selection end to the buffer offset physically below
       * the current selection end.
       */
      public static boolean extendDown(Spannable text, Layout layout) {
          int end = getSelectionEnd(text);
          int line = layout.getLineForOffset(end);
  
          if (line < layout.getLineCount() - 1) {
              setSelectionAndMemory(text, layout, line, end, 1 /* direction */, true /* extend */);
              return true;
          } else if (end != text.length()) {
              extendSelection(text, text.length(), -1);
              return true;
          }
  
          return true;
      }
  
      /**
       * Move the selection end to the buffer offset physically to the left of
       * the current selection end.
       */
      public static boolean extendLeft(Spannable text, Layout layout) {
          int end = getSelectionEnd(text);
          int to = layout.getOffsetToLeftOf(end);
  
          if (to != end) {
              extendSelection(text, to);
              return true;
          }
  
          return true;
      }
  
      /**
       * Move the selection end to the buffer offset physically to the right of
       * the current selection end.
       */
      public static boolean extendRight(Spannable text, Layout layout) {
          int end = getSelectionEnd(text);
          int to = layout.getOffsetToRightOf(end);
  
          if (to != end) {
              extendSelection(text, to);
              return true;
          }
  
          return true;
      }
  
      public static boolean extendToLeftEdge(Spannable text, Layout layout) {
          int where = findEdge(text, layout, -1);
          extendSelection(text, where);
          return true;
      }
  
      public static boolean extendToRightEdge(Spannable text, Layout layout) {
          int where = findEdge(text, layout, 1);
          extendSelection(text, where);
          return true;
      }
  
      public static boolean moveToLeftEdge(Spannable text, Layout layout) {
          int where = findEdge(text, layout, -1);
          setSelection(text, where);
          return true;
      }
  
      public static boolean moveToRightEdge(Spannable text, Layout layout) {
          int where = findEdge(text, layout, 1);
          setSelection(text, where);
          return true;
      }
  
      /** {@hide} */
      public static interface PositionIterator {
          public static final int DONE = BreakIterator.DONE;
  
          public int preceding(int position);
          public int following(int position);
      }
  
      /** {@hide} */
      @UnsupportedAppUsage
      public static boolean moveToPreceding(
              Spannable text, PositionIterator iter, boolean extendSelection) {
          final int offset = iter.preceding(getSelectionEnd(text));
          if (offset != PositionIterator.DONE) {
              if (extendSelection) {
                  extendSelection(text, offset);
              } else {
                  setSelection(text, offset);
              }
          }
          return true;
      }
  
      /** {@hide} */
      @UnsupportedAppUsage
      public static boolean moveToFollowing(
              Spannable text, PositionIterator iter, boolean extendSelection) {
          final int offset = iter.following(getSelectionEnd(text));
          if (offset != PositionIterator.DONE) {
              if (extendSelection) {
                  extendSelection(text, offset);
              } else {
                  setSelection(text, offset);
              }
          }
          return true;
      }
  
      private static int findEdge(Spannable text, Layout layout, int dir) {
          int pt = getSelectionEnd(text);
          int line = layout.getLineForOffset(pt);
          int pdir = layout.getParagraphDirection(line);
  
          if (dir * pdir < 0) {
              return layout.getLineStart(line);
          } else {
              int end = layout.getLineEnd(line);
  
              if (line == layout.getLineCount() - 1)
                  return end;
              else
                  return end - 1;
          }
      }
  
      private static int chooseHorizontal(Layout layout, int direction,
                                          int off1, int off2) {
          int line1 = layout.getLineForOffset(off1);
          int line2 = layout.getLineForOffset(off2);
  
          if (line1 == line2) {
              // same line, so it goes by pure physical direction
  
              float h1 = layout.getPrimaryHorizontal(off1);
              float h2 = layout.getPrimaryHorizontal(off2);
  
              if (direction < 0) {
                  // to left
  
                  if (h1 < h2)
                      return off1;
                  else
                      return off2;
              } else {
                  // to right
  
                  if (h1 > h2)
                      return off1;
                  else
                      return off2;
              }
          } else {
              // different line, so which line is "left" and which is "right"
              // depends upon the directionality of the text
  
              // This only checks at one end, but it's not clear what the
              // right thing to do is if the ends don't agree.  Even if it
              // is wrong it should still not be too bad.
              int line = layout.getLineForOffset(off1);
              int textdir = layout.getParagraphDirection(line);
  
              if (textdir == direction)
                  return Math.max(off1, off2);
              else
                  return Math.min(off1, off2);
          }
      }
  
      private static final class START implements NoCopySpan { }
      private static final class END implements NoCopySpan { }
      private static final class MEMORY implements NoCopySpan { }
      private static final Object SELECTION_MEMORY = new MEMORY();
  
      /*
       * Public constants
       */
  
      public static final Object SELECTION_START = new START();
      public static final Object SELECTION_END = new END();
  }
  