/* CompositeView.java -- An abstract view that manages child views
   Copyright (C) 2005, 2006  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
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package javax.swing.text;

import java.awt.Insets;
import java.awt.Rectangle;
import java.awt.Shape;

import javax.swing.SwingConstants;

/**
 * An abstract base implementation of {@link View} that manages child
 * <code>View</code>s.
 *
 * @author Roman Kennke (roman@kennke.org)
 */
public abstract class CompositeView
  extends View
{

  /**
   * The child views of this <code>CompositeView</code>.
   */
  View[] children;

  /**
   * The allocation of this <code>View</code> minus its insets. This is
   * initialized in {@link #getInsideAllocation} and reused and modified in
   * {@link #childAllocation(int, Rectangle)}.
   */
  Rectangle insideAllocation;

  /**
   * The insets of this <code>CompositeView</code>. This is initialized
   * in {@link #setInsets}.
   */
  Insets insets;

  /**
   * Creates a new <code>CompositeView</code> for the given
   * <code>Element</code>.
   *
   * @param element the element that is rendered by this CompositeView
   */
  public CompositeView(Element element)
  {
    super(element);
    children = new View[0];
    insets = new Insets(0, 0, 0, 0);
  }

  /**
   * Loads the child views of this <code>CompositeView</code>. This method
   * is called from {@link #setParent} to initialize the child views of
   * this composite view.
   *
   * @param f the view factory to use for creating new child views
   *
   * @see #setParent
   */
  protected void loadChildren(ViewFactory f)
  {
    Element el = getElement();
    int count = el.getElementCount();
    View[] newChildren = new View[count];
    for (int i = 0; i < count; ++i)
      {
        Element child = el.getElement(i);
        View view = f.create(child);
        newChildren[i] = view;
      }
    replace(0, getViewCount(), newChildren);
  }

  /**
   * Sets the parent of this <code>View</code>.
   * In addition to setting the parent, this calls {@link #loadChildren}, if
   * this <code>View</code> does not already have its children initialized.
   *
   * @param parent the parent to set
   */
  public void setParent(View parent)
  {
    super.setParent(parent);
    if (parent != null && ((children == null) || children.length == 0))
      loadChildren(getViewFactory());
  }

  /**
   * Returns the number of child views.
   *
   * @return the number of child views
   */
  public int getViewCount()
  {
    return children.length;
  }

  /**
   * Returns the child view at index <code>n</code>.
   *
   * @param n the index of the requested child view
   *
   * @return the child view at index <code>n</code>
   */
  public View getView(int n)
  {
    return children[n];
  }

  /**
   * Replaces child views by some other child views. If there are no views to
   * remove (<code>length == 0</code>), the result is a simple insert, if
   * there are no children to add (<code>view == null</code>) the result
   * is a simple removal.
   *
   * @param offset the start offset from where to remove children
   * @param length the number of children to remove
   * @param views the views that replace the removed children
   */
  public void replace(int offset, int length, View[] views)
  {
    // Check for null views to add.
    for (int i = 0; i < views.length; ++i)
      if (views[i] == null)
        throw new NullPointerException("Added views must not be null");

    int endOffset = offset + length;

    // First we set the parent of the removed children to null.
    for (int i = offset; i < endOffset; ++i)
      children[i].setParent(null);

    View[] newChildren = new View[children.length - length + views.length];
    System.arraycopy(children, 0, newChildren, 0, offset);
    System.arraycopy(views, 0, newChildren, offset, views.length);
    System.arraycopy(children, offset + length, newChildren,
                     offset + views.length,
                     children.length - (offset + length));
    children = newChildren;

    // Finally we set the parent of the added children to this.
    for (int i = 0; i < views.length; ++i)
      views[i].setParent(this);
  }

  /**
   * Returns the allocation for the specified child <code>View</code>.
   *
   * @param index the index of the child view
   * @param a the allocation for this view
   *
   * @return the allocation for the specified child <code>View</code>
   */
  public Shape getChildAllocation(int index, Shape a)
  {
    Rectangle r = getInsideAllocation(a);
    childAllocation(index, r);
    return r;
  }

  /**
   * Maps a position in the document into the coordinate space of the View.
   * The output rectangle usually reflects the font height but has a width
   * of zero.
   *
   * @param pos the position of the character in the model
   * @param a the area that is occupied by the view
   * @param bias either {@link Position.Bias#Forward} or
   *        {@link Position.Bias#Backward} depending on the preferred
   *        direction bias. If <code>null</code> this defaults to
   *        <code>Position.Bias.Forward</code>
   *
   * @return a rectangle that gives the location of the document position
   *         inside the view coordinate space
   *
   * @throws BadLocationException if <code>pos</code> is invalid
   * @throws IllegalArgumentException if b is not one of the above listed
   *         valid values
   */
  public Shape modelToView(int pos, Shape a, Position.Bias bias)
    throws BadLocationException
  {
    boolean backward = bias == Position.Bias.Backward;
    int testpos = backward ? Math.max(0, pos - 1) : pos;

    Shape ret = null;
    if (! backward || testpos >= getStartOffset())
      {
        int childIndex = getViewIndexAtPosition(testpos);
        if (childIndex != -1 && childIndex < getViewCount())
          {
            View child = getView(childIndex);
            if (child != null && testpos >= child.getStartOffset()
                && testpos < child.getEndOffset())
              {
                Shape childAlloc = getChildAllocation(childIndex, a);
                if (childAlloc != null)
                  {
                    ret = child.modelToView(pos, childAlloc, bias);
                    // Handle corner case.
                    if (ret == null && child.getEndOffset() == pos)
                      {
                        childIndex++;
                        if (childIndex < getViewCount())
                          {
                            child = getView(childIndex);
                            childAlloc = getChildAllocation(childIndex, a);
                            ret = child.modelToView(pos, childAlloc, bias);
                          }
                      }
                  }
              }
          }
        else
          {
            throw new BadLocationException("Position " + pos
                                           + " is not represented by view.", pos);
          }    
      }
    return ret;
  }

  /**
   * A helper method for {@link #modelToView(int, Position.Bias, int,
   * Position.Bias, Shape)}. This creates a default location when there is
   * no child view that can take responsibility for mapping the position to
   * view coordinates. Depending on the specified bias this will be the
   * left or right edge of this view's allocation.
   *
   * @param a the allocation for this view
   * @param bias the bias
   *
   * @return a default location
   */
  private Shape createDefaultLocation(Shape a, Position.Bias bias)
  {
    Rectangle alloc = a.getBounds();
    Rectangle location = new Rectangle(alloc.x, alloc.y, 1, alloc.height);
    if (bias == Position.Bias.Forward)
      location.x = alloc.x + alloc.width;
    return location;
  }

  /**
   * Maps a region in the document into the coordinate space of the View.
   *
   * @param p1 the beginning position inside the document
   * @param b1 the direction bias for the beginning position
   * @param p2 the end position inside the document
   * @param b2 the direction bias for the end position
   * @param a the area that is occupied by the view
   *
   * @return a rectangle that gives the span of the document region
   *         inside the view coordinate space
   *
   * @throws BadLocationException if <code>p1</code> or <code>p2</code> are
   *         invalid
   * @throws IllegalArgumentException if b1 or b2 is not one of the above
   *         listed valid values
   */
  public Shape modelToView(int p1, Position.Bias b1,
			   int p2, Position.Bias b2, Shape a)
    throws BadLocationException
  {
    // TODO: This is most likely not 100% ok, figure out what else is to
    // do here.
    return super.modelToView(p1, b1, p2, b2, a);
  }

  /**
   * Maps coordinates from the <code>View</code>'s space into a position
   * in the document model.
   *
   * @param x the x coordinate in the view space, x >= 0
   * @param y the y coordinate in the view space, y >= 0
   * @param a the allocation of this <code>View</code>
   * @param b the bias to use
   *
   * @return the position in the document that corresponds to the screen
   *         coordinates <code>x, y</code> >= 0
   */
  public int viewToModel(float x, float y, Shape a, Position.Bias[] b)
  {
    if (x >= 0 && y >= 0)
      {
        Rectangle r = getInsideAllocation(a);
        View view = getViewAtPoint((int) x, (int) y, r);
        return view.viewToModel(x, y, r, b);
      }
    return 0;
  }

  /**
   * Returns the next model location that is visible in eiter north / south
   * direction or east / west direction. This is used to determine the placement
   * of the caret when navigating around the document with the arrow keys. This
   * is a convenience method for {@link #getNextNorthSouthVisualPositionFrom}
   * and {@link #getNextEastWestVisualPositionFrom}.
   * 
   * @param pos
   *          the model position to start search from
   * @param b
   *          the bias for <code>pos</code>
   * @param a
   *          the allocated region for this view
   * @param direction
   *          the direction from the current position, can be one of the
   *          following:
   *          <ul>
   *          <li>{@link SwingConstants#WEST}</li>
   *          <li>{@link SwingConstants#EAST}</li>
   *          <li>{@link SwingConstants#NORTH}</li>
   *          <li>{@link SwingConstants#SOUTH}</li>
   *          </ul>
   * @param biasRet
   *          the bias of the return value gets stored here
   * @return the position inside the model that represents the next visual
   *         location
   * @throws BadLocationException
   *           if <code>pos</code> is not a valid location inside the document
   *           model
   * @throws IllegalArgumentException
   *           if <code>direction</code> is invalid
   */
  public int getNextVisualPositionFrom(int pos, Position.Bias b, Shape a,
                                       int direction, Position.Bias[] biasRet)
    throws BadLocationException
  {
    int retVal = -1;
    switch (direction)
      {
      case SwingConstants.WEST:
      case SwingConstants.EAST:
        retVal = getNextEastWestVisualPositionFrom(pos, b, a, direction,
                                                   biasRet);
        break;
      case SwingConstants.NORTH:
      case SwingConstants.SOUTH:
        retVal = getNextNorthSouthVisualPositionFrom(pos, b, a, direction,
                                                     biasRet);
        break;
      default:
        throw new IllegalArgumentException("Illegal value for direction.");
      }
    return retVal;
  }

  /**
   * Returns the index of the child view that represents the specified
   * model location.
   *
   * @param pos the model location for which to determine the child view index
   * @param b the bias to be applied to <code>pos</code>
   *
   * @return the index of the child view that represents the specified
   *         model location
   */
  public int getViewIndex(int pos, Position.Bias b)
  {
    if (b == Position.Bias.Backward && pos != 0)
      pos -= 1;
    int i = -1;
    if (pos >= getStartOffset() && pos < getEndOffset())
      i = getViewIndexAtPosition(pos);
    return i;
  }

  /**
   * Returns <code>true</code> if the specified point lies before the
   * given <code>Rectangle</code>, <code>false</code> otherwise.
   *
   * &quot;Before&quot; is typically defined as being to the left or above.
   *
   * @param x the X coordinate of the point
   * @param y the Y coordinate of the point
   * @param r the rectangle to test the point against
   *
   * @return <code>true</code> if the specified point lies before the
   *         given <code>Rectangle</code>, <code>false</code> otherwise
   */
  protected abstract boolean isBefore(int x, int y, Rectangle r);

  /**
   * Returns <code>true</code> if the specified point lies after the
   * given <code>Rectangle</code>, <code>false</code> otherwise.
   *
   * &quot;After&quot; is typically defined as being to the right or below.
   *
   * @param x the X coordinate of the point
   * @param y the Y coordinate of the point
   * @param r the rectangle to test the point against
   *
   * @return <code>true</code> if the specified point lies after the
   *         given <code>Rectangle</code>, <code>false</code> otherwise
   */
  protected abstract boolean isAfter(int x, int y, Rectangle r);

  /**
   * Returns the child <code>View</code> at the specified location.
   *
   * @param x the X coordinate
   * @param y the Y coordinate
   * @param r the inner allocation of this <code>BoxView</code> on entry,
   *        the allocation of the found child on exit
   *
   * @return the child <code>View</code> at the specified location
   */
  protected abstract View getViewAtPoint(int x, int y, Rectangle r);

  /**
   * Computes the allocation for a child <code>View</code>. The parameter
   * <code>a</code> stores the allocation of this <code>CompositeView</code>
   * and is then adjusted to hold the allocation of the child view.
   *
   * @param index the index of the child <code>View</code>
   * @param a the allocation of this <code>CompositeView</code> before the
   *        call, the allocation of the child on exit
   */
  protected abstract void childAllocation(int index, Rectangle a);

  /**
   * Returns the child <code>View</code> that contains the given model
   * position. The given <code>Rectangle</code> gives the parent's allocation
   * and is changed to the child's allocation on exit.
   *
   * @param pos the model position to query the child <code>View</code> for
   * @param a the parent allocation on entry and the child allocation on exit
   *
   * @return the child view at the given model position
   */
  protected View getViewAtPosition(int pos, Rectangle a)
  {
    View view = null;
    int i = getViewIndexAtPosition(pos);
    if (i >= 0 && i < getViewCount() && a != null)
      {
        view = getView(i);
        childAllocation(i, a);
      }
    return view;
  }

  /**
   * Returns the index of the child <code>View</code> for the given model
   * position.
   *
   * @param pos the model position for whicht the child <code>View</code> is
   *        queried
   *
   * @return the index of the child <code>View</code> for the given model
   *         position
   */
  protected int getViewIndexAtPosition(int pos)
  {
    // We have a 1:1 mapping of elements to views here, so we forward
    // this to the element.
    Element el = getElement();
    return el.getElementIndex(pos);
  }

  /**
   * Returns the allocation that is given to this <code>CompositeView</code>
   * minus this <code>CompositeView</code>'s insets.
   *
   * Also this translates from an immutable allocation to a mutable allocation
   * that is typically reused and further narrowed, like in
   * {@link #childAllocation}.
   *
   * @param a the allocation given to this <code>CompositeView</code>
   *
   * @return the allocation that is given to this <code>CompositeView</code>
   *         minus this <code>CompositeView</code>'s insets or
   *         <code>null</code> if a was <code>null</code>
   */
  protected Rectangle getInsideAllocation(Shape a)
  {
    if (a == null)
      return null;

    Rectangle alloc = a.getBounds();
    // Initialize the inside allocation rectangle. This is done inside
    // a synchronized block in order to avoid multiple threads creating
    // this instance simultanously.
    Rectangle inside;
    synchronized(this)
      {
        inside = insideAllocation;
        if (inside == null)
          {
            inside = new Rectangle();
            insideAllocation = inside;
          }
      }
    inside.x = alloc.x + insets.left;
    inside.y = alloc.y + insets.top;
    inside.width = alloc.width - insets.left - insets.right;
    inside.height = alloc.height - insets.top - insets.bottom;
    return inside;
  }

  /**
   * Sets the insets defined by attributes in <code>attributes</code>. This
   * queries the attribute keys {@link StyleConstants#SpaceAbove},
   * {@link StyleConstants#SpaceBelow}, {@link StyleConstants#LeftIndent} and
   * {@link StyleConstants#RightIndent} and calls {@link #setInsets} to
   * actually set the insets on this <code>CompositeView</code>.
   *
   * @param attributes the attributes from which to query the insets
   */
  protected void setParagraphInsets(AttributeSet attributes)
  {
    Float l = (Float) attributes.getAttribute(StyleConstants.LeftIndent);
    short left = 0;
    if (l != null)
      left = l.shortValue();
    Float r = (Float) attributes.getAttribute(StyleConstants.RightIndent);
    short right = 0;
    if (r != null)
      right = r.shortValue();
    Float t = (Float) attributes.getAttribute(StyleConstants.SpaceAbove);
    short top = 0;
    if (t != null)
      top = t.shortValue();
    Float b = (Float) attributes.getAttribute(StyleConstants.SpaceBelow);
    short bottom = 0;
    if (b != null)
      bottom = b.shortValue();
    setInsets(top, left, bottom, right);
  }

  /**
   * Sets the insets of this <code>CompositeView</code>.
   *
   * @param top the top inset
   * @param left the left inset
   * @param bottom the bottom inset
   * @param right the right inset
   */
  protected void setInsets(short top, short left, short bottom, short right)
  {
    insets.top = top;
    insets.left = left;
    insets.bottom = bottom;
    insets.right = right;
  }

  /**
   * Returns the left inset of this <code>CompositeView</code>.
   *
   * @return the left inset of this <code>CompositeView</code>
   */
  protected short getLeftInset()
  {
    return (short) insets.left;
  }

  /**
   * Returns the right inset of this <code>CompositeView</code>.
   *
   * @return the right inset of this <code>CompositeView</code>
   */
  protected short getRightInset()
  {
    return (short) insets.right;
  }

  /**
   * Returns the top inset of this <code>CompositeView</code>.
   *
   * @return the top inset of this <code>CompositeView</code>
   */
  protected short getTopInset()
  {
    return (short) insets.top;
  }

  /**
   * Returns the bottom inset of this <code>CompositeView</code>.
   *
   * @return the bottom inset of this <code>CompositeView</code>
   */
  protected short getBottomInset()
  {
    return (short) insets.bottom;
  }

  /**
   * Returns the next model location that is visible in north or south
   * direction.
   * This is used to determine the
   * placement of the caret when navigating around the document with
   * the arrow keys.
   *
   * @param pos the model position to start search from
   * @param b the bias for <code>pos</code>
   * @param a the allocated region for this view
   * @param direction the direction from the current position, can be one of
   *        the following:
   *        <ul>
   *        <li>{@link SwingConstants#NORTH}</li>
   *        <li>{@link SwingConstants#SOUTH}</li>
   *        </ul>
   * @param biasRet the bias of the return value gets stored here
   *
   * @return the position inside the model that represents the next visual
   *         location
   *
   * @throws BadLocationException if <code>pos</code> is not a valid location
   *         inside the document model
   * @throws IllegalArgumentException if <code>direction</code> is invalid
   */
  protected int getNextNorthSouthVisualPositionFrom(int pos, Position.Bias b,
                                                    Shape a, int direction,
                                                    Position.Bias[] biasRet)
    throws BadLocationException
  {
    // TODO: It is unknown to me how this method has to be implemented and
    // there is no specification telling me how to do it properly. Therefore
    // the implementation was done for cases that are known.
    //
    // If this method ever happens to act silly for your particular case then
    // it is likely that it is a cause of not knowing about your case when it
    // was implemented first. You are free to fix the behavior.
    //
    // Here are the assumptions that lead to the implementation:
    // If direction is NORTH chose the View preceding the one that contains the
    // offset 'pos' (imagine the views are stacked on top of each other where
    // the top is 0 and the bottom is getViewCount()-1.
    // Consecutively when the direction is SOUTH the View following the one
    // the offset 'pos' lies in is questioned.
    //
    // This limitation is described as PR 27345.
    int index = getViewIndex(pos, b);
    View v = null;
    
    if (index == -1)
      return pos;

    switch (direction)
    {
      case NORTH:
        // If we cannot calculate a proper offset return the one that was
        // provided.
        if (index <= 0)
          return pos;
        
        v = getView(index - 1);
        break;
      case SOUTH:
        // If we cannot calculate a proper offset return the one that was
        // provided.
        if (index >= getViewCount() - 1)
          return pos;
        
        v = getView(index + 1);
        break;
      default:
          throw new IllegalArgumentException();
    }
    
    return v.getNextVisualPositionFrom(pos, b, a, direction, biasRet);
  }

  /**
   * Returns the next model location that is visible in east or west
   * direction.
   * This is used to determine the
   * placement of the caret when navigating around the document with
   * the arrow keys.
   *
   * @param pos the model position to start search from
   * @param b the bias for <code>pos</code>
   * @param a the allocated region for this view
   * @param direction the direction from the current position, can be one of
   *        the following:
   *        <ul>
   *        <li>{@link SwingConstants#EAST}</li>
   *        <li>{@link SwingConstants#WEST}</li>
   *        </ul>
   * @param biasRet the bias of the return value gets stored here
   *
   * @return the position inside the model that represents the next visual
   *         location
   *
   * @throws BadLocationException if <code>pos</code> is not a valid location
   *         inside the document model
   * @throws IllegalArgumentException if <code>direction</code> is invalid
   */
  protected int getNextEastWestVisualPositionFrom(int pos, Position.Bias b,
                                                  Shape a, int direction,
                                                  Position.Bias[] biasRet)
    throws BadLocationException
  {
    // TODO: It is unknown to me how this method has to be implemented and
    // there is no specification telling me how to do it properly. Therefore
    // the implementation was done for cases that are known.
    //
    // If this method ever happens to act silly for your particular case then
    // it is likely that it is a cause of not knowing about your case when it
    // was implemented first. You are free to fix the behavior.
    //
    // Here are the assumptions that lead to the implementation:
    // If direction is EAST increase the offset by one and ask the View to
    // which that index belong to calculate the 'next visual position'.
    // If the direction is WEST do the same with offset 'pos' being decreased
    // by one.
    // This behavior will fail in a right-to-left or bidi environment!
    //
    // This limitation is described as PR 27346.
    int index;
    
    View v = null;
    
    switch (direction)
    {
      case EAST:
        index = getViewIndex(pos + 1, b);
        // If we cannot calculate a proper offset return the one that was
        // provided.
        if (index == -1)
          return pos;
        
        v  = getView(index);
        break;
      case WEST:
        index = getViewIndex(pos - 1, b);
        // If we cannot calculate a proper offset return the one that was
        // provided.
        if (index == -1)
          return pos;
        
        v  = getView(index);
        break;
      default:
        throw new IllegalArgumentException();
    }
    
    return v.getNextVisualPositionFrom(pos,
                                       b,
                                       a,
                                       direction,
                                       biasRet);
  }

  /**
   * Determines if the next view in horinzontal direction is located to
   * the east or west of the view at position <code>pos</code>. Usually
   * the <code>View</code>s are laid out from the east to the west, so
   * we unconditionally return <code>false</code> here. Subclasses that
   * support bidirectional text may wish to override this method.
   *
   * @param pos the position in the document
   * @param bias the bias to be applied to <code>pos</code>
   *
   * @return <code>true</code> if the next <code>View</code> is located
   *         to the EAST, <code>false</code> otherwise
   */
  protected boolean flipEastAndWestAtEnds(int pos, Position.Bias bias)
  {
    return false;
  }
}