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/****************************************************************************
Copyright 2004, Colorado School of Mines and others.
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 edu.mines.jtk.awt;

import java.awt.*;
import java.util.HashSet;
import java.util.Set;

/**
 * A manager for a set of modes and components. A mode manager handles 
 * activation and deactivation for all modes in its set of modes. It does 
 * this by passing the active state (true or false) to its modes, for each 
 * of the components in its set of components. Typically, when activated,
 * a mode adds input event listeners to the specified components. Then, 
 * when deactivated, such a mode removes those event listeners.
 *
 * @author Dave Hale, Colorado School of Mines
 * @version 2004.12.29
 */
public class ModeManager {

  /**
   * Constructs a mode manager with an empty set of modes.
   */
  public ModeManager() {
  }

  /**
   * Adds the specified component.
   * @param c the component.
   */
  public void add(Component c) {
    _cset.add(c);
  }

  /**
   * Removes the specified component.
   * @param c the component.
   */
  public void remove(Component c) {
    _cset.remove(c);
  }

  ///////////////////////////////////////////////////////////////////////////
  // package

  /**
   * Called by a mode when it is constructed.
   * @param m the mode.
   */
  void add(Mode m) {
    _mset.add(m);
  }

  /**
   * Called by a mode when its action is performed.
   * @param mode the mode.
   * @param active true, for active; false, otherwise.
   */
  void setActive(Mode mode, boolean active) {

    // If mode active state is unchanged, do nothing.
    if (active==mode.isActive())
      return;

    // If activating an exclusive mode, deactivate any other exclusive modes.
    // If we deactivate another node, remember it, so that we can reactivate
    // it later.
    Mode modeDeactivated = null;
    if (active && mode.isExclusive()) {
      for (Mode m : _mset) {
        if (m!=mode && m.isExclusive() && m.isActive()) {
          setActiveInternal(m,false);
          modeDeactivated = m;
          break;
        }
      }
    }

    // Activate or deactivate the mode.
    setActiveInternal(mode,active);

    // If an exclusive mode was deactivated, reactivate the most recently 
    // active exclusive mode. This enables a quick toggle between two modes.
    if (!active && mode.isExclusive() && _modeDeactivated!=null) {
      setActiveInternal(_modeDeactivated,true);
    }

    // Remember any mode that was deactivated during this call.
    _modeDeactivated = modeDeactivated;
  }

  ///////////////////////////////////////////////////////////////////////////
  // private

  private Set _mset = new HashSet();
  private Set _cset = new HashSet();
  private Mode _modeDeactivated;

  private void setActiveInternal(Mode mode, boolean active) {
    Cursor cursor = (active)?mode.getCursor():null;
    if (cursor==null)
      cursor = Cursor.getDefaultCursor();
    mode.setActiveInternal(active);
    for (Component c : _cset) {
      c.setCursor(cursor);
      mode.setActive(c,active);
    }
  }
}