Synnefo

/*

 * Copyright 2011 Electronic Business Systems Ltd.

 *

 * This file is part of GSS.

 *

 * GSS is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * GSS is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with GSS.  If not, see <http://www.gnu.org/licenses/>.

 */

package org.gss_project.gss.web.client;

/**

 * @author kman

 *

 */

import java.util.ArrayList;

import java.util.List;

import com.google.gwt.dom.client.Element;

import com.google.gwt.dom.client.InputElement;

import com.google.gwt.dom.client.NativeEvent;

import com.google.gwt.view.client.CellPreviewEvent;

import com.google.gwt.view.client.HasData;

import com.google.gwt.view.client.MultiSelectionModel;

import com.google.gwt.view.client.Range;

import com.google.gwt.view.client.SelectionModel;

/**

 * An implementation of {@link CellPreviewEvent.Handler} that adds selection

 * support via the spacebar and mouse clicks and handles the control key.

 * 

 * <p>

 * If the {@link HasData} source of the selection event uses a

 * {@link MultiSelectionModel}, this manager additionally provides support for

 * shift key to select a range of values. For all other {@link SelectionModel}s,

 * only the control key is supported.

 * </p>

 * 

 * @param <T> the data type of records in the list

 */

public class GSSSelectionEventManager<T> implements

    CellPreviewEvent.Handler<T> {

  /**

   * Implementation of {@link EventTranslator} that only triggers selection when

   * any checkbox is selected.

   * 

   * @param <T> the data type

   */

  public static class CheckboxEventTranslator<T> implements EventTranslator<T> {

    /**

     * The column index of the checkbox. Other columns are ignored.

     */

    private final int column;

    /**

     * Construct a new {@link CheckboxEventTranslator} that will trigger

     * selection when any checkbox in any column is selected.

     */

    public CheckboxEventTranslator() {

      this(-1);

    }

    /**

     * Construct a new {@link CheckboxEventTranslator} that will trigger

     * selection when a checkbox in the specified column is selected.

     * 

     * @param column the column index, or -1 for all columns

     */

    public CheckboxEventTranslator(int column) {

      this.column = column;

    }

    public boolean clearCurrentSelection(CellPreviewEvent<T> event) {

      return false;

    }

    public SelectAction translateSelectionEvent(CellPreviewEvent<T> event) {

      // Handle the event.

      NativeEvent nativeEvent = event.getNativeEvent();

      if ("click".equals(nativeEvent.getType())) {

        // Ignore if the event didn't occur in the correct column.

        if (column > -1 && column != event.getColumn()) {

          return SelectAction.IGNORE;

        }

        // Determine if we clicked on a checkbox.

        Element target = nativeEvent.getEventTarget().cast();

        if ("input".equals(target.getTagName().toLowerCase())) {

          final InputElement input = target.cast();

          if ("checkbox".equals(input.getType().toLowerCase())) {

            // Synchronize the checkbox with the current selection state.

            input.setChecked(event.getDisplay().getSelectionModel().isSelected(

                event.getValue()));

            return SelectAction.TOGGLE;

          }

        }

        return SelectAction.IGNORE;

      }

      // For keyboard events, do the default action.

      return SelectAction.DEFAULT;

    }

  }

  /**

   * Translates {@link CellPreviewEvent}s into {@link SelectAction}s.

   */

  public static interface EventTranslator<T> {

    /**

     * Check whether a user selection event should clear all currently selected

     * values.

     * 

     * @param event the {@link CellPreviewEvent} to translate

     */

    boolean clearCurrentSelection(CellPreviewEvent<T> event);

    /**

     * Translate the user selection event into a {@link SelectAction}.

     * 

     * @param event the {@link CellPreviewEvent} to translate

     */

    SelectAction translateSelectionEvent(CellPreviewEvent<T> event);

  }

  /**

   * The action that controls how selection is handled.

   */

  public static enum SelectAction {

    DEFAULT, // Perform the default action.

    SELECT, // Select the value.

    DESELECT, // Deselect the value.

    TOGGLE, // Toggle the selected state of the value.

    IGNORE; // Ignore the event.

  }

  /**

   * Construct a new {@link GSSSelectionEventManager} that triggers

   * selection when any checkbox in any column is clicked.

   * 

   * @param <T> the data type of the display

   * @return a {@link GSSSelectionEventManager} instance

   */

  public static <T> GSSSelectionEventManager<T> createCheckboxManager() {

    return new GSSSelectionEventManager<T>(new CheckboxEventTranslator<T>());

  }

  /**

   * Construct a new {@link GSSSelectionEventManager} that triggers

   * selection when a checkbox in the specified column is clicked.

   * 

   * @param <T> the data type of the display

   * @param column the column to handle

   * @return a {@link GSSSelectionEventManager} instance

   */

  public static <T> GSSSelectionEventManager<T> createCheckboxManager(

      int column) {

    return new GSSSelectionEventManager<T>(new CheckboxEventTranslator<T>(

        column));

  }

  /**

   * Create a new {@link GSSSelectionEventManager} using the specified

   * {@link EventTranslator} to control which {@link SelectAction} to take for

   * each event.

   * 

   * @param <T> the data type of the display

   * @param translator the {@link EventTranslator} to use

   * @return a {@link GSSSelectionEventManager} instance

   */

  public static <T> GSSSelectionEventManager<T> createCustomManager(

      EventTranslator<T> translator) {

    return new GSSSelectionEventManager<T>(translator);

  }

  /**

   * Create a new {@link GSSSelectionEventManager} that handles selection

   * via user interactions.

   * 

   * @param <T> the data type of the display

   * @return a new {@link GSSSelectionEventManager} instance

   */

  public static <T> GSSSelectionEventManager<T> createDefaultManager() {

    return new GSSSelectionEventManager<T>(null);

  }

  /**

   * The last {@link HasData} that was handled.

   */

  private HasData<T> lastDisplay;

  /**

   * The last page start.

   */

  private int lastPageStart;

  /**

   * The last selected row index.

   */

  private int lastSelectedIndex = -1;

  /**

   * A boolean indicating that the last shift selection was additive.

   */

  private boolean shiftAdditive;

  /**

   * The last place where the user clicked without holding shift. Multi

   * selections that use the shift key are rooted at the anchor.

   */

  private int shiftAnchor = -1;

  /**

   * The {@link EventTranslator} that controls how selection is handled.

   */

  private final EventTranslator<T> translator;

  /**

   * Construct a new {@link GSSSelectionEventManager} using the specified

   * {@link EventTranslator} to control which {@link SelectAction} to take for

   * each event.

   * 

   * @param translator the {@link EventTranslator} to use

   */

  protected GSSSelectionEventManager(EventTranslator<T> translator) {

    this.translator = translator;

  }

  /**

   * Update the selection model based on a user selection event.

   * 

   * @param selectionModel the selection model to update

   * @param row the selected row index relative to the page start

   * @param rowValue the selected row value

   * @param action the {@link SelectAction} to apply

   * @param selectRange true to select the range from the last selected row

   * @param clearOthers true to clear the current selection

   */

  public void doMultiSelection(MultiSelectionModel<? super T> selectionModel,

      HasData<T> display, int row, T rowValue, SelectAction action,

      boolean selectRange, boolean clearOthers) {

    // Determine if we will add or remove selection.

    boolean addToSelection = true;

    if (action != null) {

      switch (action) {

        case IGNORE:

          // Ignore selection.

          return;

        case SELECT:

          addToSelection = true;

          break;

        case DESELECT:

          addToSelection = false;

          break;

        case TOGGLE:

          addToSelection = !selectionModel.isSelected(rowValue);

          break;

      }

    }

    // Determine which rows will be newly selected.

    int pageStart = display.getVisibleRange().getStart();

    if (selectRange && pageStart == lastPageStart && lastSelectedIndex > -1

        && shiftAnchor > -1 && display == lastDisplay) {

      /*

       * Get the new shift bounds based on the existing shift anchor and the

       * selected row.

       */

      int start = Math.min(shiftAnchor, row); // Inclusive.

      int end = Math.max(shiftAnchor, row); // Inclusive.

      if (lastSelectedIndex < start) {

        // Revert previous selection if the user reselects a smaller range.

        setRangeSelection(selectionModel, display, new Range(lastSelectedIndex,

            start - lastSelectedIndex), !shiftAdditive, false);

      } else if (lastSelectedIndex > end) {

        // Revert previous selection if the user reselects a smaller range.

        setRangeSelection(selectionModel, display, new Range(end + 1,

            lastSelectedIndex - end), !shiftAdditive, false);

      } else {

        // Remember if we are adding or removing rows.

        shiftAdditive = addToSelection;

      }

      // Update the last selected row, but do not move the shift anchor.

      lastSelectedIndex = row;

      // Select the range.

      setRangeSelection(selectionModel, display, new Range(start, end - start

          + 1), shiftAdditive, clearOthers);

    } else {

      /*

       * If we are not selecting a range, save the last row and set the shift

       * anchor.

       */

      lastDisplay = display;

      lastPageStart = pageStart;

      lastSelectedIndex = row;

      shiftAnchor = row;

      selectOne(selectionModel, rowValue, addToSelection, clearOthers);

    }

  }

  public void onCellPreview(CellPreviewEvent<T> event) {

    // Early exit if selection is already handled or we are editing.

    if (event.isCellEditing() || event.isSelectionHandled()) {

      return;

    }

    // Early exit if we do not have a SelectionModel.

    HasData<T> display = event.getDisplay();

    SelectionModel<? super T> selectionModel = display.getSelectionModel();

    if (selectionModel == null) {

      return;

    }

    // Check for user defined actions.

    SelectAction action = (translator == null) ? SelectAction.DEFAULT

        : translator.translateSelectionEvent(event);

    // Handle the event based on the SelectionModel type.

    if (selectionModel instanceof MultiSelectionModel) {

      // Add shift key support for MultiSelectionModel.

      handleMultiSelectionEvent(event, action,

          (MultiSelectionModel<? super T>) selectionModel);

    } else {

      // Use the standard handler.

      handleSelectionEvent(event, action, selectionModel);

    }

  }

  /**

   * Removes all items from the selection.

   * 

   * @param selectionModel the {@link MultiSelectionModel} to clear

   */

  protected void clearSelection(MultiSelectionModel<? super T> selectionModel) {

    selectionModel.clear();

  }

  /**

   * Handle an event that could cause a value to be selected for a

   * {@link MultiSelectionModel}. This overloaded method adds support for both

   * the control and shift keys. If the shift key is held down, all rows between

   * the previous selected row and the current row are selected.

   * 

   * @param event the {@link CellPreviewEvent} that triggered selection

   * @param action the action to handle

   * @param selectionModel the {@link SelectionModel} to update

   */

  protected void handleMultiSelectionEvent(CellPreviewEvent<T> event,

      SelectAction action, MultiSelectionModel<? super T> selectionModel) {

    NativeEvent nativeEvent = event.getNativeEvent();

    String type = nativeEvent.getType();

    boolean rightclick = "mousedown".equals(type) && nativeEvent.getButton()==NativeEvent.BUTTON_RIGHT;

    if(rightclick){

            boolean shift = nativeEvent.getShiftKey();

        boolean ctrlOrMeta = nativeEvent.getCtrlKey() || nativeEvent.getMetaKey();

        boolean clearOthers = (translator == null) ? !ctrlOrMeta

            : translator.clearCurrentSelection(event);

        if (action == null || action == SelectAction.DEFAULT) {

          action = ctrlOrMeta ? SelectAction.TOGGLE : SelectAction.SELECT;

        }

        //if the row is selected then do nothing

        if(selectionModel.isSelected(event.getValue())){

                return;

        }

        doMultiSelection(selectionModel, event.getDisplay(), event.getIndex(),

            event.getValue(), action, shift, clearOthers);

    }

    else if ("click".equals(type)) {

      /*

       * Update selection on click. Selection is toggled only if the user

       * presses the ctrl key. If the user does not press the control key,

       * selection is additive.

       */

      boolean shift = nativeEvent.getShiftKey();

      boolean ctrlOrMeta = nativeEvent.getCtrlKey() || nativeEvent.getMetaKey();

      boolean clearOthers = (translator == null) ? !ctrlOrMeta

          : translator.clearCurrentSelection(event);

      if (action == null || action == SelectAction.DEFAULT) {

        action = ctrlOrMeta ? SelectAction.TOGGLE : SelectAction.SELECT;

      }

      doMultiSelection(selectionModel, event.getDisplay(), event.getIndex(),

          event.getValue(), action, shift, clearOthers);

      if(ctrlOrMeta){

              event.setCanceled(true);

      }

    } else if ("keyup".equals(type)) {

      int keyCode = nativeEvent.getKeyCode();

      if (keyCode == 32) {

        /*

         * Update selection when the space bar is pressed. The spacebar always

         * toggles selection, regardless of whether the control key is pressed.

         */

        boolean shift = nativeEvent.getShiftKey();

        boolean clearOthers = (translator == null) ? false

            : translator.clearCurrentSelection(event);

        if (action == null || action == SelectAction.DEFAULT) {

          action = SelectAction.TOGGLE;

        }

        doMultiSelection(selectionModel, event.getDisplay(), event.getIndex(),

            event.getValue(), action, shift, clearOthers);

      }

    }

  }

  /**

   * Handle an event that could cause a value to be selected. This method works

   * for any {@link SelectionModel}. Pressing the space bar or ctrl+click will

   * toggle the selection state. Clicking selects the row if it is not selected.

   * 

   * @param event the {@link CellPreviewEvent} that triggered selection

   * @param action the action to handle

   * @param selectionModel the {@link SelectionModel} to update

   */

  protected void handleSelectionEvent(CellPreviewEvent<T> event,

      SelectAction action, SelectionModel<? super T> selectionModel) {

    // Handle selection overrides.

    T value = event.getValue();

    if (action != null) {

      switch (action) {

        case IGNORE:

          return;

        case SELECT:

          selectionModel.setSelected(value, true);

          return;

        case DESELECT:

          selectionModel.setSelected(value, false);

          return;

        case TOGGLE:

          selectionModel.setSelected(value, !selectionModel.isSelected(value));

          return;

      }

    }

    // Handle default selection.

    NativeEvent nativeEvent = event.getNativeEvent();

    String type = nativeEvent.getType();

    if ("click".equals(type)) {

      if (nativeEvent.getCtrlKey() || nativeEvent.getMetaKey()) {

        // Toggle selection on ctrl+click.

        selectionModel.setSelected(value, !selectionModel.isSelected(value));

      } else {

        // Select on click.

        selectionModel.setSelected(value, true);

      }

    } else if ("keyup".equals(type)) {

      // Toggle selection on space.

      int keyCode = nativeEvent.getKeyCode();

      if (keyCode == 32) {

        selectionModel.setSelected(value, !selectionModel.isSelected(value));

      }

    }

  }

  /**

   * Selects the given item, optionally clearing any prior selection.

   * 

   * @param selectionModel the {@link MultiSelectionModel} to update

   * @param target the item to select

   * @param selected true to select, false to deselect

   * @param clearOthers true to clear all other selected items

   */

  protected void selectOne(MultiSelectionModel<? super T> selectionModel,

      T target, boolean selected, boolean clearOthers) {

    if (clearOthers) {

      clearSelection(selectionModel);

    }

    selectionModel.setSelected(target, selected);

  }

  /**

   * Select or deselect a range of row indexes, optionally deselecting all other

   * values.

   * 

   * @param selectionModel the {@link MultiSelectionModel} to update

   * @param display the {@link HasData} source of the selection event

   * @param range the {@link Range} of rows to select or deselect

   * @param addToSelection true to select, false to deselect the range

   * @param clearOthers true to deselect rows not in the range

   */

  protected void setRangeSelection(

      MultiSelectionModel<? super T> selectionModel, HasData<T> display,

      Range range, boolean addToSelection, boolean clearOthers) {

    // Get the list of values to select.

    List<T> toUpdate = new ArrayList<T>();

    int itemCount = display.getVisibleItemCount();

    int start = range.getStart();

    int end = start + range.getLength();

    for (int i = start; i < end ; i++) {

             toUpdate.add(display.getVisibleItem(i-display.getVisibleRange().getStart()));

        }

    // Clear all other values.

    if (clearOthers) {

      clearSelection(selectionModel);

    }

    // Update the state of the values.

    for (T value : toUpdate) {

      selectionModel.setSelected(value, addToSelection);

    }

  }

}