/*******************************************************************************
 * Copyright (c) 2005 The Regents of the University of California. 
 * This material was produced under U.S. Government contract W-7405-ENG-36 
 * for Los Alamos National Laboratory, which is operated by the University 
 * of California for the U.S. Department of Energy. The U.S. Government has 
 * rights to use, reproduce, and distribute this software. NEITHER THE 
 * GOVERNMENT NOR THE UNIVERSITY MAKES ANY WARRANTY, EXPRESS OR IMPLIED, OR 
 * ASSUMES ANY LIABILITY FOR THE USE OF THIS SOFTWARE. If software is modified 
 * to produce derivative works, such modified software should be clearly marked, 
 * so as not to confuse it with the version available from LANL.
 * 
 * Additionally, this program and the accompanying materials 
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * LA-CC 04-115
 *******************************************************************************/
package org.eclipse.ptp.debug.internal.ui.dialogfields;

import org.eclipse.core.runtime.Assert;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;

/**
 * @author Clement chu
 */
public class DialogField {
	private Label fLabel;
	protected String fLabelText;
	
	private IDialogFieldListener fDialogFieldListener;
	
	private boolean fEnabled;

	public DialogField() {
		fEnabled= true;
		fLabel= null;
		fLabelText= "";
	}
	
	/**
	 * Sets the label of the dialog field.
	 */
	public void setLabelText(String labeltext) {
		fLabelText= labeltext;
	}
		
	// ------ change listener
	
	/**
	 * Defines the listener for this dialog field.
	 */	
	public final void setDialogFieldListener(IDialogFieldListener listener) {
		fDialogFieldListener= listener;
	}

	/**
	 * Programatical invocation of a dialog field change.
	 */		
	public void dialogFieldChanged() {
		if (fDialogFieldListener != null) {
			fDialogFieldListener.dialogFieldChanged(this);
		}
	}	
	
	// ------- focus management
	/**
	 * Tries to set the focus to the dialog field.
	 * Returns <code>true</code> if the dialog field can take focus.
	 * 	To be reimplemented by dialog field implementors.
	 */
	public boolean setFocus() {
		return false;
	}

	/**
	 * Posts <code>setFocus</code> to the display event queue.
	 */	
	public void postSetFocusOnDialogField(Display display) {
		if (display != null) {
			display.asyncExec(
				new Runnable() {
					public void run() {
						setFocus();
					}
				}
			);
		}
	}		
	
	// ------- layout helpers
	/**
	 * Creates all controls of the dialog field and fills it to a composite.
	 * The composite is assumed to have <code>MGridLayout</code> as
	 * layout.
	 * The dialog field will adjust its controls' spans to the number of columns given.
	 * 	To be reimplemented by dialog field implementors.
	 */
	public Control[] doFillIntoGrid(Composite parent, int nColumns) {
		assertEnoughColumns(nColumns);
		
		Label label= getLabelControl(parent);
		label.setLayoutData(gridDataForLabel(nColumns));
		
		return new Control[] { label };
	}
	
	/**
	 * Returns the number of columns of the dialog field.
	 * 	To be reimplemented by dialog field implementors.
	 */
	public int getNumberOfControls() {
		return 1;	
	}	
	
	protected static GridData gridDataForLabel(int span) {
		GridData gd= new GridData(GridData.HORIZONTAL_ALIGN_FILL);
		gd.horizontalSpan= span;
		return gd;
	}
	
	// ------- ui creation
	/**
	 * Creates or returns the created label widget.
	 * @param parent The parent composite or <code>null</code> if the widget has
	 * already been created.
	 */			
	public Label getLabelControl(Composite parent) {
		if (fLabel == null) {
			assertCompositeNotNull(parent);
			
			fLabel= new Label(parent, SWT.LEFT | SWT.WRAP);
			fLabel.setFont(parent.getFont());
			fLabel.setEnabled(fEnabled);		
			if (fLabelText != null && !"".equals(fLabelText)) {
				fLabel.setText(fLabelText);
			} else {
				// XXX: to avoid a 16 pixel wide empty label - revisit
				fLabel.setText(".");
				fLabel.setVisible(false);
			}			
		}
		return fLabel;
	}

	/**
	 * Creates a spacer control.
	 * @param parent The parent composite
	 */		
	public static Control createEmptySpace(Composite parent) {
		return createEmptySpace(parent, 1);
	}

	/**
	 * Creates a spacer control with the given span.
	 * The composite is assumed to have <code>MGridLayout</code> as
	 * layout.
	 * @param parent The parent composite
	 */			
	public static Control createEmptySpace(Composite parent, int span) {
		Label label= new Label(parent, SWT.LEFT);
		GridData gd= new GridData();
		gd.horizontalAlignment= GridData.BEGINNING;
		gd.grabExcessHorizontalSpace= false;
		gd.horizontalSpan= span;
		gd.horizontalIndent= 0;
		gd.widthHint= 0;
		gd.heightHint= 0;
		label.setLayoutData(gd);
		return label;
	}
	
	/**
	 * Tests is the control is not <code>null</code> and not disposed.
	*/
	protected final boolean isOkToUse(Control control) {
		return (control != null) && !(control.isDisposed());
	}
	
	// --------- enable / disable management	
	/**
	 * Sets the enable state of the dialog field.
	 */
	public final void setEnabled(boolean enabled) {
		if (enabled != fEnabled) {
			fEnabled= enabled;
			updateEnableState();
		}
	}
	
	/**
	 * Called when the enable state changed.
	 * To be extended by dialog field implementors.
	 */
	protected void updateEnableState() {
		if (fLabel != null) {
			fLabel.setEnabled(fEnabled);
		}
	}

	/**
	 * Gets the enable state of the dialog field.
	 */	
	public final boolean isEnabled() {
		return fEnabled;
	}

	protected final void assertCompositeNotNull(Composite comp) {
		Assert.isNotNull(comp, "uncreated control requested with composite null");
	}

	protected final void assertEnoughColumns(int nColumns) {
		Assert.isTrue(nColumns >= getNumberOfControls(), "given number of columns is too small");
	}
}