/*
 * Copyright (c) 2003-2004 Christopher Lenz and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     Christopher Lenz - initial API and implementation
 * 
 * $Id: UncommentAction.java,v 1.1 2004-09-02 18:11:50 jsurfer Exp $
 */

package net.sourceforge.phpeclipse.css.ui.internal.editor;

import java.util.ResourceBundle;

import net.sourceforge.phpeclipse.css.ui.internal.text.CssPartitionScanner;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRewriteTarget;
import org.eclipse.jface.text.ITextSelection;
import org.eclipse.jface.text.ITypedRegion;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.ISelectionProvider;
import org.eclipse.ui.IEditorInput;
import org.eclipse.ui.texteditor.IDocumentProvider;
import org.eclipse.ui.texteditor.ITextEditor;
import org.eclipse.ui.texteditor.ITextEditorExtension2;
import org.eclipse.ui.texteditor.TextEditorAction;

/**
 * (Heavily inspired by the RemoveBlockComment class in JDT-UI)
 */
public class UncommentAction extends TextEditorAction {

	// Constructors ------------------------------------------------------------

	/**
	 * Creates a new instance.
	 * 
	 * @param bundle the resource bundle
	 * @param prefix a prefix to be prepended to the various resource keys
	 *        (described in <code>ResourceAction</code> constructor), or 
	 *        <code>null</code> if none
	 * @param editor the text editor
	 */
	public UncommentAction(ResourceBundle bundle, String prefix,
		ITextEditor editor) {
		super(bundle, prefix, editor);
	}
	
	// TextEditorAction Implementation -----------------------------------------

	/**
	 * @see org.eclipse.jface.action.Action#run()
	 */
	public void run() {
		if (!isEnabled()) {
			return;
		}
		ITextEditor editor = getTextEditor();
		if ((editor == null) || !ensureEditable(editor)) {
			return;
		}
		ITextSelection selection = getCurrentSelection();
		if (!isValidSelection(selection)) {
			return;
		}
		IDocumentProvider docProvider = editor.getDocumentProvider();
		IEditorInput input = editor.getEditorInput();
		if (docProvider == null || input == null) {
			return;
		}
		IDocument document = docProvider.getDocument(input);
		if (document == null) {
			return;
		}
		IRewriteTarget target = (IRewriteTarget)
			editor.getAdapter(IRewriteTarget.class);
		if (target != null) {
			target.beginCompoundChange();
		}
		try {
			ITypedRegion region = getBlockCommentRegion(document, selection);
			if (region != null) {
				int offset = region.getOffset();
				document.replace(offset, 2, ""); //$NON-NLS-1$
				document.replace(offset + region.getLength() - 4, 2,
					""); //$NON-NLS-1$
			}
		} catch (BadLocationException e) {
			// ignore
		} finally {
			if (target != null) {
				target.endCompoundChange();
			}
		}
	}
	
	// Private Methods ---------------------------------------------------------

	/**
	 * Ensures that the editor is modifyable. If the editor is an instance of
	 * <code>ITextEditorExtension2</code>, its 
	 * <code>validateEditorInputState</code> method is called, otherwise, the 
	 * result of <code>isEditable</code> is returned.
	 * 
	 * @param editor the editor to be checked
	 * @return <code>true</code> if the editor is editable, <code>false</code> 
	 *         otherwise
	 */
	private boolean ensureEditable(ITextEditor editor) {
		if (editor instanceof ITextEditorExtension2) {
			ITextEditorExtension2 extension = (ITextEditorExtension2) editor;
			return extension.validateEditorInputState();
		}
		return editor.isEditable();
	}

	/**
	 * Returns the block comment typed region enclosing the position at the end 
	 * of <code>selection</code> or <code>null</code> if there is no block 
	 * comment at this position.
	 * 
	 * @param selection the caret position (the end of the selection is taken as
	 *        the position)
	 * @return the block comment region at the selection's end, or 
	 *         <code>null</code>
	 */
	private ITypedRegion getBlockCommentRegion(IDocument document,
		ITextSelection selection) {
		try {
			ITypedRegion region = document.getPartition(
				selection.getOffset() + selection.getLength());
			if (CssPartitionScanner.CSS_COMMENT.equals(region.getType())) {
				return region;
			}
		} catch (BadLocationException e) {
			// ignore
		}
		return null;
	}

	/**
	 * Returns the editor's selection, or <code>null</code> if no selection can 
	 * be obtained or the editor is <code>null</code>.
	 * 
	 * @return the selection of the action's editor, or <code>null</code>
	 */
	private ITextSelection getCurrentSelection() {
		ITextEditor editor = getTextEditor();
		if (editor != null) {
			ISelectionProvider provider = editor.getSelectionProvider();
			if (provider != null) {
				ISelection selection = provider.getSelection();
				if (selection instanceof ITextSelection) {
					return (ITextSelection) selection;
				}
			}
		}
		return null;
	}

	/**
	 * Checks whether given selection is valid, i.e. neither <code>null</code> 
	 * or empty.
	 * 
	 * @param selection the selection to check
	 * @return <code>true</code> if the selection is valid, <code>false</code> 
	 *         otherwise
	 */
	private boolean isValidSelection(ITextSelection selection) {
		if (selection != null) {
			return (!selection.isEmpty() && (selection.getLength() > 0));
		}
		return false;
	}

}