/*
 * 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: SyntaxPreviewer.java,v 1.1 2004-09-02 18:11:50 jsurfer Exp $
 */

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

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import net.sourceforge.phpeclipse.css.ui.CssUI;
import net.sourceforge.phpeclipse.css.ui.internal.CssUIPreferences;
import net.sourceforge.phpeclipse.css.ui.internal.text.CssSourceViewerConfiguration;
import net.sourceforge.phpeclipse.css.ui.text.CssTextTools;

import org.eclipse.jface.preference.IPreferenceStore;
import org.eclipse.jface.preference.PreferenceConverter;
import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.jface.text.Document;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.source.SourceViewer;
import org.eclipse.jface.util.IPropertyChangeListener;
import org.eclipse.jface.util.PropertyChangeEvent;
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.StyledText;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;

/**
 * A previewer for the syntax styling preferences, used to give real time
 * feedback on changes to the preferences.
 */
public class SyntaxPreviewer extends SourceViewer {

	// Constants ---------------------------------------------------------------

	/**
	 * Alias for the preference constant <code>EDITOR_BACKGROUND_COLOR</code>.
	 */
	private static final String BACKGROUND_COLOR = 
		CssUIPreferences.EDITOR_BACKGROUND_COLOR;

	/**
	 * Alias for the preference constant
	 * <code>EDITOR_BACKGROUND_DEFAULT_COLOR</code>.
	 */
	private static final String BACKGROUND_DEFAULT_COLOR = 
		CssUIPreferences.EDITOR_BACKGROUND_DEFAULT_COLOR;

	// Instance Variables ------------------------------------------------------

	/**
	 * The preference store used for loading the style settings.
	 */
	private IPreferenceStore fStore;

	/**
	 * Listener that handles changes to the preference store.
	 */
	private IPropertyChangeListener fPropertyChangeListener =
		new IPropertyChangeListener() {
			public void propertyChange(PropertyChangeEvent event) {
				if (affectsPresentation(event)) {
					updateColors();
				}
				invalidateTextPresentation();
			}
		};

	private CssTextTools fTextTools;

	/**
	 * The cached background color of the previewer.
	 */
	private Color fBackgroundColor;

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

	/**
	 * Constructor.
	 * 
	 * @param parent The parent composite
	 * @param store The preference store to use for loading the style settings
	 */
	public SyntaxPreviewer(Composite parent, IPreferenceStore store) {
		super(parent, null, SWT.V_SCROLL | SWT.H_SCROLL | SWT.BORDER);
		this.fStore = store;
		this.fTextTools = new CssTextTools(this.fStore);

		configure(new CssSourceViewerConfiguration(
			this.fTextTools, this.fStore));
		setEditable(false);
		getTextWidget().setFont(JFaceResources.getTextFont());

		IDocument document = new Document(
			loadTextFromResource("preview.css")); //$NON-NLS-1$
		this.fTextTools.setupDocument(document);
		setDocument(document);

		this.fStore.addPropertyChangeListener(this.fPropertyChangeListener);
	}

	// SourceViewer Implementation ---------------------------------------------

	/**
	 * @see org.eclipse.jface.text.TextViewer#handleDispose()
	 */
	protected void handleDispose() {
		if (this.fStore != null) {
			if (this.fPropertyChangeListener != null) {
				this.fStore.removePropertyChangeListener(
					this.fPropertyChangeListener);
				this.fPropertyChangeListener = null;
			}
			this.fStore = null;
		}
		if (this.fTextTools != null) {
			this.fTextTools.dispose();
			this.fTextTools = null;
		}
		if ((this.fBackgroundColor != null)
		 && !this.fBackgroundColor.isDisposed()) {
			this.fBackgroundColor.dispose();
		}
		super.handleDispose();
	}

	// Private Methods ---------------------------------------------------------

	private boolean affectsPresentation(PropertyChangeEvent event) {
		String p = event.getProperty();
		if (BACKGROUND_COLOR.equals(p)
		 || BACKGROUND_DEFAULT_COLOR.equals(p)) {
			return true;
		}
		return false;
	}

	/**
	 * Creates a color from the information stored in the given preference
	 * store.
	 * 
	 * @param key The preference key under which the color is stored
	 * @param display The display
	 * @return The color found, or <code>null</code> if no corresponding 
	 *         preference is available
	 */
	private Color createColor(String key, Display display) {
		Color color = null; 	 
		if (this.fStore.contains(key)) {
			RGB rgb = null;
			if (this.fStore.isDefault(key)) {
				rgb = PreferenceConverter.getDefaultColor(this.fStore, key);
			} else {
				rgb = PreferenceConverter.getColor(this.fStore, key);
			}
			if (rgb != null) {
				color = new Color(display, rgb);
			}
		}
		return color;
	}	
	
	/**
	 * Loads and returns the text stored in the specified resource.
	 * 
	 * @param name The resource name
	 * @return The text loaded from the resource, or an empty string if there
	 *         was an error reading the resource contents
	 */
	private String loadTextFromResource(String name) {
		String line;
		String separator = System.getProperty("line.separator"); //$NON-NLS-1$
		StringBuffer buffer = new StringBuffer(512);
		BufferedReader reader = null;
		try {
			reader = new BufferedReader(new InputStreamReader(
				getClass().getResourceAsStream(name)));
			while ((line = reader.readLine()) != null) {
				buffer.append(line);
				buffer.append(separator);
			}
		} catch (IOException io) {
			CssUI.log(io);
		} finally {
			if (reader != null) {
				try {
					reader.close();
				} catch (IOException e) {
					// ignore
				}
			}
		}
		return buffer.toString();
	}
	
	/**
	 * Updates the previewer colors.
	 */
	private void updateColors() {
		if (this.fStore != null) {
			StyledText styledText = getTextWidget();
			Color color = null;
			if (!this.fStore.getBoolean(BACKGROUND_DEFAULT_COLOR)) {
				color = createColor(BACKGROUND_COLOR,
					styledText.getDisplay());
			}
			styledText.setBackground(color);
			if (this.fBackgroundColor != null) {
				this.fBackgroundColor.dispose();
			}
			this.fBackgroundColor = color;
		}
	}

}