/*******************************************************************************
 * Copyright (c) 2000, 2018 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.editors.text;

import java.io.CharConversionException;
import java.io.UnsupportedEncodingException;

import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.BusyIndicator;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;

import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.preferences.IEclipsePreferences;
import org.eclipse.core.runtime.preferences.IEclipsePreferences.IPreferenceChangeListener;
import org.eclipse.core.runtime.preferences.InstanceScope;

import org.eclipse.core.resources.ResourcesPlugin;

import org.eclipse.jface.action.IAction;

import org.eclipse.ui.IEditorInput;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.internal.editors.text.NLSUtility;

import org.eclipse.ui.texteditor.IDocumentProvider;
import org.eclipse.ui.texteditor.ITextEditorActionConstants;
import org.eclipse.ui.texteditor.StatusTextEditor;
import org.eclipse.ui.texteditor.TextEditorAction;


/**
 * The standard implementation of <code>IEncodingSupport</code>.
 * @since 2.0
 */
public class DefaultEncodingSupport implements IEncodingSupport {

	/** Internal preference change listener. */
	private IPreferenceChangeListener fPreferenceChangeListener;
	/** The editor this support is associated with. */
	private StatusTextEditor fTextEditor;

	/**
	 * Creates a new encoding support.
	 */
	public DefaultEncodingSupport() {
		super();
	}

	/**
	 * Associates this encoding support to the given text editor and initializes this encoding.
	 *
	 * @param textEditor the editor
	 */
	public void initialize(StatusTextEditor textEditor) {

		fTextEditor= textEditor;

		IEclipsePreferences prefs= InstanceScope.INSTANCE.getNode(ResourcesPlugin.PI_RESOURCES);

		fPreferenceChangeListener= event -> {
			if (ResourcesPlugin.PREF_ENCODING.equals(event.getKey())) {
				// null means: use default
				Runnable runnable= () -> setEncoding(null, false);
				if (Display.getCurrent() != null)
					runnable.run();
				else {
					// Post runnable into UI thread
					Shell shell;
					if (fTextEditor != null)
						shell= fTextEditor.getSite().getShell();
					else
						shell= getActiveWorkbenchShell();
					Display display;
					if (shell != null)
						display= shell.getDisplay();
					else
						display= Display.getDefault();
					display.asyncExec(runnable);
				}
			}
		};
		
		prefs.addPreferenceChangeListener(fPreferenceChangeListener);
	}

	/**
	 * Disposes this encoding support.
	 */
	public void dispose() {
		IEclipsePreferences prefs= InstanceScope.INSTANCE.getNode(ResourcesPlugin.PI_RESOURCES);
		prefs.removePreferenceChangeListener(fPreferenceChangeListener);
		fTextEditor= null;
	}

	/**
	 * Resets this encoding support. Should be called if, e.g., the input element of the
	 * associated editor changed.
	 */
	public void reset() {
	}

	/**
	 * Sets the encoding of the editor's input to the given value. If <code>overwrite</code> is
	 * <code>true</code> the value is set even if the encoding is already set.
	 *
	 * @param encoding the new encoding
	 * @param overwrite <code>true</code> if current encoding should be overwritten
	 */
	protected void setEncoding(String encoding, boolean overwrite) {
		IDocumentProvider p= fTextEditor.getDocumentProvider();
		if (p instanceof IStorageDocumentProvider) {
			final IEditorInput input= fTextEditor.getEditorInput();
			IStorageDocumentProvider provider= (IStorageDocumentProvider)p;
			String current= provider.getEncoding(input);
			if (!fTextEditor.isDirty()) {
				String internal= encoding == null ? "" : encoding; //$NON-NLS-1$
				boolean apply= (overwrite || current == null) && !internal.equals(current);
				if (apply) {
					provider.setEncoding(input, encoding);
					Runnable encodingSetter=
							() -> fTextEditor.doRevertToSaved();
					Display display= fTextEditor.getSite().getShell().getDisplay();
					if (display != null && !display.isDisposed())
						BusyIndicator.showWhile(display, encodingSetter);
					else
						encodingSetter.run();
				}
			}
		}
	}

	@Override
	public void setEncoding(String encoding) {
		setEncoding(encoding, true);
	}

	@Override
	public String getEncoding() {
		IDocumentProvider p= fTextEditor.getDocumentProvider();
		if (p instanceof IStorageDocumentProvider) {
			IStorageDocumentProvider provider= (IStorageDocumentProvider) p;
			return provider.getEncoding(fTextEditor.getEditorInput());
		}
		return null;
	}

	@Override
	public String getDefaultEncoding() {
		IDocumentProvider p= fTextEditor.getDocumentProvider();
		if (p instanceof IStorageDocumentProvider) {
			IStorageDocumentProvider provider= (IStorageDocumentProvider) p;
			return provider.getDefaultEncoding();
		}
		return null;
	}

	/**
	 * Returns a status header for the given status.
	 *
	 * @param status the status
	 * @return a status header for the given status.
	 */
	public String getStatusHeader(IStatus status) {
		Throwable t= status.getException();

		if (t instanceof CharConversionException)
			return TextEditorMessages.Editor_error_unreadable_encoding_header;

		if (t instanceof UnsupportedEncodingException)
			return TextEditorMessages.Editor_error_unsupported_encoding_header;

		return null;
	}

	/**
	 * Returns a banner for the given status.
	 *
	 * @param status the status
	 * @return a banner for the given status.
	 */
	public String getStatusBanner(IStatus status) {
		Throwable t= status.getException();

		if (t instanceof CharConversionException)
			return TextEditorMessages.Editor_error_unreadable_encoding_banner;

		if (t instanceof UnsupportedEncodingException)
			return TextEditorMessages.Editor_error_unsupported_encoding_banner;

		return null;

	}

	/**
	 * Returns a status message if any.
	 *
	 * @param status the status
	 * @return a status message indicating encoding problems or <code>null</code> otherwise
	 */
	public String getStatusMessage(IStatus status) {
		Throwable t= status.getException();
		if (t instanceof CharConversionException || t instanceof UnsupportedEncodingException) {

			String encoding= getEncoding();
			if (encoding == null)
				encoding= getDefaultEncoding();

			if (t instanceof CharConversionException) {
				if (encoding != null)
					return NLSUtility.format(TextEditorMessages.Editor_error_unreadable_encoding_message_arg, encoding);
				return TextEditorMessages.Editor_error_unreadable_encoding_message;
			}

			if (t instanceof UnsupportedEncodingException) {
				if (encoding != null)
					return NLSUtility.format(TextEditorMessages.Editor_error_unsupported_encoding_message_arg, encoding);
				return TextEditorMessages.Editor_error_unsupported_encoding_message;
			}
		}

		return null;
	}

	/**
	 * Returns <code>true</code> if the given status is an
	 * encoding error.
	 *
	 * @param status the status to check
	 * @return <code>true</code> if the given status is an encoding error
	 * @since 3.1
	 */
	public boolean isEncodingError(IStatus status) {
		if (status == null || status.getSeverity() != IStatus.ERROR)
			return false;

		Throwable t= status.getException();
		return t instanceof CharConversionException || t instanceof UnsupportedEncodingException;
	}

	/**
	 * Creates the control which allows to change the encoding.
	 * In case of encoding errors this control will be placed below
	 * the status of the status editor.
	 *
	 * @param parent the parent control
	 * @param status the status
	 * @since 3.1
	 */
	public void createStatusEncodingChangeControl(Composite parent, final IStatus status) {
		final IAction action= fTextEditor.getAction(ITextEditorActionConstants.CHANGE_ENCODING);
		if (action instanceof TextEditorAction)
			((TextEditorAction)action).update();

		if (action == null || !action.isEnabled())
			return;

		Shell shell= parent.getShell();
		Display display= shell.getDisplay();
		Color bgColor= display.getSystemColor(SWT.COLOR_LIST_BACKGROUND);

		Button button= new Button(parent, SWT.PUSH | SWT.FLAT);
		button.setText(action.getText());
		button.addSelectionListener(new SelectionAdapter() {
			/*
			 * @see org.eclipse.swt.events.SelectionAdapter#widgetDefaultSelected(org.eclipse.swt.events.SelectionEvent)
			 */
			@Override
			public void widgetSelected(SelectionEvent e) {
				action.run();
			}
		});
		button.setFocus();

		Label filler= new Label(parent, SWT.NONE);
		filler.setLayoutData(new GridData(GridData.FILL_BOTH));
		filler.setBackground(bgColor);
	}

	/**
	 * Returns the shell of the active workbench window.
	 *
	 * @return the shell of the active workbench window or <code>null</code> if none
	 * @since 3.2
	 */
	private static Shell getActiveWorkbenchShell() {
		 IWorkbenchWindow window= PlatformUI.getWorkbench().getActiveWorkbenchWindow();
		 if (window != null)
		 	return window.getShell();

		 return null;
	}

}