/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.ui.internal;

import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;

import org.eclipse.ui.IEditorDescriptor;
import org.eclipse.ui.IEditorInput;
import org.eclipse.ui.IEditorRegistry;
import org.eclipse.ui.IElementFactory;
import org.eclipse.ui.IMemento;
import org.eclipse.ui.IPersistableElement;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.internal.misc.Assert;

/**
 * An item in the editor history.
 */
public class EditorHistoryItem {
	
	private IEditorInput input;
	private IEditorDescriptor descriptor;
	private IMemento memento;

/**
 * Constructs a new item.
 */	
public EditorHistoryItem(IEditorInput input, IEditorDescriptor descriptor) {
	this.input = input;
	this.descriptor = descriptor;
}

/**
 * Constructs a new item from a memento.
 */	
public EditorHistoryItem(IMemento memento) {
	this.memento = memento;
}

/**
 * Returns the editor descriptor.
 * 
 * @return the editor descriptor.
 */
public IEditorDescriptor getDescriptor() {
	return descriptor;
}
/**
 * Returns the editor input.
 * 
 * @return the editor input.
 */
public IEditorInput getInput() {
	return input;
}

/**
 * Returns whether this item has been restored from the memento.
 */
public boolean isRestored() {
	return memento == null;
}

/**
 * Returns the name of this item, either from the input if restored,
 * otherwise from the memento.
 */
public String getName() {
	if (isRestored() && getInput() != null) {
		return getInput().getName();
	}
	else if (memento != null) {
		String name = memento.getString(IWorkbenchConstants.TAG_NAME);
		if (name != null) {
			return name;
		}
	}
	return ""; //$NON-NLS-1$
}

/**
 * Returns the tooltip text of this item, either from the input if restored,
 * otherwise from the memento.
 */
public String getToolTipText() {
	if (isRestored() && getInput() != null) {
		return getInput().getToolTipText();
	}
	else if (memento != null) {
		String name = memento.getString(IWorkbenchConstants.TAG_TOOLTIP);
		if (name != null) {
			return name;
		}
	}
	return ""; //$NON-NLS-1$
}

/**
 * Returns whether this item matches the given editor input.
 */
public boolean matches(IEditorInput input) {
	if (isRestored())
		return input.equals(getInput());
	// if not restored, compare name, tool tip text and factory id,
	// avoiding as much work as possible
	if (!getName().equals(input.getName()))
		return false;
	if (!getToolTipText().equals(input.getToolTipText()))
		return false;
	IPersistableElement persistable = input.getPersistable(); 
	String inputId = persistable == null ? null : persistable.getFactoryId(); 
	String myId = getFactoryId();
	return myId == null ? inputId == null : myId.equals(inputId); 		
}
/**
 * Returns the factory id of this item, either from the input if restored,
 * otherwise from the memento.
 * Returns <code>null</code> if there is no factory id.
 */
public String getFactoryId() {
	if (isRestored()) {
		if (input != null) {
			IPersistableElement persistable = input.getPersistable();
			if (persistable != null) {
				return persistable.getFactoryId(); 
			}
		}
	}
	else if (memento != null) {
		return memento.getString(IWorkbenchConstants.TAG_FACTORY_ID);
	}
	return null;
}
/**
 * Restores the object state from the memento. 
 */
public IStatus restoreState() {
	Assert.isTrue(!isRestored());

	Status result = new Status(IStatus.OK,PlatformUI.PLUGIN_ID,0,"",null); //$NON-NLS-1$
	IMemento memento = this.memento;
	this.memento = null;
	
	String factoryId = memento.getString(IWorkbenchConstants.TAG_FACTORY_ID);
	if (factoryId == null) {
		WorkbenchPlugin.log("Unable to restore mru list - no input factory ID.");//$NON-NLS-1$
		return result;
	}
	IElementFactory factory = PlatformUI.getWorkbench().getElementFactory(factoryId);
	if (factory == null) {
		return result;
	}
	IMemento persistableMemento = memento.getChild(IWorkbenchConstants.TAG_PERSISTABLE);
	if (persistableMemento == null) {
		WorkbenchPlugin.log("Unable to restore mru list - no input element state: " + factoryId);//$NON-NLS-1$
		return result;
	}
	IAdaptable adaptable = factory.createElement(persistableMemento);
	if (adaptable == null || (adaptable instanceof IEditorInput) == false) {
		return result;
	}
	input = (IEditorInput) adaptable;
	// Get the editor descriptor.
	String editorId = memento.getString(IWorkbenchConstants.TAG_ID);
	if (editorId != null) {
		IEditorRegistry registry = WorkbenchPlugin.getDefault().getEditorRegistry();
		descriptor = registry.findEditor(editorId);
	}
	return result;
}

/**
 * Returns whether this history item can be saved.
 */
public boolean canSave() {
	return !isRestored()
		|| (getInput() != null && getInput().getPersistable() != null);
}

/**
 * Saves the object state in the given memento. 
 * 
 * @param memento the memento to save the object state in
 */
public IStatus saveState(IMemento memento) {
	if (!isRestored()) {
		memento.putMemento(this.memento);
	}
	else if (input != null) {
		
		IPersistableElement persistable = input.getPersistable();
		if (persistable != null) {
			/*
			 * Store IPersistable of the IEditorInput in a separate section
			 * since it could potentially use a tag already used in the parent 
			 * memento and thus overwrite data.
			 */	
			IMemento persistableMemento = memento.createChild(IWorkbenchConstants.TAG_PERSISTABLE);
			persistable.saveState(persistableMemento);
			memento.putString(IWorkbenchConstants.TAG_FACTORY_ID, persistable.getFactoryId());
			if (descriptor != null && descriptor.getId() != null) {
				memento.putString(IWorkbenchConstants.TAG_ID, descriptor.getId());
			}
			// save the name and tooltip separately so they can be restored
			// without having to instantiate the input, which can activate plugins
			memento.putString(IWorkbenchConstants.TAG_NAME, input.getName());
			memento.putString(IWorkbenchConstants.TAG_TOOLTIP, input.getToolTipText());
		}
	}
	return new Status(IStatus.OK,PlatformUI.PLUGIN_ID,0,"",null); //$NON-NLS-1$
}

}