/*******************************************************************************
 * Copyright (c) 2007, 2011 IBM Corporation and others.
 * All rights reserved. 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
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.internal.debug.core;

import org.eclipse.core.runtime.Platform;
import org.eclipse.core.runtime.preferences.IEclipsePreferences;
import org.eclipse.core.runtime.preferences.InstanceScope;
import org.eclipse.debug.core.model.IDebugElement;
import org.eclipse.debug.core.model.IDebugTarget;
import org.eclipse.jdt.debug.core.IJavaDebugTarget;
import org.osgi.service.prefs.BackingStoreException;

/**
 * Controls preferences related to heap walking so that they are available in
 * java debug model code, but can be updated through the UI.
 *
 * @since 3.3
 */
public class HeapWalkingManager {

	private static HeapWalkingManager fgSingleton;

	/**
	 * Constructor. Intended to be called by getDefault()
	 */
	protected HeapWalkingManager() {
	}

	/**
	 * Returns whether the given parent object is a debug element with a debug
	 * target that supports retrieval of instance and reference information from
	 * the VM.
	 *
	 * @param object
	 *            the object to test, can be <code>null</code>
	 * @return whether the given object has a debug target that supports heap
	 *         walking
	 */
	public static boolean supportsHeapWalking(Object object) {
		if (object instanceof IDebugElement) {
			IDebugTarget target = ((IDebugElement) object).getDebugTarget();
			if (target instanceof IJavaDebugTarget) {
				return ((IJavaDebugTarget) target).supportsInstanceRetrieval();
			} else if (target != null) {
				Object adapter = target.getAdapter(IJavaDebugTarget.class);
				if (adapter instanceof IJavaDebugTarget) {
					return ((IJavaDebugTarget) adapter).supportsInstanceRetrieval();
				}
			}
		}
		return false;
	}

	/**
	 * @return the default singleton instance of the manager
	 */
	public static HeapWalkingManager getDefault() {
		if (fgSingleton == null) {
			fgSingleton = new HeapWalkingManager();
		}
		return fgSingleton;
	}

	/**
	 * @return preference dictating whether to display references as variables
	 *         in variables view.
	 */
	public boolean isShowReferenceInVarView() {
		return Platform.getPreferencesService().getBoolean(
				JDIDebugPlugin.getUniqueIdentifier(),
				JDIDebugPlugin.PREF_SHOW_REFERENCES_IN_VAR_VIEW,
				false,
				null);
	}

	/**
	 * @return preference dictating the maximum number of references that should
	 *         be displayed to the user
	 */
	public int getAllReferencesMaxCount() {
		return Platform.getPreferencesService().getInt(
				JDIDebugPlugin.getUniqueIdentifier(),
				JDIDebugPlugin.PREF_ALL_REFERENCES_MAX_COUNT,
				100,
				null);
	}

	/**
	 * @return preference dictating the maximum number of instances that should
	 *         be displayed to the user
	 */
	public int getAllInstancesMaxCount() {
		return Platform.getPreferencesService().getInt(
				JDIDebugPlugin.getUniqueIdentifier(),
				JDIDebugPlugin.PREF_ALL_INSTANCES_MAX_COUNT,
				100,
				null);
	}

	/**
	 * Stores the passed vale in the preference store
	 *
	 * @param value
	 *            whether to display references as variables in the variables
	 *            view
	 */
	public void setShowReferenceInVarView(boolean value) {
		IEclipsePreferences node = InstanceScope.INSTANCE.getNode(JDIDebugPlugin.getUniqueIdentifier());
		if(node != null) {
			node.putBoolean(JDIDebugPlugin.PREF_SHOW_REFERENCES_IN_VAR_VIEW, value);
			try {
				node.flush();
			} catch (BackingStoreException e) {
				JDIDebugPlugin.log(e);
			}
		}
	}

	/**
	 * Stores the passed value in the preference store
	 *
	 * @param max
	 *            the maximum number of references that should be displayed to
	 *            the user
	 */
	public void setAllReferencesMaxCount(int max) {
		IEclipsePreferences node = InstanceScope.INSTANCE.getNode(JDIDebugPlugin.getUniqueIdentifier());
		if(node != null) {
			node.putInt(JDIDebugPlugin.PREF_ALL_REFERENCES_MAX_COUNT, max);
			try {
				node.flush();
			} catch (BackingStoreException e) {
				JDIDebugPlugin.log(e);
			}
		}
	}

	/**
	 * Stores the passed value in the preference store
	 *
	 * @param max
	 *            the maximum number of instances that should be displayed to
	 *            the user
	 */
	public void setAllInstancesMaxCount(int max) {
		IEclipsePreferences node = InstanceScope.INSTANCE.getNode(JDIDebugPlugin.getUniqueIdentifier());
		if(node != null) {
			node.putInt(JDIDebugPlugin.PREF_ALL_INSTANCES_MAX_COUNT, max);
			try {
				node.flush();
			} catch (BackingStoreException e) {
				JDIDebugPlugin.log(e);
			}
		}
	}

	/**
	 * Resets the preferences controlled by this manager to their default
	 * settings
	 */
	public void resetToDefaultSettings() {
		IEclipsePreferences node = InstanceScope.INSTANCE.getNode(JDIDebugPlugin.getUniqueIdentifier());
		if(node != null) {
			node.putBoolean(JDIDebugPlugin.PREF_SHOW_REFERENCES_IN_VAR_VIEW, false);
			node.putInt(JDIDebugPlugin.PREF_ALL_REFERENCES_MAX_COUNT, 100);
			node.putInt(JDIDebugPlugin.PREF_ALL_INSTANCES_MAX_COUNT, 100);
			try {
				node.flush();
			} catch (BackingStoreException e) {
				JDIDebugPlugin.log(e);
			}
		}
	}

}