/*******************************************************************************
 * Copyright (c) 2008, 2015 Wind River Systems 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:
 *     Wind River Systems - initial API and implementation
 *******************************************************************************/
package org.eclipse.debug.internal.ui.actions.expressions;

import java.util.Iterator;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.debug.core.DebugPlugin;
import org.eclipse.debug.core.ILaunch;
import org.eclipse.debug.core.model.IDebugElement;
import org.eclipse.debug.core.model.IVariable;
import org.eclipse.debug.core.model.IWatchExpression;
import org.eclipse.debug.internal.ui.DebugUIPlugin;
import org.eclipse.debug.internal.ui.actions.ActionMessages;
import org.eclipse.debug.ui.DebugUITools;
import org.eclipse.debug.ui.IDebugUIConstants;
import org.eclipse.debug.ui.actions.IWatchExpressionFactoryAdapter;
import org.eclipse.debug.ui.actions.IWatchExpressionFactoryAdapter2;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.ui.IViewPart;
import org.eclipse.ui.IWorkbenchPage;
import org.eclipse.ui.PartInitException;
import org.eclipse.ui.handlers.HandlerUtil;

/**
 * Handler for creating a watch expression.
 *
 * @since 3.4
 */
public class WatchHandler extends AbstractHandler {

    /* (non-Javadoc)
     * @see org.eclipse.core.commands.AbstractHandler#execute(org.eclipse.core.commands.ExecutionEvent)
     */
    @Override
	public Object execute(ExecutionEvent event) throws ExecutionException {
        ISelection selection = HandlerUtil.getCurrentSelection(event);
        if (selection instanceof IStructuredSelection) {
            Iterator<?> iter = ((IStructuredSelection)selection).iterator();
            while (iter.hasNext()) {
                Object element = iter.next();
                createExpression(element);
            }
        }
        return null;
    }


    private void showExpressionsView() {
        IWorkbenchPage page = DebugUIPlugin.getDefault().getWorkbench().getActiveWorkbenchWindow().getActivePage();
        IViewPart part = page.findView(IDebugUIConstants.ID_EXPRESSION_VIEW);
        if (part == null) {
            try {
                page.showView(IDebugUIConstants.ID_EXPRESSION_VIEW);
            } catch (PartInitException e) {
            }
        } else {
            page.bringToTop(part);
        }

    }

    private void createExpression(Object element) {
        String expressionString;
        try {
            if (element instanceof IVariable) {
                IVariable variable = (IVariable)element;
                IWatchExpressionFactoryAdapter factory = getFactory(variable);
                expressionString = variable.getName();
                if (factory != null) {
                    expressionString = factory.createWatchExpression(variable);
                }
            } else {
                IWatchExpressionFactoryAdapter2 factory2 = getFactory2(element);
                if (factory2 != null) {
                    expressionString = factory2.createWatchExpression(element);
                } else {
                    // Action should not have been enabled
                    return;
                }
            }
        } catch (CoreException e) {
            DebugUIPlugin.errorDialog(DebugUIPlugin.getShell(), ActionMessages.WatchAction_0, ActionMessages.WatchAction_1, e); //
            return;
        }

        IWatchExpression expression;
            expression = DebugPlugin.getDefault().getExpressionManager().newWatchExpression(expressionString);
        DebugPlugin.getDefault().getExpressionManager().addExpression(expression);
        IAdaptable object = DebugUITools.getDebugContext();
        IDebugElement context = null;
        if (object instanceof IDebugElement) {
            context = (IDebugElement) object;
        } else if (object instanceof ILaunch) {
            context = ((ILaunch) object).getDebugTarget();
        }
        expression.setExpressionContext(context);
        showExpressionsView();
    }


    /**
     * Returns the factory adapter for the given variable or <code>null</code> if none.
     *
     * @param variable the variable to get the factory for
     * @return factory or <code>null</code>
     */
    static IWatchExpressionFactoryAdapter getFactory(IVariable variable) {
        return variable.getAdapter(IWatchExpressionFactoryAdapter.class);
    }

    /**
     * Returns the factory adapter for the given variable or <code>null</code> if none.
     *
     * @param element the element to try and adapt
     * @return factory or <code>null</code>
     */
    static IWatchExpressionFactoryAdapter2 getFactory2(Object element) {
        if (element instanceof IAdaptable) {
            return ((IAdaptable)element).getAdapter(IWatchExpressionFactoryAdapter2.class);
        }
        return null;
    }

}