/*
 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.drools.eclipse.debug;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.drools.eclipse.DroolsEclipsePlugin;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.debug.core.DebugException;
import org.eclipse.debug.core.DebugPlugin;
import org.eclipse.debug.core.ILogicalStructureType;
import org.eclipse.debug.core.model.IStackFrame;
import org.eclipse.debug.core.model.IValue;
import org.eclipse.debug.core.model.IVariable;
import org.eclipse.jface.viewers.ITreeContentProvider;
import org.eclipse.jface.viewers.Viewer;

/**
 * A generic Drools debug view content provider.
 */
public class DroolsDebugViewContentProvider implements ITreeContentProvider {
    
    private Map<Object, Object> parentCache;
    
    public DroolsDebugViewContentProvider() {
        parentCache = new HashMap<Object, Object>(10);
    }
    
    public Object[] getChildren(Object parent) {
        return null;
    }
    
    public Object[] getElements(Object parent) {
        Object[] result = getChildren(parent);
        if (result != null && result.length == 0) {
            return new Object[] { getEmptyString() };
        }
        return result;
    }
    
    protected String getEmptyString() {
        return "Empty";
    }

    protected void cache(Object parent, Object[] children) {
        for (int i = 0; i < children.length; i++) {
            parentCache.put(children[i], parent);
        }
    }
    
    public Object getParent(Object item) {
        return parentCache.get(item);
    }

    public void dispose() {
        parentCache= null;
    }
    
    protected void clearCache() {
        if (parentCache != null) {
            parentCache.clear();
        }
    }
    
    public void removeCache(Object[] children) {
        if (parentCache == null) {
            return;
        }
        for (int i = 0; i < children.length; i++) {
            parentCache.remove(children[i]);
        }
    }

    public boolean hasChildren(Object element) {
        try {
            if (element instanceof IVariable) {
                IValue v = ((IVariable)element).getValue();
                return v != null && v.hasVariables();
            }
            if (element instanceof IValue) {
                return ((IValue)element).hasVariables();
            }
            if (element instanceof IStackFrame) {
                return ((IStackFrame)element).hasVariables();
            }
        } catch (DebugException e) {
            DroolsEclipsePlugin.log(e);
            return false;
        }
        return false;
    }

    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
        clearCache();
    }
    
    public List<Object> getCachedDecendants(Object parent) {
        Iterator<Object> children = parentCache.keySet().iterator();
        List<Object> cachedChildren = new ArrayList<Object>(10);
        while (children.hasNext()) {
            Object child = children.next();
            if (isCachedDecendant(child, parent)) {
                cachedChildren.add(child);
            }
        }
        return cachedChildren;
    }
    
    protected boolean isCachedDecendant(Object child, Object parent) {
        Object p = getParent(child);
        while (p != null) {
            if (p.equals(parent)) {
                return true;
            }
            p = getParent(p);
        }
        return false;
    }
    
    protected IValue getLogicalValue(IValue value, List<String> previousStructureIds) {
        ILogicalStructureType[] types = DebugPlugin.getLogicalStructureTypes(value);
        if (types.length > 0) {
            ILogicalStructureType type = DebugPlugin.getDefaultStructureType(types);
            if (type != null && !previousStructureIds.contains(type.getId())) {
                try {
                    value = type.getLogicalStructure(value);
                    previousStructureIds.add(type.getId());
                    return getLogicalValue(value, previousStructureIds);
                } catch (CoreException e) {
                    // unable to display logical structure
                }
            }
        }
        return value;
    }
}
