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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.netbeans.lib.profiler.heap;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;


/**
 *
 * @author Tomas Hurka
 */
class NearestGCRoot {
    //~ Static fields/initializers -----------------------------------------------------------------------------------------------

    private static final int BUFFER_SIZE = (64 * 1024) / 8;
    private static final String[] REF_CLASSES = {
        "java.lang.ref.WeakReference",    // NOI18N
        "java.lang.ref.SoftReference",    // NOI18N
        "java.lang.ref.FinalReference",   // NOI18N
        "java.lang.ref.PhantomReference"  // NOI18N
    };
    private static final String JAVA_LANG_REF_REFERENCE = "java.lang.ref.Reference";   // NOI18N
    private static final String REFERENT_FILED_NAME = "referent"; // NOI18N
    private static final String SVM_REFFERENCE = "com.oracle.svm.core.heap.heapImpl.DiscoverableReference";    // NOI18N
    private static final String SVM_REFERENT_FILED_NAME = "rawReferent"; // NOI18N
    
    //~ Instance fields ----------------------------------------------------------------------------------------------------------

    private Field referentFiled;
    private HprofHeap heap;
    private LongBuffer readBuffer;
    private LongBuffer writeBuffer;
    private LongBuffer leaves;
    private LongBuffer multipleParents;
    private Set referenceClasses;
    private boolean gcRootsComputed;
    private long allInstances;
    private long processedInstances;
//private long leavesCount;
//private long firstLevel;
//private long multiParentsCount;

    //~ Constructors -------------------------------------------------------------------------------------------------------------

    NearestGCRoot(HprofHeap h) {
        heap = h;
    }

    //~ Methods ------------------------------------------------------------------------------------------------------------------

    Instance getNearestGCRootPointer(Instance instance) {
        if (heap.getGCRoot(instance) != null) {
            return instance;
        }
        computeGCRoots();
        long nextGCPathId = heap.idToOffsetMap.get(instance.getInstanceId()).getNearestGCRootPointer();
        return heap.getInstanceByID(nextGCPathId);
    }

    private boolean isSpecialReference(FieldValue value, Instance instance) {
        Field f = value.getField();

        return f.equals(referentFiled) && referenceClasses.contains(instance.getJavaClass());
    }

    private synchronized void computeGCRoots() {
        if (gcRootsComputed) {
            return;
        }
        Progress.Handle handle = Progress.COMPUTE_GC_ROOTS.start();
        if (!initHotSpotReference()) {
            if (!initSVMReference()) {
                throw new IllegalArgumentException("reference field not found"); // NOI18N
            }
        }
        heap.computeReferences(); // make sure references are computed first
        allInstances = heap.getSummary().getTotalLiveInstances();
        Set processedClasses = new HashSet(heap.getAllClasses().size()*4/3);
        
        try {
            createBuffers();
            fillZeroLevel();

            do {
                switchBuffers();
                computeOneLevel(processedClasses, handle);
            } while (hasMoreLevels());
        } catch (IOException ex) {
            Systems.printStackTrace(ex);
        }

        deleteBuffers();
        heap.idToOffsetMap.flush();
        gcRootsComputed = true;
        heap.writeToFile();
        handle.close();
    }

    private boolean initHotSpotReference() {
        referentFiled = computeReferentFiled(JAVA_LANG_REF_REFERENCE, REFERENT_FILED_NAME);
        if (referentFiled != null) {
            referenceClasses = new HashSet();
            for (int i=0; i= REF_CLASSES.length;
        }
        return false;
    }

    private boolean initSVMReference() {
        referentFiled = computeReferentFiled(SVM_REFFERENCE, SVM_REFERENT_FILED_NAME);
        if (referentFiled != null) {
            JavaClass ref = referentFiled.getDeclaringClass();

            referenceClasses = new HashSet();
            referenceClasses.add(ref);
            referenceClasses.addAll(ref.getSubClasses());
            return !referenceClasses.isEmpty();
        }
        return false;
    }

    private void computeOneLevel(Set processedClasses, Progress.Handle handle) throws IOException {
        int idSize = heap.dumpBuffer.getIDSize();
        for (;;) {
            Instance instance;
            long instanceOffset = readLong();
            List fieldValues;
            Iterator valuesIt;
            boolean hasValues = false;
            
            if (instanceOffset == 0L) { // end of level
                break;
            }
            handle.progress(processedInstances++,allInstances);
            instance = heap.getInstanceByOffset(new long[] {instanceOffset});
            if (instance instanceof ObjectArrayInstance) {
                ObjectArrayDump array = (ObjectArrayDump) instance;
                int size = array.getLength();
                long offset = array.getOffset();
                long instanceId = instance.getInstanceId();

                for (int i=0;i