/*
 * Copyright (C) 2004, 2005 Joe Walnes.
 * Copyright (C) 2006, 2007, 2010, 2011, 2013, 2014, 2016, 2018, 2020 XStream Committers.
 * All rights reserved.
 *
 * The software in this package is published under the terms of the BSD
 * style license a copy of which has been included with this distribution in
 * the LICENSE.txt file.
 * 
 * Created on 08. May 2004 by Joe Walnes
 */
package com.thoughtworks.xstream.converters.collections;

import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.converters.reflection.ObjectAccessException;
import com.thoughtworks.xstream.core.JVM;
import com.thoughtworks.xstream.core.util.Fields;
import com.thoughtworks.xstream.core.util.PresortedSet;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.mapper.Mapper;

import java.lang.reflect.Field;
import java.util.AbstractList;
import java.util.Comparator;
import java.util.Map;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

/**
 * Converts a java.util.TreeSet to XML, and serializes
 * the associated java.util.Comparator. The converter
 * assumes that the elements in the XML are already sorted 
 * according the comparator.
 *
 * @author Joe Walnes
 * @author Jörg Schaible
 */
public class TreeSetConverter extends CollectionConverter {
    private transient TreeMapConverter treeMapConverter;  

    public TreeSetConverter(Mapper mapper) {
        super(mapper, TreeSet.class);
        readResolve();
    }

    public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
        SortedSet sortedSet = (SortedSet) source;
        treeMapConverter.marshalComparator(sortedSet.comparator(), writer, context);
        super.marshal(source, writer, context);
    }

    public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
        TreeSet result = null;
        final TreeMap treeMap;
        Comparator unmarshalledComparator = treeMapConverter.unmarshalComparator(reader, context, null);
        boolean inFirstElement = unmarshalledComparator instanceof Mapper.Null;
        Comparator comparator = inFirstElement ? null : unmarshalledComparator;
        if (Reflections.sortedMapField != null) {
            TreeSet possibleResult = comparator == null ? new TreeSet() : new TreeSet(comparator);
            Object backingMap = null;
            try {
                backingMap = Reflections.sortedMapField.get(possibleResult);
            } catch (IllegalAccessException e) {
                throw new ObjectAccessException("Cannot get backing map of TreeSet", e);
            }
            if (backingMap instanceof TreeMap) {
                treeMap = (TreeMap)backingMap;
                result = possibleResult;
            } else {
                treeMap = null;
            }
        } else {
            treeMap = null;
        }
        if (treeMap == null) {
            final PresortedSet set = new PresortedSet(comparator);
            result = comparator == null ? new TreeSet() : new TreeSet(comparator);
            if (inFirstElement) {
                // we are already within the first element
                addCurrentElementToCollection(reader, context, result, set);
                reader.moveUp();
            }
            populateCollection(reader, context, result, set);
            if (set.size() > 0) {
                result.addAll(set); // comparator will not be called if internally optimized
            }
        } else {
            treeMapConverter.populateTreeMap(reader, context, treeMap, unmarshalledComparator);
        }
        return result;
    }

    private Object readResolve() {
        treeMapConverter = new TreeMapConverter(mapper()) {

            protected void populateMap(HierarchicalStreamReader reader,
                UnmarshallingContext context, Map map, final Map target) {
                populateCollection(reader, context, new AbstractList() {
                    public boolean add(Object object) {
                        return target
                            .put(object, Reflections.constantValue != null
                                ? Reflections.constantValue
                                : object) != null;
                    }

                    public Object get(int location) {
                        return null;
                    }

                    public int size() {
                        return target.size();
                    }
                });
            }

            protected void putCurrentEntryIntoMap(HierarchicalStreamReader reader, UnmarshallingContext context,
                Map map, Map target) {
                final Object key = readItem(reader, context, map);  // call readBareItem when deprecated method is removed
                target.put(key, key);
            }
        };
        return this;
    }

    private static class Reflections {

        private final static Field sortedMapField;
        private final static Object constantValue;
        static {
            Object value = null;
            sortedMapField = JVM.hasOptimizedTreeSetAddAll() ? Fields.locate(TreeSet.class, SortedMap.class, false) : null;
            if (sortedMapField != null) {
                TreeSet set = new TreeSet();
                set.add("1");
                set.add("2");

                Map backingMap = null;
                try {
                    backingMap = (Map)sortedMapField.get(set);
                } catch (final IllegalAccessException e) {
                    // give up;
                }
                if (backingMap != null) {
                    Object[] values = backingMap.values().toArray();
                    if (values[0] == values[1]) {
                        value = values[0];
                    }
                }
            } else {
                Field valueField = Fields.locate(TreeSet.class, Object.class, true);
                if (valueField != null) {
                    try {
                        value = valueField.get(null);
                    } catch (final IllegalAccessException e) {
                        // give up;
                    }
                }
            }
            constantValue = value;
        }
    }
}