/*
 * 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.apache.fluss.shaded.arrow.org.apache.arrow.vector.util;

import java.util.AbstractMap;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

// TODO: This is a temporary workaround to resolve Arrow 15's dependency on eclipse-collections,
//  which carries a Category-B license (see https://github.com/apache/arrow/issues/40896).
//  Without these override classes, ArrowReaderWriterTest fails with a ClassNotFoundException.
//  This workaround should be removed once we upgrade to Arrow 16 or later. Alternatively, these
//  override classes could be moved to `fluss-shaded-arrow` to isolate the dependency.

/**
 * An implementation of map that supports constant time look-up by a generic key or an ordinal.
 *
 * <p>This class extends the functionality a regular {@link Map} with ordinal lookup support. Upon
 * insertion an unused ordinal is assigned to the inserted (key, value) tuple. Upon update the same
 * ordinal id is re-used while value is replaced. Upon deletion of an existing item, its
 * corresponding ordinal is recycled and could be used by another item.
 *
 * <p>For any instance with N items, this implementation guarantees that ordinals are in the range
 * of [0, N). However, the ordinal assignment is dynamic and may change after an insertion or
 * deletion. Consumers of this class are responsible for explicitly checking the ordinal
 * corresponding to a key via {@link MapWithOrdinalImpl#getOrdinal(Object)} before attempting to
 * execute a lookup with an ordinal.
 *
 * @param <K> key type
 * @param <V> value type
 */
public class MapWithOrdinalImpl<K, V> implements MapWithOrdinal<K, V> {

    private final Map<K, Map.Entry<Integer, V>> primary = new LinkedHashMap<>();
    private final IntObjectHashMap<V> secondary = new IntObjectHashMap<>();

    private final Map<K, V> delegate =
            new Map<K, V>() {
                @Override
                public boolean isEmpty() {
                    return size() == 0;
                }

                @Override
                public int size() {
                    return primary.size();
                }

                @Override
                public boolean containsKey(Object key) {
                    return primary.containsKey(key);
                }

                @Override
                public boolean containsValue(Object value) {
                    return primary.containsValue(value);
                }

                @Override
                public V get(Object key) {
                    Entry<Integer, V> pair = primary.get(key);
                    if (pair != null) {
                        return pair.getValue();
                    }
                    return null;
                }

                @Override
                public V put(K key, V value) {
                    final Entry<Integer, V> oldPair = primary.get(key);
                    // if key exists try replacing otherwise, assign a new ordinal identifier
                    final int ordinal = oldPair == null ? primary.size() : oldPair.getKey();
                    primary.put(key, new AbstractMap.SimpleImmutableEntry<>(ordinal, value));
                    secondary.put(ordinal, value);
                    return oldPair == null ? null : oldPair.getValue();
                }

                @Override
                public V remove(Object key) {
                    final Entry<Integer, V> oldPair = primary.remove(key);
                    if (oldPair != null) {
                        final int lastOrdinal = secondary.size();
                        final V last = secondary.get(lastOrdinal);
                        // normalize mappings so that all numbers until primary.size() is assigned
                        // swap the last element with the deleted one
                        secondary.put(oldPair.getKey(), last);
                        primary.put(
                                (K) key,
                                new AbstractMap.SimpleImmutableEntry<>(oldPair.getKey(), last));
                    }
                    return oldPair == null ? null : oldPair.getValue();
                }

                @Override
                public void putAll(Map<? extends K, ? extends V> m) {
                    throw new UnsupportedOperationException();
                }

                @Override
                public void clear() {
                    primary.clear();
                    secondary.clear();
                }

                @Override
                public Set<K> keySet() {
                    return primary.keySet();
                }

                @Override
                public Collection<V> values() {
                    return secondary.values();
                }

                @Override
                public Set<Entry<K, V>> entrySet() {
                    return primary.entrySet().stream()
                            .map(
                                    entry ->
                                            new AbstractMap.SimpleImmutableEntry<>(
                                                    entry.getKey(), entry.getValue().getValue()))
                            .collect(Collectors.toSet());
                }
            };

    /**
     * Returns the value corresponding to the given ordinal.
     *
     * @param id ordinal value for lookup
     * @return an instance of V
     */
    @Override
    public V getByOrdinal(int id) {
        return secondary.get(id);
    }

    /**
     * Returns the ordinal corresponding to the given key.
     *
     * @param key key for ordinal lookup
     * @return ordinal value corresponding to key if it exists or -1
     */
    @Override
    public int getOrdinal(K key) {
        Map.Entry<Integer, V> pair = primary.get(key);
        if (pair != null) {
            return pair.getKey();
        }
        return -1;
    }

    @Override
    public int size() {
        return delegate.size();
    }

    @Override
    public boolean isEmpty() {
        return delegate.isEmpty();
    }

    @Override
    public Collection<V> getAll(K key) {
        if (delegate.containsKey(key)) {
            List<V> list = new ArrayList<>(1);
            list.add(get(key));
            return list;
        }
        return null;
    }

    @Override
    public V get(K key) {
        return delegate.get(key);
    }

    /**
     * Inserts the tuple (key, value) into the map extending the semantics of {@link Map#put} with
     * automatic ordinal assignment. A new ordinal is assigned if key does not exists. Otherwise the
     * same ordinal is re-used but the value is replaced.
     *
     * @see java.util.Map#put
     */
    @Override
    public boolean put(K key, V value, boolean overwrite) {
        return delegate.put(key, value) != null;
    }

    @Override
    public Collection<V> values() {
        return delegate.values();
    }

    @Override
    public boolean remove(K key, V value) {
        return false;
    }

    @Override
    public boolean containsKey(Object key) {
        return delegate.containsKey(key);
    }

    /**
     * Removes the element corresponding to the key if exists extending the semantics of {@link
     * java.util.Map#remove} with ordinal re-cycling. The ordinal corresponding to the given key may
     * be re-assigned to another tuple. It is important that consumer checks the ordinal value via
     * {@link MapWithOrdinalImpl#getOrdinal(Object)} before attempting to look-up by ordinal.
     *
     * @see java.util.Map#remove
     */
    @Override
    public boolean removeAll(K key) {
        return delegate.remove(key) != null;
    }

    @Override
    public void clear() {
        delegate.clear();
    }

    @Override
    public Set<K> keys() {
        return delegate.keySet();
    }
}
