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/*
 * Copyright 2017 ~ 2025 the original author or authors. 
 *
 * 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 com.wl4g.component.common.collection.multimap;

import java.io.Serializable;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.annotation.Nullable;

/**
 * Simple implementation of {@link MultiValueMap} that wraps a
 * {@link LinkedHashMap}, storing multiple values in a {@link LinkedList}.
 *
 * 
 * This Map implementation is generally not thread-safe. It is primarily
 * designed for data structures exposed from request objects, for use in a
 * single thread only.
 *
 * @param 
 *            the key type
 * @param 
 *            the value element type
 */
public class LinkedMultiValueMap implements MultiValueMap, Serializable, Cloneable {

	private static final long serialVersionUID = 3801124242820219131L;

	private final Map> targetMap;

	/**
	 * Create a new LinkedMultiValueMap that wraps a {@link LinkedHashMap}.
	 */
	public LinkedMultiValueMap() {
		this.targetMap = new LinkedHashMap<>();
	}

	/**
	 * Create a new LinkedMultiValueMap that wraps a {@link LinkedHashMap} with
	 * the given initial capacity.
	 * 
	 * @param initialCapacity
	 *            the initial capacity
	 */
	public LinkedMultiValueMap(int initialCapacity) {
		this.targetMap = new LinkedHashMap<>(initialCapacity);
	}

	/**
	 * Copy constructor: Create a new LinkedMultiValueMap with the same mappings
	 * as the specified Map. Note that this will be a shallow copy; its
	 * value-holding List entries will get reused and therefore cannot get
	 * modified independently.
	 * 
	 * @param otherMap
	 *            the Map whose mappings are to be placed in this Map
	 * @see #clone()
	 * @see #deepCopy()
	 */
	public LinkedMultiValueMap(Map> otherMap) {
		this.targetMap = new LinkedHashMap<>(otherMap);
	}

	// MultiValueMap implementation

	@Override
	@Nullable
	public V getFirst(K key) {
		List values = this.targetMap.get(key);
		return (values != null && !values.isEmpty() ? values.get(0) : null);
	}

	@Override
	public void add(K key, @Nullable V value) {
		List values = this.targetMap.computeIfAbsent(key, k -> new LinkedList<>());
		values.add(value);
	}

	@Override
	public void addAll(K key, List values) {
		List currentValues = this.targetMap.computeIfAbsent(key, k -> new LinkedList<>());
		currentValues.addAll(values);
	}

	@Override
	public void addAll(MultiValueMap values) {
		for (Entry> entry : values.entrySet()) {
			addAll(entry.getKey(), entry.getValue());
		}
	}

	@Override
	public void set(K key, @Nullable V value) {
		List values = new LinkedList<>();
		values.add(value);
		this.targetMap.put(key, values);
	}

	@Override
	public void setAll(Map values) {
		values.forEach(this::set);
	}

	@Override
	public Map toSingleValueMap() {
		LinkedHashMap singleValueMap = new LinkedHashMap<>(this.targetMap.size());
		this.targetMap.forEach((key, values) -> {
			if (values != null && !values.isEmpty()) {
				singleValueMap.put(key, values.get(0));
			}
		});
		return singleValueMap;
	}

	// Map implementation

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

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

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

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

	@Override
	@Nullable
	public List get(Object key) {
		return this.targetMap.get(key);
	}

	@Override
	@Nullable
	public List put(K key, List value) {
		return this.targetMap.put(key, value);
	}

	@Override
	@Nullable
	public List remove(Object key) {
		return this.targetMap.remove(key);
	}

	@Override
	public void putAll(Map> map) {
		this.targetMap.putAll(map);
	}

	@Override
	public void clear() {
		this.targetMap.clear();
	}

	@Override
	public Set keySet() {
		return this.targetMap.keySet();
	}

	@Override
	public Collection> values() {
		return this.targetMap.values();
	}

	@Override
	public Set>> entrySet() {
		return this.targetMap.entrySet();
	}

	/**
	 * Create a deep copy of this Map.
	 * 
	 * @return a copy of this Map, including a copy of each value-holding List
	 *         entry (consistently using an independent modifiable
	 *         {@link LinkedList} for each entry) along the lines of
	 *         {@code MultiValueMap.addAll} semantics
	 * @since 4.2
	 * @see #addAll(MultiValueMap)
	 * @see #clone()
	 */
	public LinkedMultiValueMap deepCopy() {
		LinkedMultiValueMap copy = new LinkedMultiValueMap<>(this.targetMap.size());
		this.targetMap.forEach((key, value) -> copy.put(key, new LinkedList<>(value)));
		return copy;
	}

	/**
	 * Create a regular copy of this Map.
	 * 
	 * @return a shallow copy of this Map, reusing this Map's value-holding List
	 *         entries (even if some entries are shared or unmodifiable) along
	 *         the lines of standard {@code Map.put} semantics
	 * @since 4.2
	 * @see #put(Object, List)
	 * @see #putAll(Map)
	 * @see LinkedMultiValueMap#LinkedMultiValueMap(Map)
	 * @see #deepCopy()
	 */
	@Override
	public LinkedMultiValueMap clone() {
		return new LinkedMultiValueMap<>(this);
	}

	@Override
	public boolean equals(@Nullable Object obj) {
		return this.targetMap.equals(obj);
	}

	@Override
	public int hashCode() {
		return this.targetMap.hashCode();
	}

	@Override
	public String toString() {
		return this.targetMap.toString();
	}

}