package com.example.springbootspringclouddemo;

import java.util.HashMap;
import java.util.Map;

public class LRUCacheDemo {

    //map负责查找，构建一个虚拟的双向链表，它里面安装的就是一个个Node节点，作为数据载体
    //1、构造一个Node节点，作为数据载体
    class Node<K,V> {
        K key;
        V value;
        Node<K,V> prev;
        Node<K,V> next;

        public Node() {
            this.prev=this.next=null;
        }

        public Node(K key,V value) {
            this.key=key;
            this.value=value;
            this.prev=this.next=null;
        }
    }

    //2、构建一个虚拟的双向链表，里面安放的就是我们的Node
    class DoubleLinkedList<K,V> {
        Node<K,V> head;
        Node<K,V> tail;

        //2.1 构造方法
        public DoubleLinkedList() {
            head = new Node<K, V>();
            tail = new Node<K, V>();
            head.next = tail;
            tail.prev = head;
        }

        //2.2 添加到头部
        public void addHead(Node<K,V> node) {
            node.next = head.next;
            node.prev = head;
            head.next.prev = node;
            head.next = node;
        }

        //2.3 删除节点
        public void removeNode(Node<K,V> node) {
            node.next.prev = node.prev;
            node.prev.next = node.next;
            node.prev = null;
            node.next = null;
        }

        //2.4 获取最后一个节点
        public Node getLast() {
            return tail.prev;
        }
    }

    //缓存大小
    private int cacheSize;
    Map<Integer,Node<Integer,Integer>> map;
    DoubleLinkedList<Integer,Integer> doubleLinkedList;

    public LRUCacheDemo(int cacheSize) {
        this.cacheSize = cacheSize;//大小
        map = new HashMap<>();//查找
        doubleLinkedList = new DoubleLinkedList<Integer, Integer>();
    }

    //查找
    public int get(int key) {
        if (!map.containsKey(key)) {
            return -1;
        }
        Node<Integer,Integer> node = map.get(key);
        doubleLinkedList.removeNode(node);
        doubleLinkedList.addHead(node);

        return node.value;
    }

    //新增或者更新
    public void put(int key,int value) {
        if (map.containsKey(key)) {
            Node<Integer,Integer> node = map.get(key);
            node.value = value;
            map.put(key,node);

            doubleLinkedList.removeNode(node);
            doubleLinkedList.addHead(node);
        } else {
            if (map.size() == cacheSize) {
                Node<Integer,Integer> lastNode = doubleLinkedList.getLast();
                map.remove(lastNode.key);
                doubleLinkedList.removeNode(lastNode);
            }
            //新增
            Node<Integer,Integer> newNode = new Node<>(key,value);
            map.put(key,newNode);
            doubleLinkedList.addHead(newNode);
        }
    }

    public static void main(String[] args) {
        LRUCacheDemo lruCacheDemo = new LRUCacheDemo(3);

        lruCacheDemo.put(1,1);
        lruCacheDemo.put(2,2);
        lruCacheDemo.put(3,3);
        System.out.println(lruCacheDemo.map.keySet());

        lruCacheDemo.put(4,1);
        System.out.println(lruCacheDemo.map.keySet());

        lruCacheDemo.put(3,1);
        System.out.println(lruCacheDemo.map.keySet());
        lruCacheDemo.put(3,1);
        System.out.println(lruCacheDemo.map.keySet());
        lruCacheDemo.put(3,1);
        System.out.println(lruCacheDemo.map.keySet());
        lruCacheDemo.put(5,1);
        System.out.println(lruCacheDemo.map.keySet());
    }
}