package top100liked

import (
	"fmt"
	"testing"
)

// https://leetcode.cn/problems/lru-cache/?envType=study-plan-v2&envId=top-100-liked

type LN struct {
	Key  int
	Val  int
	Prev *LN
	Next *LN
}

type LRUCache struct {
	length    int
	capacity  int
	dummyHead *LN
	dummyTail *LN
	kv        map[int]*LN
}

func Constructor(capacity int) LRUCache {
	head := &LN{}
	tail := &LN{}
	head.Next = tail
	tail.Prev = head
	return LRUCache{
		length:    0,
		capacity:  capacity,
		dummyHead: head,
		dummyTail: tail,
		kv:        make(map[int]*LN, capacity),
	}
}

func (this *LRUCache) removeNode(node *LN) {
	node.Prev.Next = node.Next
	node.Next.Prev = node.Prev
}

func (this *LRUCache) addToHead(node *LN) {
	node.Next = this.dummyHead.Next
	node.Prev = this.dummyHead
	this.dummyHead.Next.Prev = node
	this.dummyHead.Next = node
}

func (this *LRUCache) Get(key int) int {
	if node, ok := this.kv[key]; ok {
		this.removeNode(node)
		this.addToHead(node)
		return node.Val
	}
	return -1
}

func (this *LRUCache) Put(key int, value int) {
	if node, ok := this.kv[key]; ok {
		node.Val = value
		this.removeNode(node)
		this.addToHead(node)
		return
	}
	if this.length >= this.capacity {
		lru := this.dummyTail.Prev
		this.removeNode(lru)
		delete(this.kv, lru.Key)
	} else {
		this.length++
	}
	newNode := &LN{Key: key, Val: value}
	this.addToHead(newNode)
	this.kv[key] = newNode
}

func Test1(t *testing.T) {
	lRUCache := Constructor(2)
	lRUCache.Put(1, 1)
	lRUCache.Put(2, 2)
	fmt.Println(lRUCache.Get(1))
	lRUCache.Put(3, 3)
	fmt.Println(lRUCache.Get(2))
	lRUCache.Put(4, 4)
	fmt.Println(lRUCache.Get(1))
	fmt.Println(lRUCache.Get(3))
	fmt.Println(lRUCache.Get(4))
}