package nixmsg

import "container/list"

type lruEntry struct {
	key string
	val any
}

// lruCache 固定容量 LRU，删除时同步移除链表节点。
type lruCache struct {
	cap int
	ll  *list.List
	m   map[string]*list.Element
}

func newLRU(cap int) *lruCache {
	if cap <= 0 {
		cap = 10000
	}
	return &lruCache{
		cap: cap,
		ll:  list.New(),
		m:   make(map[string]*list.Element),
	}
}

func (c *lruCache) Get(key string) (any, bool) {
	el, ok := c.m[key]
	if !ok {
		return nil, false
	}
	c.ll.MoveToFront(el)
	return el.Value.(*lruEntry).val, true
}

func (c *lruCache) Put(key string, val any) {
	if el, ok := c.m[key]; ok {
		el.Value.(*lruEntry).val = val
		c.ll.MoveToFront(el)
		return
	}
	el := c.ll.PushFront(&lruEntry{key: key, val: val})
	c.m[key] = el
	for c.ll.Len() > c.cap {
		back := c.ll.Back()
		if back == nil {
			break
		}
		ent := back.Value.(*lruEntry)
		c.ll.Remove(back)
		delete(c.m, ent.key)
	}
}

func (c *lruCache) Delete(key string) {
	el, ok := c.m[key]
	if !ok {
		return
	}
	c.ll.Remove(el)
	delete(c.m, key)
}

func (c *lruCache) Len() int {
	return c.ll.Len()
}

func (c *lruCache) Has(key string) bool {
	_, ok := c.m[key]
	return ok
}