package ui

type CacheHashFn func(interface{}) string
type CacheHashContextFn func(Context) string

func (c CacheHashContextFn) Fn() CacheHashFn {
	return func(state interface{}) string { return c(state.(Context)) }
}

type CacheUpdateFn func(interface{}) interface{}
type CacheUpdateContextFn func(Context) interface{}

func (c CacheUpdateContextFn) Fn() CacheUpdateFn {
	return func(state interface{}) interface{} { return c(state.(Context)) }
}

type Cache struct {
	value interface{}
	hash  string

	updateFn CacheUpdateFn
	hashFn   CacheHashFn
}

func NewCache(update CacheUpdateFn, hash CacheHashFn) *Cache {
	return &Cache{updateFn: update, hashFn: hash}
}

func NewCacheContext(update CacheUpdateContextFn, hash CacheHashContextFn) *Cache {
	return NewCache(update.Fn(), hash.Fn())
}

func (c *Cache) Get(state interface{}) interface{} {
	if c.hashFn(state) != c.hash {
		c.value = c.updateFn(state)
	}
	return c.value
}