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 CachedValue

	update CacheUpdateFn
	hash   CacheHashFn
}

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

func (c *Cache) Get(state interface{}) interface{} {
	return c.value.Get(state, c.update, c.hash)
}

type CacheContext struct {
	value CachedValue

	update CacheUpdateContextFn
	hash   CacheHashContextFn
}

func NewCacheContext(update CacheUpdateContextFn, hash CacheHashContextFn) *CacheContext {
	return &CacheContext{update: update, hash: hash}
}

func (c *CacheContext) Get(ctx Context) interface{} {
	return c.value.GetContext(ctx, c.update, c.hash)
}

type CachedValue struct {
	value interface{}
	hash  string
}

func (c *CachedValue) Get(state interface{}, update CacheUpdateFn, hash CacheHashFn) interface{} {
	if hash(state) != c.hash {
		c.value = update(state)
	}
	return c.value
}

func (c *CachedValue) GetContext(ctx Context, update CacheUpdateContextFn, hash CacheHashContextFn) interface{} {
	if hash(ctx) != c.hash {
		c.value = update(ctx)
	}
	return c.value
}