acache

type BatchFetcher interface {
	Fetcher
	BatchSize() int
	BatchFetch(keys []string) (map[string]any, error)
}

type Cache struct {
	// contains filtered or unexported fields
}

type Fetcher interface {
	Fetch(key string) (any, error)
}

type FuncFetcher func(key string) (any, error)

type Options struct {

	// Fetcher fetches data from upstream system for a given key.
	// Result value or error will be cached till next refresh execution.
	//
	// The provided Fetcher implementation must return consistently
	// typed values, else it panics when storing a value of different
	// type into the underlying sync/atomic.Value.
	//
	// The returned value from this function should not be changed after
	// retrieved from the Cache, else data race happens since there may be
	// many goroutines access the same value concurrently.
	Fetcher Fetcher

	// FetchTimeout is used to timeout the fetch request if given,
	// default is zero (no timeout).
	//
	// NOTE: properly configured timeout will prevent task which take very long
	// time that don't fail fast, which may further block many requests, and
	// consume huge amount of resources, cause system overload or out of memory.
	FetchTimeout time.Duration

	// RefreshInterval specifies the interval to refresh the cache values,
	// default is zero which means don't refresh the cached values.
	//
	// If there is valid cache value and the subsequent fetch requests
	// failed, the existing cache value will be kept untouched.
	RefreshInterval time.Duration

	// ExpireInterval optionally enables purging unused cached values,
	// default is zero which means no expiration.
	//
	// Note this is mainly used to purge unused data to prevent the cache
	// growing endlessly, the timing is inaccurate. Also note that
	// it may delete unused default values set by SetDefault.
	//
	// Cached values are deleted using a mark-then-delete strategy.
	// In each tick of expire interval, an active value will be marked as inactive,
	// if it's not accessed within the next expire interval, it will be
	// deleted from the Cache by the next expire execution.
	//
	// Each access of the cache value will touch it and mark it as active, which
	// prevents it being deleted from the cache.
	ExpireInterval time.Duration

	// ErrorCallback is an optional callback which will be called when
	// an error is returned by Fetcher during refresh.
	ErrorCallback func(err error, keys []string)

	// ChangeCallback is an optional callback which will be called when
	// new value is returned by Fetcher during refresh.
	ChangeCallback func(key string, oldData, newData any)

	// DeleteCallback is an optional callback which will be called when
	// a value is deleted from the cache.
	DeleteCallback func(key string, data any)
}