package ezcache

import (
	"errors"
	"time"
)

// ErrInvalidFetcher is returned by Cache.SetFetcher if the fetcher is invalid.
// This is probably only going to happen if it's nil.
var ErrInvalidFetcher = errors.New("invalid fetcher")

// ErrInvalidExpiry is returned by Cache.SetExpiry if the duration is invalid.
// This is usually if it is <= 0.
var ErrInvalidExpiry = errors.New("invalid duration")

type Fetcher[K comparable, V any] func(K) (V, error)

// Cache represents a Cache for values.
type Cache[K comparable, V any] interface {
	// Get will fetch the value for key. If in the cache, it will fetch the cached value.
	// If not in the cache, it will use the Fetcher.
	// It may return [ErrInvalidFetcher], but if an error is returned, it's probably returned by the
	// [Fetcher] itself.
	Get(key K) (V, error)

	// SetFetcher sets the fetcher for this [Cache].
	SetFetcher(f Fetcher[K, V]) error

	// SetExpiry sets the expiry for this [Cache].
	SetExpiry(d time.Duration) error
}