package throttled

import (
	"time"
)

// GCRAStore is the interface to implement to store state for a GCRA
// rate limiter
type GCRAStore interface {
	// GetWithTime returns the value of the key if it is in the store
	// or -1 if it does not exist. It also returns the current time at
	// the Store. The time must be representable as a positive int64
	// of nanoseconds since the epoch.
	//
	// GCRA assumes that all instances sharing the same Store also
	// share the same clock. Using separate clocks will work if the
	// skew is small but not recommended in practice unless you're
	// lucky enough to be hooked up to GPS or atomic clocks.
	GetWithTime(key string) (int64, time.Time, error)

	// SetIfNotExistsWithTTL sets the value of key only if it is not
	// already set in the store it returns whether a new value was
	// set. If the store supports expiring keys and a new value was
	// set, the key will expire after the provided ttl.
	SetIfNotExistsWithTTL(key string, value int64, ttl time.Duration) (bool, error)

	// CompareAndSwapWithTTL atomically compares the value at key to
	// the old value. If it matches, it sets it to the new value and
	// returns true. Otherwise, it returns false. If the key does not
	// exist in the store, it returns false with no error. If the
	// store supports expiring keys and the swap succeeded, the key
	// will expire after the provided ttl.
	CompareAndSwapWithTTL(key string, old, new int64, ttl time.Duration) (bool, error)
}