breaker

type Acceptable func(err error) bool

type Breaker interface {
	// Name returns the name of the Breaker.
	Name() string

	// Allow checks if the request is allowed.
	// If allowed, a promise will be returned,
	// otherwise ErrServiceUnavailable will be returned as the error.
	// The caller needs to call promise.Accept() on success,
	// or call promise.Reject() on failure.
	Allow() (Promise, error)
	// AllowCtx checks if the request is allowed when ctx isn't done.
	AllowCtx(ctx context.Context) (Promise, error)

	// Do runs the given request if the Breaker accepts it.
	// Do returns an error instantly if the Breaker rejects the request.
	// If a panic occurs in the request, the Breaker handles it as an error
	// and causes the same panic again.
	Do(req func() error) error
	// DoCtx runs the given request if the Breaker accepts it when ctx isn't done.
	DoCtx(ctx context.Context, req func() error) error

	// DoWithAcceptable runs the given request if the Breaker accepts it.
	// DoWithAcceptable returns an error instantly if the Breaker rejects the request.
	// If a panic occurs in the request, the Breaker handles it as an error
	// and causes the same panic again.
	// acceptable checks if it's a successful call, even if the error is not nil.
	DoWithAcceptable(req func() error, acceptable Acceptable) error
	// DoWithAcceptableCtx runs the given request if the Breaker accepts it when ctx isn't done.
	DoWithAcceptableCtx(ctx context.Context, req func() error, acceptable Acceptable) error

	// DoWithFallback runs the given request if the Breaker accepts it.
	// DoWithFallback runs the fallback if the Breaker rejects the request.
	// If a panic occurs in the request, the Breaker handles it as an error
	// and causes the same panic again.
	DoWithFallback(req func() error, fallback Fallback) error
	// DoWithFallbackCtx runs the given request if the Breaker accepts it when ctx isn't done.
	DoWithFallbackCtx(ctx context.Context, req func() error, fallback Fallback) error

	// DoWithFallbackAcceptable runs the given request if the Breaker accepts it.
	// DoWithFallbackAcceptable runs the fallback if the Breaker rejects the request.
	// If a panic occurs in the request, the Breaker handles it as an error
	// and causes the same panic again.
	// acceptable checks if it's a successful call, even if the error is not nil.
	DoWithFallbackAcceptable(req func() error, fallback Fallback, acceptable Acceptable) error
	// DoWithFallbackAcceptableCtx runs the given request if the Breaker accepts it when ctx isn't done.
	DoWithFallbackAcceptableCtx(ctx context.Context, req func() error, fallback Fallback,
		acceptable Acceptable) error
}

type Fallback func(err error) error

type Option func(breaker *circuitBreaker)

type Promise interface {
	// Accept tells the Breaker that the call is successful.
	Accept()
	// Reject tells the Breaker that the call is failed.
	Reject(reason string)
}