backoff

type Backoff struct {
	Config Conf
	Fn     Fn
}

type Conf struct {
	Logger          Logger
	DisableRecovery bool

	// HealthChecker func will be called while waiting for Fn returning errors.
	// Once Fn returned anything, the context passed to NewHealthChecker will be canceled.
	// If error chan return nil, wait time will be reset. Otherwise, the context passed
	// to Fn and HealthChecker will be canceled.
	HealthChecker HealthChecker

	// InitialDuration means initial wait time, default 1 second
	InitialDuration time.Duration
	// MaxDuration means maximum retry wait time, default 20 minutes
	MaxDuration time.Duration
	// MaxRetry, default unlimited
	MaxRetry uint

	// ExponentFactor default 1
	ExponentFactor   int
	InterConstFactor time.Duration
	OuterConstFactor time.Duration
}

type CtxCancelFn struct {
	CtxStructKey[CtxCancelFn, context.CancelFunc]
}

type CtxResetWait struct {
	CtxStructKey[CtxResetWait, chan struct{}]
}

type CtxStructKey[Key, Value any] struct{}

type ErrorAlreadyRunning struct{}

type ErrorKeywordNotFound struct {
	Keyword string
}

type ErrorMaxRetryExceeded struct {
	LastError error
}

type ErrorPanic struct {
	Reason any
	Stack  string
}

type ErrorUnexpectedHttpStatus struct {
	HttpStatus int
}

type Fn func(ctx context.Context) error

type HealthChecker func(ctx context.Context) <-chan error

type HttpProbeHealthCheckConfig struct {
	// If http.Client is not nil, some config will not take effect.
	Client  *http.Client
	Timeout time.Duration

	FollowRedirect bool

	Method string
	URL    string
	Header http.Header
	// HttpStatusCode determines which HTTP code is
	// considered successful. If HttpStatusCode is 0,
	// any status between 200 and 299 is considered a success.
	HttpStatusCode int
	// If Keyword is empty, the health check will pass only
	// when the response body contains the keyword.
	// The keyword must not contain line breaks.
	Keyword string
}

type Logger interface {
	log.FieldLogger
	WithContext(ctx context.Context) *log.Entry
}

type ProbeHealthCheckFn func(ctx context.Context) error

type ProbeHealthCheckerConfig struct {
	Logger           log.FieldLogger
	CheckInterval    time.Duration
	InitialDelay     time.Duration
	SuccessThreshold int
	FailureThreshold int
}

type TcpProbeHealthCheckConfig struct {
	Addr    string
	Timeout time.Duration
	Dialer  net.Dialer
}