add past and future time throttlers

README.MD

@@ -149,6 +149,8 @@ You can find list of returning error types for all existing throttlers in thrott
 | each | `func NewThrottlerEach(threshold uint64) Throttler` | Throttles each periodic *i-th* call defined by the specified threshold.<br> - could return `ErrorThreshold`; |
 | before | `func NewThrottlerBefore(threshold uint64) Throttler` | Throttles each call below the *i-th* call defined by the specified threshold.<br> - could return `ErrorThreshold`; |
 | after | `func NewThrottlerAfter(threshold uint64) Throttler` | Throttles each call after the *i-th* call defined by the specified threshold.<br> - could return `ErrorThreshold`; |
+| past | `func NewThrottlerPast(threshold time.Time) Throttler` | Throttles each call befor timestamp defined by the specified UTC time threshold.<br> - could return `ErrorThreshold`; |
+| future | `func NewThrottlerFuture(threshold time.Time) Throttler` | Throttles each call after timestamp defined by the specified UTC time threshold.<br> - could return `ErrorThreshold`; |
 | chance | `func NewThrottlerChance(threshold float64) Throttler` | Throttles each call with the chance *p* defined by the specified threshold.<br> Chance value is normalized to *[0.0, 1.0]* range.<br> Implementation uses `math/rand` as PRNG function and expects rand seeding by a client.<br> - could return `ErrorThreshold`; |
 | running | `func NewThrottlerRunning(threshold uint64) Throttler` | Throttles each call which exeeds the running quota *acquired - release* *q* defined by the specified threshold.<br> - could return `ErrorThreshold`; |
 | buffered | `func NewThrottlerBuffered(threshold uint64) Throttler` | Waits on call which exeeds the running quota *acquired - release* *q* defined by the specified threshold until the running quota is available again. |

errors.go

@@ -35,6 +35,19 @@ func (d strdurations) String() string {
 	return fmt.Sprintf("%s out of %s", d.current, d.threshold)
 }
 
+type strtimes struct {
+	current   time.Time
+	threshold time.Time
+}
+
+func (d strtimes) String() string {
+	return fmt.Sprintf(
+		"%s out of %s",
+		d.current.Format(time.RFC3339Nano),
+		d.threshold.Format(time.RFC3339Nano),
+	)
+}
+
 type strstats struct {
 	current   Stats
 	threshold Stats

throttlers.go

@@ -263,6 +263,56 @@ func (thr *tafter) Release(context.Context) error {
 	return nil
 }
 
+type tpast struct {
+	threshold time.Time
+}
+
+// NewThrottlerPast creates new throttler instance that
+// throttles each call before timestamp defined by the specified UTC time threshold.
+// - could return `ErrorThreshold`;
+func NewThrottlerPast(threshold time.Time) Throttler {
+	return tpast{threshold: threshold.UTC()}
+}
+
+func (thr tpast) Acquire(ctx context.Context) error {
+	if ts := ctxTimestamp(ctx); ts.UnixNano() <= thr.threshold.UnixNano() {
+		return ErrorThreshold{
+			Throttler: "past",
+			Threshold: strtimes{current: ts, threshold: thr.threshold},
+		}
+	}
+	return nil
+}
+
+func (thr tpast) Release(context.Context) error {
+	return nil
+}
+
+type tfuture struct {
+	threshold time.Time
+}
+
+// NewThrottlerFuture creates new throttler instance that
+// throttles each call after timestamp defined by the specified UTC time threshold.
+// - could return `ErrorThreshold`;
+func NewThrottlerFuture(threshold time.Time) Throttler {
+	return tfuture{threshold: threshold.UTC()}
+}
+
+func (thr tfuture) Acquire(ctx context.Context) error {
+	if ts := ctxTimestamp(ctx); ts.UnixNano() > thr.threshold.UnixNano() {
+		return ErrorThreshold{
+			Throttler: "future",
+			Threshold: strtimes{current: ts, threshold: thr.threshold},
+		}
+	}
+	return nil
+}
+
+func (thr tfuture) Release(context.Context) error {
+	return nil
+}
+
 type tchance struct {
 	threshold float64
 }

throttlers_test.go

@@ -299,6 +299,52 @@ func TestThrottlers(t *testing.T) {
 				},
 			},
 		},
+		"Throttler past should throttle before time threshold": {
+			tms: 3,
+			thr: NewThrottlerPast(time.Date(2000, 1, 1, 10, 0, 0, 0, time.Local)),
+			ctxs: []context.Context{
+				WithTimestamp(context.Background(), time.Date(1900, 1, 1, 10, 0, 0, 0, time.UTC)),
+				WithTimestamp(context.Background(), time.Date(2000, 1, 1, 9, 59, 0, 0, time.Local)),
+				WithTimestamp(context.Background(), time.Date(2000, 1, 1, 10, 59, 0, 0, time.Local)),
+			},
+			errs: []error{
+				ErrorThreshold{
+					Throttler: "past",
+					Threshold: strtimes{
+						current:   time.Date(1900, 1, 1, 10, 0, 0, 0, time.UTC),
+						threshold: time.Date(2000, 1, 1, 10, 0, 0, 0, time.Local).UTC(),
+					},
+				},
+				ErrorThreshold{
+					Throttler: "past",
+					Threshold: strtimes{
+						current:   time.Date(2000, 1, 1, 9, 59, 0, 0, time.Local).UTC(),
+						threshold: time.Date(2000, 1, 1, 10, 0, 0, 0, time.Local).UTC(),
+					},
+				},
+				nil,
+			},
+		},
+		"Throttler future should throttle before time threshold": {
+			tms: 3,
+			thr: NewThrottlerFuture(time.Date(2000, 1, 1, 10, 0, 0, 0, time.Local)),
+			ctxs: []context.Context{
+				WithTimestamp(context.Background(), time.Date(1900, 1, 1, 10, 0, 0, 0, time.UTC)),
+				WithTimestamp(context.Background(), time.Date(2000, 1, 1, 9, 59, 0, 0, time.Local)),
+				WithTimestamp(context.Background(), time.Date(2000, 1, 1, 10, 59, 0, 0, time.Local)),
+			},
+			errs: []error{
+				nil,
+				nil,
+				ErrorThreshold{
+					Throttler: "future",
+					Threshold: strtimes{
+						current:   time.Date(2000, 1, 1, 10, 59, 0, 0, time.Local).UTC(),
+						threshold: time.Date(2000, 1, 1, 10, 0, 0, 0, time.Local).UTC(),
+					},
+				},
+			},
+		},
 		"Throttler chance should throttle on 1": {
 			tms: 3,
 			thr: NewThrottlerChance(1),