Update current period in autopilot within for-loop (#1216)

Fixes #1215

autopilot/autopilot.go

@@ -876,7 +876,7 @@ func (ap *Autopilot) buildState(ctx context.Context) (*contractor.MaintenanceSta
 				return nil, err
 			}
 			ap.logger.Infof("initialised current period to %d", autopilot.CurrentPeriod)
-		} else if nextPeriod := autopilot.CurrentPeriod + autopilot.Config.Contracts.Period; cs.BlockHeight >= nextPeriod {
+		} else if nextPeriod := computeNextPeriod(cs.BlockHeight, autopilot.CurrentPeriod, autopilot.Config.Contracts.Period); nextPeriod != autopilot.CurrentPeriod {
 			prevPeriod := autopilot.CurrentPeriod
 			autopilot.CurrentPeriod = nextPeriod
 			err := ap.bus.UpdateAutopilot(ctx, autopilot)
@@ -950,3 +950,12 @@ func compatV105UsabilityFilterModeCheck(usabilityMode string) error {
 	}
 	return nil
 }
+
+func computeNextPeriod(bh, currentPeriod, period uint64) uint64 {
+	prevPeriod := currentPeriod
+	nextPeriod := prevPeriod
+	for bh >= nextPeriod+period {
+		nextPeriod += period
+	}
+	return nextPeriod
+}

autopilot/autopilot_test.go

@@ -0,0 +1,35 @@
+package autopilot
+
+import "testing"
+
+func TestComputeNextPeriod(t *testing.T) {
+	currentPeriod := uint64(100)
+	period := uint64(100)
+	tests := []struct {
+		blockHeight uint64
+		nextPeriod  uint64
+	}{
+		{
+			blockHeight: 100,
+			nextPeriod:  100,
+		},
+		{
+			blockHeight: 150,
+			nextPeriod:  100,
+		},
+		{
+			blockHeight: 200,
+			nextPeriod:  200,
+		},
+		{
+			blockHeight: 400,
+			nextPeriod:  400,
+		},
+	}
+	for _, test := range tests {
+		nextPeriod := computeNextPeriod(test.blockHeight, currentPeriod, period)
+		if nextPeriod != test.nextPeriod {
+			t.Fatalf("expected next period to be %d, got %d", test.nextPeriod, nextPeriod)
+		}
+	}
+}