refactor(rotation): enhance calcAdvance to handle multiple rotation v…

…ersions and return error for unknown versions

engine/rotationmanager/advance.go

@@ -23,15 +23,20 @@ type rotState struct {
 }
 
 // calcAdvance will calculate rotation advancement if it is required. If not, nil is returned
-func calcAdvance(ctx context.Context, t time.Time, rot *rotation.Rotation, state rotState, partCount int) *advance {
+func calcAdvance(ctx context.Context, t time.Time, rot *rotation.Rotation, state rotState, partCount int) (*advance, error) {
 	var mustUpdate bool
 	origPos := state.Position
 
 	// get next shift start time
 	newStart := rot.EndTime(state.ShiftStart)
-	if state.Version == 1 {
+	switch state.Version {
+	case 1:
 		newStart = calcVersion1EndTime(rot, state.ShiftStart)
 		mustUpdate = true
+	case 2:
+		// no-op
+	default:
+		return nil, fmt.Errorf("unknown rotation version (supported: 1,2): %d", state.Version)
 	}
 
 	if state.Position >= partCount {
@@ -49,10 +54,10 @@ func calcAdvance(ctx context.Context, t time.Time, rot *rotation.Rotation, state
 				// If migrating from version 1 to 2 without changing
 				// who's on-call do so silently.
 				silent: state.Version == 1 && state.Position == origPos,
-			}
+			}, nil
 		}
 		// in the future, so nothing to do yet
-		return nil
+		return nil, nil
 	}
 
 	if !newStart.After(t.Add(-15 * time.Minute)) {
@@ -79,5 +84,5 @@ func calcAdvance(ctx context.Context, t time.Time, rot *rotation.Rotation, state
 	return &advance{
 		id:          rot.ID,
 		newPosition: state.Position,
-	}
+	}, nil
 }

engine/rotationmanager/updaterotation.go

@@ -78,7 +78,10 @@ func (db *DB) updateRotation(ctx context.Context, j *river.Job[UpdateArgs]) erro
 			Position:   int(row.Position.Int32),
 			Version:    int(row.Version.Int32),
 		}
-		adv := calcAdvance(ctx, row.Now, &r, s, len(row.Participants))
+		adv, err := calcAdvance(ctx, row.Now, &r, s, len(row.Participants))
+		if err != nil {
+			return fmt.Errorf("calc advance: %w", err)
+		}
 		if adv == nil {
 			// no advancement needed
 			return nil