feat: Split sortedSetFetch up into ByRank and ByScore functions (#280)

* feat: Split sortedSetFetch up into ByRank and ByScore functions

As per the API design discussion and the pattern we established
in the node.js SDK, this commit splits the SortedSetFetch into
two functions, one for fetching by score and one for by rank.
This prevents the user from needing to reason about which
combinations of arguments are and are not legal together.

momento/cache_client.go

@@ -34,9 +34,11 @@ type CacheClient interface {
 	// KeysExist checks if provided keys exist in the cache.
 	KeysExist(ctx context.Context, r *KeysExistRequest) (responses.KeysExistResponse, error)
 
-	// SortedSetFetch fetches the elements in the given sorted set by index rank or by score.
-	SortedSetFetch(ctx context.Context, r *SortedSetFetchRequest) (responses.SortedSetFetchResponse, error)
-	// SortedSetElement adds an element to the given sorted set. If the element already exists,
+	// SortedSetFetchByRank fetches the elements in the given sorted set by rank.
+	SortedSetFetchByRank(ctx context.Context, r *SortedSetFetchByRankRequest) (responses.SortedSetFetchResponse, error)
+	// SortedSetFetchByScore fetches the elements in the given sorted set by score.
+	SortedSetFetchByScore(ctx context.Context, r *SortedSetFetchByScoreRequest) (responses.SortedSetFetchResponse, error)
+	// SortedSetPutElement adds an element to the given sorted set. If the element already exists,
 	// its score is updated. Creates the sorted set if it does not exist.
 	SortedSetPutElement(ctx context.Context, r *SortedSetPutElementRequest) (responses.SortedSetPutElementResponse, error)
 	// SortedSetPutElements adds elements to the given sorted set. If an element already exists,
@@ -271,7 +273,14 @@ func (c defaultScsClient) KeysExist(ctx context.Context, r *KeysExistRequest) (r
 	return r.response, nil
 }
 
-func (c defaultScsClient) SortedSetFetch(ctx context.Context, r *SortedSetFetchRequest) (responses.SortedSetFetchResponse, error) {
+func (c defaultScsClient) SortedSetFetchByRank(ctx context.Context, r *SortedSetFetchByRankRequest) (responses.SortedSetFetchResponse, error) {
+	if err := c.dataClient.makeRequest(ctx, r); err != nil {
+		return nil, err
+	}
+	return r.response, nil
+}
+
+func (c defaultScsClient) SortedSetFetchByScore(ctx context.Context, r *SortedSetFetchByScoreRequest) (responses.SortedSetFetchResponse, error) {
 	if err := c.dataClient.makeRequest(ctx, r); err != nil {
 		return nil, err
 	}

momento/sorted_set_fetch_by_rank.go

@@ -0,0 +1,100 @@
+package momento
+
+import (
+	"context"
+
+	"github.com/momentohq/client-sdk-go/responses"
+
+	pb "github.com/momentohq/client-sdk-go/internal/protos"
+)
+
+type SortedSetFetchByRankRequest struct {
+	CacheName string
+	SetName   string
+	Order     SortedSetOrder
+	StartRank *int32
+	EndRank   *int32
+
+	grpcRequest  *pb.XSortedSetFetchRequest
+	grpcResponse *pb.XSortedSetFetchResponse
+	response     responses.SortedSetFetchResponse
+}
+
+func (r *SortedSetFetchByRankRequest) cacheName() string { return r.CacheName }
+
+func (r *SortedSetFetchByRankRequest) requestName() string { return "Sorted set fetch" }
+
+func (r *SortedSetFetchByRankRequest) initGrpcRequest(scsDataClient) error {
+	var err error
+
+	if _, err = prepareName(r.SetName, "Set name"); err != nil {
+		return err
+	}
+
+	grpcReq := &pb.XSortedSetFetchRequest{
+		SetName:    []byte(r.SetName),
+		Order:      pb.XSortedSetFetchRequest_Order(r.Order),
+		WithScores: true,
+	}
+
+	// This is the default: fetch everything in ascending order.
+	by_index := pb.XSortedSetFetchRequest_ByIndex{
+		ByIndex: &pb.XSortedSetFetchRequest_XByIndex{
+			Start: &pb.XSortedSetFetchRequest_XByIndex_UnboundedStart{},
+			End:   &pb.XSortedSetFetchRequest_XByIndex_UnboundedEnd{},
+		},
+	}
+
+	if r.StartRank != nil {
+
+		by_index.ByIndex.Start = &pb.XSortedSetFetchRequest_XByIndex_InclusiveStartIndex{
+			InclusiveStartIndex: *r.StartRank,
+		}
+	}
+
+	if r.EndRank != nil {
+		by_index.ByIndex.End = &pb.XSortedSetFetchRequest_XByIndex_ExclusiveEndIndex{
+			ExclusiveEndIndex: *r.EndRank,
+		}
+	}
+
+	grpcReq.Range = &by_index
+
+	r.grpcRequest = grpcReq
+
+	return nil
+}
+
+func (r *SortedSetFetchByRankRequest) makeGrpcRequest(metadata context.Context, client scsDataClient) (grpcResponse, error) {
+	resp, err := client.grpcClient.SortedSetFetch(metadata, r.grpcRequest)
+	if err != nil {
+		return nil, err
+	}
+
+	r.grpcResponse = resp
+
+	return resp, nil
+}
+
+func (r *SortedSetFetchByRankRequest) interpretGrpcResponse() error {
+	switch grpcResp := r.grpcResponse.SortedSet.(type) {
+	case *pb.XSortedSetFetchResponse_Found:
+		r.response = responses.NewSortedSetFetchHit(sortedSetByRankGrpcElementToModel(grpcResp.Found.GetValuesWithScores().Elements))
+	case *pb.XSortedSetFetchResponse_Missing:
+		r.response = &responses.SortedSetFetchMiss{}
+	default:
+		return errUnexpectedGrpcResponse(r, r.grpcResponse)
+	}
+	return nil
+}
+
+func sortedSetByRankGrpcElementToModel(grpcSetElements []*pb.XSortedSetElement) []responses.SortedSetBytesElement {
+	var returnList []responses.SortedSetBytesElement
+	for _, element := range grpcSetElements {
+		returnList = append(returnList, responses.SortedSetBytesElement{
+			Value: element.Value,
+			Score: element.Score,
+		})
+	}
+	return returnList
+}