epoching: bugfix of LatestEpochMsgs API (#140)

proto/babylon/epoching/v1/query.proto

@@ -37,27 +37,27 @@ service Query {
   }
 }
 
-// QueryParamsRequest is request type for the Query/Params RPC method.
+// QueryParamsRequest is the request type for the Query/Params RPC method.
 message QueryParamsRequest {}
 
-// QueryParamsResponse is response type for the Query/Params RPC method.
+// QueryParamsResponse is the response type for the Query/Params RPC method.
 message QueryParamsResponse {
   // params holds all the parameters of this module.
   babylon.epoching.v1.Params params = 1 [ (gogoproto.nullable) = false ];
 }
 
-// QueryCurrentEpochRequest is request type for the Query/CurrentEpoch RPC method
+// QueryCurrentEpochRequest is the request type for the Query/CurrentEpoch RPC method
 message QueryCurrentEpochRequest {}
 
-// QueryCurrentEpochResponse is response type for the Query/CurrentEpoch RPC method
+// QueryCurrentEpochResponse is the response type for the Query/CurrentEpoch RPC method
 message QueryCurrentEpochResponse { 
   // current_epoch is the current epoch number
   uint64 current_epoch = 1;
   // epoch_boundary is the height of this epoch's last block
   uint64 epoch_boundary = 2;
 }
 
-// QueryEpochMsgsRequest is request type for the Query/EpochMsgs RPC method
+// QueryEpochMsgsRequest is the request type for the Query/EpochMsgs RPC method
 message QueryEpochMsgsRequest {
   // epoch_num is the number of epoch of the requested msg queue
   uint64 epoch_num = 1;
@@ -66,16 +66,16 @@ message QueryEpochMsgsRequest {
   cosmos.base.query.v1beta1.PageRequest pagination = 2;
 }
 
-// QueryEpochMsgsResponse is response type for the Query/EpochMsgs RPC method
+// QueryEpochMsgsResponse is the response type for the Query/EpochMsgs RPC method
 message QueryEpochMsgsResponse {
   // msgs is the list of messages queued in the current epoch
   repeated babylon.epoching.v1.QueuedMessage msgs = 1;
   // pagination defines the pagination in the response
   cosmos.base.query.v1beta1.PageResponse pagination = 2;
 }
 
-// QueryLatestEpochMsgsRequest is request type for the Query/LatestEpochMsgs RPC method
-// it returns epoch msgs within epoch [min(1, end_epoch-epoch_count+1), end_epoch]
+// QueryLatestEpochMsgsRequest is the request type for the Query/LatestEpochMsgs RPC method
+// it returns epoch msgs within epoch [max(1, end_epoch-epoch_count+1), end_epoch]
 message QueryLatestEpochMsgsRequest {
   // end_epoch is the number of the last epoch to query
   uint64 end_epoch = 1;
@@ -85,7 +85,7 @@ message QueryLatestEpochMsgsRequest {
   cosmos.base.query.v1beta1.PageRequest pagination = 3;
 }
 
-// QueryLatestEpochMsgsResponse is response type for the Query/LatestEpochMsgs RPC method
+// QueryLatestEpochMsgsResponse is the response type for the Query/LatestEpochMsgs RPC method
 message QueryLatestEpochMsgsResponse {
   // epoch_msg_map is a list of QueuedMessageList
   // each QueuedMessageList has a field identifying the epoch number

x/epoching/keeper/grpc_query.go

@@ -86,17 +86,16 @@ func (k Keeper) LatestEpochMsgs(c context.Context, req *types.QueryLatestEpochMs
 		)
 	}
 
-	// the API will return epoch msgs between [min(1, end_epoch-epoch_count+1), end_epoch].
-	// NOTE:
-	// - epoch 0 does not have any queued msg
-	// - if not specified, endEpoch will be the current epoch
+	// the API will return epoch msgs between [max(1, end_epoch-epoch_count+1), end_epoch].
+	// NOTE: epoch 0 does not have any queued msg
 	endEpoch := req.EndEpoch
+	// If not specified, endEpoch will be the current epoch
 	if endEpoch == 0 {
 		endEpoch = k.GetEpoch(ctx).EpochNumber
 	}
-	beginEpoch := endEpoch - req.EpochCount + 1
-	if beginEpoch <= 1 {
-		beginEpoch = 1
+	beginEpoch := uint64(1)
+	if req.EpochCount < endEpoch { // i.e., 1 < endEpoch - req.EpochCount + 1
+		beginEpoch = endEpoch - req.EpochCount + 1
 	}
 
 	latestEpochMsgs := []*types.QueuedMessageList{}