Add gRPC protobufs to SDK

zcash-client-sdk-js/src/service.proto

@@ -0,0 +1,49 @@
+syntax = "proto3";
+package cash.z.wallet.sdk.rpc;
+option go_package = "walletrpc";
+
+import "compact_formats.proto";
+
+// A BlockID message contains identifiers to select a block: a height or a
+// hash. If the hash is present it takes precedence.
+message BlockID {
+     uint64 height = 1;
+     bytes hash = 2;
+}
+
+// BlockRange technically allows ranging from hash to hash etc but this is not
+// currently intended for support, though there is no reason you couldn't do
+// it. Further permutations are left as an exercise.
+message BlockRange {
+    BlockID start = 1;
+    BlockID end = 2;
+}
+
+// A TxFilter contains the information needed to identify a particular
+// transaction: either a block and an index, or a direct transaction hash.
+message TxFilter {
+     BlockID block = 1;
+     uint64 index = 2;
+     bytes hash = 3;
+}
+
+// RawTransaction contains the complete transaction data.
+message RawTransaction {
+    bytes data = 1;
+}
+
+message SendResponse {
+    int32 errorCode = 1;
+    string errorMessage = 2;
+}
+
+// Empty placeholder. Someday we may want to specify e.g. a particular chain fork.
+message ChainSpec {}
+
+service CompactTxStreamer {
+    rpc GetLatestBlock(ChainSpec) returns (BlockID) {}
+    rpc GetBlock(BlockID) returns (CompactBlock) {}
+    rpc GetBlockRange(BlockRange) returns (stream CompactBlock) {}
+    rpc GetTransaction(TxFilter) returns (RawTransaction) {}
+    rpc SendTransaction(RawTransaction) returns (SendResponse) {}
+}