Hello World gRPC call

rust-lightclient/proto/compact_formats.proto

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+syntax = "proto3";
+package cash.z.wallet.sdk.rpc;
+option go_package = "walletrpc";
+
+// Remember that proto3 fields are all optional. A field that is not present will be set to its zero value.
+// bytes fields of hashes are in canonical little-endian format.
+
+// CompactBlock is a packaging of ONLY the data from a block that's needed to:
+//   1. Detect a payment to your shielded Sapling address
+//   2. Detect a spend of your shielded Sapling notes
+//   3. Update your witnesses to generate new Sapling spend proofs.
+message CompactBlock {
+    uint32 protoVersion = 1; // the version of this wire format, for storage
+    uint64 height = 2; // the height of this block
+    bytes hash = 3;
+    bytes prevHash = 4;
+    uint32 time = 5;
+    bytes header = 6; // (hash, prevHash, and time) OR (full header)
+    repeated CompactTx vtx = 7; // compact transactions from this block
+}
+
+message CompactTx {
+    // Index and hash will allow the receiver to call out to chain
+    // explorers or other data structures to retrieve more information
+    // about this transaction.
+    uint64 index = 1;
+    bytes hash = 2;
+
+    // The transaction fee: present if server can provide. In the case of a
+    // stateless server and a transaction with transparent inputs, this will be
+    // unset because the calculation requires reference to prior transactions.
+    // in a pure-Sapling context, the fee will be calculable as:
+    //    valueBalance + (sum(vPubNew) - sum(vPubOld) - sum(tOut))
+    uint32 fee = 3;
+
+    repeated CompactSpend spends = 4;
+    repeated CompactOutput outputs = 5;
+}
+
+message CompactSpend {
+    bytes nf = 1;
+}
+
+message CompactOutput {
+    bytes cmu = 1;
+    bytes epk = 2;
+    bytes ciphertext = 3;
+}

rust-lightclient/proto/service.proto

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+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) {}
+}