Add off-chain-data go client application

Created project structure, fixed typos. Implemented connect.go and
getAllAssets.go. The latter uses an assetTransferBasic struct which
provides a simple API for basic asset operations like create, transfer,
etc.

Added transact.go with some util functions. Using google uuid package to
generate random UUIDs for the transactions.

Implemented pretty printing of JSON results.

Signed-off-by: Stanislav Jakuschevskij <stas@two-giants.com>

asset-transfer-private-data/application-gateway-go/connect.go

@@ -1,5 +1,5 @@
 /*
-Copyright 2022 IBM All Rights Reserved.
+Copyright 2024 IBM All Rights Reserved.
 
 SPDX-License-Identifier: Apache-2.0
 */
@@ -77,8 +77,8 @@ func newIdentity(certDirectoryPath, mspId string) *identity.X509Identity {
 }
 
 // newSign creates a function that generates a digital signature from a message digest using a private key.
-func newSign(keyDirectoryPash string) identity.Sign {
-	privateKeyPEM, err := readFirstFile(keyDirectoryPash)
+func newSign(keyDirectoryPath string) identity.Sign {
+	privateKeyPEM, err := readFirstFile(keyDirectoryPath)
 	if err != nil {
 		panic(fmt.Errorf("failed to read private key file: %w", err))
 	}

off_chain_data/README.md

@@ -28,7 +28,7 @@ The client application provides several "commands" that can be invoked using the
 
 To keep the sample code concise, the **listen** command writes ledger updates to an output file named `store.log` in the current working directory (which for the Java sample is the `application-java/app` directory). A real implementation could write ledger updates directly to an off-chain data store of choice. You can inspect the information captured in this file as you run the sample.
 
-Note that the **listen** command is is restartable and will resume event listening after the last successfully processed block / transaction. This is achieved using a checkpointer to persist the current listening position. Checkpoint state is persisted to a file named `checkpoint.json` in the current working directory. If no checkpoint state is present, event listening begins from the start of the ledger (block number zero).
+Note that the **listen** command is restartable and will resume event listening after the last successfully processed block / transaction. This is achieved using a checkpointer to persist the current listening position. Checkpoint state is persisted to a file named `checkpoint.json` in the current working directory. If no checkpoint state is present, event listening begins from the start of the ledger (block number zero).
 
 ### Smart Contract
 
@@ -112,4 +112,4 @@ When you are finished, you can bring down the test network (from the `test-netwo
 
 ```
 ./network.sh down
-```
+```

off_chain_data/application-go/app.go

@@ -0,0 +1,14 @@
+/*
+ * Copyright 2024 IBM All Rights Reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package main
+
+func main() {
+	client := newGrpcConnection()
+	defer client.Close()
+
+	getAllAssets(client)
+}

off_chain_data/application-go/connect.go

@@ -0,0 +1,142 @@
+/*
+ * Copyright 2024 IBM All Rights Reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package main
+
+import (
+	"crypto/x509"
+	"fmt"
+	"os"
+	"path"
+	"time"
+
+	"github.com/hyperledger/fabric-gateway/pkg/client"
+	"github.com/hyperledger/fabric-gateway/pkg/hash"
+	"github.com/hyperledger/fabric-gateway/pkg/identity"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+)
+
+const peerName = "peer0.org1.example.com"
+
+var (
+	channelName   = envOrDefault("CHANNEL_NAME", "mychannel")
+	chaincodeName = envOrDefault("CHAINCODE_NAME", "basic")
+	mspID         = envOrDefault("MSP_ID", "Org1MSP")
+
+	// Path to crypto materials.
+	cryptoPath = envOrDefault("CRYPTO_PATH", "../../test-network/organizations/peerOrganizations/org1.example.com")
+
+	// Path to user private key directory.
+	keyDirectoryPath = envOrDefault("KEY_DIRECTORY_PATH", cryptoPath+"/users/User1@org1.example.com/msp/keystore")
+
+	// Path to user certificate.
+	certPath = envOrDefault("CERT_PATH", cryptoPath+"/users/User1@org1.example.com/msp/signcerts/cert.pem")
+
+	// Path to peer tls certificate.
+	tlsCertPath = envOrDefault("TLS_CERT_PATH", cryptoPath+"/peers/peer0.org1.example.com/tls/ca.crt")
+
+	// Gateway peer endpoint.
+	peerEndpoint = envOrDefault("PEER_ENDPOINT", "dns:///localhost:7051")
+
+	// Gateway peer SSL host name override.
+	peerHostAlias = envOrDefault("PEER_HOST_ALIAS", peerName)
+)
+
+func envOrDefault(key, defaultValue string) string {
+	result := os.Getenv(key)
+	if result == "" {
+		return defaultValue
+	}
+	return result
+}
+
+func newGrpcConnection() *grpc.ClientConn {
+	certificatePEM, err := os.ReadFile(tlsCertPath)
+	if err != nil {
+		panic(fmt.Errorf("failed to read TLS certificate file: %w", err))
+	}
+
+	certificate, err := identity.CertificateFromPEM(certificatePEM)
+	if err != nil {
+		panic(err)
+	}
+
+	certPool := x509.NewCertPool()
+	certPool.AddCert(certificate)
+	transportCredentials := credentials.NewClientTLSFromCert(certPool, peerHostAlias)
+
+	connection, err := grpc.NewClient(peerEndpoint, grpc.WithTransportCredentials(transportCredentials))
+	if err != nil {
+		panic(fmt.Errorf("failed to create gRPC connection: %w", err))
+	}
+
+	return connection
+}
+
+func newConnectOptions(clientConnection *grpc.ClientConn) (identity.Identity, []client.ConnectOption) {
+	return newIdentity(), []client.ConnectOption{
+		client.WithSign(newSign()),
+		client.WithHash(hash.SHA256),
+		client.WithClientConnection(clientConnection),
+		client.WithEvaluateTimeout(5 * time.Second),
+		client.WithEndorseTimeout(15 * time.Second),
+		client.WithSubmitTimeout(5 * time.Second),
+		client.WithCommitStatusTimeout(1 * time.Minute),
+	}
+}
+
+func newIdentity() *identity.X509Identity {
+	certificatePEM, err := os.ReadFile(certPath)
+	if err != nil {
+		panic(fmt.Errorf("failed to read certificate file: %w", err))
+	}
+
+	certificate, err := identity.CertificateFromPEM(certificatePEM)
+	if err != nil {
+		panic(err)
+	}
+
+	id, err := identity.NewX509Identity(mspID, certificate)
+	if err != nil {
+		panic(err)
+	}
+
+	return id
+}
+
+func newSign() identity.Sign {
+	privateKeyPEM, err := readFirstFile(keyDirectoryPath)
+	if err != nil {
+		panic(fmt.Errorf("failed to read private key file: %w", err))
+	}
+
+	privateKey, err := identity.PrivateKeyFromPEM(privateKeyPEM)
+	if err != nil {
+		panic(err)
+	}
+
+	sign, err := identity.NewPrivateKeySign(privateKey)
+	if err != nil {
+		panic(err)
+	}
+
+	return sign
+}
+
+func readFirstFile(dirPath string) ([]byte, error) {
+	dir, err := os.Open(dirPath)
+	if err != nil {
+		return nil, err
+	}
+
+	fileNames, err := dir.Readdirnames(1)
+	if err != nil {
+		return nil, err
+	}
+
+	return os.ReadFile(path.Join(dirPath, fileNames[0]))
+}

off_chain_data/application-go/contract.go

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2024 IBM All Rights Reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package main
+
+import (
+	"strconv"
+
+	"github.com/hyperledger/fabric-gateway/pkg/client"
+)
+
+type asset struct {
+	ID             string
+	Color          string
+	Size           uint64
+	Owner          string
+	AppraisedValue uint64
+}
+
+type assetTransferBasic struct {
+	contract *client.Contract
+}
+
+func newAssetTransferBasic(contract *client.Contract) *assetTransferBasic {
+	return &assetTransferBasic{contract}
+}
+
+func (atb *assetTransferBasic) createAsset(anAsset asset) {
+	if _, err := atb.contract.Submit(
+		"CreateAsset",
+		client.WithArguments(
+			anAsset.ID,
+			anAsset.Color,
+			strconv.FormatUint(anAsset.Size, 10),
+			anAsset.Owner,
+			strconv.FormatUint(anAsset.AppraisedValue, 10),
+		)); err != nil {
+		panic(err)
+	}
+}
+
+func (atb *assetTransferBasic) transferAsset(id, newOwner string) string {
+	result, err := atb.contract.Submit(
+		"TransferAsset",
+		client.WithArguments(
+			id,
+			newOwner,
+		),
+	)
+	if err != nil {
+		panic(err)
+	}
+
+	return string(result)
+}
+
+func (atb *assetTransferBasic) deleteAsset(id string) {
+	if _, err := atb.contract.Submit(
+		"DeleteAsset",
+		client.WithArguments(
+			id,
+		),
+	); err != nil {
+		panic(err)
+	}
+}
+
+func (atb *assetTransferBasic) getAllAssets() []byte {
+	result, err := atb.contract.Evaluate("GetAllAssets")
+	if err != nil {
+		panic(err)
+	}
+	return result
+}

off_chain_data/application-go/getAllAssets.go

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2024 IBM All Rights Reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+
+	"github.com/hyperledger/fabric-gateway/pkg/client"
+	"google.golang.org/grpc"
+)
+
+func getAllAssets(clientConnection *grpc.ClientConn) {
+	id, options := newConnectOptions(clientConnection)
+	gateway, err := client.Connect(id, options...)
+	if err != nil {
+		panic((err))
+	}
+	defer gateway.Close()
+
+	contract := gateway.GetNetwork(channelName).GetContract(chaincodeName)
+	smartContract := newAssetTransferBasic(contract)
+	assets := smartContract.getAllAssets()
+
+	fmt.Printf("%s\n", formatJSON(assets))
+}
+
+func formatJSON(data []byte) string {
+	var prettyJSON bytes.Buffer
+	if err := json.Indent(&prettyJSON, data, "", "  "); err != nil {
+		panic(fmt.Errorf("failed to parse JSON: %w", err))
+	}
+	return prettyJSON.String()
+}

off_chain_data/application-go/go.mod

@@ -0,0 +1,20 @@
+module offChainData
+
+go 1.22.0
+
+require (
+	github.com/hyperledger/fabric-gateway v1.7.0
+	google.golang.org/grpc v1.67.1
+)
+
+require (
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/hyperledger/fabric-protos-go-apiv2 v0.3.4 // indirect
+	github.com/miekg/pkcs11 v1.1.1 // indirect
+	golang.org/x/crypto v0.28.0 // indirect
+	golang.org/x/net v0.28.0 // indirect
+	golang.org/x/sys v0.26.0 // indirect
+	golang.org/x/text v0.19.0 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 // indirect
+	google.golang.org/protobuf v1.35.1 // indirect
+)

off_chain_data/application-go/go.sum

@@ -0,0 +1,34 @@
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