Add Go smart contract implementation for full-stack-asset-transfer-guide

Author: vishalmore90

full-stack-asset-transfer-guide/contracts/asset-transfer-go/asset-transfer-chaincode-vars.yml

@@ -0,0 +1,11 @@
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+---
+smart_contract_name: "asset-transfer"
+smart_contract_version: "1.0.0"
+smart_contract_sequence: 1
+smart_contract_package: "asset-transfer.tgz"
+# smart_contract_constructor: "initLedger"
+smart_contract_endorsement_policy: ""
+smart_contract_collections_file: ""

full-stack-asset-transfer-guide/contracts/asset-transfer-go/asset_transfer.go

@@ -0,0 +1,363 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/hyperledger/fabric-chaincode-go/v2/pkg/statebased"
+	"github.com/hyperledger/fabric-contract-api-go/v2/contractapi"
+)
+
+type SmartContract struct {
+	contractapi.Contract
+}
+
+type Asset struct {
+	AppraisedValue int    `json:"AppraisedValue"`
+	Color          string `json:"Color"`
+	ID             string `json:"ID"`
+	Owner          string `json:"Owner"`
+	Size           int    `json:"Size"`
+}
+
+type OwnerIdentifier struct {
+	Org  string `json:"org"`
+	User string `json:"user"`
+}
+
+type AssetCreateInput struct {
+	ID             string  `json:"ID"`
+	Color          string  `json:"Color,omitempty"`
+	Owner          *string `json:"Owner,omitempty"`
+	AppraisedValue *int    `json:"AppraisedValue,omitempty"`
+	Size           *int    `json:"Size,omitempty"`
+}
+
+type AssetUpdateInput struct {
+	ID             string  `json:"ID"`
+	Color          *string `json:"Color,omitempty"`
+	AppraisedValue *int    `json:"AppraisedValue,omitempty"`
+	Size           *int    `json:"Size,omitempty"`
+	Owner          *string `json:"Owner,omitempty"`
+}
+
+func (s *SmartContract) CreateAsset(ctx contractapi.TransactionContextInterface, assetJSON string) error {
+	input, err := parseCreateInput(assetJSON)
+	if err != nil {
+		return err
+	}
+
+	exists, err := s.AssetExists(ctx, input.ID)
+	if err != nil {
+		return err
+	}
+	if exists {
+		return fmt.Errorf("the asset %s already exists", input.ID)
+	}
+
+	owner, err := clientIdentifier(ctx, input.Owner)
+	if err != nil {
+		return err
+	}
+
+	asset := Asset{
+		ID:             input.ID,
+		Color:          input.Color,
+		Size:           valueOrDefault(input.Size, 0),
+		Owner:          marshalOwner(owner),
+		AppraisedValue: valueOrDefault(input.AppraisedValue, 0),
+	}
+
+	assetBytes, err := json.Marshal(asset)
+	if err != nil {
+		return err
+	}
+
+	if err := ctx.GetStub().PutState(asset.ID, assetBytes); err != nil {
+		return fmt.Errorf("failed to put asset in world state: %w", err)
+	}
+
+	if err := setEndorsingOrgs(ctx, asset.ID, owner.Org); err != nil {
+		return err
+	}
+
+	return ctx.GetStub().SetEvent("CreateAsset", assetBytes)
+}
+
+func (s *SmartContract) ReadAsset(ctx contractapi.TransactionContextInterface, id string) (*Asset, error) {
+	asset, err := s.readAsset(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	return asset, nil
+}
+
+func (s *SmartContract) UpdateAsset(ctx contractapi.TransactionContextInterface, assetJSON string) error {
+	input, err := parseUpdateInput(assetJSON)
+	if err != nil {
+		return err
+	}
+
+	existingAsset, err := s.readAsset(ctx, input.ID)
+	if err != nil {
+		return err
+	}
+
+	if err := hasWritePermission(ctx, existingAsset); err != nil {
+		return err
+	}
+
+	updatedAsset := *existingAsset
+	if input.Color != nil {
+		updatedAsset.Color = *input.Color
+	}
+	if input.Size != nil {
+		updatedAsset.Size = *input.Size
+	}
+	if input.AppraisedValue != nil {
+		updatedAsset.AppraisedValue = *input.AppraisedValue
+	}
+	// Owner cannot be updated via UpdateAsset. TransferAsset must be used for ownership changes.
+
+	assetBytes, err := json.Marshal(updatedAsset)
+	if err != nil {
+		return err
+	}
+
+	if err := ctx.GetStub().PutState(updatedAsset.ID, assetBytes); err != nil {
+		return fmt.Errorf("failed to put updated asset in world state: %w", err)
+	}
+
+	clientOrg, err := getClientOrg(ctx)
+	if err != nil {
+		return err
+	}
+	if err := setEndorsingOrgs(ctx, updatedAsset.ID, clientOrg); err != nil {
+		return err
+	}
+
+	if err := ctx.GetStub().SetEvent("UpdateAsset", assetBytes); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (s *SmartContract) DeleteAsset(ctx contractapi.TransactionContextInterface, id string) error {
+	asset, err := s.readAsset(ctx, id)
+	if err != nil {
+		return err
+	}
+
+	if err := hasWritePermission(ctx, asset); err != nil {
+		return err
+	}
+
+	if err := ctx.GetStub().DelState(id); err != nil {
+		return fmt.Errorf("failed to delete asset %s: %w", id, err)
+	}
+
+	return ctx.GetStub().SetEvent("DeleteAsset", []byte(id))
+}
+
+func (s *SmartContract) AssetExists(ctx contractapi.TransactionContextInterface, id string) (bool, error) {
+	assetBytes, err := ctx.GetStub().GetState(id)
+	if err != nil {
+		return false, fmt.Errorf("failed to read world state: %w", err)
+	}
+
+	return len(assetBytes) > 0, nil
+}
+
+func (s *SmartContract) TransferAsset(ctx contractapi.TransactionContextInterface, id string, newOwner string, newOwnerOrg string) error {
+	asset, err := s.readAsset(ctx, id)
+	if err != nil {
+		return err
+	}
+
+	if err := hasWritePermission(ctx, asset); err != nil {
+		return err
+	}
+
+	owner := ownerIdentifier(newOwner, newOwnerOrg)
+	ownerJSON, err := json.Marshal(owner)
+	if err != nil {
+		return err
+	}
+	asset.Owner = string(ownerJSON)
+
+	assetBytes, err := json.Marshal(asset)
+	if err != nil {
+		return err
+	}
+
+	if err := ctx.GetStub().PutState(id, assetBytes); err != nil {
+		return fmt.Errorf("failed to update asset owner in world state: %w", err)
+	}
+
+	if err := setEndorsingOrgs(ctx, id, newOwnerOrg); err != nil {
+		return err
+	}
+
+	return ctx.GetStub().SetEvent("TransferAsset", assetBytes)
+}
+
+func (s *SmartContract) GetAllAssets(ctx contractapi.TransactionContextInterface) ([]Asset, error) {
+	resultsIterator, err := ctx.GetStub().GetStateByRange("", "")
+	if err != nil {
+		return nil, err
+	}
+	defer resultsIterator.Close()
+
+	var assets []Asset
+	for resultsIterator.HasNext() {
+		queryResponse, err := resultsIterator.Next()
+		if err != nil {
+			return nil, err
+		}
+
+		var asset Asset
+		if err := json.Unmarshal(queryResponse.Value, &asset); err != nil {
+			continue
+		}
+		assets = append(assets, asset)
+	}
+
+	return assets, nil
+}
+
+func (s *SmartContract) readAsset(ctx contractapi.TransactionContextInterface, id string) (*Asset, error) {
+	assetBytes, err := ctx.GetStub().GetState(id)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read world state: %w", err)
+	}
+	if assetBytes == nil || len(assetBytes) == 0 {
+		return nil, fmt.Errorf("sorry, asset %s has not been created", id)
+	}
+
+	var asset Asset
+	if err := json.Unmarshal(assetBytes, &asset); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal asset %s: %w", id, err)
+	}
+
+	return &asset, nil
+}
+
+func parseCreateInput(assetJSON string) (*AssetCreateInput, error) {
+	var input AssetCreateInput
+	if err := json.Unmarshal([]byte(assetJSON), &input); err != nil {
+		return nil, fmt.Errorf("failed to parse asset JSON: %w", err)
+	}
+
+	if input.ID == "" {
+		return nil, fmt.Errorf("missing ID")
+	}
+
+	return &input, nil
+}
+
+func parseUpdateInput(assetJSON string) (*AssetUpdateInput, error) {
+	var input AssetUpdateInput
+	if err := json.Unmarshal([]byte(assetJSON), &input); err != nil {
+		return nil, fmt.Errorf("failed to parse asset JSON: %w", err)
+	}
+
+	if input.ID == "" {
+		return nil, fmt.Errorf("no asset ID specified")
+	}
+
+	return &input, nil
+}
+
+func valueOrDefault(value *int, def int) int {
+	if value == nil {
+		return def
+	}
+
+	return *value
+}
+
+func hasWritePermission(ctx contractapi.TransactionContextInterface, asset *Asset) error {
+	clientOrg, err := getClientOrg(ctx)
+	if err != nil {
+		return err
+	}
+
+	var owner OwnerIdentifier
+	if err := json.Unmarshal([]byte(asset.Owner), &owner); err != nil {
+		return fmt.Errorf("invalid owner identity: %w", err)
+	}
+
+	if clientOrg != owner.Org {
+		return fmt.Errorf("only owner can update assets")
+	}
+
+	return nil
+}
+
+func getClientOrg(ctx contractapi.TransactionContextInterface) (string, error) {
+	return ctx.GetClientIdentity().GetMSPID()
+}
+
+func clientIdentifier(ctx contractapi.TransactionContextInterface, user *string) (OwnerIdentifier, error) {
+	clientOrg, err := getClientOrg(ctx)
+	if err != nil {
+		return OwnerIdentifier{}, err
+	}
+
+	userName := ""
+	if user != nil {
+		userName = *user
+	} else {
+		userName, err = clientCommonName(ctx)
+		if err != nil {
+			return OwnerIdentifier{}, err
+		}
+	}
+
+	return OwnerIdentifier{
+		Org:  clientOrg,
+		User: userName,
+	}, nil
+}
+
+func clientCommonName(ctx contractapi.TransactionContextInterface) (string, error) {
+	cert, err := ctx.GetClientIdentity().GetX509Certificate()
+	if err != nil {
+		return "", fmt.Errorf("unable to get client certificate: %w", err)
+	}
+
+	if cert.Subject.CommonName == "" {
+		return "", fmt.Errorf("unable to identify client identity common name")
+	}
+
+	return cert.Subject.CommonName, nil
+}
+
+func marshalOwner(owner OwnerIdentifier) string {
+	ownerBytes, _ := json.Marshal(owner)
+	return string(ownerBytes)
+}
+
+func ownerIdentifier(user string, org string) OwnerIdentifier {
+	return OwnerIdentifier{Org: org, User: user}
+}
+
+func setEndorsingOrgs(ctx contractapi.TransactionContextInterface, ledgerKey string, orgs ...string) error {
+	policy, err := statebased.NewStateEP(nil)
+	if err != nil {
+		return err
+	}
+
+	if err = policy.AddOrgs(statebased.RoleTypePeer, orgs...); err != nil {
+		return err
+	}
+
+	policyBytes, err := policy.Policy()
+	if err != nil {
+		return err
+	}
+
+	return ctx.GetStub().SetStateValidationParameter(ledgerKey, policyBytes)
+}