FABG-933 Gateway package for Go SDK (#51)

* FABG-933 Gateway package for Go SDK

First user story for Gateway SDK
Basic framework
Unit tests
Integration test

Signed-off-by: andrew-coleman <andrew_coleman@uk.ibm.com>

* FABG-933 Gateway package for Go SDK

Incorporate review feedback

Signed-off-by: andrew-coleman <andrew_coleman@uk.ibm.com>

pkg/gateway/contract.go

@@ -0,0 +1,63 @@
+/*
+Copyright 2020 IBM All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package gateway
+
+import "github.com/hyperledger/fabric-sdk-go/pkg/client/channel"
+
+// A Contract object represents a smart contract instance in a network.
+// Applications should get a Contract instance from a Network using the GetContract method
+type Contract struct {
+	chaincodeID string
+	name        string
+	network     *Network
+	client      *channel.Client
+}
+
+func newContract(network *Network, chaincodeID string, name string) *Contract {
+	return &Contract{network: network, client: network.client, chaincodeID: chaincodeID, name: name}
+}
+
+// Name returns the name of the smart contract
+func (c *Contract) Name() string {
+	return c.chaincodeID
+}
+
+// EvaluateTransaction will evaluate a transaction function and return its results.
+// The transaction function 'name'
+// will be evaluated on the endorsing peers but the responses will not be sent to
+// the ordering service and hence will not be committed to the ledger.
+// This can be used for querying the world state.
+func (c *Contract) EvaluateTransaction(name string, args ...string) ([]byte, error) {
+	txn, err := c.CreateTransaction(name)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return txn.Evaluate(args...)
+}
+
+// SubmitTransaction will submit a transaction to the ledger. The transaction function 'name'
+// will be evaluated on the endorsing peers and then submitted to the ordering service
+// for committing to the ledger.
+func (c *Contract) SubmitTransaction(name string, args ...string) ([]byte, error) {
+	txn, err := c.CreateTransaction(name)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return txn.Submit(args...)
+}
+
+// CreateTransaction creates an object representing a specific invocation of a transaction
+// function implemented by this contract, and provides more control over
+// the transaction invocation using the optional arguments. A new transaction object must
+// be created for each transaction invocation.
+func (c *Contract) CreateTransaction(name string, args ...TransactionOption) (*Transaction, error) {
+	return newTransaction(name, c, args...)
+}

pkg/gateway/contract_test.go

@@ -0,0 +1,84 @@
+/*
+Copyright 2020 IBM All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package gateway
+
+import (
+	"testing"
+)
+
+func TestCreateTransaction(t *testing.T) {
+	c := mockChannelProvider("mychannel")
+
+	gw := &Gateway{}
+
+	nw, err := newNetwork(gw, c)
+
+	if err != nil {
+		t.Fatalf("Failed to create network: %s", err)
+	}
+
+	contr := nw.GetContract("contract1")
+
+	txn, err := contr.CreateTransaction("txn1")
+
+	if err != nil {
+		t.Fatalf("Failed to create transaction: %s", err)
+	}
+
+	name := txn.name
+	if name != "txn1" {
+		t.Fatalf("Incorrect transaction name: %s", name)
+	}
+}
+
+func TestSubmitTransaction(t *testing.T) {
+	c := mockChannelProvider("mychannel")
+
+	gw := &Gateway{}
+
+	nw, err := newNetwork(gw, c)
+
+	if err != nil {
+		t.Fatalf("Failed to create network: %s", err)
+	}
+
+	contr := nw.GetContract("contract1")
+
+	result, err := contr.SubmitTransaction("txn1")
+
+	if err != nil {
+		t.Fatalf("Failed to submit transaction: %s", err)
+	}
+
+	if string(result) != "abc" {
+		t.Fatalf("Incorrect transaction result: %s", result)
+	}
+}
+
+func TestEvaluateTransaction(t *testing.T) {
+	c := mockChannelProvider("mychannel")
+
+	gw := &Gateway{}
+
+	nw, err := newNetwork(gw, c)
+
+	if err != nil {
+		t.Fatalf("Failed to create network: %s", err)
+	}
+
+	contr := nw.GetContract("contract1")
+
+	result, err := contr.EvaluateTransaction("txn1")
+
+	if err != nil {
+		t.Fatalf("Failed to evaluate transaction: %s", err)
+	}
+
+	if string(result) != "abc" {
+		t.Fatalf("Incorrect transaction result: %s", result)
+	}
+}

pkg/gateway/defaultcommithandlers.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2020 IBM All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package gateway
+
+type list struct {
+	None       CommitHandlerFactory
+	OrgAll     CommitHandlerFactory
+	OrgAny     CommitHandlerFactory
+	NetworkAll CommitHandlerFactory
+	NetworkAny CommitHandlerFactory
+}
+
+// DefaultCommitHandlers provides the built-in commit handler implementations.
+var DefaultCommitHandlers = &list{
+	None:       nil,
+	OrgAll:     orgAll,
+	OrgAny:     orgAny,
+	NetworkAll: networkAll,
+	NetworkAny: networkAny,
+}
+
+type commithandler struct {
+	transactionID string
+	network       Network
+}
+
+func (ch *commithandler) StartListening() {
+}
+
+func (ch *commithandler) WaitForEvents(timeout int64) {
+}
+
+func (ch *commithandler) CancelListening() {
+}
+
+type commithandlerfactory struct {
+}
+
+func (chf *commithandlerfactory) Create(txid string, network Network) CommitHandler {
+	return &commithandler{
+		transactionID: txid,
+		network:       network,
+	}
+}
+
+var orgAll = &commithandlerfactory{}
+var orgAny = &commithandlerfactory{}
+var networkAll = &commithandlerfactory{}
+var networkAny = &commithandlerfactory{}