Add comments to ledgernext example client application

Change-Id: I34edfd399ebfe05045477f7a46e0b741c18dc64c
Signed-off-by: denyeart <enyeart@us.ibm.com>

core/ledgernext/kvledger/example/app.go

@@ -56,6 +56,8 @@ func (app *App) Init(initialBalances map[string]int) (*protos.Transaction2, erro
 
 // TransferFunds simulates a transaction for transferring fund from fromAccount to toAccount
 func (app *App) TransferFunds(fromAccount string, toAccount string, transferAmt int) (*protos.Transaction2, error) {
+
+	// act as endorsing peer shim code to simulate a transaction on behalf of chaincode
 	var txSimulator ledger.TxSimulator
 	var err error
 	if txSimulator, err = app.ledger.NewTxSimulator(); err != nil {
@@ -83,6 +85,9 @@ func (app *App) TransferFunds(fromAccount string, toAccount string, transferAmt
 	if txSimulationResults, err = txSimulator.GetTxSimulationResults(); err != nil {
 		return nil, err
 	}
+
+	// act as endorsing peer to create an Action with the SimulationResults
+	// then act as SDK to create a Transaction with the EndorsedAction
 	tx := constructTransaction(txSimulationResults)
 	return tx, nil
 }

core/ledgernext/kvledger/example/main/example.go

@@ -38,6 +38,10 @@ var consenter *example.Consenter
 var accounts = []string{"account1", "account2", "account3", "account4"}
 
 func init() {
+
+	// Initialization will get a handle to the ledger at the specified path
+	// Note, if subledgers are supported in the future,
+	// the various ledgers could be created/managed at this level
 	os.RemoveAll(ledgerPath)
 	ledgerConf := kvledger.NewConf(ledgerPath, 0)
 	var err error
@@ -52,12 +56,31 @@ func init() {
 
 func main() {
 	defer finalLedger.Close()
+
+	// Each of the functions here will emulate endorser, orderer,
+	// and committer by calling ledger APIs to similate the proposal,
+	// get simulation results, create a transaction, add it to a block,
+	// and then commit the block.
+
+	// Initialize account balances by setting each account to 100
 	initApp()
+
 	printBalances()
+
+	// Transfer money between accounts. Exercises happy path.
 	transferFunds()
+
 	printBalances()
+
+	// Attempt to transfer more money than account balance
+	// Exercises simulation failure
 	tryInvalidTransfer()
+
+	// Attempt two transactions, the first one will have sufficient funds,
+	// the second one should fail since the account balance was updated
+	// (by the first tran) since simulation time. This exercises the MVCC check.
 	tryDoubleSpend()
+
 	printBalances()
 }
 
@@ -79,7 +102,11 @@ func transferFunds() {
 	handleError(err, true)
 	tx2, err := app.TransferFunds("account3", "account4", 50)
 	handleError(err, true)
+
+	// act as ordering service (consenter) to create a Raw Block from the Transaction
 	rawBlock := consenter.ConstructBlock(tx1, tx2)
+
+	// act as committing peer to commit the Raw Block
 	finalBlock, invalidTx, err := committer.CommitBlock(rawBlock)
 	handleError(err, true)
 	printBlocksInfo(rawBlock, finalBlock, invalidTx)