Implement 'getbalance' command

cli.go

@@ -13,10 +13,27 @@ type CLI struct {
 	bc *Blockchain
 }
 
+func (cli *CLI) getBalance(address string) {
+	balance := 0
+
+	utxs := cli.bc.FindUnspentTransactions(address)
+
+	for _, tx := range utxs {
+		for _, out := range tx.Vout {
+			if out.Unlock(address) {
+				balance += out.Value
+			}
+		}
+	}
+
+	fmt.Printf("Balance of '%s': %d\n", address, balance)
+}
+
 func (cli *CLI) printUsage() {
 	fmt.Println("Usage:")
-	fmt.Println("  printchain - print all the blocks of the blockchain")
+	fmt.Println("  getbalance -address ADDRESS - Get balance of ADDRESS")
-	fmt.Println("  send -from FROM -to TO -amount AMOUNT - send AMOUNT of coins from FROM address to TO")
+	fmt.Println("  printchain - Print all the blocks of the blockchain")
+	fmt.Println("  send -from FROM -to TO -amount AMOUNT - Send AMOUNT of coins from FROM address to TO")
 }
 
 func (cli *CLI) validateArgs() {
@@ -54,14 +71,21 @@ func (cli *CLI) send(from, to string, amount int) {
 func (cli *CLI) Run() {
 	cli.validateArgs()
 
+	getBalanceCmd := flag.NewFlagSet("getbalance", flag.ExitOnError)
 	sendCmd := flag.NewFlagSet("send", flag.ExitOnError)
 	printChainCmd := flag.NewFlagSet("printchain", flag.ExitOnError)
 
+	getBalanceAddress := getBalanceCmd.String("address", "", "The address to get balance for")
 	sendFrom := sendCmd.String("from", "", "Source wallet address")
 	sendTo := sendCmd.String("to", "", "Destination wallet address")
 	sendAmount := sendCmd.Int("amount", 0, "Amount to send")
 
 	switch os.Args[1] {
+	case "getbalance":
+		err := getBalanceCmd.Parse(os.Args[2:])
+		if err != nil {
+			log.Panic(err)
+		}
 	case "printchain":
 		err := printChainCmd.Parse(os.Args[2:])
 		if err != nil {
@@ -77,6 +101,14 @@ func (cli *CLI) Run() {
 		os.Exit(1)
 	}
 
+	if getBalanceCmd.Parsed() {
+		if *getBalanceAddress == "" {
+			getBalanceCmd.Usage()
+			os.Exit(1)
+		}
+		cli.getBalance(*getBalanceAddress)
+	}
+
 	if printChainCmd.Parsed() {
 		cli.printChain()
 	}