Implement 'createblockchain' command

blockchain.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"log"
+	"os"
 
 	"github.com/boltdb/bolt"
 )
@@ -160,8 +161,21 @@ func (i *BlockchainIterator) Next() *Block {
 	return block
 }
 
+func dbExists() bool {
+	if _, err := os.Stat(dbFile); os.IsNotExist(err) {
+		return false
+	}
+
+	return true
+}
+
 // NewBlockchain creates a new Blockchain with genesis Block
 func NewBlockchain(address string) *Blockchain {
+	if dbExists() == false {
+		fmt.Println("No existing blockchain found. Creating one first.")
+		os.Exit(1)
+	}
+
 	var tip []byte
 	db, err := bolt.Open(dbFile, 0600, nil)
 	if err != nil {
@@ -170,9 +184,34 @@ func NewBlockchain(address string) *Blockchain {
 
 	err = db.Update(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte(blocksBucket))
+		tip = b.Get([]byte("l"))
 
-		if b == nil {
+		return nil
-			fmt.Println("No existing blockchain found. Creating a new one...")
+	})
+
+	if err != nil {
+		log.Panic(err)
+	}
+
+	bc := Blockchain{tip, db}
+
+	return &bc
+}
+
+// CreateBlockchain creates a new blockchain DB
+func CreateBlockchain(address string) *Blockchain {
+	if dbExists() {
+		fmt.Println("Blockchain already exists.")
+		os.Exit(1)
+	}
+
+	var tip []byte
+	db, err := bolt.Open(dbFile, 0600, nil)
+	if err != nil {
+		log.Panic(err)
+	}
+
+	err = db.Update(func(tx *bolt.Tx) error {
 		cbtx := NewCoinbaseTX(address, genesisCoinbase)
 		genesis := NewGenesisBlock(cbtx)
 
@@ -191,9 +230,6 @@ func NewBlockchain(address string) *Blockchain {
 			log.Panic(err)
 		}
 		tip = genesis.Hash
-		} else {
-			tip = b.Get([]byte("l"))
-		}
 
 		return nil
 	})

cli.go

@@ -9,14 +9,21 @@ import (
 )
 
 // CLI responsible for processing command line arguments
-type CLI struct {
+type CLI struct{}
-	bc *Blockchain
+
+func (cli *CLI) createBlockchain(address string) {
+	bc := CreateBlockchain(address)
+	bc.db.Close()
+	fmt.Println("Done!")
 }
 
 func (cli *CLI) getBalance(address string) {
+	bc := NewBlockchain(address)
+	defer bc.db.Close()
+
 	balance := 0
 
-	utxs := cli.bc.FindUnspentTransactions(address)
+	utxs := bc.FindUnspentTransactions(address)
 
 	for _, tx := range utxs {
 		for _, out := range tx.Vout {
@@ -32,6 +39,7 @@ func (cli *CLI) getBalance(address string) {
 func (cli *CLI) printUsage() {
 	fmt.Println("Usage:")
 	fmt.Println("  getbalance -address ADDRESS - Get balance of ADDRESS")
+	fmt.Println("  createblockchain -address ADDRESS - Create a blockchain and send genesis block reward to ADDRESS")
 	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")
 }
@@ -44,7 +52,11 @@ func (cli *CLI) validateArgs() {
 }
 
 func (cli *CLI) printChain() {
-	bci := cli.bc.Iterator()
+	// TODO: Fix this
+	bc := NewBlockchain("")
+	defer bc.db.Close()
+
+	bci := bc.Iterator()
 
 	for {
 		block := bci.Next()
@@ -62,8 +74,11 @@ func (cli *CLI) printChain() {
 }
 
 func (cli *CLI) send(from, to string, amount int) {
-	tx := NewUTXOTransaction(from, to, amount)
+	bc := NewBlockchain(from)
-	cli.bc.AddBlock([]*Transaction{tx})
+	defer bc.db.Close()
+
+	tx := NewUTXOTransaction(from, to, amount, bc)
+	bc.AddBlock([]*Transaction{tx})
 	fmt.Println("Success!")
 }
 
@@ -72,10 +87,12 @@ func (cli *CLI) Run() {
 	cli.validateArgs()
 
 	getBalanceCmd := flag.NewFlagSet("getbalance", flag.ExitOnError)
+	createBlockchainCmd := flag.NewFlagSet("createblockchain", flag.ExitOnError)
 	sendCmd := flag.NewFlagSet("send", flag.ExitOnError)
 	printChainCmd := flag.NewFlagSet("printchain", flag.ExitOnError)
 
 	getBalanceAddress := getBalanceCmd.String("address", "", "The address to get balance for")
+	createBlockchainAddress := createBlockchainCmd.String("address", "", "The address to send genesis block reward to")
 	sendFrom := sendCmd.String("from", "", "Source wallet address")
 	sendTo := sendCmd.String("to", "", "Destination wallet address")
 	sendAmount := sendCmd.Int("amount", 0, "Amount to send")
@@ -86,6 +103,11 @@ func (cli *CLI) Run() {
 		if err != nil {
 			log.Panic(err)
 		}
+	case "createblockchain":
+		err := createBlockchainCmd.Parse(os.Args[2:])
+		if err != nil {
+			log.Panic(err)
+		}
 	case "printchain":
 		err := printChainCmd.Parse(os.Args[2:])
 		if err != nil {
@@ -109,6 +131,14 @@ func (cli *CLI) Run() {
 		cli.getBalance(*getBalanceAddress)
 	}
 
+	if createBlockchainCmd.Parsed() {
+		if *createBlockchainAddress == "" {
+			createBlockchainCmd.Usage()
+			os.Exit(1)
+		}
+		cli.createBlockchain(*createBlockchainAddress)
+	}
+
 	if printChainCmd.Parsed() {
 		cli.printChain()
 	}

main.go

@@ -1,9 +1,6 @@
 package main
 
 func main() {
-	bc := NewBlockchain()
+	cli := CLI{}
-	defer bc.db.Close()
-
-	cli := CLI{bc}
 	cli.Run()
 }