ndinh215 · February 23, 2023 03:23 · Dec 6, 2021 · Dec 2, 2021 · Nov 30, 2021
diff --git a/blockchain.go b/blockchain.go
@@ -76,9 +76,15 @@ func (b Blockchain) isValid() bool {
 	return true
 }
 
+
 func main() {
-	blockchain := CreateBlockchain(2)
-	blockchain.addBlock("Alice", "Bob", 5)
-	blockchain.addBlock("John", "Bob", 2)
-	fmt.Println(blockchain.isValid())
+        // create a new blockchain instance with a mining difficulty of 2
+        blockchain := CreateBlockchain(2)
+
+        // record transactions on the blockchain for Alice, Bob, and John
+        blockchain.addBlock("Alice", "Bob", 5)
+        blockchain.addBlock("John", "Bob", 2)
+
+        // check if the blockchain is valid; expecting true
+        fmt.Println(blockchain.isValid())
 }
diff --git a/blockchain.go b/blockchain.go
@@ -10,17 +10,17 @@ import (
 )
 
 type Block struct {
-	data map[string]string
-	hash string
+	data         map[string]interface{}
+	hash         string
 	previousHash string
-	timestamp time.Time
-	pow int
+	timestamp    time.Time
+	pow          int
 }
 
 type Blockchain struct {
 	genesisBlock Block
-	chain []Block
-	difficulty int
+	chain        []Block
+	difficulty   int
 }
 
 func (b Block) calculateHash() string {
@@ -39,7 +39,7 @@ func (b *Block) mine(difficulty int) {
 
 func CreateBlockchain(difficulty int) Blockchain {
 	genesisBlock := Block{
-		hash: "0",
+		hash:      "0",
 		timestamp: time.Now(),
 	}
 	return Blockchain{
@@ -50,16 +50,16 @@ func CreateBlockchain(difficulty int) Blockchain {
 }
 
 func (b *Blockchain) addBlock(from, to string, amount float64) {
-	blockData := map[string]string{
-		"from": from,
-		"to": to,
-		"amount": fmt.Sprintf("%f", amount),
+	blockData := map[string]interface{}{
+		"from":   from,
+		"to":     to,
+		"amount": amount,
 	}
-	lastBlock := b.chain[len(b.chain) - 1]
+	lastBlock := b.chain[len(b.chain)-1]
 	newBlock := Block{
-		data: blockData,
+		data:         blockData,
 		previousHash: lastBlock.hash,
-		timestamp: time.Now(),
+		timestamp:    time.Now(),
 	}
 	newBlock.mine(b.difficulty)
 	b.chain = append(b.chain, newBlock)
@@ -68,7 +68,7 @@ func (b *Blockchain) addBlock(from, to string, amount float64) {
 func (b Blockchain) isValid() bool {
 	for i := range b.chain[1:] {
 		previousBlock := b.chain[i]
-		currentBlock := b.chain[i + 1]
+		currentBlock := b.chain[i+1]
 		if currentBlock.hash != currentBlock.calculateHash() || currentBlock.previousHash != previousBlock.hash {
 			return false
 		}

diff --git a/blockchain.go b/blockchain.go
@@ -0,0 +1,84 @@
+package main
+
+import (
+	"crypto/sha256"
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type Block struct {
+	data map[string]string
+	hash string
+	previousHash string
+	timestamp time.Time
+	pow int
+}
+
+type Blockchain struct {
+	genesisBlock Block
+	chain []Block
+	difficulty int
+}
+
+func (b Block) calculateHash() string {
+	data, _ := json.Marshal(b.data)
+	blockData := b.previousHash + string(data) + b.timestamp.String() + strconv.Itoa(b.pow)
+	blockHash := sha256.Sum256([]byte(blockData))
+	return fmt.Sprintf("%x", blockHash)
+}
+
+func (b *Block) mine(difficulty int) {
+	for !strings.HasPrefix(b.hash, strings.Repeat("0", difficulty)) {
+		b.pow++
+		b.hash = b.calculateHash()
+	}
+}
+
+func CreateBlockchain(difficulty int) Blockchain {
+	genesisBlock := Block{
+		hash: "0",
+		timestamp: time.Now(),
+	}
+	return Blockchain{
+		genesisBlock,
+		[]Block{genesisBlock},
+		difficulty,
+	}
+}
+
+func (b *Blockchain) addBlock(from, to string, amount float64) {
+	blockData := map[string]string{
+		"from": from,
+		"to": to,
+		"amount": fmt.Sprintf("%f", amount),
+	}
+	lastBlock := b.chain[len(b.chain) - 1]
+	newBlock := Block{
+		data: blockData,
+		previousHash: lastBlock.hash,
+		timestamp: time.Now(),
+	}
+	newBlock.mine(b.difficulty)
+	b.chain = append(b.chain, newBlock)
+}
+
+func (b Blockchain) isValid() bool {
+	for i := range b.chain[1:] {
+		previousBlock := b.chain[i]
+		currentBlock := b.chain[i + 1]
+		if currentBlock.hash != currentBlock.calculateHash() || currentBlock.previousHash != previousBlock.hash {
+			return false
+		}
+	}
+	return true
+}
+
+func main() {
+	blockchain := CreateBlockchain(2)
+	blockchain.addBlock("Alice", "Bob", 5)
+	blockchain.addBlock("John", "Bob", 2)
+	fmt.Println(blockchain.isValid())
+}