refactor transaction and add logic of FindUTXO and FindSpendableOutputs and FindUnspentTransactions

blockchain.go

@@ -1,5 +1,9 @@
 package main
 
+import (
+	"encoding/hex"
+)
+
 // Blockchain keeps a sequence of Blocks
 type Blockchain struct {
 	blocks []*Block
@@ -18,3 +22,76 @@ func (bc *Blockchain) AddBlock(data string) {
 func NewBlockchain() *Blockchain {
 	return &Blockchain{[]*Block{NewGenesisBlock()}}
 }
+
+// FindUnspentTransactions returns a list of transactions containing unspent outputs
+func (bc *Blockchain) FindUnspentTransactions(address string) []Transaction {
+	var unspentTXs []Transaction
+	spentTXOs := make(map[string][]int)
+
+	for index := len(bc.blocks); index >= 0; index-- {
+		block := bc.blocks[index];
+
+		BreakTransaction:
+		for _, tx := range block.Transactions {
+			txId := hex.EncodeToString(tx.Id)
+
+			idx := -1
+			if spentTXOs[txId] != nil {
+				idx = 0
+			}
+			for outIdx, txOutput  := range tx.txOutput {
+				if idx >= 0  spentTXOs[txId][idx] == outIdx {
+					continue
+				}
+
+				if txOutput.address == address {
+					unspentTXs = append(unspentTXs, *tx)
+					continue BreakTransaction
+				}
+			}
+		}
+	}
+	return unspentTXs
+}
+
+// FindUTXO finds and returns all unspent transaction outputs
+func (bc *Blockchain) FindUTXO(address string) []TXOutput {
+	var UTXOs []TXOutput
+	unspentTXs := bc.FindUnspentTransactions(address)
+
+	for _, tx := range unspentTXs {
+		for _, txOutput := range tx.txOutput {
+			if txOutput.address == address {
+				UTXOs = append(UTXOs, txOutput)
+				break
+			}
+		}
+	}
+
+	return UTXOs
+}
+
+// FindSpendableOutputs finds and returns unspent outputs to reference in inputs
+func (bc *Blockchain) FindSpendableOutputs(address string, amount int) (int, map[string][]int) {
+	unspentOutputs := make(map[string][]int)
+	unspentTXs := bc.FindUnspentTransactions(address)
+	accumulated := 0
+
+Work:
+	for _, tx := range unspentTXs {
+		txID := hex.EncodeToString(tx.ID)
+
+		for outIdx, txOutput := range tx.txOutput {
+			if txOutput.address == address && accumulated < amount {
+				accumulated += txOutput.value
+				unspentOutputs[txID] = append(unspentOutputs[txID], outIdx)
+
+				if accumulated >= amount {
+					break Work
+				}
+			}
+		}
+	}
+
+	return accumulated, unspentOutputs
+}

transaction.go

@@ -9,24 +9,24 @@ import (
 
 // Transaction represents a Bitcoin transaction
 type Transaction struct {
-	ID   []byte
-	Vin  []TXInput
-	Vout []TXOutput
+	id       []byte
+	txInput  []TXInput
+	txOutput []TXOutput
 }
 
 type TXOutput struct {
-	Addresss string
-	Value    int
+	address string
+	value   int
 }
 
 type TXInput struct {
-	Txid     []byte
-	outIndex int
-	Address  string
+	txId          []byte
+	txOutputIndex int
+	address       string
 }
 
 // SetID sets ID of a transaction
-func (tx *Transaction) SetID() {
+func (tx *Transaction) SetId() {
 	var encoded bytes.Buffer
 	var hash [32]byte