From 8efe9e2c0aa16288fb34a3c5465766ee4a3ca3c1 Mon Sep 17 00:00:00 2001
From: Nicholas Rodrigues <nicholasgabriel65@gmail.com>
Date: Thu, 23 May 2024 16:16:48 -0300
Subject: [PATCH] test: transactions integrated with blocks and blockchain

---
 internal/blockchain/blockchain.go     | 57 +++++++++++++++++++++++++++
 internal/transactions/transactions.go | 17 ++++++++
 2 files changed, 74 insertions(+)

diff --git a/internal/blockchain/blockchain.go b/internal/blockchain/blockchain.go
index ba7bd82..d0aa126 100644
--- a/internal/blockchain/blockchain.go
+++ b/internal/blockchain/blockchain.go
@@ -2,6 +2,7 @@ package blockchain
 
 import (
 	"bytes"
+	"encoding/hex"
 	"github.com/NicholasRodrigues/go-chain/internal/transactions"
 )
 
@@ -52,3 +53,59 @@ func (bc *Blockchain) IsValid() bool {
 
 	return true
 }
+
+// FindUnspentTransactions returns a list of transactions containing unspent outputs for an address
+func (bc *Blockchain) FindUnspentTransactions(pubKeyHash []byte) []transactions.Transaction {
+	var unspentTxs []transactions.Transaction
+	spentTXOs := make(map[string][]int)
+
+	for _, block := range bc.Blocks {
+		for _, tx := range block.Transactions {
+			txID := hex.EncodeToString(tx.ID)
+
+		Outputs:
+			for outIdx, out := range tx.Vout {
+				// Check if the output was already spent
+				if spentTXOs[txID] != nil {
+					for _, spentOutIdx := range spentTXOs[txID] {
+						if spentOutIdx == outIdx {
+							continue Outputs
+						}
+					}
+				}
+
+				if out.IsLockedWithKey(pubKeyHash) {
+					unspentTxs = append(unspentTxs, *tx)
+				}
+			}
+
+			// Collect spent outputs
+			if !tx.IsCoinbase() {
+				for _, in := range tx.Vin {
+					if in.UsesKey(pubKeyHash) {
+						inTxID := hex.EncodeToString(in.Txid)
+						spentTXOs[inTxID] = append(spentTXOs[inTxID], in.Vout)
+					}
+				}
+			}
+		}
+	}
+
+	return unspentTxs
+}
+
+// FindUTXO returns unspent transaction outputs for a given address
+func (bc *Blockchain) FindUTXO(pubKeyHash []byte) []transactions.TransactionOutput {
+	var UTXOs []transactions.TransactionOutput
+	unspentTransactions := bc.FindUnspentTransactions(pubKeyHash)
+
+	for _, tx := range unspentTransactions {
+		for _, out := range tx.Vout {
+			if out.IsLockedWithKey(pubKeyHash) {
+				UTXOs = append(UTXOs, out)
+			}
+		}
+	}
+
+	return UTXOs
+}
diff --git a/internal/transactions/transactions.go b/internal/transactions/transactions.go
index 1d53628..730f205 100644
--- a/internal/transactions/transactions.go
+++ b/internal/transactions/transactions.go
@@ -166,3 +166,20 @@ func (tx *Transaction) String() string {
 
 	return strings.Join(lines, "\n")
 }
+
+// IsLockedWithKey checks if the output can be used by the owner of the pubKeyHash
+func (out *TransactionOutput) IsLockedWithKey(pubKeyHash []byte) bool {
+	return bytes.Compare([]byte(out.ScriptPubKey), pubKeyHash) == 0
+}
+
+// UsesKey checks if the input uses the pubKeyHash to unlock the output
+func (in *TransactionInput) UsesKey(pubKeyHash []byte) bool {
+	lockingHash := HashPubKey(in.PubKey)
+	return bytes.Compare(lockingHash, pubKeyHash) == 0
+}
+
+// HashPubKey hashes public key
+func HashPubKey(pubKey []byte) []byte {
+	publicSHA256 := sha256.Sum256(pubKey)
+	return publicSHA256[:]
+}