From 7c6761d4e1e8425523d407fcb7a143eb89c447bb Mon Sep 17 00:00:00 2001
From: ssilagadze <ssilagadze@purestorage.com>
Date: Thu, 7 Sep 2023 21:38:05 +0200
Subject: [PATCH] add building/decoding merkle path binary from/to merkle path
 json data

---
 merklepathbinary.go      | 72 ++++++++++++++++++++++++++++++++++++++++
 merklepathbinary_test.go | 59 ++++++++++++++++++++++++++++++++
 2 files changed, 131 insertions(+)
 create mode 100644 merklepathbinary.go
 create mode 100644 merklepathbinary_test.go

diff --git a/merklepathbinary.go b/merklepathbinary.go
new file mode 100644
index 0000000..36c0971
--- /dev/null
+++ b/merklepathbinary.go
@@ -0,0 +1,72 @@
+package bc
+
+import (
+	"encoding/hex"
+
+	"github.com/libsv/go-bt/v2"
+)
+
+// Merkle path data model json format according to BRC-58
+type MerklePathData struct {
+	Index uint64   `json:"index"`
+	Path  []string `json:"path"`
+}
+
+// Merkle Path Binary Format according to BRC-71 [index, nLeaves, [leaf0, leaf1, leaf2, ... leafnLeaves-1]]
+type MerklePath string
+
+// Based on merkle path data model builds merkle path binary format
+func BuildMerklePathBinary(merklePath *MerklePathData) (MerklePath, error) {
+	index := bt.VarInt(merklePath.Index)
+	nLeaves := bt.VarInt(len(merklePath.Path))
+
+	// first two arguments in merkle path bynary format are index of the transaction and number of leaves
+	bytes := []byte{}
+	bytes = append(bytes, index.Bytes()...)
+	bytes = append(bytes, nLeaves.Bytes()...)
+
+	// now add each leave into the binary path
+	for _, leave := range merklePath.Path {
+		// decode hex leave into bytes
+		leaveBytes, err := hex.DecodeString(leave)
+		if err != nil {
+			return "", err
+		}
+
+		// append leave bytes into binary path
+		bytes = append(bytes, leaveBytes...)
+	}
+
+	return MerklePath(hex.EncodeToString(bytes)), nil
+}
+
+// from merkle path binary decodes MerklePathData
+func DecodeMerklePathBinary(merklePath MerklePath) (*MerklePathData, error) {
+	// convert hex to byte array
+	merklePathBinary, err := hex.DecodeString(string(merklePath))
+	if err != nil {
+		return nil, err
+	}
+
+	merklePathData := &MerklePathData{}
+	merklePathData.Path = make([]string, 0)
+
+	// start paring transaction index
+	var offset int
+	index, size := bt.NewVarIntFromBytes(merklePathBinary[offset:])
+	merklePathData.Index = uint64(index)
+	offset += size
+
+	// next value in the byte array is nLeaves (number of leaves in merkle path)
+	nLeaves, size := bt.NewVarIntFromBytes(merklePathBinary[offset:])
+	offset += size
+
+	// parse each leaf from the binary path
+	for k := 0; k < int(nLeaves); k++ {
+		leaf := merklePathBinary[offset : offset+32]
+		merklePathData.Path = append(merklePathData.Path, hex.EncodeToString(leaf))
+		offset += 32
+	}
+
+	return merklePathData, nil
+}
diff --git a/merklepathbinary_test.go b/merklepathbinary_test.go
new file mode 100644
index 0000000..563da9c
--- /dev/null
+++ b/merklepathbinary_test.go
@@ -0,0 +1,59 @@
+package bc_test
+
+import (
+	"testing"
+
+	"github.com/libsv/go-bc"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBuildingMerklePathBinary(t *testing.T) {
+	t.Parallel()
+
+	// build example merkle path data
+	merklePathData := bc.MerklePathData{
+		Index: 136,
+		Path: []string{"0c82025f47b31054e9ad52109ef25b00fd9aaae7153564619bab031d4112f56c",
+			"3b6ea708d7b84a078179b53cf2cb2f0636162ffd60a96f81815564bbc6c073cd",
+			"efac0f077fca2a10730400da62ebaebaba852bd5fc3fb7770e090a1919d9c8b4",
+			"1e81e396da7f63e3989a8bc9bdbefddf95c75da1eb3936944b6a55cf82d87034"},
+	}
+
+	// build binary path from it
+	merklePathBinary, err := bc.BuildMerklePathBinary(&merklePathData)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	// assert binary path is expected
+	assert.Equal(t, bc.MerklePath("88040c82025f47b31054e9ad52109ef25b00fd9aaae7153564619bab031d4112f56c3b6ea708d7b84a078179b53cf2cb2f0636162ffd60a96f81815564bbc6c073cdefac0f077fca2a10730400da62ebaebaba852bd5fc3fb7770e090a1919d9c8b41e81e396da7f63e3989a8bc9bdbefddf95c75da1eb3936944b6a55cf82d87034"), merklePathBinary)
+}
+
+func TestDecodingMerklePathBinary(t *testing.T) {
+	t.Parallel()
+
+	merklePath := bc.MerklePath("88040c82025f47b31054e9ad52109ef25b00fd9aaae7153564619bab031d4112f56c3b6ea708d7b84a078179b53cf2cb2f0636162ffd60a96f81815564bbc6c073cdefac0f077fca2a10730400da62ebaebaba852bd5fc3fb7770e090a1919d9c8b41e81e396da7f63e3989a8bc9bdbefddf95c75da1eb3936944b6a55cf82d87034")
+	merklePathData, err := bc.DecodeMerklePathBinary(merklePath)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	// merklePathData := bc.MerklePathData{
+	// 	Index: 136,
+	// 	Path: []string{"0c82025f47b31054e9ad52109ef25b00fd9aaae7153564619bab031d4112f56c",
+	// 		"3b6ea708d7b84a078179b53cf2cb2f0636162ffd60a96f81815564bbc6c073cd",
+	// 		"efac0f077fca2a10730400da62ebaebaba852bd5fc3fb7770e090a1919d9c8b4",
+	// 		"1e81e396da7f63e3989a8bc9bdbefddf95c75da1eb3936944b6a55cf82d87034"},
+	// }
+
+	// assert binary path is expected
+	assert.Equal(t, uint64(136), merklePathData.Index)
+	assert.Equal(t, 4, len(merklePathData.Path))
+	assert.Equal(t, "0c82025f47b31054e9ad52109ef25b00fd9aaae7153564619bab031d4112f56c", merklePathData.Path[0])
+	assert.Equal(t, "3b6ea708d7b84a078179b53cf2cb2f0636162ffd60a96f81815564bbc6c073cd", merklePathData.Path[1])
+	assert.Equal(t, "efac0f077fca2a10730400da62ebaebaba852bd5fc3fb7770e090a1919d9c8b4", merklePathData.Path[2])
+	assert.Equal(t, "1e81e396da7f63e3989a8bc9bdbefddf95c75da1eb3936944b6a55cf82d87034", merklePathData.Path[3])
+}