From 10624beaf21ef5243e5a1bdce3af0a02d6852152 Mon Sep 17 00:00:00 2001
From: Minh Doan <minh@simple-rules.com>
Date: Tue, 21 Aug 2018 17:54:55 -0700
Subject: [PATCH] add merkel tree data structure

---
 blockchain/merkle_tree.go | 65 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 blockchain/merkle_tree.go

diff --git a/blockchain/merkle_tree.go b/blockchain/merkle_tree.go
new file mode 100644
index 000000000..c4ffa4c9d
--- /dev/null
+++ b/blockchain/merkle_tree.go
@@ -0,0 +1,65 @@
+package blockchain
+
+import (
+	"crypto/sha256"
+)
+
+// MerkleTree represent a Merkle tree
+type MerkleTree struct {
+	RootNode *MerkleNode
+}
+
+// MerkleNode represent a Merkle tree node
+type MerkleNode struct {
+	Left  *MerkleNode
+	Right *MerkleNode
+	Data  []byte
+}
+
+// NewMerkleTree creates a new Merkle tree from a sequence of data
+func NewMerkleTree(data [][]byte) *MerkleTree {
+	var nodes []MerkleNode
+
+	if len(data)%2 != 0 {
+		data = append(data, data[len(data)-1])
+	}
+
+	for _, datum := range data {
+		node := NewMerkleNode(nil, nil, datum)
+		nodes = append(nodes, *node)
+	}
+
+	for i := 0; i < len(data)/2; i++ {
+		var newLevel []MerkleNode
+
+		for j := 0; j < len(nodes); j += 2 {
+			node := NewMerkleNode(&nodes[j], &nodes[j+1], nil)
+			newLevel = append(newLevel, *node)
+		}
+
+		nodes = newLevel
+	}
+
+	mTree := MerkleTree{&nodes[0]}
+
+	return &mTree
+}
+
+// NewMerkleNode creates a new Merkle tree node
+func NewMerkleNode(left, right *MerkleNode, data []byte) *MerkleNode {
+	mNode := MerkleNode{}
+
+	if left == nil && right == nil {
+		hash := sha256.Sum256(data)
+		mNode.Data = hash[:]
+	} else {
+		prevHashes := append(left.Data, right.Data...)
+		hash := sha256.Sum256(prevHashes)
+		mNode.Data = hash[:]
+	}
+
+	mNode.Left = left
+	mNode.Right = right
+
+	return &mNode
+}