From 3f3e0534cc742c76b1bf356c8cdeef2b18198f91 Mon Sep 17 00:00:00 2001
From: Alexey <peretsmobil@gmail.com>
Date: Thu, 18 Jul 2019 00:25:16 +0300
Subject: [PATCH] merkle tree update - getIndexByElement

---
 lib/MerkleTree.js                  | 10 ++++++++++
 test/MerkleTreeWithHistory.test.js | 21 +++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/lib/MerkleTree.js b/lib/MerkleTree.js
index f0e6ffa..6c7cbac 100644
--- a/lib/MerkleTree.js
+++ b/lib/MerkleTree.js
@@ -179,6 +179,16 @@ class MerkleTree {
       current_index = Math.floor(current_index / 2)
     }
   }
+
+  getIndexByElement(element) {
+    for(let i = this.totalElements - 1; i >= 0; i--) {
+      const elementFromTree = this.storage.get(MerkleTree.index_to_key(this.prefix, 0, i))
+      if (elementFromTree === element) {
+        return i
+      }
+    }
+    return false
+  }
 }
 
 module.exports = MerkleTree
diff --git a/test/MerkleTreeWithHistory.test.js b/test/MerkleTreeWithHistory.test.js
index e5241a0..63a5cfb 100644
--- a/test/MerkleTreeWithHistory.test.js
+++ b/test/MerkleTreeWithHistory.test.js
@@ -102,6 +102,27 @@ contract('MerkleTreeWithHistory', accounts => {
       }
     })
 
+    it('should find an element', async () => {
+      const elements = [12, 13, 14, 15, 16, 17, 18, 19, 20]
+      for(const [, el] of Object.entries(elements)) {
+        await tree.insert(el)
+      }
+      let index = tree.getIndexByElement(13)
+      index.should.be.equal(1)
+
+      index = tree.getIndexByElement(19)
+      index.should.be.equal(7)
+
+      index = tree.getIndexByElement(12)
+      index.should.be.equal(0)
+
+      index = tree.getIndexByElement(20)
+      index.should.be.equal(8)
+
+      index = tree.getIndexByElement(42)
+      index.should.be.equal(false)
+    })
+
     it('creation even elements count', async () => {
       const elements = [12, 13, 14, 15, 16, 17]
       for(const [, el] of Object.entries(elements)) {