Add tests, docs and MerkleTree helper

test/helpers/merkleTree.js

@@ -0,0 +1,135 @@
+import { sha3 } from "ethereumjs-util";
+
+export default class MerkleTree {
+  constructor(elements) {
+    // Filter empty strings
+    this.elements = elements.filter(el => el);
+
+    // Check if elements are 32 byte buffers
+    if (this.elements.some(el => el.length !== 32 || !Buffer.isBuffer(el))) {
+      throw new Error("Elements must be 32 byte buffers");
+    }
+
+    // Deduplicate elements
+    this.elements = this.bufDedup(this.elements);
+    // Sort elements
+    this.elements.sort(Buffer.compare);
+
+    // Create layers
+    this.layers = this.getLayers(this.elements);
+  }
+
+  getLayers(elements) {
+    if (elements.length == 0) {
+      return [[""]];
+    }
+
+    const layers = [];
+    layers.push(elements);
+
+    // Get next layer until we reach the root
+    while (layers[layers.length - 1].length > 1) {
+      layers.push(this.getNextLayer(layers[layers.length - 1]));
+    }
+
+    return layers;
+  }
+
+  getNextLayer(elements) {
+    return elements.reduce((layer, el, idx, arr) => {
+      if (idx % 2 === 0) {
+        // Hash the current element with its pair element
+        layer.push(this.combinedHash(el, arr[idx + 1]));
+      }
+
+      return layer;
+    }, []);
+  }
+
+  combinedHash(first, second) {
+    if (!first) { return second; }
+    if (!second) { return first; }
+
+    return sha3(this.sortAndConcat(first, second));
+  }
+
+  getRoot() {
+    return this.layers[this.layers.length - 1][0];
+  }
+
+  getHexRoot() {
+    return this.bufToHex(this.getRoot());
+  }
+
+  getProof(el) {
+    let idx = this.bufIndexOf(el, this.elements);
+
+    if (idx === -1) {
+      throw new Error("Element does not exist in Merkle tree");
+    }
+
+    return this.layers.reduce((proof, layer) => {
+      const pairElement = this.getPairElement(idx, layer);
+
+      if (pairElement) {
+        proof.push(pairElement);
+      }
+
+      idx = Math.floor(idx / 2);
+
+      return proof;
+    }, []);
+  }
+
+  getHexProof(el) {
+    const proof = this.getProof(el);
+
+    return this.bufArrToHex(proof);
+  }
+
+  getPairElement(idx, layer) {
+    const pairIdx = idx % 2 === 0 ? idx + 1 : idx - 1;
+
+    if (pairIdx < layer.length) {
+      return layer[pairIdx];
+    } else {
+      return null;
+    }
+  }
+
+  bufIndexOf(el, arr) {
+    for (let i = 0; i < arr.length; i++) {
+      if (el.equals(arr[i])) {
+        return i;
+      }
+    }
+
+    return -1;
+  }
+
+  bufDedup(elements) {
+    return elements.filter((el, idx) => {
+      return this.bufIndexOf(el, elements) === idx;
+    });
+  }
+
+  bufToHex(el) {
+    if (!Buffer.isBuffer(el)) {
+      throw new Error("Element is not a buffer");
+    }
+
+    return "0x" + el.toString("hex");
+  }
+
+  bufArrToHex(arr) {
+    if (arr.some(el => !Buffer.isBuffer(el))) {
+      throw new Error("Array is not an array of buffers");
+    }
+
+    return "0x" + arr.map(el => el.toString("hex")).join("");
+  }
+
+  sortAndConcat(...args) {
+    return Buffer.concat([...args].sort(Buffer.compare));
+  }
+}