Merge pull request #3 from Uniswap/verify-mroot2

feat: verify that the merkle roots match

scripts/verify-merkle-root.ts

@@ -26,34 +26,78 @@ const combinedHash = (first: Buffer, second: Buffer): Buffer => {
   )
 }
 
+const toNode = (index: number | BigNumber, account: string, amount: BigNumber): Buffer => {
+  const pairHex = utils.solidityKeccak256(['uint256', 'address', 'uint256'], [index, account, amount])
+  return Buffer.from(pairHex.slice(2), 'hex')
+}
+
 const verifyProof = (
   index: number | BigNumber,
   account: string,
   amount: BigNumber,
   proof: Buffer[],
   root: Buffer
 ): boolean => {
-  const pairHex = utils.solidityKeccak256(['uint256', 'address', 'uint256'], [index, account, amount])
-  let pair = Buffer.from(pairHex.slice(2), 'hex')
-
+  let pair = toNode(index, account, amount)
   for (const item of proof) {
     pair = combinedHash(pair, item)
   }
 
   return pair.equals(root)
 }
 
+const getNextLayer = (elements: Buffer[]): Buffer[] => {
+  return elements.reduce<Buffer[]>((layer, el, idx, arr) => {
+    if (idx % 2 === 0) {
+      // Hash the current element with its pair element
+      layer.push(combinedHash(el, arr[idx + 1]))
+    }
+
+    return layer
+  }, [])
+}
+
+const getRoot = (balances: { account: string; amount: BigNumber }[]): Buffer => {
+  let nodes = balances.map(({ account, amount }, index) => {
+    return toNode(index, account, amount)
+  })
+  nodes = [...nodes]
+  nodes.sort(Buffer.compare)
+
+  // deduplicate any eleents
+  nodes = nodes.filter((el, idx) => {
+    return idx === 0 || !nodes[idx - 1].equals(el)
+  })
+
+  const layers = []
+  layers.push(nodes)
+
+  // Get next layer until we reach the root
+  while (layers[layers.length - 1].length > 1) {
+    layers.push(getNextLayer(layers[layers.length - 1]))
+  }
+
+  return layers[layers.length - 1][0]
+}
+
 if (typeof json !== 'object') throw new Error('Invalid JSON')
 
 const merkleRootHex = json.merkleRoot
 const merkleRoot = Buffer.from(merkleRootHex.slice(2), 'hex')
 
+let balances = []
 for (const address in json.claims) {
   const claim = json.claims[address]
+  balances.push({ account: address, amount: BigNumber.from(claim.amount) })
   if (verifyProof(claim.index, address, claim.amount, claim.proof, merkleRoot)) {
     console.log('Verified proof for', address)
   } else {
     console.log('Verification for', address, 'failed')
   }
 }
 console.log('Done!')
+
+// Root
+const root = getRoot(balances).toString('hex')
+console.log('Reconstructed merkle root', root)
+console.log('Root matches the one read from the JSON?', root === merkleRootHex.slice(2))