From 2b4d5771d1463cf8ec95e6a4fb00f9d1630996bc Mon Sep 17 00:00:00 2001
From: christopherbrumm <christopherbrumm2000@gmail.com>
Date: Mon, 3 Jun 2024 11:28:36 +0200
Subject: [PATCH] update: add merkle root to tendermint bundle summary

---
 integrations/tendermint/src/runtime.ts  | 10 ++++-
 integrations/tendermint/utils/merkle.ts | 56 +++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 2 deletions(-)
 create mode 100644 integrations/tendermint/utils/merkle.ts

diff --git a/integrations/tendermint/src/runtime.ts b/integrations/tendermint/src/runtime.ts
index da60d30e..b7b33726 100644
--- a/integrations/tendermint/src/runtime.ts
+++ b/integrations/tendermint/src/runtime.ts
@@ -4,6 +4,7 @@ import axios from 'axios';
 import Ajv from 'ajv';
 import block_schema from './schemas/block.json';
 import block_results_schema from './schemas/block_result.json';
+import { createHashesFromTendermintBundle, generateMerkleRoot } from "../utils/merkle";
 
 const ajv = new Ajv();
 
@@ -236,8 +237,13 @@ export default class Tendermint implements IRuntime {
   }
 
   async summarizeDataBundle(_: Validator, bundle: DataItem[]): Promise<string> {
-    // use latest block height as bundle summary
-    return bundle.at(-1)?.value?.block?.block?.header?.height ?? '';
+    const hashes: Uint8Array[] = createHashesFromTendermintBundle(bundle);
+
+    const merkleRoot: Uint8Array = generateMerkleRoot(hashes);
+
+    return JSON.stringify({
+      "merkle_root": Buffer.from(merkleRoot).toString("hex")
+    })
   }
 
   async nextKey(_: Validator, key: string): Promise<string> {
diff --git a/integrations/tendermint/utils/merkle.ts b/integrations/tendermint/utils/merkle.ts
new file mode 100644
index 00000000..ffa6e822
--- /dev/null
+++ b/integrations/tendermint/utils/merkle.ts
@@ -0,0 +1,56 @@
+import * as crypto from '@cosmjs/crypto';
+
+// Creates an Array of hashes from an array of data items (bundle).
+// The hash of a data item consists of the Merkle root from the block and the block
+// results (only two leafs) and the key of the data item. This allows the
+// Trustless API to serve block and block results independently.
+export function createHashesFromTendermintBundle(bundle: any[]): Uint8Array[] {
+  return bundle.map(dataItem => {
+    const blockHashes: Uint8Array[] = [dataItemToSha256(dataItem.value?.block), dataItemToSha256(dataItem.value?.block_results)];
+
+    const merkleRoot: Uint8Array = generateMerkleRoot(blockHashes);
+
+    return tendermintDataItemToSha256(dataItem.key, merkleRoot)
+  })
+}
+
+function tendermintDataItemToSha256(key: string, merkleRoot: Uint8Array): Uint8Array {
+  const keyBytes = crypto.sha256(Buffer.from(key, 'utf-8'));
+
+  const combined = Buffer.concat([keyBytes, merkleRoot]);
+
+  return crypto.sha256(combined);
+}
+
+function dataItemToSha256(data: any): Uint8Array {
+  // Encode the serialized object to UTF-8
+  const encoded_obj: Uint8Array = Buffer.from(JSON.stringify(data), 'utf-8');
+  // Calculate the SHA-256 hash
+  return crypto.sha256(encoded_obj)
+}
+
+export function generateMerkleRoot(hashes: Uint8Array[]): Uint8Array {
+  if (!hashes || hashes.length == 0) {
+    return Buffer.from("");
+  }
+
+  // Ensure number of hashes (leafs) are even by copying the
+  // last hash (the very right leaf) if the amount is odd
+  if (hashes.length % 2 !== 0) {
+    hashes.push(hashes[hashes.length - 1]);
+  }
+
+  const combinedHashes: Uint8Array[] = [];
+  for(let i = 0; i < hashes.length; i += 2) {
+    const hashesConcatenated = new Uint8Array([ ...hashes[i], ...hashes[i+1]])
+    const hash = crypto.sha256(hashesConcatenated);
+    combinedHashes.push(hash);
+  }
+
+  // If the combinedHashes length is 1, it means that we have the merkle root already,
+  // and we can return the hex representation
+  if (combinedHashes.length === 1) {
+    return combinedHashes[0];
+  }
+  return generateMerkleRoot(combinedHashes);
+}
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