From d85179e0b6d0f2ab48e18f91dd9aca4582d8e512 Mon Sep 17 00:00:00 2001
From: David Katz <15Dkatz@shcp.edu>
Date: Wed, 28 Sep 2022 14:10:10 -0700
Subject: [PATCH] Validate Transaction Chain

---
 app/pubsub.js            |  2 +-
 blockchain/index.js      |  7 ++++++-
 blockchain/index.test.js | 13 +++++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/app/pubsub.js b/app/pubsub.js
index 5aa9e45..40ed6d9 100644
--- a/app/pubsub.js
+++ b/app/pubsub.js
@@ -29,7 +29,7 @@ class PubSub {
 
     switch(channel) {
       case CHANNELS.BLOCKCHAIN:
-        this.blockchain.replaceChain(parsedMessage, () => {
+        this.blockchain.replaceChain(parsedMessage, true, () => {
           this.transactionPool.clearBlockchainTransactions({
              chain: parsedMessage
           });
diff --git a/blockchain/index.js b/blockchain/index.js
index 00111ed..c6b6004 100644
--- a/blockchain/index.js
+++ b/blockchain/index.js
@@ -18,7 +18,7 @@ class Blockchain {
     this.chain.push(newBlock);
   }
 
-  replaceChain(chain, onSuccess) {
+  replaceChain(chain, validateTransactions, onSuccess) {
     if (chain.length <= this.chain.length) {
       console.error('The incoming chain must be longer');
       return;
@@ -29,6 +29,11 @@ class Blockchain {
       return;
     }
 
+    if (validateTransactions && !this.validTransactionData({ chain })) {
+      console.error('The incoming chain has invalid data');
+      return;
+    }
+
     if (onSuccess) onSuccess();
     console.log('replacing chain with', chain);
     this.chain = chain;
diff --git a/blockchain/index.test.js b/blockchain/index.test.js
index 70a7907..cbecee0 100644
--- a/blockchain/index.test.js
+++ b/blockchain/index.test.js
@@ -156,6 +156,19 @@ describe('Blockchain', () => {
         });
       });
     });
+
+    describe('and the `validateTransactions` flag is true', () => {
+      it('calls validateTransactionData()', () => {
+        const validateTransactionDataMock = jest.fn();
+
+        blockchain.validTransactionData = validateTransactionDataMock;
+
+        newChain.addBlock({ data: 'foo' });
+        blockchain.replaceChain(newChain.chain, true);
+
+        expect(validateTransactionDataMock).toHaveBeenCalled();
+      });
+    });
   });
 
   describe('validTransactionData()', () => {