From 4c897fdeb504055f99c8b1e41814201f6c68297d Mon Sep 17 00:00:00 2001
From: Trevor Buckner <calculuschild@gmail.com>
Date: Mon, 7 Jul 2025 21:00:03 +0000
Subject: [PATCH] Add MD5 hash check

---
 client/homebrew/pages/editPage/editPage.jsx | 2 ++
 server/homebrew.api.js                      | 6 ++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/client/homebrew/pages/editPage/editPage.jsx b/client/homebrew/pages/editPage/editPage.jsx
index 3181df816..dc2f0f2a5 100644
--- a/client/homebrew/pages/editPage/editPage.jsx
+++ b/client/homebrew/pages/editPage/editPage.jsx
@@ -4,6 +4,7 @@ const React = require('react');
 const _ = require('lodash');
 const createClass = require('create-react-class');
 import {makePatches, applyPatches, stringifyPatches, parsePatches} from '@sanity/diff-match-patch';
+import { md5 } from 'hash-wasm';
 
 import request from '../../utils/request-middleware.js';
 const { Meta } = require('vitreum/headtags');
@@ -263,6 +264,7 @@ const EditPage = createClass({
 		brew.pageCount = ((brew.renderer=='legacy' ? brew.text.match(/\\page/g) : brew.text.match(/^\\page$/gm)) || []).length + 1;
 
 		brew.patches = makePatches(this.savedBrew.text, brew.text);
+		brew.hash    = await md5(this.savedBrew.text);
 		brew.text    = undefined;
 		brew.textBin = undefined;
 		console.log('Saving Brew', brew);
diff --git a/server/homebrew.api.js b/server/homebrew.api.js
index 9a2aa8c0a..384031c77 100644
--- a/server/homebrew.api.js
+++ b/server/homebrew.api.js
@@ -9,6 +9,7 @@ import yaml                          from 'js-yaml';
 import asyncHandler                  from 'express-async-handler';
 import { nanoid }                    from 'nanoid';
 import {makePatches, applyPatches, stringifyPatches, parsePatch} from '@sanity/diff-match-patch';
+import { md5 }                       from 'hash-wasm';
 import { splitTextStyleAndMetadata, 
 		 brewSnippetsToJSON }        from '../shared/helpers.js';
 import checkClientVersion            from './middleware/check-client-version.js';
@@ -338,11 +339,12 @@ const api = {
 		// Initialize brew from request and body, destructure query params, and set the initial value for the after-save method
 		const brewFromClient = api.excludePropsFromUpdate(req.body);
 		const brewFromServer = req.brew;
+		const serverHash     = md5(brewFromServer.text);
 
-		if(brewFromServer.version && brewFromClient.version && brewFromServer.version > brewFromClient.version) {
+		if((brewFromServer?.version !== brewFromClient?.version) || (serverHash !== brewFromClient.hash)) {
 			console.log(`Version mismatch on brew ${brewFromClient.editId}`);
 			res.setHeader('Content-Type', 'application/json');
-			return res.status(409).send(JSON.stringify({ message: `The brew has been changed on a different device. Please save your changes elsewhere, refresh, and try again.` }));
+			return res.status(409).send(JSON.stringify({ message: `The server copy is out of sync with the saved brew. Please save your changes elsewhere, refresh, and try again.` }));
 		}
 
 		console.log(`Brewfromserver: ${JSON.stringify(brewFromServer)}`);