From b2f3b566c0c0edd41b0314fcbf516a3d7876e14b Mon Sep 17 00:00:00 2001
From: Roland Reichwein <mail@reichwein.it>
Date: Sun, 29 Jan 2023 17:54:14 +0100
Subject: Fix concurrent edit, tests

---
 html/whiteboard.js | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

(limited to 'html')

diff --git a/html/whiteboard.js b/html/whiteboard.js
index a6dc089..b11dc96 100644
--- a/html/whiteboard.js
+++ b/html/whiteboard.js
@@ -4,6 +4,7 @@ function init() {
 }
 
 var revision;
+var modify_in_progress = 0;
 var baseline = ""; // data contents relating to revision, acknowledged by server
 var baseline_candidate = ""; // will become baseline, after ack by server
 
@@ -51,7 +52,7 @@ function on_getfile(data, rev, pos)
 function on_getdiff(diff, rev, pos)
 {
         if (rev != revision + 1)
-         alert("Revision skipped: " + rev + " after " + revision);
+         console.log("Revision skipped on diff receive: " + rev + " after " + revision);
 
 	var board = document.getElementById("board");
 
@@ -95,8 +96,12 @@ function on_version(version)
 
 function on_modify_ack(rev)
 {
+        if (rev != revision + 1)
+         console.log("Revision skipped on published local change: " + rev + " after " + revision);
+
 	revision = rev;
         baseline = baseline_candidate;
+        modify_in_progress = 0;
 }
 
 function on_message(e) {
@@ -228,6 +233,13 @@ function redirect_to_new_page()
 // local change done
 function on_input()
 {
+        if (modify_in_progress == 1) {
+                console.log("Deferring on_input handler by 100ms");
+                setTimeout(function(){on_input();}, 100); // re-try after 100ms
+                return;
+        }
+        modify_in_progress = 1;
+
 	var parser = new DOMParser();
 	var xmlDocument = parser.parseFromString("<request></request>", "text/xml");
 	
@@ -243,6 +255,11 @@ function on_input()
 
         baseline_candidate = document.getElementById("board").value;
 
+        if (baseline == baseline_candidate) {
+         modify_in_progress = 0;
+         return;
+        }
+
 	var revisionElement = xmlDocument.createElement("baserev");
 	revisionElement.appendChild(document.createTextNode(revision));
 	requestElement.appendChild(revisionElement);
-- 
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