From 413afef9c89396cd80647743f4e966e3ba4a1508 Mon Sep 17 00:00:00 2001
From: Chris Nelson <superchrisnelson@gmail.com>
Date: Tue, 29 Aug 2023 13:54:43 -0400
Subject: [PATCH] accept version number rollover

---
 src/LiveState.ts        |  6 +++++-
 test/live-state-test.ts | 27 +++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/LiveState.ts b/src/LiveState.ts
index b2dcea6..11646bd 100644
--- a/src/LiveState.ts
+++ b/src/LiveState.ts
@@ -168,7 +168,7 @@ export class LiveState implements EventTarget {
     this.eventTarget.dispatchEvent(new CustomEvent<LiveStatePatch>('livestate-patch', {
       detail: {patch, version}
     }));
-    if (version === this.stateVersion + 1) {
+    if (this.versionMatches(version)) {
       const { doc, res } = applyPatch(this.state, patch, { mutate: false });
       this.state = doc;
       this.stateVersion = version;
@@ -183,6 +183,10 @@ export class LiveState implements EventTarget {
     }
   }
 
+  versionMatches(version) {
+    return (version === this.stateVersion + 1) || (version === 0);
+  }
+
   pushEvent(eventName, payload) {
     this.dispatchEvent(new CustomEvent(eventName, {detail: payload}));
   }
diff --git a/test/live-state-test.ts b/test/live-state-test.ts
index 44f7210..1b06764 100644
--- a/test/live-state-test.ts
+++ b/test/live-state-test.ts
@@ -87,6 +87,33 @@ describe('LiveState', () => {
     expect(state).to.deep.equal(newState);
   });
 
+  it('accepts version number rollover in json patch', () => {
+    const initialState = { foo: "bar" };
+    const newState = { foo: "baz"};
+    const patch = compare(initialState, newState);
+    socketMock.expects('connect').exactly(1);
+    liveState.connect();
+    let state = {};
+    let receivedPatch;
+
+    liveState.addEventListener('livestate-change', ({detail: {state: newState}}) => state = newState);
+    liveState.addEventListener('livestate-patch', ({detail: {patch: thePatch}}) => receivedPatch = thePatch);
+
+    const onChangeArgs = liveState.channel.on.getCall(0).args;
+    expect(onChangeArgs[0]).to.equal("state:change");
+    const onChangeHandler = onChangeArgs[1];
+    onChangeHandler({state: initialState, version: 1000});
+
+    const onPatchArgs = liveState.channel.on.getCall(1).args;
+    expect(onPatchArgs[0]).to.equal("state:patch");
+    const onPatchHandler = onPatchArgs[1];
+    onPatchHandler({patch, version: 0});
+
+    expect(receivedPatch).to.equal(patch);
+    expect(state).to.deep.equal(newState);
+
+  })
+
   it('requests new state when receiving patch with incorrect version', () => {
     const initialState = { foo: "bar" };
     const newState = { foo: "baz", bing: [1, 2] };