Rebase pending Automerge field edits

dist/src/crdt-automerge.d.ts

@@ -18,7 +18,8 @@ export declare const loadAutomergeFieldDoc: (value: CaminoCrdtEnvelope, type: st
 export declare const saveAutomergeFieldDoc: (doc: Automerge.Doc<AutomergeFieldDoc>, type: string) => CaminoCrdtEnvelope;
 export declare const createAutomergeFieldValue: (value: unknown, type: string) => CaminoCrdtEnvelope;
 export declare const isAutomergeFieldDoc: (value: unknown) => value is Automerge.Doc<AutomergeFieldDoc>;
-export declare const createAutomergeFieldChanges: (base: Automerge.Doc<AutomergeFieldDoc>, next: Automerge.Doc<AutomergeFieldDoc>, type: string) => CaminoCrdtEnvelope;
+export declare const reconcileAutomergeFieldDocs: <T>(base: CaminoAutomergeDoc<T>, desired: CaminoAutomergeDoc<T>) => CaminoAutomergeDoc<T>;
+export declare const createAutomergeFieldChanges: (base: Automerge.Doc<AutomergeFieldDoc>, desired: Automerge.Doc<AutomergeFieldDoc>, type: string) => CaminoCrdtEnvelope;
 export declare const encodeAutomergeFieldWrite: (value: unknown, type: string) => CaminoCrdtEnvelope;
 export declare const normalizeAutomergeFieldValue: (value: unknown, type: string) => CaminoCrdtEnvelope;
 export declare const materializeAutomergeFieldValue: (value: CaminoCrdtEnvelope, type: string) => unknown;

dist/src/crdt-automerge.js

@@ -107,11 +107,15 @@ const decodeChanges = (payload) => {
     }
     return changes;
 };
-export const createAutomergeFieldChanges = (base, next, type) => ({
-    $caminoCrdtType: type,
-    $caminoCrdtEncoding: AUTOMERGE_CHANGES_ENCODING,
-    $caminoCrdtPayload: bytesToBase64(encodeChanges(Automerge.getChanges(base, next))),
-});
+export const reconcileAutomergeFieldDocs = (base, desired) => Automerge.merge(Automerge.clone(base), Automerge.clone(desired));
+export const createAutomergeFieldChanges = (base, desired, type) => {
+    const next = reconcileAutomergeFieldDocs(base, desired);
+    return {
+        $caminoCrdtType: type,
+        $caminoCrdtEncoding: AUTOMERGE_CHANGES_ENCODING,
+        $caminoCrdtPayload: bytesToBase64(encodeChanges(Automerge.getChanges(base, next))),
+    };
+};
 // Full snapshots remain an explicit escape hatch for initialization, import,
 // and recovery when a client cannot establish a shared Automerge history.
 export const encodeAutomergeFieldWrite = (value, type) => {

src/crdt-automerge.ts

@@ -162,17 +162,26 @@ const decodeChanges = (payload: Uint8Array): Automerge.Change[] => {
   return changes;
 };
 
+export const reconcileAutomergeFieldDocs = <T>(
+  base: CaminoAutomergeDoc<T>,
+  desired: CaminoAutomergeDoc<T>,
+): CaminoAutomergeDoc<T> =>
+  Automerge.merge(Automerge.clone(base), Automerge.clone(desired));
+
 export const createAutomergeFieldChanges = (
   base: Automerge.Doc<AutomergeFieldDoc>,
-  next: Automerge.Doc<AutomergeFieldDoc>,
+  desired: Automerge.Doc<AutomergeFieldDoc>,
   type: string,
-): CaminoCrdtEnvelope => ({
-  $caminoCrdtType: type,
-  $caminoCrdtEncoding: AUTOMERGE_CHANGES_ENCODING,
-  $caminoCrdtPayload: bytesToBase64(
-    encodeChanges(Automerge.getChanges(base, next)),
-  ),
-});
+): CaminoCrdtEnvelope => {
+  const next = reconcileAutomergeFieldDocs(base, desired);
+  return {
+    $caminoCrdtType: type,
+    $caminoCrdtEncoding: AUTOMERGE_CHANGES_ENCODING,
+    $caminoCrdtPayload: bytesToBase64(
+      encodeChanges(Automerge.getChanges(base, next)),
+    ),
+  };
+};
 
 // Full snapshots remain an explicit escape hatch for initialization, import,
 // and recovery when a client cannot establish a shared Automerge history.

test/crdt-automerge.test.ts

@@ -11,6 +11,7 @@ import {
   loadAutomergeFieldDoc,
   materializeAutomergeFieldValue,
   mergeAutomergeFieldValues,
+  reconcileAutomergeFieldDocs,
   saveAutomergeFieldDoc,
 } from "../src/crdt-automerge.js";
 
@@ -105,6 +106,32 @@ test("Automerge change application is idempotent", () => {
   assert.deepEqual(twice.materialized, { count: 1 });
 });
 
+test("Automerge changes retain remote history while local writes are pending", () => {
+  const stored = createAutomergeFieldValue({ local: false, remote: false }, type);
+  const base = loadAutomergeFieldDoc(stored, type);
+  const local = Automerge.change(
+    Automerge.clone(base, "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"),
+    (doc) => {
+      (doc.value as { local: boolean }).local = true;
+    },
+  );
+  const remote = Automerge.change(
+    Automerge.clone(base, "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"),
+    (doc) => {
+      (doc.value as { remote: boolean }).remote = true;
+    },
+  );
+  const rebased = reconcileAutomergeFieldDocs(remote, local);
+  const update = createAutomergeFieldChanges(remote, rebased, type);
+  const result = mergeAutomergeFieldValues({
+    existing: saveAutomergeFieldDoc(remote, type),
+    incoming: update,
+    type,
+  });
+
+  assert.deepEqual(result.materialized, { local: true, remote: true });
+});
+
 test("Automerge change batches reject malformed framing", () => {
   const stored = createAutomergeFieldValue({ count: 0 }, type);
   assert.throws(