feat(grain): add support for remote grainMaps

packages/grain/src/captp.js

@@ -4,13 +4,30 @@ import { makeIteratorRef } from '@endo/daemon/reader-ref.js';
 import { makeRefIterator } from '@endo/daemon/ref-reader.js';
 import { makeArrayGrainFromSyncGrain, makeSubscribedSyncGrainFromAsyncGrain } from './index.js';
 
-// given a grain, returns a remote grain for sending over captp
-export const makeRemoteGrain = (localSyncGrain, name = 'grain') => {
-  return Far(name, {
+const makeRemoteGrainInterface = (localSyncGrain) => {
+  return {
     ...localSyncGrain,
     follow: async (canceled) => {
       return makeIteratorRef(localSyncGrain.follow(canceled))
     },
+  }
+}
+
+// given a grain, returns a remote grain for sending over captp
+export const makeRemoteGrain = (localSyncGrain, name = 'grain') => {
+  return Far(name, {
+    ...makeRemoteGrainInterface(localSyncGrain),
+  })
+}
+
+export const makeRemoteGrainMap = (localSyncGrainMap, name = 'grainmap') => {
+  const getGrain = async (key, childName = `${name}/${key}`) => {
+    const childLocalSyncGrain = localSyncGrainMap.getGrain(key)
+    return makeRemoteGrain(childLocalSyncGrain, childName)
+  }
+  return Far(name, {
+    ...makeRemoteGrainInterface(localSyncGrainMap),
+    getGrain,
   })
 }
 
@@ -75,6 +92,19 @@ export const makeLocalAsyncGrainFromRemote = (remoteGrain) => {
   return asyncGrain
 }
 
+export const makeLocalAsyncGrainMapFromRemote = (remoteGrain) => {
+  const asyncGrain = makeLocalAsyncGrainFromRemote(remoteGrain)
+  const getGrain = (key) => {
+    const childRemoteGrain = E(remoteGrain).getGrain(key)
+    const childLocalAsyncGrain = makeLocalAsyncGrainFromRemote(childRemoteGrain)
+   return childLocalAsyncGrain
+  }
+  return {
+    ...asyncGrain,
+    getGrain,
+  }
+}
+
 export const makeReadonlyGrainFromRemote = (remoteGrain, initValue) => {
   const localAsyncGrain = makeLocalAsyncGrainFromRemote(remoteGrain)
   const localSyncGrain = localAsyncGrain.makeSubscribedSyncGrain(initValue)
@@ -90,3 +120,18 @@ export const makeReadonlyArrayGrainFromRemote = (remoteGrain, initValue = []) =>
   const localArrayGrain = makeArrayGrainFromSyncGrain(localSyncGrain).readonly()
   return localArrayGrain
 }
+
+export const makeReadonlyGrainMapFromRemote = (remoteGrainMap, initValue = {}) => {
+  const localAsyncGrain = makeLocalAsyncGrainFromRemote(remoteGrainMap)
+  const localAsyncGrainMap = makeLocalAsyncGrainMapFromRemote(remoteGrainMap)
+  const localSyncGrain = localAsyncGrain.makeSubscribedSyncGrain(initValue)
+  const getGrain = (key) => {
+    const childLocalAsyncGrain = localAsyncGrainMap.getGrain(key)
+    const childLocalSyncGrain = childLocalAsyncGrain.makeSubscribedSyncGrain()
+    return childLocalSyncGrain
+  }
+  return {
+    ...localSyncGrain,
+    getGrain,
+  }
+}

packages/grain/test/test-index.js

@@ -1,6 +1,9 @@
 import { makePromiseKit } from '@endo/promise-kit';
 import { test } from './prepare-test-env-ava.js';
-import { makeSyncGrain, makeSyncArrayGrain } from '../src/index.js';
+import { makeSyncGrain, makeSyncArrayGrain, makeSyncGrainMap } from '../src/index.js';
+import { makeReadonlyGrainMapFromRemote, makeRemoteGrainMap } from '../src/captp.js';
+
+const delay = (duration) => new Promise(resolve => setTimeout(resolve, duration))
 
 test('grain / set + get', async t => {
   const grain = makeSyncGrain();
@@ -15,12 +18,12 @@ test('grain / subscribe + follow', async t => {
   let latestSubscribeValue;
   let latestFollowValue;
 
-  const unsubscribe = grain.subscribe((start) => {
-    latestSubscribeValue = start;
+  const unsubscribe = grain.subscribe((value) => {
+    latestSubscribeValue = value;
   })
   ;(async function () {
-    for await (const start of grain.follow(canceled)) {
-      latestFollowValue = start;
+    for await (const value of grain.follow(canceled)) {
+      latestFollowValue = value;
     }
   })()
   const cleanup = () => {
@@ -32,7 +35,7 @@ test('grain / subscribe + follow', async t => {
   grain.set({ hello: 123 });
   grain.set({ hello: 123, foo: 'bar' });
 
-  await new Promise(resolve => setTimeout(resolve, 1000))
+  await delay(500)
   cleanup();
 
   t.deepEqual(latestSubscribeValue, { hello: 123, foo: 'bar' });
@@ -46,12 +49,12 @@ test('array grain / subscribe + follow', async t => {
   let latestSubscribeValue;
   let latestFollowValue;
 
-  const unsubscribe = grain.subscribe((start) => {
-    latestSubscribeValue = start;
+  const unsubscribe = grain.subscribe((value) => {
+    latestSubscribeValue = value;
   })
   ;(async function () {
-    for await (const start of grain.follow(canceled)) {
-      latestFollowValue = start;
+    for await (const value of grain.follow(canceled)) {
+      latestFollowValue = value;
     }
   })()
   const cleanup = () => {
@@ -63,7 +66,7 @@ test('array grain / subscribe + follow', async t => {
   grain.push({ count: 123 });
   grain.push({ foo: 'bar' });
 
-  await new Promise(resolve => setTimeout(resolve, 1000))
+  await delay(500)
   cleanup();
 
   t.deepEqual(latestSubscribeValue, [
@@ -78,3 +81,31 @@ test('array grain / subscribe + follow', async t => {
   ]);
 });
 
+test('remote grainMap', async t => {
+  // create source grainMap
+  const sourceGrainA = makeSyncGrain('hello');
+  const sourceGrainB = makeSyncGrain('world');
+  const sourceGrainMap = makeSyncGrainMap({
+    a: sourceGrainA,
+    b: sourceGrainB,
+  });
+  const sourceGrainMapRemote = makeRemoteGrainMap(sourceGrainMap);
+  // --- network boundary ---
+  const destGrainMap = makeReadonlyGrainMapFromRemote(sourceGrainMapRemote);
+  const destGrainA = destGrainMap.getGrain('a');
+  const destGrainB = destGrainMap.getGrain('b');
+  // test
+  const { promise: canceled, resolve: cancel } = makePromiseKit();
+  const followA = destGrainA.follow(canceled);
+  const followB = destGrainB.follow(canceled);
+  // skip initial uninitialized values
+  await followA.next();
+  await followB.next();
+  // test
+  const { value: valueA } = await followA.next();
+  const { value: valueB } = await followB.next();
+  t.deepEqual(valueA, 'hello');
+  t.deepEqual(valueB, 'world');
+  // cleanup
+  cancel()
+});