add tests for meta decoding of updates and state vector comparison of update and ydoc approach

src/index.js

@@ -76,5 +76,9 @@ export {
   AbstractConnector,
   logType,
   mergeUpdates,
-  mergeUpdatesV2
+  mergeUpdatesV2,
+  parseUpdateMeta,
+  parseUpdateMetaV2,
+  encodeStateVectorFromUpdate,
+  encodeStateVectorFromUpdateV2
 } from './internals.js'

src/utils/updates.js

@@ -183,6 +183,51 @@ export const encodeStateVectorFromUpdateV2 = (update, YEncoder = DSEncoderV2, YD
  */
 export const encodeStateVectorFromUpdate = update => encodeStateVectorFromUpdateV2(update, DSEncoderV1, UpdateDecoderV2)
 
+/**
+ * @param {Uint8Array} update
+ * @param {typeof UpdateDecoderV1 | typeof UpdateDecoderV2} YDecoder
+ * @return {{ from: Map<number,number>, to: Map<number,number> }}
+ */
+export const parseUpdateMetaV2 = (update, YDecoder = UpdateDecoderV2) => {
+  /**
+   * @type {Map<number, number>}
+   */
+  const from = new Map()
+  /**
+   * @type {Map<number, number>}
+   */
+  const to = new Map()
+  const updateDecoder = new LazyStructReader(new YDecoder(decoding.createDecoder(update)))
+  let curr = updateDecoder.curr
+  if (curr !== null) {
+    let currClient = curr.id.client
+    let currClock = curr.id.clock
+    // write the beginning to `from`
+    from.set(currClient, currClock)
+    for (; curr !== null; curr = updateDecoder.next()) {
+      if (currClient !== curr.id.client) {
+        // We found a new client
+        // write the end to `to`
+        to.set(currClient, currClock)
+        // write the beginning to `from`
+        from.set(curr.id.client, curr.id.clock)
+        // update currClient
+        currClient = curr.id.client
+      }
+      currClock = curr.id.clock + curr.length
+    }
+    // write the end to `to`
+    to.set(currClient, currClock)
+  }
+  return { from, to }
+}
+
+/**
+ * @param {Uint8Array} update
+ * @return {{ from: Map<number,number>, to: Map<number,number> }}
+ */
+export const parseUpdateMeta = update => parseUpdateMetaV2(update, UpdateDecoderV1)
+
 /**
  * This method is intended to slice any kind of struct and retrieve the right part.
  * It does not handle side-effects, so it should only be used by the lazy-encoder.

tests/updates.tests.js

@@ -8,6 +8,9 @@ import * as Y from '../src/index.js'
  * @property {function(Y.Doc):Uint8Array} Enc.encodeStateAsUpdate
  * @property {function(Y.Doc, Uint8Array):void} Enc.applyUpdate
  * @property {function(Uint8Array):void} Enc.logUpdate
+ * @property {function(Uint8Array):{from:Map<number,number>,to:Map<number,number>}} Enc.parseUpdateMeta
+ * @property {function(Y.Doc):Uint8Array} Enc.encodeStateVector
+ * @property {function(Uint8Array):Uint8Array} Enc.encodeStateVectorFromUpdate
  * @property {string} Enc.updateEventName
  * @property {string} Enc.description
  */
@@ -20,6 +23,9 @@ const encV1 = {
   encodeStateAsUpdate: Y.encodeStateAsUpdate,
   applyUpdate: Y.applyUpdate,
   logUpdate: Y.logUpdate,
+  parseUpdateMeta: Y.parseUpdateMeta,
+  encodeStateVectorFromUpdate: Y.encodeStateVectorFromUpdate,
+  encodeStateVector: Y.encodeStateVector,
   updateEventName: 'update',
   description: 'V1'
 }
@@ -32,6 +38,9 @@ const encV2 = {
   encodeStateAsUpdate: Y.encodeStateAsUpdateV2,
   applyUpdate: Y.applyUpdateV2,
   logUpdate: Y.logUpdateV2,
+  parseUpdateMeta: Y.parseUpdateMetaV2,
+  encodeStateVectorFromUpdate: Y.encodeStateVectorFromUpdateV2,
+  encodeStateVector: Y.encodeStateVectorV2,
   updateEventName: 'updateV2',
   description: 'V2'
 }
@@ -50,6 +59,9 @@ const encDoc = {
   encodeStateAsUpdate: Y.encodeStateAsUpdate,
   applyUpdate: Y.applyUpdate,
   logUpdate: Y.logUpdate,
+  parseUpdateMeta: Y.parseUpdateMetaV2,
+  encodeStateVectorFromUpdate: Y.encodeStateVectorFromUpdateV2,
+  encodeStateVector: Y.encodeStateVector,
   updateEventName: 'update',
   description: 'Merge via Y.Doc'
 }
@@ -129,6 +141,14 @@ const checkUpdateCases = (ydoc, updates, enc) => {
     const merged = new Y.Doc()
     enc.applyUpdate(merged, updates)
     t.compareArrays(merged.getArray().toArray(), ydoc.getArray().toArray())
+    t.compare(enc.encodeStateVector(merged), enc.encodeStateVectorFromUpdate(updates))
+    const meta = enc.parseUpdateMeta(updates)
+    meta.from.forEach((clock, client) => t.assert(clock === 0))
+    meta.to.forEach((clock, client) => {
+      const structs = /** @type {Array<Y.Item>} */ (merged.store.clients.get(client))
+      const lastStruct = structs[structs.length - 1]
+      t.assert(lastStruct.id.clock + lastStruct.length === clock)
+    })
   })
 }