Merge pull request #243 from yjs/create-doc-from-snapshot-3

Create doc from snapshot 3

src/index.js

@@ -47,6 +47,7 @@ export {
   findRootTypeKey,
   typeListToArraySnapshot,
   typeMapGetSnapshot,
+  createDocFromSnapshot,
   iterateDeletedStructs,
   applyUpdate,
   applyUpdateV2,

src/utils/Snapshot.js

@@ -12,13 +12,17 @@ import {
   createDeleteSet,
   createID,
   getState,
-  AbstractDSDecoder, AbstractDSEncoder, DSEncoderV1, DSEncoderV2, DSDecoderV1, DSDecoderV2, Transaction, Doc, DeleteSet, Item // eslint-disable-line
+  findIndexSS,
+  UpdateEncoderV2,
+  DefaultDSEncoder,
+  applyUpdateV2,
+  AbstractDSDecoder, AbstractDSEncoder, DSEncoderV2, DSDecoderV1, DSDecoderV2, Transaction, Doc, DeleteSet, Item // eslint-disable-line
 } from '../internals.js'
 
 import * as map from 'lib0/map.js'
 import * as set from 'lib0/set.js'
 import * as decoding from 'lib0/decoding.js'
-import { DefaultDSEncoder } from './encoding.js'
+import * as encoding from 'lib0/encoding.js'
 
 export class Snapshot {
   /**
@@ -148,3 +152,51 @@ export const splitSnapshotAffectedStructs = (transaction, snapshot) => {
     meta.add(snapshot)
   }
 }
+
+/**
+ * @param {Doc} originDoc
+ * @param {Snapshot} snapshot
+ * @param {Doc} [newDoc] Optionally, you may define the Yjs document that receives the data from originDoc
+ * @return {Doc}
+ */
+export const createDocFromSnapshot = (originDoc, snapshot, newDoc = new Doc()) => {
+  if (originDoc.gc) {
+    // we should not try to restore a GC-ed document, because some of the restored items might have their content deleted
+    throw new Error('originDoc must not be garbage collected')
+  }
+  const { sv, ds } = snapshot
+
+  const encoder = new UpdateEncoderV2()
+  originDoc.transact(transaction => {
+    let size = 0
+    sv.forEach(clock => {
+      if (clock > 0) {
+        size++
+      }
+    })
+    encoding.writeVarUint(encoder.restEncoder, size)
+    // splitting the structs before writing them to the encoder
+    for (const [client, clock] of sv) {
+      if (clock === 0) {
+        continue
+      }
+      if (clock < getState(originDoc.store, client)) {
+        getItemCleanStart(transaction, createID(client, clock))
+      }
+      const structs = originDoc.store.clients.get(client) || []
+      const lastStructIndex = findIndexSS(structs, clock - 1)
+      // write # encoded structs
+      encoding.writeVarUint(encoder.restEncoder, lastStructIndex + 1)
+      encoder.writeClient(client)
+      // first clock written is 0
+      encoding.writeVarUint(encoder.restEncoder, 0)
+      for (let i = 0; i <= lastStructIndex; i++) {
+        structs[i].write(encoder, 0)
+      }
+    }
+    writeDeleteSet(encoder, ds)
+  })
+
+  applyUpdateV2(newDoc, encoder.toUint8Array(), 'snapshot')
+  return newDoc
+}