implement snapshot & event.changes

src/utils/Snapshot.js

@@ -6,18 +6,26 @@ import {
   getItemCleanStart,
   createID,
   iterateDeletedStructs,
+  writeDeleteSet,
+  writeStateVector,
+  readDeleteSet,
+  readStateVector,
+  createDeleteSet,
+  getState,
   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 encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
 
 export class Snapshot {
   /**
    * @param {DeleteSet} ds
-   * @param {Map<number,number>} sm state map
+   * @param {Map<number,number>} sv state map
    */
-  constructor (ds, sm) {
+  constructor (ds, sv) {
     /**
      * @type {DeleteSet}
      * @private
@@ -28,10 +36,64 @@ export class Snapshot {
      * @type {Map<number,number>}
      * @private
      */
-    this.sm = sm
+    this.sv = sv
   }
 }
 
+/**
+ * @param {Snapshot} snap1
+ * @param {Snapshot} snap2
+ * @return {boolean}
+ */
+export const equalSnapshots = (snap1, snap2) => {
+  const ds1 = snap1.ds.clients
+  const ds2 = snap2.ds.clients
+  const sv1 = snap1.sv
+  const sv2 = snap2.sv
+  if (sv1.size !== sv2.size || ds1.size !== ds2.size) {
+    return false
+  }
+  for (const [key, value] of sv1) {
+    if (sv2.get(key) !== value) {
+      return false
+    }
+  }
+  for (const [client, dsitems1] of ds1) {
+    const dsitems2 = ds2.get(client) || []
+    if (dsitems1.length !== dsitems2.length) {
+      return false
+    }
+    for (let i = 0; i < dsitems1.length; i++) {
+      const dsitem1 = dsitems1[i]
+      const dsitem2 = dsitems2[i]
+      if (dsitem1.clock !== dsitem2.clock || dsitem1.len !== dsitem2.len) {
+        return false
+      }
+    }
+  }
+  return true
+}
+
+/**
+ * @param {Snapshot} snapshot
+ * @return {Uint8Array}
+ */
+export const encodeSnapshot = snapshot => {
+  const encoder = encoding.createEncoder()
+  writeDeleteSet(encoder, snapshot.ds)
+  writeStateVector(encoder, snapshot.sv)
+  return encoding.toUint8Array(encoder)
+}
+
+/**
+ * @param {Uint8Array} buf
+ * @return {Snapshot}
+ */
+export const decodeSnapshot = buf => {
+  const decoder = decoding.createDecoder(buf)
+  return new Snapshot(readDeleteSet(decoder), readStateVector(decoder))
+}
+
 /**
  * @param {DeleteSet} ds
  * @param {Map<number,number>} sm
@@ -39,11 +101,13 @@ export class Snapshot {
  */
 export const createSnapshot = (ds, sm) => new Snapshot(ds, sm)
 
+export const emptySnapshot = createSnapshot(createDeleteSet(), new Map())
+
 /**
  * @param {Doc} doc
  * @return {Snapshot}
  */
-export const createSnapshotFromDoc = doc => createSnapshot(createDeleteSetFromStructStore(doc.store), getStateVector(doc.store))
+export const snapshot = doc => createSnapshot(createDeleteSetFromStructStore(doc.store), getStateVector(doc.store))
 
 /**
  * @param {Item} item
@@ -53,7 +117,7 @@ export const createSnapshotFromDoc = doc => createSnapshot(createDeleteSetFromSt
  * @function
  */
 export const isVisible = (item, snapshot) => snapshot === undefined ? !item.deleted : (
-  snapshot.sm.has(item.id.client) && (snapshot.sm.get(item.id.client) || 0) > item.id.clock && !isDeleted(snapshot.ds, item.id)
+  snapshot.sv.has(item.id.client) && (snapshot.sv.get(item.id.client) || 0) > item.id.clock && !isDeleted(snapshot.ds, item.id)
 )
 
 /**
@@ -65,8 +129,10 @@ export const splitSnapshotAffectedStructs = (transaction, snapshot) => {
   const store = transaction.doc.store
   // check if we already split for this snapshot
   if (!meta.has(snapshot)) {
-    snapshot.sm.forEach((clock, client) => {
-      getItemCleanStart(transaction, store, createID(client, clock))
+    snapshot.sv.forEach((clock, client) => {
+      if (clock < getState(store, client)) {
+        getItemCleanStart(transaction, store, createID(client, clock))
+      }
     })
     iterateDeletedStructs(transaction, snapshot.ds, store, item => {})
     meta.add(snapshot)