Method checkLocalDiffChanges

packages/core/src/engine/engine.ts:391–436

(checkVersion?: number)

  // Check the version gap between the local snapshot and the local changeset.
  // If there is a gap, transform and rebase the localChangeset.
  async checkLocalDiffChanges(checkVersion?: number) {
    if (!this.bufferStorage.localPendingChangeset) {
      checkVersion != null && this.checkMissChanges(checkVersion);
      return;
    }

    Player.doTrigger(Events.app_error_logger, {
      error: new Error(t(Strings.error_an_unsynchronized_changeset_is_detected)),
      metaData: this.bufferStorage.localPendingChangeset,
    });
    const revision = this.getRevision();
    const baseRevision = this.bufferStorage.localPendingChangeset.baseRevision;

    if (baseRevision > revision) {
      throw new Error('localRevision greater than remoteRevision');
    }

    console.log('checkLocalDiffChanges: ', { baseRevision, revision });

    if (baseRevision < revision) {
      let changesetList = await this.fetchMissVersion(baseRevision + 1, revision + 1);
      /**
        * Check if localChangeset is already in changesetList, if so
        * 1. It means that localChangeset has been applied to the snapshot, so it does not need to be sent locally
        * 2. This changeset before this needs to be transformed, and the latter does not need to be transformed
        */
      const transformEndIndex = changesetList.findIndex(changeset => {
        return changeset.messageId === this.bufferStorage.localPendingChangeset!.messageId;
      });

      changesetList = changesetList.slice(0, transformEndIndex);

      if (transformEndIndex >= 0) {
        // 1. Discard localChangeset.
        // 2. opBuffer becomes the new localChangeset, and baseRevision is set to the revision
        // in the changesetList where the original localChangeset is located.
        console.log('Detected that the local localPendingChangeset has been consumed, delete it directly', this.bufferStorage.localPendingChangeset);
        this.bufferStorage.deOpBuffer(revision);
        console.log('The local opBuffer enters localPendingChangeset', this.bufferStorage.localPendingChangeset);
      }

      changesetList.forEach(changeset => {
        this.doTransform(changeset);
      });
    }
  }

  private doTransform(cs: IRemoteChangeset) {
    let remoteActions = cs.operations.reduce<IJOTAction[]>((pre, op) => {