notesnook/packages/core/api/sync/merger.js

import { migrations } from "../../migrations";
import { areAllEmpty } from "./utils";
import SparkMD5 from "spark-md5";
import setManipulator from "../../utils/set";

class Merger {
  /**
   *
   * @param {import("../index").default} db
   */
  constructor(db) {
    this._db = db;
  }

  _migrate(deserialized, version) {
    // it is a locked note, bail out.
    if (deserialized.alg && deserialized.cipher) return deserialized;

    let type = deserialized.type;
    if (!type && deserialized.data) type = "tiny";

    const migrate = migrations[version][type];
    if (migrate) return migrate(deserialized);
    return deserialized;
  }

  async _deserialize(item, migrate = true) {
    const deserialized = JSON.parse(
      await this._db.storage.decrypt(this.key, item)
    );
    deserialized.remote = true;
    if (!migrate) return deserialized;
    return this._migrate(deserialized, item.v);
  }

  async _mergeItem(remoteItem, get, add) {
    let localItem = await get(remoteItem.id);
    remoteItem = await this._deserialize(remoteItem);
    if (!localItem || remoteItem.dateEdited > localItem.dateEdited) {
      await add(remoteItem);
    }
  }

  async _mergeArray(array, get, set) {
    if (!array) return;
    for (let item of array) {
      await this._mergeItem(item, get, set);
    }
  }

  async _mergeItemWithConflicts(remoteItem, get, add, markAsConflicted) {
    let localItem = await get(remoteItem.id);
    remoteItem = await this._deserialize(remoteItem);
    if (!localItem) {
      await add(remoteItem);
    } else if (
      localItem.dateResolved !== remoteItem.dateEdited &&
      localItem.dateEdited > this._lastSynced
    ) {
      // If time difference between local item's edits & remote item's edits
      // is less than 1 minute, we shouldn't trigger a merge conflict; instead
      // we will keep the most recently changed item.
      const timeDiff =
        Math.max(remoteItem.dateEdited, localItem.dateEdited) -
        Math.min(remoteItem.dateEdited, localItem.dateEdited);
      const ONE_MINUTE = 60 * 1000;
      if (timeDiff < ONE_MINUTE) {
        if (remoteItem.dateEdited > localItem.dateEdited) await add(remoteItem);
        return;
      }

      await markAsConflicted(localItem, remoteItem);
    } else {
      await add(remoteItem);
    }
  }

  async _mergeArrayWithConflicts(array, mergeItem) {
    if (!array) return;
    for (let item of array) {
      await mergeItem(item);
    }
  }

  async merge(serverResponse, lastSynced) {
    if (!serverResponse) return false;
    this._lastSynced = lastSynced;
    const {
      notes = [],
      synced,
      notebooks = [],
      content = [],
      vaultKey,
      settings = [],
      attachments = [],
    } = serverResponse;

    if (synced || areAllEmpty(serverResponse)) return false;
    this.key = await this._db.user.getEncryptionKey();

    if (vaultKey) {
      await this._db.vault._setKey(await this._deserialize(vaultKey, false));
    }

    await this._mergeArrayWithConflicts(attachments, async (item) => {
      const remoteAttachment = await this._deserialize(item);
      const localAttachment = this._db.attachments.attachment(
        remoteAttachment.metadata.hash
      );
      if (
        localAttachment &&
        localAttachment.dateUploaded !== remoteAttachment.dateUploaded
      ) {
        const noteIds = localAttachment.noteIds.slice();
        const isRemoved = await this._db.attachments.remove(
          localAttachment.metadata.hash,
          true
        );
        if (!isRemoved)
          throw new Error(
            "Conflict could not be resolved in one of the attachments."
          );
        remoteAttachment.noteIds = setManipulator.union(
          remoteAttachment.noteIds,
          noteIds
        );
      }
      await this._db.attachments.add(remoteAttachment);
    });

    await this._mergeArray(
      settings,
      () => this._db.settings.raw,
      (item) => this._db.settings.merge(item)
    );

    await this._mergeArray(
      notes,
      (id) => this._db.notes.note(id),
      (item) => this._db.notes.add(item)
    );

    await this._mergeArray(
      notebooks,
      (id) => this._db.notebooks.notebook(id),
      (item) => this._db.notebooks.merge(item)
    );

    await this._mergeArrayWithConflicts(content, (item) =>
      this._mergeItemWithConflicts(
        item,
        (id) => this._db.content.raw(id, false),
        (item) => this._db.content.add(item),
        async (local, remote) => {
          let note = this._db.notes.note(local.noteId);
          if (!note || !note.data) return;
          note = note.data;

          // if hashes are equal do nothing
          if (
            !note.locked &&
            (!remote ||
              !local ||
              !local.data ||
              !remote.data ||
              remote.data === "undefined" || //TODO not sure about this
              SparkMD5.hash(local.data) === SparkMD5.hash(remote.data))
          )
            return;

          if (remote.deleted || local.deleted || note.locked) {
            // if note is locked or content is deleted we keep the most recent version.
            if (remote.dateEdited > local.dateEdited)
              await this._db.content.add({ id: local.id, ...remote });
          } else {
            // otherwise we trigger the conflicts
            await this._db.content.add({ ...local, conflicted: remote });
            await this._db.notes.add({ id: local.noteId, conflicted: true });
            await this._db.storage.write("hasConflicts", true);
          }
        }
      )
    );

    return true;
  }
}
export default Merger;