recoder-code/collaboration-service/node_modules/sharedb/lib/client/presence/remote-doc-presence.js

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var RemotePresence = require('./remote-presence');
var ot = require('../../ot');

module.exports = RemoteDocPresence;
function RemoteDocPresence(presence, presenceId) {
  RemotePresence.call(this, presence, presenceId);

  this.collection = this.presence.collection;
  this.id = this.presence.id;
  this.src = null;
  this.presenceVersion = null;

  this._doc = this.connection.get(this.collection, this.id);
  this._emitter = this.connection._docPresenceEmitter;
  this._pending = null;
  this._opCache = null;
  this._pendingSetPending = false;

  this._opHandler = this._handleOp.bind(this);
  this._createDelHandler = this._handleCreateDel.bind(this);
  this._loadHandler = this._handleLoad.bind(this);
  this._registerWithDoc();
}

RemoteDocPresence.prototype = Object.create(RemotePresence.prototype);

RemoteDocPresence.prototype.receiveUpdate = function(message) {
  if (this._pending && message.pv < this._pending.pv) return;
  this.src = message.src;
  this._pending = message;
  this._setPendingPresence();
};

RemoteDocPresence.prototype.destroy = function(callback) {
  this._emitter.removeEventListener(this._doc, 'op', this._opHandler);
  this._emitter.removeEventListener(this._doc, 'create', this._createDelHandler);
  this._emitter.removeEventListener(this._doc, 'del', this._createDelHandler);
  this._emitter.removeEventListener(this._doc, 'load', this._loadHandler);

  RemotePresence.prototype.destroy.call(this, callback);
};

RemoteDocPresence.prototype._registerWithDoc = function() {
  this._emitter.addEventListener(this._doc, 'op', this._opHandler);
  this._emitter.addEventListener(this._doc, 'create', this._createDelHandler);
  this._emitter.addEventListener(this._doc, 'del', this._createDelHandler);
  this._emitter.addEventListener(this._doc, 'load', this._loadHandler);
};

RemoteDocPresence.prototype._setPendingPresence = function() {
  if (this._pendingSetPending) return;
  this._pendingSetPending = true;
  var presence = this;
  this._doc.whenNothingPending(function() {
    presence._pendingSetPending = false;
    if (!presence._pending) return;
    if (presence._pending.pv < presence.presenceVersion) return presence._pending = null;

    if (presence._pending.v > presence._doc.version) {
      return presence._doc.fetch();
    }

    if (!presence._catchUpStalePresence()) return;

    presence.value = presence._pending.p;
    presence.presenceVersion = presence._pending.pv;
    presence._pending = null;
    presence.presence._updateRemotePresence(presence);
  });
};

RemoteDocPresence.prototype._handleOp = function(op, source, connectionId) {
  var isOwnOp = connectionId === this.src;
  this._transformAgainstOp(op, isOwnOp);
  this._cacheOp(op, isOwnOp);
  this._setPendingPresence();
};

RemotePresence.prototype._handleCreateDel = function() {
  this._cacheOp(null);
  this._setPendingPresence();
};

RemotePresence.prototype._handleLoad = function() {
  this.value = null;
  this._pending = null;
  this._opCache = null;
  this.presence._updateRemotePresence(this);
};

RemoteDocPresence.prototype._transformAgainstOp = function(op, isOwnOp) {
  if (!this.value) return;

  try {
    this.value = this._doc.type.transformPresence(this.value, op, isOwnOp);
  } catch (error) {
    return this.presence.emit('error', error);
  }
  this.presence._updateRemotePresence(this);
};

RemoteDocPresence.prototype._catchUpStalePresence = function() {
  if (this._pending.v >= this._doc.version) return true;

  if (!this._opCache) {
    this._startCachingOps();
    this._doc.fetch();
    this.presence._requestRemotePresence();
    return false;
  }

  while (this._opCache[this._pending.v]) {
    var item = this._opCache[this._pending.v];
    var op = item.op;
    var isOwnOp = item.isOwnOp;
    // We use a null op to signify a create or a delete operation. In both
    // cases we just want to reset the presence (which doesn't make sense
    // in a new document), so just set the presence to null.
    if (op === null) {
      this._pending.p = null;
      this._pending.v++;
    } else {
      ot.transformPresence(this._pending, op, isOwnOp);
    }
  }

  var hasCaughtUp = this._pending.v >= this._doc.version;
  if (hasCaughtUp) {
    this._stopCachingOps();
  }

  return hasCaughtUp;
};

RemoteDocPresence.prototype._startCachingOps = function() {
  this._opCache = [];
};

RemoteDocPresence.prototype._stopCachingOps = function() {
  this._opCache = null;
};

RemoteDocPresence.prototype._cacheOp = function(op, isOwnOp) {
  if (this._opCache) {
    op = op ? {op: op} : null;
    // Subtract 1 from the current doc version, because an op with v3
    // should be read as the op that takes a doc from v3 -> v4
    this._opCache[this._doc.version - 1] = {op: op, isOwnOp: isOwnOp};
  }
};