632 lines
16 KiB
JavaScript
632 lines
16 KiB
JavaScript
/*!
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* Module Dependencies.
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*/
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var PersistedModel = require('../../lib/loopback').PersistedModel;
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var loopback = require('../../lib/loopback');
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var crypto = require('crypto');
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var CJSON = {stringify: require('canonical-json')};
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var async = require('async');
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var assert = require('assert');
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var debug = require('debug')('loopback:change');
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/**
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* Change list entry.
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*
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* @property {String} id Hash of the modelName and id
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* @property {String} rev The current model revision
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* @property {String} prev The previous model revision
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* @property {Number} checkpoint The current checkpoint at time of the change
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* @property {String} modelName Model name
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* @property {String} modelId Model ID
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*
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* @class Change
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* @inherits {PersistedModel}
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*/
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module.exports = function(Change) {
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/*!
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* Constants
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*/
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Change.UPDATE = 'update';
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Change.CREATE = 'create';
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Change.DELETE = 'delete';
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Change.UNKNOWN = 'unknown';
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/*!
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* Conflict Class
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*/
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Change.Conflict = Conflict;
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/*!
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* Setup the extended model.
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*/
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Change.setup = function() {
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PersistedModel.setup.call(this);
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var Change = this;
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Change.getter.id = function() {
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var hasModel = this.modelName && this.modelId;
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if (!hasModel) return null;
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return Change.idForModel(this.modelName, this.modelId);
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};
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};
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Change.setup();
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/**
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* Track the recent change of the given modelIds.
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*
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* @param {String} modelName
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* @param {Array} modelIds
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* @callback {Function} callback
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* @param {Error} err
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* @param {Array} changes Changes that were tracked
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*/
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Change.rectifyModelChanges = function(modelName, modelIds, callback) {
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var tasks = [];
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var Change = this;
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modelIds.forEach(function(id) {
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tasks.push(function(cb) {
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Change.findOrCreateChange(modelName, id, function(err, change) {
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if (err) return Change.handleError(err, cb);
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change.rectify(cb);
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});
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});
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});
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async.parallel(tasks, callback);
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};
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/**
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* Get an identifier for a given model.
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*
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* @param {String} modelName
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* @param {String} modelId
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* @return {String}
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*/
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Change.idForModel = function(modelName, modelId) {
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return this.hash([modelName, modelId].join('-'));
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};
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/**
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* Find or create a change for the given model.
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*
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* @param {String} modelName
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* @param {String} modelId
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* @callback {Function} callback
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* @param {Error} err
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* @param {Change} change
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* @end
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*/
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Change.findOrCreateChange = function(modelName, modelId, callback) {
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assert(loopback.findModel(modelName), modelName + ' does not exist');
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var id = this.idForModel(modelName, modelId);
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var Change = this;
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this.findById(id, function(err, change) {
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if (err) return callback(err);
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if (change) {
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callback(null, change);
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} else {
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var ch = new Change({
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id: id,
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modelName: modelName,
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modelId: modelId
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});
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ch.debug('creating change');
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ch.save(callback);
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}
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});
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};
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/**
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* Update (or create) the change with the current revision.
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*
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* @callback {Function} callback
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* @param {Error} err
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* @param {Change} change
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*/
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Change.prototype.rectify = function(cb) {
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var change = this;
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var tasks = [
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updateRevision,
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updateCheckpoint
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];
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var currentRev = this.rev;
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change.debug('rectify change');
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cb = cb || function(err) {
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if (err) throw new Error(err);
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};
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async.parallel(tasks, function(err) {
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if (err) return cb(err);
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if (change.prev === Change.UNKNOWN) {
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// this occurs when a record of a change doesn't exist
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// and its current revision is null (not found)
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change.remove(cb);
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} else {
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change.save(cb);
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}
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});
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function updateRevision(cb) {
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// get the current revision
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change.currentRevision(function(err, rev) {
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if (err) return Change.handleError(err, cb);
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if (rev) {
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// avoid setting rev and prev to the same value
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if (currentRev !== rev) {
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change.rev = rev;
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change.prev = currentRev;
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} else {
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change.debug('rev and prev are equal (not updating rev)');
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}
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} else {
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change.rev = null;
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if (currentRev) {
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change.prev = currentRev;
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} else if (!change.prev) {
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change.debug('ERROR - could not determing prev');
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change.prev = Change.UNKNOWN;
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}
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}
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change.debug('updated revision (was ' + currentRev + ')');
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cb();
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});
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}
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function updateCheckpoint(cb) {
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change.constructor.getCheckpointModel().current(function(err, checkpoint) {
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if (err) return Change.handleError(err);
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debug('updated checkpoint to', checkpoint);
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change.checkpoint = checkpoint;
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cb();
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});
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}
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};
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/**
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* Get a change's current revision based on current data.
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* @callback {Function} callback
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* @param {Error} err
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* @param {String} rev The current revision
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*/
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Change.prototype.currentRevision = function(cb) {
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var model = this.getModelCtor();
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var id = this.getModelId();
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model.findById(id, function(err, inst) {
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if (err) return Change.handleError(err, cb);
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if (inst) {
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cb(null, Change.revisionForInst(inst));
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} else {
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cb(null, null);
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}
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});
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};
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/**
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* Create a hash of the given `string` with the `options.hashAlgorithm`.
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* **Default: `sha1`**
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*
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* @param {String} str The string to be hashed
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* @return {String} The hashed string
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*/
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Change.hash = function(str) {
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return crypto
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.createHash(Change.settings.hashAlgorithm || 'sha1')
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.update(str)
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.digest('hex');
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};
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/**
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* Get the revision string for the given object
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* @param {Object} inst The data to get the revision string for
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* @return {String} The revision string
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*/
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Change.revisionForInst = function(inst) {
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return this.hash(CJSON.stringify(inst));
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};
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/**
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* Get a change's type. Returns one of:
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*
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* - `Change.UPDATE`
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* - `Change.CREATE`
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* - `Change.DELETE`
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* - `Change.UNKNOWN`
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*
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* @return {String} the type of change
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*/
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Change.prototype.type = function() {
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if (this.rev && this.prev) {
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return Change.UPDATE;
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}
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if (this.rev && !this.prev) {
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return Change.CREATE;
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}
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if (!this.rev && this.prev) {
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return Change.DELETE;
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}
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return Change.UNKNOWN;
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};
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/**
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* Compare two changes.
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* @param {Change} change
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* @return {Boolean}
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*/
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Change.prototype.equals = function(change) {
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if (!change) return false;
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var thisRev = this.rev || null;
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var thatRev = change.rev || null;
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return thisRev === thatRev;
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};
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/**
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* Does this change conflict with the given change.
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* @param {Change} change
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* @return {Boolean}
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*/
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Change.prototype.conflictsWith = function(change) {
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if (!change) return false;
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if (this.equals(change)) return false;
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if (Change.bothDeleted(this, change)) return false;
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if (this.isBasedOn(change)) return false;
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return true;
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};
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/**
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* Are both changes deletes?
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* @param {Change} a
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* @param {Change} b
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* @return {Boolean}
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*/
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Change.bothDeleted = function(a, b) {
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return a.type() === Change.DELETE &&
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b.type() === Change.DELETE;
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};
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/**
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* Determine if the change is based on the given change.
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* @param {Change} change
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* @return {Boolean}
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*/
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Change.prototype.isBasedOn = function(change) {
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return this.prev === change.rev;
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};
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/**
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* Determine the differences for a given model since a given checkpoint.
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*
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* The callback will contain an error or `result`.
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*
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* **result**
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*
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* ```js
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* {
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* deltas: Array,
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* conflicts: Array
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* }
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* ```
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*
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* **deltas**
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*
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* An array of changes that differ from `remoteChanges`.
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*
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* **conflicts**
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*
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* An array of changes that conflict with `remoteChanges`.
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*
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* @param {String} modelName
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* @param {Number} since Compare changes after this checkpoint
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* @param {Change[]} remoteChanges A set of changes to compare
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* @callback {Function} callback
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* @param {Error} err
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* @param {Object} result See above.
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*/
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Change.diff = function(modelName, since, remoteChanges, callback) {
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if (!Array.isArray(remoteChanges) || remoteChanges.length === 0) {
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return callback(null, {deltas: [], conflicts: []});
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}
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var remoteChangeIndex = {};
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var modelIds = [];
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remoteChanges.forEach(function(ch) {
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modelIds.push(ch.modelId);
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remoteChangeIndex[ch.modelId] = new Change(ch);
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});
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// normalize `since`
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since = Number(since) || 0;
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this.find({
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where: {
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modelName: modelName,
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modelId: {inq: modelIds},
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checkpoint: {gte: since}
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}
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}, function(err, localChanges) {
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if (err) return callback(err);
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var deltas = [];
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var conflicts = [];
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var localModelIds = [];
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localChanges.forEach(function(localChange) {
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localChange = new Change(localChange);
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localModelIds.push(localChange.modelId);
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var remoteChange = remoteChangeIndex[localChange.modelId];
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if (remoteChange && !localChange.equals(remoteChange)) {
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if (remoteChange.conflictsWith(localChange)) {
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remoteChange.debug('remote conflict');
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localChange.debug('local conflict');
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conflicts.push(localChange);
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} else {
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remoteChange.debug('remote delta');
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deltas.push(remoteChange);
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}
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}
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});
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modelIds.forEach(function(id) {
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if (localModelIds.indexOf(id) === -1) {
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deltas.push(remoteChangeIndex[id]);
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}
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});
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callback(null, {
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deltas: deltas,
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conflicts: conflicts
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});
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});
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};
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/**
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* Correct all change list entries.
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* @param {Function} cb
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*/
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Change.rectifyAll = function(cb) {
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debug('rectify all');
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var Change = this;
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// this should be optimized
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this.find(function(err, changes) {
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if (err) return cb(err);
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async.each(
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changes,
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function(c, next) { c.rectify(next); },
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cb);
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});
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};
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/**
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* Get the checkpoint model.
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* @return {Checkpoint}
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*/
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Change.getCheckpointModel = function() {
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var checkpointModel = this.Checkpoint;
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if (checkpointModel) return checkpointModel;
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this.Checkpoint = checkpointModel = loopback.Checkpoint.extend('checkpoint');
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assert(this.dataSource, 'Cannot getCheckpointModel(): ' + this.modelName +
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' is not attached to a dataSource');
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checkpointModel.attachTo(this.dataSource);
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return checkpointModel;
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};
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Change.handleError = function(err) {
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if (!this.settings.ignoreErrors) {
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throw err;
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}
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};
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Change.prototype.debug = function() {
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if (debug.enabled) {
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var args = Array.prototype.slice.call(arguments);
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debug.apply(this, args);
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debug('\tid', this.id);
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debug('\trev', this.rev);
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debug('\tprev', this.prev);
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debug('\tmodelName', this.modelName);
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debug('\tmodelId', this.modelId);
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debug('\ttype', this.type());
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}
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};
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/**
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* Get the `Model` class for `change.modelName`.
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* @return {Model}
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*/
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Change.prototype.getModelCtor = function() {
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return this.constructor.settings.trackModel;
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};
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Change.prototype.getModelId = function() {
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// TODO(ritch) get rid of the need to create an instance
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var Model = this.getModelCtor();
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var id = this.modelId;
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var m = new Model();
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m.setId(id);
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return m.getId();
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};
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Change.prototype.getModel = function(callback) {
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var Model = this.constructor.settings.trackModel;
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var id = this.getModelId();
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Model.findById(id, callback);
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};
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/**
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* When two changes conflict a conflict is created.
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*
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* **Note**: call `conflict.fetch()` to get the `target` and `source` models.
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*
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* @param {*} modelId
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* @param {PersistedModel} SourceModel
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* @param {PersistedModel} TargetModel
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* @property {ModelClass} source The source model instance
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* @property {ModelClass} target The target model instance
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* @class Change.Conflict
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*/
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function Conflict(modelId, SourceModel, TargetModel) {
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this.SourceModel = SourceModel;
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this.TargetModel = TargetModel;
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this.SourceChange = SourceModel.getChangeModel();
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this.TargetChange = TargetModel.getChangeModel();
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this.modelId = modelId;
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}
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/**
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* Fetch the conflicting models.
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*
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* @callback {Function} callback
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* @param {Error} err
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* @param {PersistedModel} source
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* @param {PersistedModel} target
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*/
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Conflict.prototype.models = function(cb) {
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var conflict = this;
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var SourceModel = this.SourceModel;
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var TargetModel = this.TargetModel;
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var source;
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var target;
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async.parallel([
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getSourceModel,
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getTargetModel
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], done);
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function getSourceModel(cb) {
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SourceModel.findById(conflict.modelId, function(err, model) {
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if (err) return cb(err);
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source = model;
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cb();
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});
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}
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function getTargetModel(cb) {
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TargetModel.findById(conflict.modelId, function(err, model) {
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if (err) return cb(err);
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target = model;
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cb();
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});
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}
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function done(err) {
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if (err) return cb(err);
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cb(null, source, target);
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}
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};
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/**
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* Get the conflicting changes.
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*
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* @callback {Function} callback
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* @param {Error} err
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* @param {Change} sourceChange
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* @param {Change} targetChange
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*/
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Conflict.prototype.changes = function(cb) {
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var conflict = this;
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var sourceChange;
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var targetChange;
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async.parallel([
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getSourceChange,
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getTargetChange
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], done);
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function getSourceChange(cb) {
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conflict.SourceChange.findOne({where: {
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modelId: conflict.modelId
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}}, function(err, change) {
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if (err) return cb(err);
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sourceChange = change;
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cb();
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});
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}
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function getTargetChange(cb) {
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conflict.TargetChange.findOne({where: {
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modelId: conflict.modelId
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}}, function(err, change) {
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if (err) return cb(err);
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targetChange = change;
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cb();
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});
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}
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function done(err) {
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if (err) return cb(err);
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cb(null, sourceChange, targetChange);
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}
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};
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/**
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* Resolve the conflict.
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*
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* @callback {Function} callback
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* @param {Error} err
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*/
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Conflict.prototype.resolve = function(cb) {
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var conflict = this;
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conflict.changes(function(err, sourceChange, targetChange) {
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if (err) return cb(err);
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sourceChange.prev = targetChange.rev;
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sourceChange.save(cb);
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});
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};
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/**
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* Determine the conflict type.
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*
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* Possible results are
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*
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* - `Change.UPDATE`: Source and target models were updated.
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* - `Change.DELETE`: Source and or target model was deleted.
|
|
* - `Change.UNKNOWN`: the conflict type is uknown or due to an error.
|
|
*
|
|
* @callback {Function} callback
|
|
* @param {Error} err
|
|
* @param {String} type The conflict type.
|
|
*/
|
|
|
|
Conflict.prototype.type = function(cb) {
|
|
var conflict = this;
|
|
this.changes(function(err, sourceChange, targetChange) {
|
|
if (err) return cb(err);
|
|
var sourceChangeType = sourceChange.type();
|
|
var targetChangeType = targetChange.type();
|
|
if (sourceChangeType === Change.UPDATE && targetChangeType === Change.UPDATE) {
|
|
return cb(null, Change.UPDATE);
|
|
}
|
|
if (sourceChangeType === Change.DELETE || targetChangeType === Change.DELETE) {
|
|
return cb(null, Change.DELETE);
|
|
}
|
|
return cb(null, Change.UNKNOWN);
|
|
});
|
|
};
|
|
};
|