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542 lines
15 KiB
542 lines
15 KiB
/**
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* Handle models (i.e. docs)
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* Serialization/deserialization
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* Copying
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*/
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var dateToJSON = function () { return { $$date: this.getTime() }; }
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, originalDateToJSON = Date.prototype.toJSON
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, util = require('util')
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, _ = require('underscore')
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, modifierFunctions = {}
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, comparisonFunctions = {}
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, logicalOperators = {}
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;
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/**
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* Check a key, throw an error if the key is non valid
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* @param {String} k key
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* @param {Model} v value, needed to treat the Date edge case
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* Non-treatable edge cases here: if part of the object if of the form { $$date: number } or { $$deleted: true }
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* Its serialized-then-deserialized version it will transformed into a Date object
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* But you really need to want it to trigger such behaviour, even when warned not to use '$' at the beginning of the field names...
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*/
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function checkKey (k, v) {
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if (k[0] === '$' && !(k === '$$date' && typeof v === 'number') && !(k === '$$deleted' && v === true)) {
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throw 'Field names cannot begin with the $ character';
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}
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if (k.indexOf('.') !== -1) {
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throw 'Field names cannot contain a .';
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}
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}
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/**
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* Check a DB object and throw an error if it's not valid
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* Works by applying the above checkKey function to all fields recursively
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*/
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function checkObject (obj) {
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if (util.isArray(obj)) {
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obj.forEach(function (o) {
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checkObject(o);
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});
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}
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if (typeof obj === 'object') {
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Object.keys(obj).forEach(function (k) {
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checkKey(k, obj[k]);
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checkObject(obj[k]);
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});
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}
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}
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/**
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* Serialize an object to be persisted to a one-line string
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* For serialization/deserialization, we use the native JSON parser and not eval or Function
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* That gives us less freedom but data entered in the database may come from users
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* so eval and the like are not safe
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* Accepted primitive types: Number, String, Boolean, Date, null
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* Accepted secondary types: Objects, Arrays
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*/
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function serialize (obj) {
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var res;
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// Keep track of the fact that this is a Date object
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Date.prototype.toJSON = dateToJSON;
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res = JSON.stringify(obj, function (k, v) {
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checkKey(k, v);
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if (typeof v === undefined) { return null; }
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if (typeof v === 'string' || typeof v === 'number' || typeof v === 'boolean' || v === null) { return v; }
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return v;
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});
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// Return Date to its original state
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Date.prototype.toJSON = originalDateToJSON;
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return res;
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}
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/**
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* From a one-line representation of an object generate by the serialize function
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* Return the object itself
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*/
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function deserialize (rawData) {
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return JSON.parse(rawData, function (k, v) {
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if (k === '$$date') { return new Date(v); }
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if (typeof v === 'string' || typeof v === 'number' || typeof v === 'boolean' || v === null) { return v; }
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if (v && v.$$date) { return v.$$date; }
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return v;
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});
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}
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/**
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* Deep copy a DB object
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*/
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function deepCopy (obj) {
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var res;
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if ( typeof obj === 'boolean' ||
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typeof obj === 'number' ||
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typeof obj === 'string' ||
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obj === null ||
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(obj && obj.constructor && obj.constructor.name === 'Date') ) {
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return obj;
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}
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if (obj instanceof Array) {
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res = [];
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obj.forEach(function (o) { res.push(o); });
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return res;
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}
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if (typeof obj === 'object') {
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res = {};
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Object.keys(obj).forEach(function (k) {
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res[k] = deepCopy(obj[k]);
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});
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return res;
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}
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return undefined; // For now everything else is undefined. We should probably throw an error instead
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}
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/**
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* Utility functions for comparing things
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* Assumes type checking was already done (a and b already have the same type)
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* compareNSB works for numbers, strings and booleans
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*/
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function compareNSB (a, b) {
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if (a < b) { return -1; }
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if (a > b) { return 1; }
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return 0;
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}
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function compareArrays (a, b) {
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var i, comp;
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for (i = 0; i < Math.min(a.length, b.length); i += 1) {
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comp = compareThings(a[i], b[i]);
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if (comp !== 0) { return comp; }
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}
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// Common section was identical, longest one wins
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return compareNSB(a.length, b.length);
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}
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/**
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* Compare things
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* Things are defined as any native types (string, number, boolean, null, date) and objects
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* In the case of objects and arrays, we compare the serialized versions
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* If two objects dont have the same type, the (arbitrary) type hierarchy is: null, number, strings, boolean, dates, arrays, objects
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* Return -1 if a < b, 1 if a > b and 0 if a = b (note that equality here is NOT the same as defined in areThingsEqual!)
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*/
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function compareThings (a, b) {
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// null is less than everything except null
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if (a === null) { return b === null ? 0 : -1; }
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if (b === null) { return a === null ? 0 : 1; }
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// Numbers
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if (typeof a === 'number') { return typeof b === 'number' ? compareNSB(a, b) : -1; }
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if (typeof b === 'number') { return typeof a === 'number' ? compareNSB(a, b) : 1; }
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// Strings
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if (typeof a === 'string') { return typeof b === 'string' ? compareNSB(a, b) : -1; }
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if (typeof b === 'string') { return typeof a === 'string' ? compareNSB(a, b) : 1; }
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// Booleans
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if (typeof a === 'boolean') { return typeof b === 'boolean' ? compareNSB(a, b) : -1; }
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if (typeof b === 'boolean') { return typeof a === 'boolean' ? compareNSB(a, b) : 1; }
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// Dates
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if (util.isDate(a)) { return util.isDate(b) ? compareNSB(a.getTime(), b.getTime()) : -1; }
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if (util.isDate(b)) { return util.isDate(a) ? compareNSB(a.getTime(), b.getTime()) : 1; }
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// Arrays (first element is most significant and so on)
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if (util.isArray(a)) { return util.isArray(b) ? compareArrays(a, b) : -1; }
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if (util.isArray(b)) { return util.isArray(a) ? compareArrays(a, b) : 1; }
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}
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// ==============================================================
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// Updating documents
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// ==============================================================
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/**
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* Set field to value in a model
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* Create it if it doesn't exist
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* @param {Object} obj The model to set a field for
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* @param {String} field Can contain dots, in that case that means we will set a subfield recursively
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* @param {Model} value
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*/
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modifierFunctions.$set = function (obj, field, value) {
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var fieldParts = typeof field === 'string' ? field.split('.') : field;
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if (fieldParts.length === 1) {
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obj[fieldParts[0]] = value;
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} else {
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obj[fieldParts[0]] = obj[fieldParts[0]] || {};
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modifierFunctions.$set(obj[fieldParts[0]], fieldParts.slice(1), value);
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}
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};
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/**
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* Increase (or decrease) a 'number' field
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* Create and initialize it if needed
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* @param {Object} obj The model to set a field for
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* @param {String} field Can contain dots, in that case that means we will set a subfield recursively
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* @param {Model} value
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*/
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modifierFunctions.$inc = function (obj, field, value) {
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var fieldParts = typeof field === 'string' ? field.split('.') : field;
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if (typeof value !== 'number') { throw value + " must be a number"; }
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if (fieldParts.length === 1) {
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if (typeof obj[fieldParts[0]] !== 'number') {
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if (!_.has(obj, fieldParts[0])) {
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obj[fieldParts[0]] = value;
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} else {
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throw "Don't use the $inc modifier on non-number fields";
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}
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} else {
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obj[fieldParts[0]] += value;
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}
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} else {
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obj[fieldParts[0]] = obj[fieldParts[0]] || {};
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modifierFunctions.$inc(obj[fieldParts[0]], fieldParts.slice(1), value);
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}
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};
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/**
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* Modify a DB object according to an update query
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* For now the updateQuery only replaces the object
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*/
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function modify (obj, updateQuery) {
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var keys = Object.keys(updateQuery)
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, firstChars = _.map(keys, function (item) { return item[0]; })
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, dollarFirstChars = _.filter(firstChars, function (c) { return c === '$'; })
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, newDoc, modifiers
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;
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if (keys.indexOf('_id') !== -1 && updateQuery._id !== obj._id) { throw "You cannot change a document's _id"; }
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if (dollarFirstChars.length !== 0 && dollarFirstChars.length !== firstChars.length) {
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throw "You cannot mix modifiers and normal fields";
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}
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if (dollarFirstChars.length === 0) {
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// Simply replace the object with the update query contents
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newDoc = deepCopy(updateQuery);
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newDoc._id = obj._id;
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} else {
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// Apply modifiers
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modifiers = _.uniq(keys);
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newDoc = deepCopy(obj);
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modifiers.forEach(function (m) {
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var keys;
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if (!modifierFunctions[m]) { throw "Unknown modifier " + m; }
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try {
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keys = Object.keys(updateQuery[m]);
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} catch (e) {
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throw "Modifier " + m + "'s argument must be an object";
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}
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keys.forEach(function (k) {
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modifierFunctions[m](newDoc, k, updateQuery[m][k]);
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});
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});
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}
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// Check result is valid and return it
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checkObject(newDoc);
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if (obj._id !== newDoc._id) { throw "You can't change a document's _id"; }
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return newDoc;
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};
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// ==============================================================
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// Finding documents
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// ==============================================================
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/**
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* Get a value from object with dot notation
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* @param {Object} obj
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* @param {String} field
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*/
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function getDotValue (obj, field) {
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var fieldParts = typeof field === 'string' ? field.split('.') : field;
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if (!obj) { return undefined; } // field cannot be empty so that means we should return undefined so that nothing can match
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if (fieldParts.length === 1) {
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return obj[fieldParts[0]];
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} else {
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return getDotValue(obj[fieldParts[0]], fieldParts.slice(1));
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}
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}
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/**
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* Check whether 'things' are equal
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* Things are defined as any native types (string, number, boolean, null, date) and objects
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* In the case of object, we check deep equality
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* Returns true if they are, false otherwise
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*/
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function areThingsEqual (a, b) {
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var aKeys , bKeys , i;
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// Strings, booleans, numbers, null
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if (a === null || typeof a === 'string' || typeof a === 'boolean' || typeof a === 'number' ||
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b === null || typeof b === 'string' || typeof b === 'boolean' || typeof b === 'number') { return a === b; }
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// Dates
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if (util.isDate(a) || util.isDate(b)) { return util.isDate(a) && util.isDate(b) && a.getTime() === b.getTime(); }
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// Arrays (no match since arrays are used as a $in)
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// undefined (no match since they mean field doesn't exist and can't be serialized)
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if (util.isArray(a) || util.isArray(b) || a === undefined || b === undefined) { return false; }
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// Objects (check for deep equality)
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// a and b should be objects at this point
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try {
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aKeys = Object.keys(a);
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bKeys = Object.keys(b);
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} catch (e) {
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return false;
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}
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if (aKeys.length !== bKeys.length) { return false; }
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for (i = 0; i < aKeys.length; i += 1) {
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if (bKeys.indexOf(aKeys[i]) === -1) { return false; }
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if (!areThingsEqual(a[aKeys[i]], b[aKeys[i]])) { return false; }
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}
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return true;
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}
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/**
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* Check that two values are comparable
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*/
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function areComparable (a, b) {
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if (typeof a !== 'string' && typeof a !== 'number' && !util.isDate(a) &&
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typeof b !== 'string' && typeof b !== 'number' && !util.isDate(b)) {
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return false;
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}
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if (typeof a !== typeof b) { return false; }
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return true;
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}
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/**
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* Arithmetic and comparison operators
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* @param {Native value} a Value in the object
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* @param {Native value} b Value in the query
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*/
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comparisonFunctions.$lt = function (a, b) {
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return areComparable(a, b) && a < b;
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};
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comparisonFunctions.$lte = function (a, b) {
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return areComparable(a, b) && a <= b;
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};
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comparisonFunctions.$gt = function (a, b) {
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return areComparable(a, b) && a > b;
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};
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comparisonFunctions.$gte = function (a, b) {
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return areComparable(a, b) && a >= b;
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};
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comparisonFunctions.$ne = function (a, b) {
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if (!a) { return true; }
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return !areThingsEqual(a, b);
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};
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comparisonFunctions.$in = function (a, b) {
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var i;
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if (!util.isArray(b)) { throw "$in operator called with a non-array"; }
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for (i = 0; i < b.length; i += 1) {
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if (areThingsEqual(a, b[i])) { return true; }
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}
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return false;
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};
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comparisonFunctions.$nin = function (a, b) {
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if (!util.isArray(b)) { throw "$nin operator called with a non-array"; }
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return !comparisonFunctions.$in(a, b);
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};
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/**
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* Match any of the subqueries
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* @param {Model} obj
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* @param {Array of Queries} query
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*/
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logicalOperators.$or = function (obj, query) {
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var i;
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if (!util.isArray(query)) { throw "$or operator used without an array"; }
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for (i = 0; i < query.length; i += 1) {
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if (match(obj, query[i])) { return true; }
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}
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return false;
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};
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/**
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* Match all of the subqueries
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* @param {Model} obj
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* @param {Array of Queries} query
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*/
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logicalOperators.$and = function (obj, query) {
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var i;
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if (!util.isArray(query)) { throw "$and operator used without an array"; }
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for (i = 0; i < query.length; i += 1) {
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if (!match(obj, query[i])) { return false; }
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}
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return true;
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};
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/**
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* Inverted match of the query
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* @param {Model} obj
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* @param {Query} query
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*/
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logicalOperators.$not = function (obj, query) {
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return !match(obj, query);
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};
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/**
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* Tell if a given document matches a query
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* @param {Object} obj Document to check
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* @param {Object} query
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*/
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function match (obj, query) {
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var queryKeys = Object.keys(query)
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, i
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;
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for (i = 0; i < queryKeys.length; i += 1) {
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if (!matchQueryPart(obj, queryKeys[i], query[queryKeys[i]])) { return false; }
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}
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return true;
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};
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/**
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* Match an object against a specific { key: value } part of a query
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*/
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function matchQueryPart (obj, queryKey, queryValue) {
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var objValue = getDotValue(obj, queryKey)
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, i
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, keys, firstChars, dollarFirstChars
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;
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// Query part begins with a logical operator: apply it
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if (queryKey[0] === '$') {
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if (!logicalOperators[queryKey]) { throw "Unknown logical operator " + queryKey; }
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return logicalOperators[queryKey](obj, queryValue);
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}
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// Check if the object value is an array treat it as an array of { obj, query }
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// Where there needs to be at least one match
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if (util.isArray(objValue)) {
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for (i = 0; i < objValue.length; i += 1) {
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if (matchQueryPart({ k: objValue[i] }, 'k', queryValue)) { return true; } // k here could be any string
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}
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return false;
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}
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// queryValue is an actual object. Determine whether it contains comparison operators
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// or only normal fields. Mixed objects are not allowed
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if (queryValue !== null && typeof queryValue === 'object') {
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keys = Object.keys(queryValue);
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firstChars = _.map(keys, function (item) { return item[0]; })
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dollarFirstChars = _.filter(firstChars, function (c) { return c === '$'; })
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if (dollarFirstChars.length !== 0 && dollarFirstChars.length !== firstChars.length) {
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throw "You cannot mix operators and normal fields";
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}
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// queryValue is an object of this form: { $comparisonOperator1: value1, ... }
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if (dollarFirstChars.length > 0) {
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for (i = 0; i < keys.length; i += 1) {
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if (!comparisonFunctions[keys[i]]) { throw "Unknown comparison function " + keys[i]; }
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if (!comparisonFunctions[keys[i]](objValue, queryValue[keys[i]])) { return false; }
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}
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return true;
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}
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}
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// queryValue is either a native value or a normal object
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// Simple matching is possible
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if (!areThingsEqual(objValue, queryValue)) { return false; }
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return true;
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}
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// Interface
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module.exports.serialize = serialize;
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module.exports.deserialize = deserialize;
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module.exports.deepCopy = deepCopy;
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module.exports.checkObject = checkObject;
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module.exports.modify = modify;
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module.exports.getDotValue = getDotValue;
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module.exports.match = match;
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module.exports.areThingsEqual = areThingsEqual;
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module.exports.compareThings = compareThings;
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