mungedb-aggregate/lib/pipeline/documentSources/MatchDocumentSource.js

"use strict";
var sift = require("sift");	//TODO: DEVIATION FROM MONGO: this was a temporary hack to get this done quickly but it is too inconsistent to keep; need a real port of MatchDocumentSource

/**
 * A match document source built off of FilterBaseDocumentSource
 *
 * NOTE: THIS IS A DEVIATION FROM THE MONGO IMPLEMENTATION.
 * TODO: internally uses `sift` to fake it, which has bugs, so we need to reimplement this by porting the MongoDB implementation
 *
 * @class MatchDocumentSource
 * @namespace mungedb-aggregate.pipeline.documentSources
 * @module mungedb-aggregate
 * @constructor
 * @param {Object} query the match query to use
 * @param [ctx] {ExpressionContext}
 **/
var MatchDocumentSource = module.exports = function MatchDocumentSource(query, ctx){
	if (arguments.length > 2) throw new Error("up to two args expected");
	if (!query) throw new Error("arg `query` is required");
	base.call(this, ctx);
	this.query = query; // save the query, so we can check it for deps later. THIS IS A DEVIATION FROM THE MONGO IMPLEMENTATION
	this.matcher = sift(query);
}, klass = MatchDocumentSource, base = require('./FilterBaseDocumentSource'), proto = klass.prototype = Object.create(base.prototype, {constructor:{value:klass}});

klass.matchName = "$match";

proto.getSourceName = function getSourceName(){
	return klass.matchName;
};

/**
 * Create an object that represents the document source.  The object
 * will have a single field whose name is the source's name.  This
 * will be used by the default implementation of addToJsonArray()
 * to add this object to a pipeline being represented in JSON.
 *
 * @method	sourceToJson
 * @param	{Object} builder	JSONObjBuilder: a blank object builder to write to
 * @param	{Boolean}	explain	create explain output
 **/
proto.sourceToJson = function sourceToJson(builder, explain) {
	builder[this.getSourceName()] = this.matcher.query;
};

/**
 *  Test the given document against the predicate and report if it should be accepted or not.
 * @param {object} document the document to test
 * @returns {bool} true if the document matches the filter, false otherwise
 **/
proto.accept = function accept(document) {
	/**
	* The matcher only takes BSON documents, so we have to make one.
	*
	* LATER
	* We could optimize this by making a document with only the
	* fields referenced by the Matcher.  We could do this by looking inside
	* the Matcher's BSON before it is created, and recording those.  The
	* easiest implementation might be to hold onto an ExpressionDocument
	* in here, and give that pDocument to create the created subset of
	* fields, and then convert that instead.
	**/
	return this.matcher.test(document);
};

/**
 * Create a JSONObj suitable for Matcher construction.
 *
 * This is used after filter analysis has moved as many filters to
 * as early a point as possible in the document processing pipeline.
 * See db/Matcher.h and the associated wiki documentation for the
 * format.  This conversion is used to move back to the low-level
 * find() Cursor mechanism.
 *
 * @param builder the builder to write to
 **/
proto.toMatcherJson = function toMatcherJson(builder) {
	var q = this.matcher.query;
	for(var k in q){
		builder[k] = q[k];
	}
};

klass.uassertNoDisallowedClauses = function uassertNoDisallowedClauses(query) {
	for(var key in query){
		if(query.hasOwnProperty(key)){
			// can't use the Matcher API because this would segfault the constructor
			if (query[key] == "$where") throw new Error("code 16395; $where is not allowed inside of a $match aggregation expression");
			// geo breaks if it is not the first portion of the pipeline
			if (query[key] == "$near") throw new Error("code 16424; $near is not allowed inside of a $match aggregation expression");
			if (query[key] == "$within") throw new Error("code 16425; $within is not allowed inside of a $match aggregation expression");
			if (query[key] == "$nearSphere") throw new Error("code 16426; $nearSphere is not allowed inside of a $match aggregation expression");
			if (query[key] instanceof Object && query[key].constructor === Object) this.uassertNoDisallowedClauses(query[key]);
		}
	}
};

klass.createFromJson = function createFromJson(jsonElement, ctx) {
	if (!(jsonElement instanceof Object) || jsonElement.constructor !== Object) throw new Error("code 15959 ; the match filter must be an expression in an object");
	klass.uassertNoDisallowedClauses(jsonElement);
	var matcher = new MatchDocumentSource(jsonElement, ctx);
	return matcher;
};