mungedb-aggregate/lib/index.js

"use strict";
/**
 * Used to aggregate `inputs` using a MongoDB-style `pipeline`
 *
 * If `inputs` is given, it will run the `inputs` through the `pipeline` and call the `callback` with the results.
 * If `inputs` is omitted, it will return an "aggregator" function so you can reuse the given `pipeline` against various `inputs`.
 *
 * NOTE: you should be mindful about reusing the same `pipeline` against disparate `inputs` because document coming in can alter the state of it's `DocumentSource`s
 *
 * @method aggregate
 * @namespace mungedb
 * @module mungedb-aggregate
 * @param pipeline  {Array}   The list of pipeline document sources in JSON format
 * @param [ctx]     {Object}  Optional context object to pass through to pipeline
 * @param [inputs]  {Array}   Optional inputs to pass through the `docSrcs` pipeline
 * @param [callback]             {Function}                                 Optional callback if using async extensions, called when done
 * @param   callback.err           {Error}                                    The Error if one occurred
 * @param   callback.docs          {Array}                                    The resulting documents
 **/
exports = module.exports = function aggregate(cmdObject, ctx, inputs, callback) {	// function-style interface; i.e., return the utility function directly as the require
	var DocumentSource = exports.pipeline.documentSources.DocumentSource;
	if (ctx instanceof Array || ctx instanceof DocumentSource) callback = inputs, inputs = ctx, ctx = {};
	var pipelineInst;
	
	try {
		//Set up the command Object
		cmdObject = (cmdObject instanceof Array) ? {pipeline: cmdObject} : cmdObject;
		if (!cmdObject instanceof Object) throw new Error("cmdObject must be either an Object or an Array");
		for (var key in exports.cmdDefaults){
			if (exports.cmdDefaults.hasOwnProperty(key) && cmdObject[key] === undefined){
				cmdObject[key] = exports.cmdDefaults[key];
			}
		}
		pipelineInst = exports.pipeline.Pipeline.parseCommand(cmdObject, ctx);
	} catch(ex) {
		// Error handling is funky since this can be used multiple different ways
		if (callback){
			if (inputs) return callback(ex);
			else {
				return function aggregator(ctx, inputs, callback) {
					if (ctx instanceof Array || ctx instanceof DocumentSource) callback = inputs, inputs = ctx, ctx = {};
					return callback(ex);
				};
			}
		} else {
			throw ex;
		}
	}
	
	if (cmdObject.explain){
		return pipelineInst.writeExplainOps();
	}
	
	var aggregator = function aggregator(ctx, inputs, callback) {
			if (ctx instanceof Array || ctx instanceof DocumentSource) callback = inputs, inputs = ctx, ctx = {};
			var batchSize = cmdObject.batchSize;
			if (!callback) {
				batchSize = Infinity;
				callback = exports.SYNC_CALLBACK;
			}
			if (!inputs) return callback("arg `inputs` is required");
			
			try {
				// rebuild the pipeline on subsequent calls
				if (!pipelineInst) {
					pipelineInst = exports.pipeline.Pipeline.parseCommand(cmdObject, ctx);
				}
				ctx.ns = inputs;	//NOTE: use the given `inputs` directly; hacking so that the cursor source will be our inputs instead of the context namespace
				exports.pipeline.PipelineD.prepareCursorSource(pipelineInst, ctx);

				// run the pipeline against
				pipelineInst.stitch();
			} catch(err) {
				return callback(err);
			}

			var batch = [];
			var runCallback = function aggregated(err, document){
				if (!callback) return;//make sure the callback doesn't get called anymore after an error
				if(err) {
					pipelineInst = null;
					callback(err);
					callback = undefined;
					return;
				}
				if (document === null){
					pipelineInst = null;
					callback(null, batch);
					callback = undefined;
					return;
				}
				batch.push(document);
				if (batch.length >= batchSize){
					return callback(null, batch);
				}
			};
			pipelineInst.run(runCallback);
			return batch;
		};
	if(inputs) return aggregator(ctx, inputs, callback);
	return aggregator;
};

// sync callback for aggregate if none was provided
exports.SYNC_CALLBACK = function(err, docs){
	if (err) throw err;
	return docs;
};

exports.cmdDefaults = {
	batchSize: 150,
	explain: false
};

// package-style interface; i.e., return a function underneath of the require
exports.aggregate = exports;

//Expose these so that mungedb-aggregate can be extended.
exports.pipeline = require("./pipeline/");
exports.query = require("./query/");

// version info
exports.version = "r2.6.5";
exports.gitVersion = "e99d4fcb4279c0279796f237aa92fe3b64560bf6";

// error code constants
exports.ERRORS = require('./Errors.js');