"use strict";
var AggregationCursor = require("./AggregationCursor");

/**
 * 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`.
 *
 * @method aggregate
 * @namespace mungedb
 * @module mungedb-aggregate
 * @param pipelineObj  {Array|Object}   The list of pipeline document sources in JSON format or object with pipeline and options
 * @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(pipelineObj, ctx, inputs, callback) {	// export directly for a function-style interface
	var DocumentSource = exports.pipeline.documentSources.DocumentSource;
	if (ctx instanceof Array || ctx instanceof DocumentSource) callback = inputs, inputs = ctx, ctx = {};
	ctx = ctx || {};
	var pipelineInst;

	try {
		//Set up the command Object
		pipelineObj = pipelineObj instanceof Array ? {pipeline: pipelineObj} : pipelineObj;
		if (!(pipelineObj instanceof Object)) throw new Error("pipelineObj must be either an Object or an Array");
		for (var key in exports.cmdDefaults) {
			if (exports.cmdDefaults.hasOwnProperty(key) && pipelineObj[key] === undefined) {
				pipelineObj[key] = exports.cmdDefaults[key];
			}
		}
		pipelineInst = exports.pipeline.Pipeline.parseCommand(pipelineObj, 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 (pipelineObj.explain) {
		if (inputs) {
			ctx.ns = inputs; //NOTE: use given `inputs` directly; hacking cursor source to use our inputs instead of the ctx namespace
			exports.pipeline.PipelineD.prepareCursorSource(pipelineInst, ctx);
		}
		return pipelineInst.writeExplainOps();
	}

	var aggregator = function aggregator(ctx, inputs, callback) {
		if (ctx instanceof Array || ctx instanceof DocumentSource) callback = inputs, inputs = ctx, ctx = {};
		if (!inputs) return callback("arg `inputs` is required");

		try {
			// rebuild the pipeline on subsequent calls
			if (!pipelineInst) {
				pipelineInst = exports.pipeline.Pipeline.parseCommand(pipelineObj, ctx);
			}
			ctx.ns = inputs; //NOTE: use given `inputs` directly; hacking cursor source to use our inputs instead of the ctx namespace
			exports.pipeline.PipelineD.prepareCursorSource(pipelineInst, ctx);
			pipelineInst.stitch();
		} catch(err) {
			return callback(err);
		}

		var cursor = new AggregationCursor(pipelineInst);
		pipelineInst = null;

		return callback ? cursor.toArray(callback) : cursor;
	};

	if (inputs) return aggregator(ctx, inputs, callback);
	return aggregator;
};

exports.AggregationCursor = AggregationCursor;

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/");
exports.errors = require("./errors");

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