index.js

/*jshint node:true */

"use strict";

var sequence = function (tasks, names, results, missing, recursive, nest) {
	names.forEach(function (name) {
		if (results.indexOf(name) !== -1) {
			return; // de-dup results
		}
		var node = tasks[name];
		if (!node) {
			missing.push(name);
		} else if (nest.indexOf(name) > -1) {
			nest.push(name);
			recursive.push(nest.slice(0));
			nest.pop(name);
		} else if (node.dep.length) {
			nest.push(name);
			sequence(tasks, node.dep, results, missing, recursive, nest); // recurse
			nest.pop(name);
		}
		results.push(name);
	});
};

// tasks: object with keys as task names
// names: array of task names
module.exports = function (tasks, names) {
	var results = []; // the final sequence
	var missing = []; // missing tasks
	var recursive = []; // recursive task dependencies

	sequence(tasks, names, results, missing, recursive, []);

	if (missing.length || recursive.length) {
		results = []; // results are incomplete at best, completely wrong at worst, remove them to avoid confusion
	}

	return {
		sequence: results,
		missingTasks: missing,
		recursiveDependencies: recursive
	};
};