todos_backend.js

// This is a sample backend for the SproutCore todos demo using node-router.
// It uses an in-memory data store and writes it to disk on change
// for persistance.
// This provides the same REST style api as the merb example and even hosts
// on port 4000. It's a drop in replacement for the sample merb backend.

include('file');

var server = require('./node-router')

var tasks;

// Simple utility that allows mapping over any object
// as if it were a hash.  Calls fn(key, value) for each pair.
Object.prototype.map_pairs = function (fn) {
	var accum = [];
	for (key in this) {
		if (this.hasOwnProperty(key)) {
			accum.push(fn(key, this[key]));
		}
	}
	return accum;
};

// Convert raw data to part of REST response
function json_for_task(id, task) {
	task = task || {};
	return {
		guid: "/tasks/" + id,
		description: task.description,
		order: task.order,
		isDone: task.is_done
	};
}

function apply_json_to_task(task, json_hash) {
  task.description = json_hash['description'];
  task.order = json_hash['order'];
  task.is_done = json_hash['isDone'];
}

// Serialize the data to the disk
function save_data() {
  var file = new File("tasks.db", "w");
  file.write(JSON.stringify(tasks));
  file.close();
}

// Load the data from the disk
function load_data(callback) {
	// Load the database from disk
	var promise = process.fs.cat("tasks.db", "utf8");
	promise.addCallback(function (json) {
		tasks = JSON.parse(json);
		callback(true);
	});
	promise.addErrback(function () {
		tasks = [];
		callback(false);
	});
}

// This handles the REST requests and generates the responses
var tasksController = {
	index: function (req, res) {
		res.simpleJson(200, {content: tasks.map_pairs(json_for_task), self: '/tasks'});
	},
	show: function (req, res, id) {
		var task = tasks[id];
		if (task) {
			res.simpleJson(200, {content: json_for_task(id, task), self: '/tasks/' + id});
		} else {
			res.notFound();
		}
	},
	create: function (req, res) {
		req.jsonBody(function (json) {
			var task = {}, id, url;
			json = json && json.content;
			if (!json) {
				res.notFound();
			} else {
				apply_json_to_task(task, json);
				id = tasks.length + 1;
				tasks[id] = task;
				tasks.length += 1;
				save_data();
				url = "/tasks/" + id;
				res.simpleJson(201, {content: json_for_task(id, task), self: url}, [["Location", url]]);
			}
		});
	},
	update: function (req, res, id) {
		puts("Update");
		req.jsonBody(function (json) {
			var task = {}, new_id, url;
			json = json && json.content;
			if (!json) {
				res.notFound();
			} else {
				apply_json_to_task(task, json);
				tasks[id] = task;
				save_data();
				res.simpleJson(200, {content: json_for_task(id, task), self: "/tasks/" + id});
			}
		});
	},
	destroy: function (req, res, id) {
		delete(tasks[id]);
		save_data();
		res.simpleJson(200, "200 Destroyed");
	}
};

// Mount our controller as a RESTful resource
server.resource('tasks', tasksController);

// Load the datastore
puts("Loading data from file...");
load_data(function (success) {
	// Kickoff the server
	if (success) {
		puts("Loaded");
	} else {
		puts("Error, creating empty tasks array");
		save_data();
	}
	// And start the server when done
	server.listen(4000);
});