var fs = require("fs");
var http = require("http");
var crypto = require("crypto");
var pathlib = require("path");
var urllib = require("url");

var index = fs.readFileSync("index.html");
var conf = JSON.parse(fs.readFileSync("conf.json"));

function error(res, err) {
	console.trace(err);
	res.end(err.toString());
}

// The individual slide
function Slide(dir) {
	var self = {};

	self.dir = dir;

	function serve(parts, res) {
		if (parts.pathname === "/slide") {
			fs.createReadStream(pathlib.join(dir, "index.html"))
				.on("error", err => error(res, err))
				.pipe(res);
		} else {
			fs.createReadStream(pathlib.join(dir, parts.pathname))
				.on("error", err => error(res, err))
				.pipe(res);
		}
	}

	self.serve = function(parts, res) {
		try {
			serve(parts, res);
		} catch (err) {
			if (err.code && err.code === "ENOENT")
				res.writeHead(404);

			error(res, err);
		}
	}

	return self;
}

// The slideshow, whose job it is to manage all slides
// and tell the client whether it has to update or not
function Slideshow(dir, changeInterval) {
	var self = {};

	var currentSlide = null;
	var awaiters = [];

	self.serve = function(req, res) {
		var parts = urllib.parse(req.url);

		// /: Send the base site to the client
		if (parts.pathname === "/") {
			res.end(index);

		// /await: long polling, request won't end before a new slide comes
		} else if (parts.pathname === "/await") {
			awaiters.push(res);

		// There's a current slide: leave serving files up to the slide
		} else if (currentSlide) {
			currentSlide.serve(parts, res);

		// There's no current slide show
		} else {
			res.end("No current slideshow.");
		}
	}

	// This function starts the slideshow and goes through the slides
	// one by one. When done, it starts again by calling this function again.
	function init() {
		var slides = fs.readdirSync(dir)
			.sort()
			.map(file => Slide(pathlib.join(dir, file)));

		var slideIndex = 0;
		currentSlide = slides[slideIndex];

		var interval = setInterval(() => {
			slideIndex += 1;

			// Go to the next slide, or restart
			if (slideIndex >= slides.length) {
				clearInterval(interval);
				init();
			} else {
				currentSlide = slides[slideIndex];
			}

			// End all awaiting connections to notify slide change
			awaiters.forEach(res => res.end());
		}, changeInterval);
	}
	init();

	return self;
}

var slideshow = Slideshow(conf.slides, conf.interval);

http.createServer((req, res) => {
	slideshow.serve(req, res);
}).listen(conf.port);