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

var conf = JSON.parse(fs.readFileSync("conf.json"));
var index = fs.readFileSync("index.html", "utf-8")
	.replace("{{transition_time}}", conf.transition_time);

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

function mimetype(path) {
	var ext = pathlib.extname(path)
		.substring(1)
		.toLowerCase();

	switch (ext) {

	case "html":
	case "xml":
		return "text/"+ext;

	case "png":
	case "jpg":
	case "jpeg":
	case "gif":
		return "image/"+ext;

	case "svg":
		return "image/svg+xml";

	case "mov":
	case "mp4":
	case "ogv":
	case "webm":
		return "video/"+ext;

	case "mp3":
	case "ogg":
	case "flac":
	case "m4a":
		return "audio/"+ext;

	default:
		return "application/octet-stream";
	}
}

function sendfile(res, path) {
	res.writeHead(200, {
		"content-type": mimetype(path)
	});

	fs.createReadStream(path)
		.on("error", err => error(res, err))
		.pipe(res);
}

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

	self.dir = dir;
	self.name = pathlib.parse(dir).name;

	self.serveSlide = function(parts, res) {
		sendfile(res, pathlib.join(dir, "index.html"));
	}

	self.serveFiles = function(parts, res) {

		// Redirect to / if /{name} is requested
		if (parts.pathname.replace(/\//g, "") === self.name) {
			res.writeHead(302, { location: "/" });
			return res.end();
		}

		var name = parts.pathname.substring(1).replace(self.name, "");
		sendfile(res, pathlib.join(dir, name));
	}

	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 = [];
	var slides = [];

	self.sendEvent = function(evt, args) {
		awaiters.forEach(res => res.end(JSON.stringify({
			evt: evt,
			args: args
		})));
	}

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

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

		// /init: send initial information about current slide
		} else if (parts.pathname === "/init") {
			res.end(currentSlide ? currentSlide.name : "");

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

		// /slide: serve the current slide's html
		} else if (parts.pathname === "/slide" && currentSlide) {
			currentSlide.serveSlide(parts, res);

		// Serve other files
		} else {
			var served = false;

			for (var slide of slides) {

				// If client requests /{slide-name}/*
				if (slide.name === parts.pathname.substr(1, slide.name.length)) {
					slide.serveFiles(parts, res);
					served = true;
					break;
				}
			}

			if (!served) {
				res.writeHead(404);
				res.end("404");
			}
		}
	}

	// 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() {
		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
			self.sendEvent("next", { name: currentSlide.name });
		}, changeInterval);
	}
	init();

	return self;
}

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

function onexit() {
	slideshow.sendEvent("reload");
	process.exit();
}
process.on("exit", onexit);
process.on("SIGINT", onexit);
process.on("SIGTERM", onexit);

var server = http.createServer((req, res) => {
	slideshow.serve(req, res);
});
server.on("error", err => {
	console.error(err.toString());
	system.exit(1);
});
server.listen(conf.port);
console.log("Server running on port "+conf.port+".");