var fs = require("fs");
var pathlib = require("path");

var sendfile = require("./sendfile");
var error = require("./error");

module.exports = Slideshow;

// 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));
	}

	self.indexExists = function() {
		try {
			fs.accessSync(pathlib.join(dir, "index.html"));
			return true;
		} catch (err) {
			return false;
		}
	}

	try {
		self.meta = JSON.parse(
			fs.readFileSync(pathlib.join(dir, "meta.json")));
	} catch (err) {
		if (err.code !== "ENOENT")
			error(err);

		self.meta = {};
	}

	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 = [];
	var slideIndex = 0;
	var nextTimeout;

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

	// Get the current slide's interval
	function currentInterval() {
		var itv = currentSlide.meta.interval;
		if (itv === undefined)
			itv = changeInterval;
		return itv;
	}

	// Return if the current slide is enabled and valid
	function currentEnabled() {
		return currentSlide.indexExists() && !currentSlide.disabled;
	}

	self.getSlideName = getSlideName;
	function getSlideName() {
		return currentSlide ? currentSlide.name : ""
	}

	self.pushAwaiter = pushAwaiter;
	function pushAwaiter(res) {
		awaiters.push(res);
	}

	self.serveCurrentSlide = serveCurrentSlide;
	function serveCurrentSlide(parts, res) {
		if (currentSlide)
			currentSlide.serveSlide(parts, res);
		else
			error("Current slide requested while no current slide exists", res);
	}

	self.getSlides = getSlides;
	function getSlides() {
		return slides;
	}

	self.next = next;
	function next() {
		slideIndex += 1;

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

			nextTimeout = setTimeout(next, currentInterval());
		}

		// End all awaiting connections to notify slide change,
		if (currentEnabled()) {
			self.sendEvent("next", { name: currentSlide.name });

		// Or go to the next slide if the current one doesn't have an index.html
		// or if the slide is disabled
		} else {
			clearTimeout(nextTimeout);
			setTimeout(next, 0);
		}
	}

	// 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)));

		slideIndex = 0;
		currentSlide = slides[slideIndex];

		nextTimeout = setTimeout(next, currentInterval());
	}
	init();

	return self;
}