server.js

"use strict";

const fs = require("fs");
const sass = require("node-sass");
const express = require("express");
const bodyParser = require("body-parser");

const THEME = "node_modules/reveal.js/css/theme/";
const SOURCE = THEME + "source/";
const TEMPLATE = THEME + "template/";

const mixins = fs.readFileSync(TEMPLATE + "mixins.scss");
const settings = fs.readFileSync(TEMPLATE + "settings.scss");
const theme = fs.readFileSync(TEMPLATE + "theme.scss");

var app = express();
app.set("port", process.env.PORT || 8080);
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(express.static(__dirname));

// generated css
var custom = "";

// called by the angular app
app.post("/convert", (req, res) => {
	var scss = mixins + settings + req.body.scss + theme;
	sass.render({
		data: scss,
	}, (err, result) => {
		if (err) {
			console.error("sass error", err);
			res.send("sass error");
		} else {
			custom = result.css;
			res.send(result.css);
		}
	});
});

// called by the reveal iframe
app.get("/custom.css", (req, res) => {
	res.type("css");
	res.send(custom);
});

app.get("/themes/:id", (req, res) => {
	fs.readFile(SOURCE + req.params.id + ".scss", "utf-8", (err, file) => {
		if (err) console.error(err);

		res.send(mapScss(file));
	});
});

app.get("/themes", (req, res) => {
	fs.readdir(SOURCE, (err, files) => {
		if (err) console.error(err);
		// extension irrelevant
		files = files.map(file => file.split(".")[0]);
		res.send(files);
	});
});

app.listen(app.get("port"), () => {
	console.log(`Express server listening on port ${app.get("port")}`);
});

// convert a scss into a map of vars/value
var mapScss = (file) => {
	return file
	.split("\n")
	// only vars
	.filter(line => line[0] === "$")
	// trim $ and ;
	.map(line => line.slice(1, -1))
	.reduce((o, v) => {
		v = v.split(":");
		o[v[0].trim()] = v[1].trim();
		return o;
	}, {});
}