paas/server.js

let fs = require("fs");
let http = require("http");
let pathlib = require("path");
let spawn = require("child_process").spawn;
let tmp = require("tmp");

function processPandoc(req, res) {
	let tmpf = tmp.fileSync({ postfix: ".pdf" });

	let child = spawn("pandoc",
		[ "--standalone", "--output", tmpf.name ]);

	child.on("error", err => {
		res.writeHead(500);
		res.end(JSON.stringify({ output: err.toString() }));
		tmpf.removeCallback();
	});

	let output = "";
	child.stdout.on("data", d => output += d.toString());
	child.stderr.on("data", d => output += d.toString());

	child.on("exit", (code, sig) => {
		if (code === 0) {
			res.end(JSON.stringify({
				pdf: fs.readFileSync(tmpf.name).toString("base64"),
				output
			}));
			tmpf.removeCallback();
		} else {
			res.end(JSON.stringify({ output }));
			tmpf.removeCallback();
		}
	});

	req.pipe(child.stdin);
}

function mime(path) {
	if (path.endsWith(".html"))
		return "text/html";
	if (path.endsWith(".css"))
		return "text/css";
	if (path.endsWith(".js"))
		return "application/javascript";

	return "application/octet-stream";
}

function serve(url, res) {
	let path = pathlib.join(__dirname, "web", url);
	let rs = fs.createReadStream(path);
	rs.once("error", err => {
		if (err.code == "ENOENT") {
			res.writeHead(404);
			res.end("404 Not Found");
		} else {
			res.writeHead(500);
			res.end("500 Internal Server Error");
			console.error(err);
		}
	});
	rs.once("open", () => {
		res.writeHead(200, {
			"Content-Type": mime(path)
		});
		rs.pipe(res);
	});
}

let server = http.createServer((req, res) => {
	if (req.url == "/") {
		serve("/index.html", res);
	} else if (req.method == "POST" && req.url == "/pandoc") {
		processPandoc(req, res);
	} else {
		serve(req.url, res);
	}
});

let port = process.env.PORT || 8080;
server.listen(port, "127.0.0.1");
console.log("Listening to 127.0.0.1:" + port);