const cmn = require("../$common.js");
const fs = require("fs");
const express = require("express");
const child_process = require("child_process");

// NOTE:
// This module expects a buienradar-store instance in the 'buienradar-store'
// directory within this module's directory. The database therein should be
// named 'db', and the background image should be stored under key 'mode'
// (which should probably be the cmpref).


// cb : (err, status, stdout : Buffer) -> ()
function runDbmanage(bdir, args, cb) {
	const options = {
		cwd: bdir,
		stdio: ["inherit", "pipe", "inherit"],
		timeout: 5000,  // milliseconds
	};
	const proc = child_process.spawn(bdir + "/dbmanage", args, options);

	const outbufs = [];
	proc.stdout.on("data", data => {
		outbufs.push(data);
	});

	let callbackInvoked = false;

	proc.on("error", err => {
		if (callbackInvoked) return;
		callbackInvoked = true;
		cb(err, null, null);
	});

	proc.on("exit", (code, sig) => {
		if (callbackInvoked) return;
		callbackInvoked = true;
		if (code != null) cb(null, code, Buffer.concat(outbufs));
		else cb("Process terminated by signal", null, null);
	});
}

// cb : (err, frames : [String]) -> ()
function getFramesList(bdir, cb) {
	runDbmanage(bdir, ["list", bdir + "/db"], (err, status, out) => {
		if (err) cb(err, null);
		else if (status != 0) cb("Error getting list of frames from DB", null);
		else cb(null, out.toString("utf8").trim().split("\n").filter(s => s != "mode"));
	});
}

// cb : (err, pngs : Buffer) -> ()
function getFramesPng(bdir, stamps, cb) {
	runDbmanage(bdir, ["getmultiple", bdir + "/db"].concat(stamps), (err, status, out) => {
		if (err) { cb(err, null); return; }
		if (status != 0) { cb("Error getting frames from DB", null); return; }
		cb(null, out);

		// const pngs = [];

		// let cursor = 0;
		// while (cursor < out.length) {
		//     let pnglen = out.readBigUInt64LE(cursor);
		//     if (Number(pnglen) != pnglen) {
		//         cb("PNG too large", null);
		//         return;
		//     }
		//     pnglen = Number(pnglen);

		//     pngs.push(out.slice(cursor + 8, cursor + 8 + pnglen));
		//     cursor += 8 + pnglen;
		// }

		// cb(null, pngs);
	});
}

// cb : (err, present : Bool) -> ()
function checkFramePresent(bdir, stamp, cb) {
	runDbmanage(bdir, ["has", bdir + "/db", stamp], (err, status, out) => {
		if (err) { cb(err, null); return; }
		if (status == 1) { cb("Error getting status from DB", null); return; }
		if (status == 0) cb(null, true);
		else cb(null, false);
	});
}

module.exports = function (app, io, moddir) {
	const buiendir = moddir + "/buienradar-store";
	console.log(`buien: Using buienradar-store directory '${buiendir}'`);

	const router = express.Router();

	router.get("/", function (req, res) {
		res.sendFile(moddir + "/index.html");
	});

	router.get("/api/list/json", function (req, res) {
		getFramesList(buiendir, (err, frames) => {
			if (err) {
				console.log(err);
				res.sendStatus(500);
			} else res.json(frames);
		});
	});

	router.get("/api/images", function (req, res) {
		const url = new URL(req.url, `https://${req.headers.host}`);
		const stamps = url.searchParams.getAll("s").flatMap(s => s.split(","));
		getFramesPng(buiendir, stamps, (err, buf) => {
			if (err) {
				console.log(err);
				res.sendStatus(500);
			} else res.send(buf);
		});
	});

	router.get("/api/has/:stamp", function (req, res) {
		checkFramePresent(buiendir, req.params.stamp, (err, present) => {
			if (err) {
				console.log(err);
				res.sendStatus(500);
			} else if (present) res.sendStatus(200);
			else res.sendStatus(404);
		});
	});

	app.use(function (req, res, next) {
		if (req.subdomains.length && req.subdomains[req.subdomains.length - 1] == "buien") { 
			router.handle(req, res, next);
		} else next();
	});
};