const fs = require("fs");
const path = require("path");

const Koa = require("koa");
const koaPug = require("koa-pug");
const koaRouter = require("koa-router");
const koaRange = require("koa-range");

const config = require("./config");
const util = require("./util");
const { ENOENT, ECONNRESET } = require("constants");

const SIZE_UNITS = [ "B", "KiB", "MiB", "GiB" ];

function makeCurrentPathField(path) {
	let current = `<a href="/">root</a>`;
	if (path.endsWith("/"))
		path = path.slice(1, path.length-1);
	const path_parts = path.split("/");

	for (i = 0; i < path_parts.length; ++i) {
		let lnk = "";
		for (j = 0; j < i+1; ++j) {
			lnk += `/${path_parts[j]}`;
		}
		current += `/<a href="${encodeURI(lnk)}/">${path_parts[i]}</a>`;
	}

	return current;
}

function convertSize(size) {
	let i = 0;
	for (; size > 1024; size /= 1024) { ++i; }
	return [i > 0 ? size.toFixed(2) : size, SIZE_UNITS[i]];
}

function sortByNameField(a, b) {
	if (a.name > b.name)
		return 1;
	else if (a.name < b.name)
		return -1;
	return 0;
}

async function getDirectoryList(dir_path, orig_url) {
	let dirs = [];
	let files = [];
	let total_files_size = 0;
	let d = await fs.promises.opendir(dir_path);
	for await (const dirent of d) {
		const stat = fs.lstatSync(path.join(dir_path, dirent.name));
		const [s, u] = convertSize(stat.size);
		if (stat.isDirectory())
			dirs.push({
				name: dirent.name,
				link: `${encodeURIComponent(dirent.name)}/`,
				datetime: util.datetime(stat.mtime, util.formats.file_date),
				size: "DIR",
				size_unit: '' });
		else {
			total_files_size += stat.size;
			files.push({
				name: dirent.name,
				link: `/files${orig_url}${encodeURIComponent(dirent.name)}`,
				datetime: util.datetime(stat.mtime, util.formats.file_date),
				size: +s,
				size_unit: u });
		}
	}

	dirs.sort(sortByNameField);
	files.sort(sortByNameField);

	return [dirs.concat(files), dirs.length, files.length,
		convertSize(total_files_size).join(' ')];
}

function setRoutes(router) {
	router.get('/(.*)?', async ctx => {
		const file_path = path.join(config.files.file_path, decodeURI(ctx.originalUrl));
		let stat = fs.lstatSync(file_path);
		if (stat.isDirectory()) {
			const [items, total_directories, total_files, total_files_size]
				= await getDirectoryList(file_path, decodeURI(ctx.originalUrl));
			await ctx.render('index', {
				title: "/ Files",
				description: "File share.",
				main_site: util.getServiceByHost(ctx.header.host),
				current_path: makeCurrentPathField(decodeURI(ctx.originalUrl)),
				total_files: total_files,
				total_files_size: total_files_size,
				total_directories: total_directories,
				items: items });
		}
	});
}

module.exports = () => {
	const app = new Koa();
	const pug = new koaPug({
		viewPath: path.join(__dirname, "views", "files"),
		locals: {
			moment: date => util.datetime(date, util.formats.file_date) },
		app: app
	});

	const radio_router = koaRouter();
	setRoutes(radio_router);

	app.proxy = true;
	app
		.use(koaRange)
		.use(radio_router.routes())
		.on("error", err => { if (!err.code == ECONNRESET || !err.code == ENOENT) console.log(err.code); })
		.listen(config.files.port, config.files.host);

	return app;
}