#!/bin/env -S deno run --allow-read --allow-net

async function main() {
	const [program_path] = Deno.args;
	if (program_path === undefined) fail_with("Usage: host.ts <program_path>");
	const port = 1728;
	const server = Deno.serve({ port }, () => handle(program_path));
	await server.finished;
}

async function handle(program_path: string) {
	console.log("Serving", program_path);
	const file = await try_else(
		() => Deno.open(program_path, { read: true }),
		() => fail_with("Program at", program_path, "does not exists"),
	);
	return new Response(file.readable);
}

function fail_with(...message: string[]) {
	console.error(...message);
	return Deno.exit(1);
}

async function try_else<T>(operation: () => T | Promise<T>, on_error: (error: unknown) => T | Promise<T>) {
	try {
		return await operation();
	} catch (error) {
		return await on_error(error);
	}
}

if (import.meta.main) await main();