diachron/express/cli.ts

import { parseArgs } from "node:util";

const { values } = parseArgs({
    options: {
        listen: {
            type: "string",
            short: "l",
        },
    },
    strict: true,
    allowPositionals: false,
});

function parseListenAddress(listen: string | undefined): {
    host: string;
    port: number;
} {
    const defaultHost = "127.0.0.1";
    const defaultPort = 3500;

    if (!listen) {
        return { host: defaultHost, port: defaultPort };
    }

    const lastColon = listen.lastIndexOf(":");
    if (lastColon === -1) {
        // Just a port number
        const port = parseInt(listen, 10);
        if (isNaN(port)) {
            throw new Error(`Invalid listen address: ${listen}`);
        }
        return { host: defaultHost, port };
    }

    const host = listen.slice(0, lastColon);
    const port = parseInt(listen.slice(lastColon + 1), 10);

    if (isNaN(port)) {
        throw new Error(`Invalid port in listen address: ${listen}`);
    }

    return { host, port };
}

const listenAddress = parseListenAddress(values.listen);

export const cli = {
    listen: listenAddress,
};