Projects

Projects#

TypeScript projects build when the surface is big enough that types are cheaper than tests, or when shipping to a team that will read the code on call.

Typed CLI tool#

A small CLI built with commander and strict typing. The operator runs it against a list of targets and pipes the JSON output downstream.

// src/cli.ts
import { Command } from "commander";
import { resolve } from "node:dns/promises";

interface Result { host: string; addrs: string[]; }

const program = new Command()
  .name("op-resolve")
  .argument("<file>", "one hostname per line")
  .option("-c, --concurrency <n>", "parallel queries", (v) => parseInt(v, 10), 50)
  .action(async (file: string, opts: { concurrency: number }) => {
    const fs = await import("node:fs/promises");
    const hosts = (await fs.readFile(file, "utf8"))
      .split("\n").map(h => h.trim()).filter(Boolean);

    const results: Result[] = [];
    for (const h of hosts) {
      try {
        results.push({ host: h, addrs: await resolve(h) });
      } catch {
        results.push({ host: h, addrs: [] });
      }
    }
    console.log(JSON.stringify(results, null, 2));
  });

program.parse();

HTTP server#

A typed Fastify service run as a small backend for their tooling.

// src/server.ts
import Fastify from "fastify";

interface Target { host: string; port: number; }

const app = Fastify({ logger: true });

app.post<{ Body: Target }>("/scan", async (req, reply) => {
  const { host, port } = req.body;
  // ...spawn scanner...
  return { host, port, scanned_at: Date.now() };
});

app.listen({ host: "0.0.0.0", port: 9000 });

Parser library#

A typed library that parses an operator-relevant format (syslog, JSON-Lines, custom protocol). The library ships type declarations so its callers get full IDE support.

// src/parser.ts
export interface SyslogEntry {
  pri: number;
  timestamp: Date;
  host: string;
  program: string;
  msg: string;
}

const RFC3164 = /^<(\d+)>(\w{3} +\d+ \d{2}:\d{2}:\d{2}) (\S+) (\S+?):? (.*)$/;

export function parseSyslog(line: string): SyslogEntry | null {
  const m = RFC3164.exec(line);
  if (!m) return null;
  return {
    pri:       parseInt(m[1], 10),
    timestamp: new Date(`${new Date().getFullYear()} ${m[2]}`),
    host:      m[3],
    program:   m[4],
    msg:       m[5],
  };
}

References#

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