i-like-trains.ts

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

const api = async (path: string) => {
  const url = `https://svc.metrotransit.org/NexTrip/${path}?format=json`;
  const resp = await fetch(url);
  if (!resp.ok) {
    console.error(`Got back status ${resp.status} ${resp.statusText}`);
    Deno.exit(1);
  }
  return await resp.json();
};

const getRoutes = () => api("Routes");
const getDirections = (route: number) => api(`Directions/${route}`);
const getStops = (route: number, direction: number) =>
    api(`Stops/${route}/${direction}`);
const getDepartures = (route: number, direction: number, stop: string) =>
    api(`${route}/${direction}/${stop}`);

enum UsageKind {
  Routes,
  Directions,
  Stops
}

const usage = async (kind: UsageKind) => {
  console.error("Usage: ./i-like-trains.ts <route> <direction> <stop>");
  console.error("  e.g. ./i-like-trains.ts 902 0 <stop>");
  switch (kind) {
  case UsageKind.Routes:
    console.error("Available routes:");
    for (const route of await getRoutes())
      console.log(`  ${route.Route}  ${JSON.stringify(route.Description)}`);
    break;
  case UsageKind.Directions:
    console.error("Available directions:");
    for (const dir of await getDirections(parseInt(Deno.args[0])))
      console.log(`  ${dir.Value}  ${JSON.stringify(dir.Text)}`);
    break;
  case UsageKind.Stops:
    console.error("Available stop:");
    for (const stop of await getStops(parseInt(Deno.args[0]),
                                      parseInt(Deno.args[1])))
      console.log(`  ${stop.Value}  ${JSON.stringify(stop.Text)}`);
    break;
  }
  Deno.exit(-1);
};

const isInt = (x: string) => !isNaN(parseInt(x));

if (Deno.args.length == 0 || Deno.args.length > 3 || !isInt(Deno.args[0])) {
  usage(UsageKind.Routes);
} else if (Deno.args.length == 1 || !isInt(Deno.args[1])) {
  usage(UsageKind.Directions);
} else if (Deno.args.length == 2 ||
           (await getStops(parseInt(Deno.args[0]), parseInt(Deno.args[1])))
               .some((x: string) => Deno.args[2] === x)) {
  usage(UsageKind.Stops);
} else if (Deno.args.length == 3) {
  const departures = await getDepartures(parseInt(Deno.args[0]),
                                         parseInt(Deno.args[1]), Deno.args[2]);
  for (const departure of departures)
    console.log(departure.DepartureText);
}