Weather CLI

// ── Formatting (pure — no I/O) ────────────────────────────────────────────
export function formatWeather(data, units = "metric") {
  const { name, sys, main, weather, wind, clouds } = data;
  const desc    = weather[0]?.description ?? "unknown";
  const unit    = units === "metric" ? "°C" : "°F";
  const temp    = units === "metric"
    ? (main.temp - 273.15).toFixed(1)
    : ((main.temp - 273.15) * 9/5 + 32).toFixed(1);
  const feels   = units === "metric"
    ? (main.feels_like - 273.15).toFixed(1)
    : ((main.feels_like - 273.15) * 9/5 + 32).toFixed(1);
  const windKph = (wind.speed * 3.6).toFixed(1);

  return [
    `
📍 ${name}, ${sys?.country ?? ""}`,
    `  ${desc.charAt(0).toUpperCase() + desc.slice(1)}`,
    `  🌡  ${temp}${unit}  (feels like ${feels}${unit})`,
    `  💧 Humidity: ${main.humidity}%`,
    `  💨 Wind: ${windKph} km/h`,
    `  ☁️  Cloud cover: ${clouds?.all ?? "?"}%`,
    `  🌅 Sunrise: ${new Date(sys.sunrise * 1000).toLocaleTimeString()}`,
    `  🌇 Sunset:  ${new Date(sys.sunset  * 1000).toLocaleTimeString()}`,
  ].join("
");
}

// ── API layer ──────────────────────────────────────────────────────────────
export async function fetchWeather(city, apiKey) {
  const url = `https://api.openweathermap.org/data/2.5/weather?q=${encodeURIComponent(city)}&appid=${apiKey}`;
  const res = await fetch(url);
  const data = await res.json();   // read body even on error (has error message)

  if (!res.ok) {
    const msg = data.message ?? `HTTP ${res.status}`;
    throw new Error(msg.includes("city not found")
      ? `City "${city}" not found. Check the spelling.`
      : `API error: ${msg}`);
  }
  return data;
}

// ── Retry with exponential backoff ─────────────────────────────────────────
async function withRetry(fn, maxAttempts = 3, baseDelay = 500) {
  for (let attempt = 1; attempt <= maxAttempts; attempt++) {
    try {
      return await fn();
    } catch (e) {
      const isNetwork = e.cause?.code === "ECONNREFUSED" || e.message.includes("fetch failed");
      if (attempt === maxAttempts || !isNetwork) throw e;
      const delay = baseDelay * 2 ** (attempt - 1);
      console.error(`  Retry ${attempt}/${maxAttempts} in ${delay}ms...`);
      await new Promise(r => setTimeout(r, delay));
    }
  }
}

// ── CLI ────────────────────────────────────────────────────────────────────
const apiKey = process.env.OWM_API_KEY;
if (!apiKey) {
  console.error("Error: set the OWM_API_KEY environment variable.");
  console.error("  Get a free key at https://openweathermap.org/api");
  console.error("  Then: export OWM_API_KEY=your_key_here");
  process.exit(1);
}

const city = process.argv.slice(2).join(" ");
if (!city) {
  console.error("Usage: node weather.mjs <city name>");
  console.error("  Example: node weather.mjs Mumbai");
  process.exit(1);
}

try {
  const data = await withRetry(() => fetchWeather(city, apiKey));
  console.log(formatWeather(data));
} catch (e) {
  console.error("Error:", e.message);
  process.exit(1);
}

import { formatWeather } from "./weather.mjs";

// Mock response matching the OpenWeatherMap API shape:
const mock = {
  name: "Mumbai",
  sys:  { country: "IN", sunrise: 1719456600, sunset: 1719502800 },
  main: { temp: 308.15, feels_like: 315.0, humidity: 88 },
  weather: [{ description: "broken clouds" }],
  wind:   { speed: 4.5 },
  clouds: { all: 75 },
};

let pass=0, fail=0;
function test(desc,fn){try{fn();console.log("  ✓",desc);pass++;}catch(e){console.log("  ✗",desc,"—",e.message);fail++;}}

const output = formatWeather(mock);

test("contains city name",   () => { if (!output.includes("Mumbai")) throw new Error(); });
test("shows country code",   () => { if (!output.includes("IN")) throw new Error(); });
test("converts K to C",      () => { if (!output.includes("35.0°C")) throw new Error(output); });
test("shows humidity",       () => { if (!output.includes("88%")) throw new Error(); });
test("converts m/s to km/h", () => { if (!output.includes("16.2")) throw new Error(output); });  // 4.5*3.6
test("shows description",    () => { if (!output.includes("Broken clouds")) throw new Error(output); });

console.log(\`
\${pass} passed, \${fail} failed\`);

export OWM_API_KEY=your_key_here  # set once per terminal session
node weather.mjs Mumbai
node weather.mjs "New Delhi"
node weather.mjs London
node weather.test.mjs  # runs without API key