init

lib/weather/http.ts

@@ -0,0 +1,93 @@
+/**
+ * Small server-side helpers shared by every provider adapter.
+ */
+
+/** An error that knows which HTTP status the API route should answer with. */
+export class ProviderError extends Error {
+  constructor(
+    message: string,
+    public readonly status: number = 502,
+  ) {
+    super(message);
+    this.name = "ProviderError";
+  }
+}
+
+/** Reads an API key from the environment, or fails with a clear message. */
+export function readKey(envKey: string): string {
+  const key = process.env[envKey]?.trim();
+  if (!key) {
+    throw new ProviderError(`${envKey} is not configured`, 500);
+  }
+  return key;
+}
+
+interface FetchOptions {
+  /** Seconds to cache the response. Weather barely changes in 10 minutes. */
+  cacheSeconds?: number;
+  headers?: Record<string, string>;
+}
+
+/**
+ * Fetches JSON with caching (default 10 minutes) to protect free-tier quotas.
+ * The URL often contains an API key, so it is never logged or echoed back.
+ */
+export async function fetchJson<T>(url: string, providerLabel: string, options: FetchOptions = {}): Promise<T> {
+  const { cacheSeconds = 600, headers } = options;
+
+  let response: Response;
+  try {
+    response = await fetch(url, { headers, next: { revalidate: cacheSeconds } });
+  } catch {
+    // DNS failure, offline, firewall… the request never got an answer.
+    throw new ProviderError(`Couldn't reach ${providerLabel}. Check your connection and try again.`, 503);
+  }
+
+  if (response.status === 401 || response.status === 403) {
+    throw new ProviderError(`${providerLabel} rejected the API key`, 401);
+  }
+  if (response.status === 429) {
+    throw new ProviderError(`${providerLabel} rate limit reached. Try again shortly.`, 429);
+  }
+  if (!response.ok) {
+    throw new ProviderError(`${providerLabel} responded with HTTP ${response.status}`, 502);
+  }
+
+  return (await response.json()) as T;
+}
+
+// ---------- Number and time helpers ----------
+
+/** Rounds to one decimal place so the JSON stays tidy. */
+export function round1(value: number): number {
+  return Math.round(value * 10) / 10;
+}
+
+/** Same as round1, but passes null/undefined/NaN through as null. */
+export function maybe(value: number | null | undefined): number | null {
+  return value === null || value === undefined || !Number.isFinite(value) ? null : round1(value);
+}
+
+/** Metres per second → km/h. */
+export function msToKph(ms: number): number {
+  return round1(ms * 3.6);
+}
+
+export function maybeMsToKph(ms: number | null | undefined): number | null {
+  return ms === null || ms === undefined ? null : msToKph(ms);
+}
+
+/** Unix seconds → ISO instant. */
+export function fromUnix(seconds: number): string {
+  return new Date(seconds * 1000).toISOString();
+}
+
+/** Keeps the first `hours` of an hourly list, starting from the current hour. */
+export function nextHours<T extends { time: string }>(items: T[], hours: number): T[] {
+  const startOfThisHour = Date.now() - 60 * 60 * 1000;
+  return items.filter((item) => Date.parse(item.time) >= startOfThisHour).slice(0, hours);
+}
+
+/** The app shows at most 7 days of hourly data and 14 days of daily data. */
+export const MAX_HOURS = 168;
+export const MAX_DAYS = 14;