import { toSeverity } from "../describe";
import { fetchJson } from "../http";
import type { WeatherAlert } from "../types";

/**
 * Active US weather alerts from the National Weather Service (free, no key).
 * Docs: https://www.weather.gov/documentation/services-web-api
 *
 * NWS asks every app to identify itself with a User-Agent containing contact
 * info, so set NWS_CONTACT in .env.local (an email or website).
 * Outside the US this returns nothing, which is fine.
 */

interface NwsResponse {
  features: {
    properties: {
      event: string;
      headline: string | null;
      severity: string;
      senderName: string;
      onset: string | null;
      effective: string;
      ends: string | null;
      expires: string;
      description: string;
      instruction: string | null;
    };
  }[];
}

/** Rough boxes around US states and territories — skips pointless calls elsewhere. */
function mightBeInUS(lat: number, lon: number): boolean {
  const mainland = lat > 24 && lat < 50 && lon > -125 && lon < -66;
  const alaska = lat > 51 && lat < 72 && (lon < -129 || lon > 172);
  const hawaii = lat > 18 && lat < 23 && lon > -161 && lon < -154;
  const caribbean = lat > 17 && lat < 19 && lon > -68 && lon < -64; // Puerto Rico, USVI
  const pacific = lat > 13 && lat < 21 && lon > 144 && lon < 146; // Guam, Northern Marianas
  return mainland || alaska || hawaii || caribbean || pacific;
}

let warnedMissingContact = false;

function buildNwsUserAgent(): string {
  const explicit = process.env.NWS_CONTACT?.trim();
  if (explicit) return `WayfarerWeather/1.0 (${explicit})`;

  const deployedHost = process.env.VERCEL_PROJECT_PRODUCTION_URL?.trim() || process.env.VERCEL_URL?.trim();
  if (deployedHost) return `WayfarerWeather/1.0 (https://${deployedHost})`;

  if (process.env.NODE_ENV === "production" && !warnedMissingContact) {
    warnedMissingContact = true;
    console.warn("[Wayfarer] Set NWS_CONTACT (email or site URL) so api.weather.gov requests include contact details.");
  }
  return "WayfarerWeather/1.0 (local-dev)";
}

export async function getNwsAlerts(lat: number, lon: number): Promise<WeatherAlert[]> {
  if (!mightBeInUS(lat, lon)) return [];

  const point = `${lat.toFixed(4)},${lon.toFixed(4)}`;
  const data = await fetchJson<NwsResponse>(`https://api.weather.gov/alerts/active?point=${point}`, "National Weather Service", {
    cacheSeconds: 300, // alerts matter; refresh more often
    headers: { "User-Agent": buildNwsUserAgent(), Accept: "application/geo+json" },
  });

  return data.features.map(({ properties: p }) => ({
    title: p.headline ?? p.event,
    severity: toSeverity(p.severity),
    source: p.senderName,
    starts: p.onset ?? p.effective,
    ends: p.ends ?? p.expires,
    description: p.description,
    instruction: p.instruction,
  }));
}