import { NextResponse, type NextRequest } from "next/server";
import { getLocalContext, type LocalContext } from "@/lib/weather/extras/air-quality";
import { getNwsAlerts } from "@/lib/weather/extras/nws-alerts";
import { isProviderId, isReady, PROVIDERS } from "@/lib/weather/providers";
import { badRequest, errorResponse, forbidCrossSite, parseCoords } from "@/lib/weather/respond";
import type { WeatherAlert, WeatherReport } from "@/lib/weather/types";

/**
 * GET /api/weather?provider=openweather&lat=44.77&lon=-93.27
 *
 * Runs on the server so API keys stay in .env / .env.local and never reach the browser.
 *
 * Three things are fetched at once:
 *   1. the forecast from the chosen provider       (required — failure is an error)
 *   2. air quality + time zone from Open-Meteo     (optional — failure just hides it)
 *   3. NWS alerts for US locations                 (optional — failure just hides them)
 */
export async function GET(request: NextRequest) {
  const blocked = forbidCrossSite(request);
  if (blocked) return blocked;

  const params = request.nextUrl.searchParams;
  const providerId = params.get("provider") ?? "openweather";
  const coords = parseCoords(params);

  if (!isProviderId(providerId)) return badRequest(`Unknown provider "${providerId}"`);
  if (!coords) return badRequest("lat and lon are required");

  const provider = PROVIDERS[providerId];
  if (!isReady(provider)) return badRequest(`${provider.label} has no API key configured`);

  const [forecast, context, nwsAlerts] = await Promise.allSettled([
    provider.getForecast(coords.lat, coords.lon),
    getLocalContext(coords.lat, coords.lon),
    getNwsAlerts(coords.lat, coords.lon),
  ]);

  if (forecast.status === "rejected") return errorResponse(forecast.reason);

  const local: LocalContext | null = context.status === "fulfilled" ? context.value : null;
  const official: WeatherAlert[] = nwsAlerts.status === "fulfilled" ? nwsAlerts.value : [];

  // Prefer official NWS alerts in the US; elsewhere use whatever the provider gave us.
  const alerts = official.length > 0 ? official : forecast.value.alerts;
  const alertSource = official.length > 0 ? "National Weather Service" : alerts.length > 0 ? provider.label : null;

  const report: WeatherReport = {
    ...forecast.value,
    provider: providerId,
    timeZone: forecast.value.timeZone ?? local?.timeZone ?? null,
    airQuality: local?.airQuality ?? null,
    alerts,
    alertSource,
    fetchedAt: new Date().toISOString(),
  };
  return NextResponse.json(report);
}