import { NextResponse } from "next/server";

const FORECAST_URL = "https://api.open-meteo.com/v1/forecast";

function parseCoordinate(value: string | null, min: number, max: number) {
  if (!value?.trim()) return null;
  const coordinate = Number(value);
  return Number.isFinite(coordinate) && coordinate >= min && coordinate <= max ? coordinate : null;
}

export async function GET(request: Request) {
  const { searchParams } = new URL(request.url);
  const latitude = parseCoordinate(searchParams.get("latitude"), -90, 90);
  const longitude = parseCoordinate(searchParams.get("longitude"), -180, 180);
  if (latitude === null || longitude === null) {
    return NextResponse.json({ error: "Invalid coordinates." }, { status: 400 });
  }

  const params = new URLSearchParams({
    latitude: String(latitude),
    longitude: String(longitude),
    hourly: "temperature_2m,apparent_temperature,precipitation_probability,precipitation,weather_code,wind_speed_10m",
    daily: "weather_code,temperature_2m_max,temperature_2m_min,precipitation_probability_max,precipitation_sum,sunrise,sunset",
    timezone: "Europe/Warsaw",
    forecast_hours: "24",
    forecast_days: "7",
    wind_speed_unit: "ms",
  });

  try {
    const response = await fetch(`${FORECAST_URL}?${params}`, { next: { revalidate: 900 } });
    if (!response.ok) return NextResponse.json({ error: "Forecast service is unavailable." }, { status: 502 });
    return NextResponse.json(await response.json(), {
      headers: { "Cache-Control": "public, s-maxage=900, stale-while-revalidate=1800" },
    });
  } catch {
    return NextResponse.json({ error: "Forecast service is unavailable." }, { status: 502 });
  }
}