import { mergeForecastSources } from "@/lib/forecast-merge";
import type { RawImgwForecastResponse, RawWeatherForecast } from "@/types/forecast";

const OPEN_METEO_FORECAST_URL = "https://api.open-meteo.com/v1/forecast";
const IMGW_FORECAST_URL = "https://meteo.imgw.pl/api/v1/forecast/fcapi";
// This browser token is published by the official meteo.imgw.pl frontend.
const IMGW_FORECAST_TOKEN = "p4DXKjsYadfBV21TYrDk";
const OPEN_METEO_TIMEOUT_MS = 12_000;
const IMGW_TIMEOUT_MS = 5_000;

export function parseForecastCoordinate(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;
}

async function readImgwPayload(response: Response | null) {
  if (!response?.ok) return null;
  try {
    return await response.json() as RawImgwForecastResponse;
  } catch {
    return null;
  }
}

export async function fetchServerForecast(latitude: number, longitude: number) {
  const openMeteoParams = 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_days: "7",
    wind_speed_unit: "ms",
  });
  const imgwParams = new URLSearchParams({
    token: IMGW_FORECAST_TOKEN,
    lat: String(latitude),
    lon: String(longitude),
    m: "alaro",
  });

  const [openMeteoResponse, imgwResponse] = await Promise.all([
    fetch(`${OPEN_METEO_FORECAST_URL}?${openMeteoParams}`, { next: { revalidate: 900 }, signal: AbortSignal.timeout(OPEN_METEO_TIMEOUT_MS) }),
    fetch(`${IMGW_FORECAST_URL}?${imgwParams}`, { next: { revalidate: 900 }, signal: AbortSignal.timeout(IMGW_TIMEOUT_MS) }).catch(() => null),
  ]);
  if (!openMeteoResponse.ok) throw new Error("Forecast service is unavailable.");

  const openMeteoPayload = await openMeteoResponse.json() as RawWeatherForecast;
  const imgwPayload = await readImgwPayload(imgwResponse);
  return mergeForecastSources(openMeteoPayload, imgwPayload);
}