import type { DailyForecast, ForecastSource, HourlyForecast, WeatherForecast } from "@/types/forecast";

function readNumber(value: unknown) {
  return typeof value === "number" && Number.isFinite(value) ? value : null;
}

function readString(value: unknown) {
  return typeof value === "string" && value ? value : null;
}

function isForecastSource(value: unknown): value is ForecastSource {
  return value === "imgw-alaro" || value === "open-meteo";
}

function normalizeSources(value: unknown): ForecastSource[] {
  return Array.isArray(value) ? value.filter(isForecastSource) : [];
}

function normalizeHourlyForecast(value: unknown): HourlyForecast[] {
  return Array.isArray(value) ? value.flatMap((candidate) => {
    if (!candidate || typeof candidate !== "object") return [];
    const row = candidate as Partial<HourlyForecast>;
    const time = readString(row.time);
    if (!time) return [];
    return [{
      time,
      temperature: readNumber(row.temperature),
      feelsLike: readNumber(row.feelsLike),
      precipitationProbability: readNumber(row.precipitationProbability),
      precipitation: readNumber(row.precipitation),
      weatherCode: readNumber(row.weatherCode),
      windSpeed: readNumber(row.windSpeed),
      source: isForecastSource(row.source) ? row.source : "open-meteo",
    }];
  }) : [];
}

function normalizeDailyForecast(value: unknown): DailyForecast[] {
  return Array.isArray(value) ? value.flatMap((candidate) => {
    if (!candidate || typeof candidate !== "object") return [];
    const row = candidate as Partial<DailyForecast>;
    const date = readString(row.date);
    if (!date) return [];
    return [{
      date,
      temperatureMax: readNumber(row.temperatureMax),
      temperatureMin: readNumber(row.temperatureMin),
      precipitationProbability: readNumber(row.precipitationProbability),
      precipitation: readNumber(row.precipitation),
      weatherCode: readNumber(row.weatherCode),
      sunrise: readString(row.sunrise),
      sunset: readString(row.sunset),
      sources: normalizeSources(row.sources),
    }];
  }) : [];
}

function normalizeForecast(raw: Partial<WeatherForecast>): WeatherForecast {
  const latitude = Number(raw.latitude);
  const longitude = Number(raw.longitude);
  if (!Number.isFinite(latitude) || !Number.isFinite(longitude)) throw new Error("Forecast service returned invalid coordinates.");
  return {
    latitude,
    longitude,
    timezone: typeof raw.timezone === "string" ? raw.timezone : "Europe/Warsaw",
    hourly: normalizeHourlyForecast(raw.hourly),
    daily: normalizeDailyForecast(raw.daily),
    sources: normalizeSources(raw.sources),
  };
}

export async function fetchForecast(latitude: number, longitude: number, signal?: AbortSignal) {
  const params = new URLSearchParams({ latitude: String(latitude), longitude: String(longitude) });
  const response = await fetch(`/api/forecast?${params}`, { signal });
  if (!response.ok) throw new Error("Unable to load forecast.");
  return normalizeForecast(await response.json() as Partial<WeatherForecast>);
}