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

function asArray(value: unknown): unknown[] {
  return Array.isArray(value) ? value : [];
}

function readString(series: RawForecastSeries, key: keyof RawForecastSeries, index: number) {
  const value = asArray(series[key])[index];
  return typeof value === "string" && value ? value : null;
}

function readNumber(series: RawForecastSeries, key: keyof RawForecastSeries, index: number) {
  const value = asArray(series[key])[index];
  return typeof value === "number" && Number.isFinite(value) ? value : null;
}

function normalizeHourlyForecast(series: RawForecastSeries = {}): HourlyForecast[] {
  return asArray(series.time).flatMap((_, index) => {
    const time = readString(series, "time", index);
    if (!time) return [];
    return [{
      time,
      temperature: readNumber(series, "temperature_2m", index),
      feelsLike: readNumber(series, "apparent_temperature", index),
      precipitationProbability: readNumber(series, "precipitation_probability", index),
      precipitation: readNumber(series, "precipitation", index),
      weatherCode: readNumber(series, "weather_code", index),
      windSpeed: readNumber(series, "wind_speed_10m", index),
    }];
  });
}

function normalizeDailyForecast(series: RawForecastSeries = {}): DailyForecast[] {
  return asArray(series.time).flatMap((_, index) => {
    const date = readString(series, "time", index);
    if (!date) return [];
    return [{
      date,
      temperatureMax: readNumber(series, "temperature_2m_max", index),
      temperatureMin: readNumber(series, "temperature_2m_min", index),
      precipitationProbability: readNumber(series, "precipitation_probability_max", index),
      precipitation: readNumber(series, "precipitation_sum", index),
      weatherCode: readNumber(series, "weather_code", index),
      sunrise: readString(series, "sunrise", index),
      sunset: readString(series, "sunset", index),
    }];
  });
}

function normalizeForecast(raw: RawWeatherForecast): 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),
  };
}

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 RawWeatherForecast);
}