// ── Interfaces ──────────────────────────────────────────────────────────

export interface WeatherResult {
  temp: number;
  temp_max?: number;
  temp_min?: number;
  main: string;
  description: string;
  type: string;
  sunrise?: string | null;
  sunset?: string | null;
  precipitation_sum?: number;
  precipitation_probability_max?: number;
  wind_max?: number;
  hourly?: HourlyEntry[];
  error?: string;
}

export interface HourlyEntry {
  hour: number;
  temp: number;
  precipitation: number;
  precipitation_probability: number;
  main: string;
  wind: number;
  humidity: number;
}

interface OpenMeteoForecast {
  error?: boolean;
  reason?: string;
  current?: { temperature_2m: number; weathercode: number };
  daily?: {
    time: string[];
    temperature_2m_max: number[];
    temperature_2m_min: number[];
    weathercode: number[];
    precipitation_sum?: number[];
    precipitation_probability_max?: number[];
    windspeed_10m_max?: number[];
    sunrise?: string[];
    sunset?: string[];
  };
  hourly?: {
    time: string[];
    temperature_2m: number[];
    precipitation_probability?: number[];
    precipitation?: number[];
    weathercode?: number[];
    windspeed_10m?: number[];
    relativehumidity_2m?: number[];
  };
}

// ── WMO code mappings ───────────────────────────────────────────────────

const WMO_MAP: Record<number, string> = {
  0: 'Clear', 1: 'Clear', 2: 'Clouds', 3: 'Clouds',
  45: 'Fog', 48: 'Fog',
  51: 'Drizzle', 53: 'Drizzle', 55: 'Drizzle', 56: 'Drizzle', 57: 'Drizzle',
  61: 'Rain', 63: 'Rain', 65: 'Rain', 66: 'Rain', 67: 'Rain',
  71: 'Snow', 73: 'Snow', 75: 'Snow', 77: 'Snow',
  80: 'Rain', 81: 'Rain', 82: 'Rain',
  85: 'Snow', 86: 'Snow',
  95: 'Thunderstorm', 96: 'Thunderstorm', 99: 'Thunderstorm',
};

const WMO_DESCRIPTION_DE: Record<number, string> = {
  0: 'Klar', 1: 'Uberwiegend klar', 2: 'Teilweise bewolkt', 3: 'Bewolkt',
  45: 'Nebel', 48: 'Nebel mit Reif',
  51: 'Leichter Nieselregen', 53: 'Nieselregen', 55: 'Starker Nieselregen',
  56: 'Gefrierender Nieselregen', 57: 'Starker gefr. Nieselregen',
  61: 'Leichter Regen', 63: 'Regen', 65: 'Starker Regen',
  66: 'Gefrierender Regen', 67: 'Starker gefr. Regen',
  71: 'Leichter Schneefall', 73: 'Schneefall', 75: 'Starker Schneefall', 77: 'Schneekorner',
  80: 'Leichte Regenschauer', 81: 'Regenschauer', 82: 'Starke Regenschauer',
  85: 'Leichte Schneeschauer', 86: 'Starke Schneeschauer',
  95: 'Gewitter', 96: 'Gewitter mit Hagel', 99: 'Starkes Gewitter mit Hagel',
};

const WMO_DESCRIPTION_EN: Record<number, string> = {
  0: 'Clear sky', 1: 'Mainly clear', 2: 'Partly cloudy', 3: 'Overcast',
  45: 'Fog', 48: 'Rime fog',
  51: 'Light drizzle', 53: 'Drizzle', 55: 'Heavy drizzle',
  56: 'Freezing drizzle', 57: 'Heavy freezing drizzle',
  61: 'Light rain', 63: 'Rain', 65: 'Heavy rain',
  66: 'Freezing rain', 67: 'Heavy freezing rain',
  71: 'Light snowfall', 73: 'Snowfall', 75: 'Heavy snowfall', 77: 'Snow grains',
  80: 'Light rain showers', 81: 'Rain showers', 82: 'Heavy rain showers',
  85: 'Light snow showers', 86: 'Heavy snow showers',
  95: 'Thunderstorm', 96: 'Thunderstorm with hail', 99: 'Severe thunderstorm with hail',
};

// ── Cache management ────────────────────────────────────────────────────

const weatherCache = new Map<string, { data: WeatherResult; expiresAt: number }>();
const CACHE_MAX_ENTRIES = 1000;
const CACHE_PRUNE_TARGET = 500;
const CACHE_CLEANUP_INTERVAL = 5 * 60 * 1000; // 5 minutes

setInterval(() => {
  const now = Date.now();
  for (const [key, entry] of weatherCache) {
    if (now > entry.expiresAt) weatherCache.delete(key);
  }
  if (weatherCache.size > CACHE_MAX_ENTRIES) {
    const entries = [...weatherCache.entries()].sort((a, b) => a[1].expiresAt - b[1].expiresAt);
    const toDelete = entries.slice(0, entries.length - CACHE_PRUNE_TARGET);
    toDelete.forEach(([key]) => weatherCache.delete(key));
  }
}, CACHE_CLEANUP_INTERVAL);

const TTL_FORECAST_MS = 60 * 60 * 1000;      // 1 hour
const TTL_CURRENT_MS  = 15 * 60 * 1000;      // 15 minutes
const TTL_CLIMATE_MS  = 24 * 60 * 60 * 1000; // 24 hours

export function cacheKey(lat: string, lng: string, date?: string): string {
  const rlat = parseFloat(lat).toFixed(2);
  const rlng = parseFloat(lng).toFixed(2);
  return `${rlat}_${rlng}_${date || 'current'}`;
}

function getCached(key: string): WeatherResult | null {
  const entry = weatherCache.get(key);
  if (!entry) return null;
  if (Date.now() > entry.expiresAt) {
    weatherCache.delete(key);
    return null;
  }
  return entry.data;
}

function setCache(key: string, data: WeatherResult, ttlMs: number): void {
  weatherCache.set(key, { data, expiresAt: Date.now() + ttlMs });
}

// ── Helpers ─────────────────────────────────────────────────────────────

export function estimateCondition(tempAvg: number, precipMm: number): string {
  if (precipMm > 5) return tempAvg <= 0 ? 'Snow' : 'Rain';
  if (precipMm > 1) return tempAvg <= 0 ? 'Snow' : 'Drizzle';
  if (precipMm > 0.3) return 'Clouds';
  return tempAvg > 15 ? 'Clear' : 'Clouds';
}

// ── getWeather ──────────────────────────────────────────────────────────

export async function getWeather(
  lat: string,
  lng: string,
  date: string | undefined,
  lang: string,
): Promise<WeatherResult> {
  const ck = cacheKey(lat, lng, date);

  if (date) {
    const cached = getCached(ck);
    if (cached) return cached;

    const targetDate = new Date(date);
    const now = new Date();
    const diffDays = (targetDate.getTime() - now.getTime()) / (1000 * 60 * 60 * 24);

    // Forecast range (-1 .. +16 days)
    if (diffDays >= -1 && diffDays <= 16) {
      const url = `https://api.open-meteo.com/v1/forecast?latitude=${lat}&longitude=${lng}&daily=temperature_2m_max,temperature_2m_min,weathercode&timezone=auto&forecast_days=16`;
      const response = await fetch(url);
      const data = await response.json() as OpenMeteoForecast;

      if (!response.ok || data.error) {
        throw new ApiError(response.status || 500, data.reason || 'Open-Meteo API error');
      }

      const dateStr = targetDate.toISOString().slice(0, 10);
      const idx = (data.daily?.time || []).indexOf(dateStr);

      if (idx !== -1) {
        const code = data.daily!.weathercode[idx];
        const descriptions = lang === 'de' ? WMO_DESCRIPTION_DE : WMO_DESCRIPTION_EN;

        const result: WeatherResult = {
          temp: Math.round((data.daily!.temperature_2m_max[idx] + data.daily!.temperature_2m_min[idx]) / 2),
          temp_max: Math.round(data.daily!.temperature_2m_max[idx]),
          temp_min: Math.round(data.daily!.temperature_2m_min[idx]),
          main: WMO_MAP[code] || 'Clouds',
          description: descriptions[code] || '',
          type: 'forecast',
        };

        setCache(ck, result, TTL_FORECAST_MS);
        return result;
      }
    }

    // Climate / archive fallback (far-future dates)
    if (diffDays > -1) {
      const month = targetDate.getMonth() + 1;
      const day = targetDate.getDate();
      const refYear = targetDate.getFullYear() - 1;
      const startDate = new Date(refYear, month - 1, day - 2);
      const endDate = new Date(refYear, month - 1, day + 2);
      const startStr = startDate.toISOString().slice(0, 10);
      const endStr = endDate.toISOString().slice(0, 10);

      const url = `https://archive-api.open-meteo.com/v1/archive?latitude=${lat}&longitude=${lng}&start_date=${startStr}&end_date=${endStr}&daily=temperature_2m_max,temperature_2m_min,precipitation_sum&timezone=auto`;
      const response = await fetch(url);
      const data = await response.json() as OpenMeteoForecast;

      if (!response.ok || data.error) {
        throw new ApiError(response.status || 500, data.reason || 'Open-Meteo Climate API error');
      }

      const daily = data.daily;
      if (!daily || !daily.time || daily.time.length === 0) {
        return { temp: 0, main: '', description: '', type: '', error: 'no_forecast' };
      }

      let sumMax = 0, sumMin = 0, sumPrecip = 0, count = 0;
      for (let i = 0; i < daily.time.length; i++) {
        if (daily.temperature_2m_max[i] != null && daily.temperature_2m_min[i] != null) {
          sumMax += daily.temperature_2m_max[i];
          sumMin += daily.temperature_2m_min[i];
          sumPrecip += daily.precipitation_sum![i] || 0;
          count++;
        }
      }

      if (count === 0) {
        return { temp: 0, main: '', description: '', type: '', error: 'no_forecast' };
      }

      const avgMax = sumMax / count;
      const avgMin = sumMin / count;
      const avgTemp = (avgMax + avgMin) / 2;
      const avgPrecip = sumPrecip / count;
      const main = estimateCondition(avgTemp, avgPrecip);

      const result: WeatherResult = {
        temp: Math.round(avgTemp),
        temp_max: Math.round(avgMax),
        temp_min: Math.round(avgMin),
        main,
        description: '',
        type: 'climate',
      };

      setCache(ck, result, TTL_CLIMATE_MS);
      return result;
    }

    return { temp: 0, main: '', description: '', type: '', error: 'no_forecast' };
  }

  // No date supplied -> current weather
  const cached = getCached(ck);
  if (cached) return cached;

  const url = `https://api.open-meteo.com/v1/forecast?latitude=${lat}&longitude=${lng}&current=temperature_2m,weathercode&timezone=auto`;
  const response = await fetch(url);
  const data = await response.json() as OpenMeteoForecast;

  if (!response.ok || data.error) {
    throw new ApiError(response.status || 500, data.reason || 'Open-Meteo API error');
  }

  const code = data.current!.weathercode;
  const descriptions = lang === 'de' ? WMO_DESCRIPTION_DE : WMO_DESCRIPTION_EN;

  const result: WeatherResult = {
    temp: Math.round(data.current!.temperature_2m),
    main: WMO_MAP[code] || 'Clouds',
    description: descriptions[code] || '',
    type: 'current',
  };

  setCache(ck, result, TTL_CURRENT_MS);
  return result;
}

// ── getDetailedWeather ──────────────────────────────────────────────────

export async function getDetailedWeather(
  lat: string,
  lng: string,
  date: string,
  lang: string,
): Promise<WeatherResult> {
  const ck = `detailed_${cacheKey(lat, lng, date)}`;

  const cached = getCached(ck);
  if (cached) return cached;

  const targetDate = new Date(date);
  const now = new Date();
  const diffDays = (targetDate.getTime() - now.getTime()) / (1000 * 60 * 60 * 24);
  const dateStr = targetDate.toISOString().slice(0, 10);
  const descriptions = lang === 'de' ? WMO_DESCRIPTION_DE : WMO_DESCRIPTION_EN;

  // Climate / archive path (> 16 days out)
  if (diffDays > 16) {
    const refYear = targetDate.getFullYear() - 1;
    const refDateStr = `${refYear}-${String(targetDate.getMonth() + 1).padStart(2, '0')}-${String(targetDate.getDate()).padStart(2, '0')}`;

    const url = `https://archive-api.open-meteo.com/v1/archive?latitude=${lat}&longitude=${lng}`
      + `&start_date=${refDateStr}&end_date=${refDateStr}`
      + `&hourly=temperature_2m,precipitation,weathercode,windspeed_10m,relativehumidity_2m`
      + `&daily=temperature_2m_max,temperature_2m_min,weathercode,precipitation_sum,windspeed_10m_max,sunrise,sunset`
      + `&timezone=auto`;
    const response = await fetch(url);
    const data = await response.json() as OpenMeteoForecast;

    if (!response.ok || data.error) {
      throw new ApiError(response.status || 500, data.reason || 'Open-Meteo Climate API error');
    }

    const daily = data.daily;
    const hourly = data.hourly;
    if (!daily || !daily.time || daily.time.length === 0) {
      return { temp: 0, main: '', description: '', type: '', error: 'no_forecast' };
    }

    const idx = 0;
    const code = daily.weathercode?.[idx];
    const avgMax = daily.temperature_2m_max[idx];
    const avgMin = daily.temperature_2m_min[idx];

    const hourlyData: HourlyEntry[] = [];
    if (hourly?.time) {
      for (let i = 0; i < hourly.time.length; i++) {
        const hour = new Date(hourly.time[i]).getHours();
        const hCode = hourly.weathercode?.[i];
        hourlyData.push({
          hour,
          temp: Math.round(hourly.temperature_2m[i]),
          precipitation: hourly.precipitation?.[i] || 0,
          precipitation_probability: 0,
          main: WMO_MAP[hCode!] || 'Clouds',
          wind: Math.round(hourly.windspeed_10m?.[i] || 0),
          humidity: hourly.relativehumidity_2m?.[i] || 0,
        });
      }
    }

    let sunrise: string | null = null, sunset: string | null = null;
    if (daily.sunrise?.[idx]) sunrise = daily.sunrise[idx].split('T')[1]?.slice(0, 5);
    if (daily.sunset?.[idx]) sunset = daily.sunset[idx].split('T')[1]?.slice(0, 5);

    const result: WeatherResult = {
      type: 'climate',
      temp: Math.round((avgMax + avgMin) / 2),
      temp_max: Math.round(avgMax),
      temp_min: Math.round(avgMin),
      main: WMO_MAP[code!] || estimateCondition((avgMax + avgMin) / 2, daily.precipitation_sum?.[idx] || 0),
      description: descriptions[code!] || '',
      precipitation_sum: Math.round((daily.precipitation_sum?.[idx] || 0) * 10) / 10,
      wind_max: Math.round(daily.windspeed_10m_max?.[idx] || 0),
      sunrise,
      sunset,
      hourly: hourlyData,
    };

    setCache(ck, result, TTL_CLIMATE_MS);
    return result;
  }

  // Forecast path (<= 16 days)
  const url = `https://api.open-meteo.com/v1/forecast?latitude=${lat}&longitude=${lng}`
    + `&hourly=temperature_2m,precipitation_probability,precipitation,weathercode,windspeed_10m,relativehumidity_2m`
    + `&daily=temperature_2m_max,temperature_2m_min,weathercode,sunrise,sunset,precipitation_probability_max,precipitation_sum,windspeed_10m_max`
    + `&timezone=auto&start_date=${dateStr}&end_date=${dateStr}`;

  const response = await fetch(url);
  const data = await response.json() as OpenMeteoForecast;

  if (!response.ok || data.error) {
    throw new ApiError(response.status || 500, data.reason || 'Open-Meteo API error');
  }

  const daily = data.daily;
  const hourly = data.hourly;

  if (!daily || !daily.time || daily.time.length === 0) {
    return { temp: 0, main: '', description: '', type: '', error: 'no_forecast' };
  }

  const dayIdx = 0;
  const code = daily.weathercode[dayIdx];

  const formatTime = (isoStr: string) => {
    if (!isoStr) return '';
    const d = new Date(isoStr);
    return `${String(d.getHours()).padStart(2, '0')}:${String(d.getMinutes()).padStart(2, '0')}`;
  };

  const hourlyData: HourlyEntry[] = [];
  if (hourly && hourly.time) {
    for (let i = 0; i < hourly.time.length; i++) {
      const h = new Date(hourly.time[i]).getHours();
      hourlyData.push({
        hour: h,
        temp: Math.round(hourly.temperature_2m[i]),
        precipitation_probability: hourly.precipitation_probability![i] || 0,
        precipitation: hourly.precipitation![i] || 0,
        main: WMO_MAP[hourly.weathercode![i]] || 'Clouds',
        wind: Math.round(hourly.windspeed_10m![i] || 0),
        humidity: Math.round(hourly.relativehumidity_2m![i] || 0),
      });
    }
  }

  const result: WeatherResult = {
    type: 'forecast',
    temp: Math.round((daily.temperature_2m_max[dayIdx] + daily.temperature_2m_min[dayIdx]) / 2),
    temp_max: Math.round(daily.temperature_2m_max[dayIdx]),
    temp_min: Math.round(daily.temperature_2m_min[dayIdx]),
    main: WMO_MAP[code] || 'Clouds',
    description: descriptions[code] || '',
    sunrise: formatTime(daily.sunrise![dayIdx]),
    sunset: formatTime(daily.sunset![dayIdx]),
    precipitation_sum: daily.precipitation_sum![dayIdx] || 0,
    precipitation_probability_max: daily.precipitation_probability_max![dayIdx] || 0,
    wind_max: Math.round(daily.windspeed_10m_max![dayIdx] || 0),
    hourly: hourlyData,
  };

  setCache(ck, result, TTL_FORECAST_MS);
  return result;
}

// ── ApiError ────────────────────────────────────────────────────────────

export class ApiError extends Error {
  status: number;
  constructor(status: number, message: string) {
    super(message);
    this.status = status;
  }
}