import {
  BadRequestException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { PrismaService } from '../prisma/prisma.service';
import {
  WeatherHistoryConfig,
  weatherHistoryConfig,
  roundPoint,
} from './history/weather-history.config';

const PAST_DAYS = 14;
const FORECAST_DAYS = 7;
const RECENT_WINDOW_DAYS = 7;
const FETCH_TIMEOUT_MS = 8_000;
const GOOD_TEMP_THRESHOLD_C = 18;
const GOOD_PRECIPITATION_THRESHOLD_MM = 15;
const POOR_TEMP_THRESHOLD_C = 12;
const POOR_PRECIPITATION_THRESHOLD_MM = 30;

// Rule-of-thumb minimums for opening a hive without unduly stressing the
// colony or making the inspection unpleasant/risky for the beekeeper:
// below ~14-15°C bees cluster and brood chills when the hive is opened,
// noticeable rain and strong wind both make bees more defensive and the
// frames harder to handle safely.
const INSPECTION_MIN_TEMP_C = 15;
const INSPECTION_MAX_PRECIPITATION_MM = 1;
const INSPECTION_MAX_WIND_KMH = 25;

export interface DailyWeather {
  date: string;
  tempMaxC: number | null;
  tempMinC: number | null;
  precipitationMm: number | null;
  windSpeedMaxKmh: number | null;
  // WMO weather interpretation code (Open-Meteo `weather_code`); null when
  // the provider omits it.
  weatherCode: number | null;
  // null when a required value is missing (rather than a misleading guess).
  inspectionSuitable: boolean | null;
}

export interface ApiaryWeather {
  daily: DailyWeather[];
}

export type TrachtprognoseRating =
  'GUT' | 'MAESSIG' | 'SCHWACH' | 'KEINE_TRACHT' | 'UNBEKANNT';

export interface Trachtprognose {
  rating: TrachtprognoseRating;
  season: string;
  reasoning: string[];
  historicalAverageYieldKg: number | null;
}

interface OpenMeteoDaily {
  time: string[];
  temperature_2m_max: (number | null)[];
  temperature_2m_min: (number | null)[];
  precipitation_sum: (number | null)[];
  wind_speed_10m_max: (number | null)[];
  weather_code?: (number | null)[];
}

interface OpenMeteoResponse {
  daily?: OpenMeteoDaily;
}

@Injectable()
export class WeatherService {
  // Same variables as the history source (one place for URL and key); a bad
  // setting stops the process at startup.
  private readonly config: WeatherHistoryConfig = weatherHistoryConfig();

  constructor(private readonly prisma: PrismaService) {}

  async getWeather(apiaryId: string): Promise<ApiaryWeather> {
    const { latitude, longitude } = await this.getCoordinates(apiaryId);
    return { daily: await this.fetchDailyWeather(latitude, longitude) };
  }

  async getTrachtprognose(apiaryId: string): Promise<Trachtprognose> {
    const { latitude, longitude } = await this.getCoordinates(apiaryId);
    const daily = await this.fetchDailyWeather(latitude, longitude);
    const today = new Date().toISOString().slice(0, 10);
    const recentDays = daily
      .filter((day) => day.date <= today)
      .slice(-RECENT_WINDOW_DAYS);
    const historicalAverageYieldKg =
      await this.getHistoricalAverageYield(apiaryId);
    return this.computeTrachtprognose(recentDays, historicalAverageYieldKg);
  }

  private async getCoordinates(
    apiaryId: string,
  ): Promise<{ latitude: number; longitude: number }> {
    const apiary = await this.prisma.apiary.findUnique({
      where: { id: apiaryId },
      select: { latitude: true, longitude: true },
    });
    if (!apiary) {
      throw new NotFoundException('Apiary not found');
    }
    if (apiary.latitude === null || apiary.longitude === null) {
      throw new BadRequestException(
        'Apiary has no coordinates; weather data requires latitude and longitude',
      );
    }
    return { latitude: apiary.latitude, longitude: apiary.longitude };
  }

  private async fetchDailyWeather(
    latitude: number,
    longitude: number,
  ): Promise<DailyWeather[]> {
    const url = new URL(this.config.forecastUrl);
    // 0.01 degrees: no exact stand location leaves the app.
    const point = roundPoint(latitude, longitude);
    url.searchParams.set('latitude', String(point.lat));
    url.searchParams.set('longitude', String(point.lon));
    url.searchParams.set(
      'daily',
      'temperature_2m_max,temperature_2m_min,precipitation_sum,wind_speed_10m_max,weather_code',
    );
    url.searchParams.set('wind_speed_unit', 'kmh');
    url.searchParams.set('past_days', String(PAST_DAYS));
    url.searchParams.set('forecast_days', String(FORECAST_DAYS));
    url.searchParams.set('timezone', 'auto');
    if (this.config.apiKey) {
      url.searchParams.set('apikey', this.config.apiKey);
    }

    let response: Response;
    try {
      response = await fetch(url, {
        signal: AbortSignal.timeout(FETCH_TIMEOUT_MS),
        headers: { 'User-Agent': this.config.userAgent },
      });
    } catch {
      throw new BadRequestException('Wetterdaten konnten nicht geladen werden');
    }
    if (!response.ok) {
      throw new BadRequestException('Wetterdaten konnten nicht geladen werden');
    }
    const body = (await response.json()) as OpenMeteoResponse;
    if (!body.daily) {
      return [];
    }
    const {
      time,
      temperature_2m_max,
      temperature_2m_min,
      precipitation_sum,
      wind_speed_10m_max,
      weather_code,
    } = body.daily;
    return time.map((date, index) => {
      const tempMaxC = temperature_2m_max[index] ?? null;
      const precipitationMm = precipitation_sum[index] ?? null;
      const windSpeedMaxKmh = wind_speed_10m_max[index] ?? null;
      return {
        date,
        tempMaxC,
        tempMinC: temperature_2m_min[index] ?? null,
        precipitationMm,
        windSpeedMaxKmh,
        weatherCode: weather_code?.[index] ?? null,
        inspectionSuitable:
          tempMaxC === null ||
          precipitationMm === null ||
          windSpeedMaxKmh === null
            ? null
            : tempMaxC >= INSPECTION_MIN_TEMP_C &&
              precipitationMm <= INSPECTION_MAX_PRECIPITATION_MM &&
              windSpeedMaxKmh <= INSPECTION_MAX_WIND_KMH,
      };
    });
  }

  private getSeason(month: number): { season: string; inBloom: boolean } {
    if (month >= 3 && month <= 5) {
      return { season: 'Frühtracht', inBloom: true };
    }
    if (month >= 6 && month <= 7) {
      return { season: 'Sommertracht', inBloom: true };
    }
    if (month === 8) {
      return { season: 'Spättracht', inBloom: true };
    }
    return { season: 'Winterruhe', inBloom: false };
  }

  private async getHistoricalAverageYield(
    apiaryId: string,
  ): Promise<number | null> {
    const currentMonth = new Date().getMonth() + 1;
    const harvests = await this.prisma.harvest.findMany({
      where: { apiaryId },
      select: { date: true, netWeight: true },
    });
    const sameMonthYields = harvests
      .filter((harvest) => harvest.date.getMonth() + 1 === currentMonth)
      .map((harvest) => harvest.netWeight)
      .filter((weight): weight is number => weight !== null);
    if (sameMonthYields.length === 0) {
      return null;
    }
    const total = sameMonthYields.reduce((sum, weight) => sum + weight, 0);
    return Math.round((total / sameMonthYields.length) * 10) / 10;
  }

  private computeTrachtprognose(
    recentDays: DailyWeather[],
    historicalAverageYieldKg: number | null,
  ): Trachtprognose {
    const { season, inBloom } = this.getSeason(new Date().getMonth() + 1);
    const reasoning: string[] = [];

    if (!inBloom) {
      reasoning.push(`Aktuell keine Haupttrachtperiode (${season}).`);
      return {
        rating: 'KEINE_TRACHT',
        season,
        reasoning,
        historicalAverageYieldKg,
      };
    }

    const validTemps = recentDays
      .map((day) => day.tempMaxC)
      .filter((value): value is number => value !== null);
    const avgTempMax = validTemps.length
      ? validTemps.reduce((sum, value) => sum + value, 0) / validTemps.length
      : null;
    const totalPrecipitation = recentDays.reduce(
      (sum, day) => sum + (day.precipitationMm ?? 0),
      0,
    );

    let rating: TrachtprognoseRating = 'UNBEKANNT';
    if (avgTempMax === null) {
      reasoning.push('Keine ausreichenden Wetterdaten für eine Einschätzung.');
    } else if (
      avgTempMax >= GOOD_TEMP_THRESHOLD_C &&
      totalPrecipitation < GOOD_PRECIPITATION_THRESHOLD_MM
    ) {
      rating = 'GUT';
      reasoning.push(
        `Warmes, trockenes Wetter der letzten 7 Tage (Ø ${avgTempMax.toFixed(1)}°C, ${totalPrecipitation.toFixed(0)} mm Niederschlag) begünstigt Bienenflug.`,
      );
    } else if (
      avgTempMax < POOR_TEMP_THRESHOLD_C ||
      totalPrecipitation > POOR_PRECIPITATION_THRESHOLD_MM
    ) {
      rating = 'SCHWACH';
      reasoning.push(
        `Kühles oder nasses Wetter der letzten 7 Tage (Ø ${avgTempMax.toFixed(1)}°C, ${totalPrecipitation.toFixed(0)} mm Niederschlag) schränkt Bienenflug ein.`,
      );
    } else {
      rating = 'MAESSIG';
      reasoning.push(
        `Durchwachsenes Wetter der letzten 7 Tage (Ø ${avgTempMax.toFixed(1)}°C, ${totalPrecipitation.toFixed(0)} mm Niederschlag).`,
      );
    }

    reasoning.push(`Saison: ${season}.`);
    if (historicalAverageYieldKg !== null) {
      reasoning.push(
        `Historischer Ernteschnitt für diesen Zeitraum an diesem Standort: ${historicalAverageYieldKg} kg.`,
      );
    }

    return { rating, season, reasoning, historicalAverageYieldKg };
  }
}