import { useState, useEffect, useRef } from 'react';
import {
  convertToGridCoords,
  getUltraShortForecast,
  getCurrentBaseDateTime,
} from '@tabs/weather/services/weatherApi';
import type { StabilityClass, WeatherFetchResult } from '../utils/dispersionTypes';

/**
 * Turner 간이법으로 Pasquill-Gifford 안정도 산출
 * 풍속 + 시간대(주간/야간) 기반
 */
function deriveStabilityClass(windSpeed: number, hour: number): StabilityClass {
  const isNight = hour < 6 || hour >= 18;
  if (isNight) {
    if (windSpeed < 2) return 'F';
    if (windSpeed < 3) return 'E';
    return 'D';
  }
  // 주간 (중간 수준 일사량 가정)
  if (windSpeed < 2) return 'A';
  if (windSpeed < 3) return 'B';
  if (windSpeed < 5) return 'C';
  return 'D';
}

/** 풍향(도) → 16방위 문자열 */
export function windDirToCompass(deg: number): string {
  const dirs = ['N', 'NNE', 'NE', 'ENE', 'E', 'ESE', 'SE', 'SSE',
                'S', 'SSW', 'SW', 'WSW', 'W', 'WNW', 'NW', 'NNW'];
  const idx = Math.round(((deg % 360) + 360) % 360 / 22.5) % 16;
  return dirs[idx];
}

const DEFAULT_WEATHER: WeatherFetchResult = {
  windSpeed: 5.0,
  windDirection: 270,
  temperature: 15,
  humidity: 60,
  stability: 'D',
  isLoading: false,
  error: null,
  lastUpdate: null,
};

/**
 * 위치 기반 기상정보 자동조회 훅
 * KMA 초단기실황 API 활용, 500ms 디바운스
 * baseDate: 'YYYY-MM-DD' (선택), baseTime: 'HH:mm' (선택)
 * 미제공 시 getCurrentBaseDateTime()으로 현재 시각 사용
 */
export function useWeatherFetch(lat: number, lon: number, baseDate?: string, baseTime?: string): WeatherFetchResult {
  const [weather, setWeather] = useState<WeatherFetchResult>({
    ...DEFAULT_WEATHER,
    isLoading: true,
  });
  const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null);

  useEffect(() => {
    if (timerRef.current) clearTimeout(timerRef.current);

    timerRef.current = setTimeout(async () => {
      setWeather(prev => ({ ...prev, isLoading: true, error: null }));

      try {
        const { nx, ny } = convertToGridCoords(lat, lon);

        let apiBaseDate: string;
        let apiBaseTime: string;
        let stabilityHour: number;

        if (baseDate && baseTime) {
          // 'YYYY-MM-DD' → 'YYYYMMDD'
          apiBaseDate = baseDate.replace(/-/g, '');
          // 'HH:mm' → 'HH00'
          apiBaseTime = baseTime.slice(0, 2) + '00';
          stabilityHour = parseInt(baseTime.slice(0, 2), 10);
        } else {
          const current = getCurrentBaseDateTime();
          apiBaseDate = current.baseDate;
          apiBaseTime = current.baseTime;
          stabilityHour = new Date().getHours();
        }

        const forecasts = await getUltraShortForecast(nx, ny, apiBaseDate, apiBaseTime);

        if (forecasts.length > 0) {
          const f = forecasts[0];
          const stability = deriveStabilityClass(f.windSpeed, stabilityHour);

          setWeather({
            windSpeed: f.windSpeed,
            windDirection: f.windDirection,
            temperature: f.temperature,
            humidity: f.humidity,
            stability,
            isLoading: false,
            error: null,
            lastUpdate: new Date(),
          });
        } else {
          setWeather({
            ...DEFAULT_WEATHER,
            isLoading: false,
            error: 'API 응답 데이터 없음',
            lastUpdate: new Date(),
          });
        }
      } catch {
        setWeather({
          ...DEFAULT_WEATHER,
          isLoading: false,
          error: 'KMA API 조회 실패 (기본값 사용)',
          lastUpdate: new Date(),
        });
      }
    }, 500);

    return () => {
      if (timerRef.current) clearTimeout(timerRef.current);
    };
  }, [lat, lon, baseDate, baseTime]);

  return weather;
}