package forecast

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"net/url"
	"time"

	"weatherstation/internal/database"
)

type openMeteoResponse struct {
	Hourly struct {
		Time        []string  `json:"time"`
		Rain        []float64 `json:"rain"`
		Temperature []float64 `json:"temperature_2m"`
		Humidity    []float64 `json:"relative_humidity_2m"`
		WindSpeed   []float64 `json:"wind_speed_10m"`
		WindGusts   []float64 `json:"wind_gusts_10m"`
		WindDir     []float64 `json:"wind_direction_10m"`
		PrecipProb  []float64 `json:"precipitation_probability"`
		SurfacePres []float64 `json:"surface_pressure"`
	} `json:"hourly"`
}

// RunOpenMeteoFetch 拉取各站点未来三小时并写入 forecast_hourly
func RunOpenMeteoFetch(ctx context.Context) error {
	db := database.GetDB()
	stations, err := loadStationsWithLatLon(ctx, db)
	if err != nil {
		return err
	}

	client := &http.Client{Timeout: 15 * time.Second}
	loc, _ := time.LoadLocation("Asia/Shanghai")
	if loc == nil {
		loc = time.FixedZone("CST", 8*3600)
	}

	issuedAt := time.Now().In(loc)
	startHour := issuedAt.Truncate(time.Hour)
	targets := []time.Time{startHour.Add(1 * time.Hour), startHour.Add(2 * time.Hour), startHour.Add(3 * time.Hour)}

	for _, s := range stations {
		apiURL := buildOpenMeteoURL(s.lat, s.lon)
		req, _ := http.NewRequestWithContext(ctx, http.MethodGet, apiURL, nil)
		resp, err := client.Do(req)
		if err != nil {
			log.Printf("open-meteo 请求失败 station=%s err=%v", s.id, err)
			continue
		}
		var data openMeteoResponse
		if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
			resp.Body.Close()
			log.Printf("open-meteo 解码失败 station=%s err=%v", s.id, err)
			continue
		}
		resp.Body.Close()

		// 建立 time->vals 映射（按CST解析）
		table := map[time.Time]struct {
			rain float64
			temp float64
			rh   float64
			ws   float64
			gust float64
			wdir float64
			prob float64
			pres float64
		}{}
		for i := range data.Hourly.Time {
			t, err := time.ParseInLocation("2006-01-02T15:04", data.Hourly.Time[i], loc)
			if err != nil {
				continue
			}
			v := table[t]
			if i < len(data.Hourly.Rain) {
				v.rain = data.Hourly.Rain[i]
			}
			if i < len(data.Hourly.Temperature) {
				v.temp = data.Hourly.Temperature[i]
			}
			if i < len(data.Hourly.Humidity) {
				v.rh = data.Hourly.Humidity[i]
			}
			if i < len(data.Hourly.WindSpeed) {
				// 将 km/h 转换为 m/s: m/s = km/h ÷ 3.6
				v.ws = data.Hourly.WindSpeed[i] / 3.6
			}
			if i < len(data.Hourly.WindGusts) {
				// 将 km/h 转换为 m/s: m/s = km/h ÷ 3.6
				v.gust = data.Hourly.WindGusts[i] / 3.6
			}
			if i < len(data.Hourly.WindDir) {
				v.wdir = data.Hourly.WindDir[i]
			}
			if i < len(data.Hourly.PrecipProb) {
				v.prob = data.Hourly.PrecipProb[i]
			}
			if i < len(data.Hourly.SurfacePres) {
				v.pres = data.Hourly.SurfacePres[i]
			}
			table[t] = v
		}

		for _, ft := range targets {
			if v, ok := table[ft]; ok {
				if err := upsertForecast(ctx, db, s.id, issuedAt, ft,
					int64(v.rain*1000.0),
					int64(v.temp*100.0),
					int64(v.rh),
					int64(v.ws*1000.0),
					int64(v.gust*1000.0),
					int64(v.wdir),
					int64(v.prob),
					int64(v.pres*100.0),
				); err != nil {
					log.Printf("写入forecast失败 station=%s time=%s err=%v", s.id, ft.Format(time.RFC3339), err)
				}
			}
		}
	}
	return nil
}

type station struct {
	id  string
	lat sql.NullFloat64
	lon sql.NullFloat64
}

func loadStationsWithLatLon(ctx context.Context, db *sql.DB) ([]station, error) {
	rows, err := db.QueryContext(ctx, `SELECT station_id, latitude, longitude FROM stations WHERE latitude IS NOT NULL AND longitude IS NOT NULL`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var list []station
	for rows.Next() {
		var s station
		if err := rows.Scan(&s.id, &s.lat, &s.lon); err != nil {
			continue
		}
		list = append(list, s)
	}
	return list, nil
}

func buildOpenMeteoURL(lat, lon sql.NullFloat64) string {
	q := url.Values{}
	q.Set("latitude", fmt.Sprintf("%f", lat.Float64))
	q.Set("longitude", fmt.Sprintf("%f", lon.Float64))
	q.Set("hourly", "rain,temperature_2m,relative_humidity_2m,wind_speed_10m,wind_gusts_10m,wind_direction_10m,precipitation_probability,surface_pressure")
	q.Set("timezone", "Asia/Shanghai")
	// 可以添加单位参数，但我们已经在代码中处理了单位转换，所以保持默认单位即可
	// 默认单位：风速 km/h，温度 °C，降水量 mm，气压 hPa
	return "https://api.open-meteo.com/v1/forecast?" + q.Encode()
}

func upsertForecast(ctx context.Context, db *sql.DB, stationID string, issuedAt, forecastTime time.Time,
	rainMmX1000, tempCx100, humidityPct, wsMsX1000, gustMsX1000, wdirDeg, probPct, pressureHpaX100 int64,
) error {
	_, err := db.ExecContext(ctx, `
		INSERT INTO forecast_hourly (
			station_id, provider, issued_at, forecast_time,
			rain_mm_x1000, temp_c_x100, humidity_pct, wind_speed_ms_x1000,
			wind_gust_ms_x1000, wind_dir_deg, precip_prob_pct, pressure_hpa_x100
		) VALUES ($1, 'open-meteo', $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)
		ON CONFLICT (station_id, provider, issued_at, forecast_time)
		DO UPDATE SET 
			rain_mm_x1000 = EXCLUDED.rain_mm_x1000,
			temp_c_x100 = EXCLUDED.temp_c_x100,
			humidity_pct = EXCLUDED.humidity_pct,
			wind_speed_ms_x1000 = EXCLUDED.wind_speed_ms_x1000,
			wind_gust_ms_x1000 = EXCLUDED.wind_gust_ms_x1000,
			wind_dir_deg = EXCLUDED.wind_dir_deg,
			precip_prob_pct = EXCLUDED.precip_prob_pct,
			pressure_hpa_x100 = EXCLUDED.pressure_hpa_x100
	`, stationID, issuedAt, forecastTime,
		rainMmX1000, tempCx100, humidityPct, wsMsX1000, gustMsX1000, wdirDeg, probPct, pressureHpaX100)
	return err
}