package providers

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"time"
)

type OpenMeteo struct {
	Client *http.Client
}

func (o *OpenMeteo) Name() string { return "open_meteo" }

func (o *OpenMeteo) Fetch(ctxDone <-chan struct{}, site Site, model string) (*ForecastResult, error) {
	if o.Client == nil {
		o.Client = &http.Client{Timeout: 15 * time.Second}
	}

	// Hourly fields that are useful for bias-correction / training
	hourly := []string{
		"temperature_2m",
		"relative_humidity_2m",
		"pressure_msl",
		"wind_speed_10m",
		"wind_gusts_10m",
		"wind_direction_10m",
		"precipitation",
		"precipitation_probability",
		"cloud_cover",
	}

	u, _ := url.Parse("https://api.open-meteo.com/v1/forecast")
	q := u.Query()
	q.Set("latitude", fmt.Sprintf("%.6f", site.Latitude))
	q.Set("longitude", fmt.Sprintf("%.6f", site.Longitude))
	q.Set("hourly", join(hourly))
	q.Set("timezone", "UTC")
	q.Set("models", model)      // e.g. "ecmwf"
	q.Set("forecast_days", "7") // keep it short; you can increase later
	u.RawQuery = q.Encode()

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	go func() { <-ctxDone; cancel() }()

	req, _ := http.NewRequestWithContext(ctx, "GET", u.String(), nil)
	resp, err := o.Client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode/100 != 2 {
		return nil, fmt.Errorf("open-meteo HTTP %d", resp.StatusCode)
	}

	var raw map[string]any
	if err := json.NewDecoder(resp.Body).Decode(&raw); err != nil {
		return nil, err
	}

	// Parse the hourly arrays
	hr, ok := raw["hourly"].(map[string]any)
	if !ok {
		return nil, fmt.Errorf("unexpected open-meteo payload: missing hourly")
	}

	times, err := parseTimeArray(hr["time"])
	if err != nil {
		return nil, err
	}

	// Helpers pull float arrays (may be absent)
	temp := floatArray(hr["temperature_2m"])
	rh := floatArray(hr["relative_humidity_2m"])
	msl := floatArray(hr["pressure_msl"])
	ws := floatArray(hr["wind_speed_10m"])
	gust := floatArray(hr["wind_gusts_10m"])
	wd := floatArray(hr["wind_direction_10m"])
	precip := floatArray(hr["precipitation"])
	pprob := floatArray(hr["precipitation_probability"])
	cloud := floatArray(hr["cloud_cover"])

	points := make([]HourlyForecastPoint, 0, len(times))
	for i := range times {
		points = append(points, HourlyForecastPoint{
			TS:           times[i],
			TempC:        idx(temp, i),
			RH:           idx(rh, i),
			PressureMSLH: idx(msl, i),
			WindMS:       idx(ws, i),
			WindGustMS:   idx(gust, i),
			WindDirDeg:   idx(wd, i),
			PrecipMM:     idx(precip, i),
			PrecipProb:   idx(pprob, i),
			CloudCover:   idx(cloud, i),
		})
	}

	return &ForecastResult{
		RetrievedAt: time.Now().UTC(),
		Model:       model,
		Hourly:      points,
		Raw:         raw,
	}, nil
}

func join(items []string) string {
	out := ""
	for i, s := range items {
		if i > 0 {
			out += ","
		}
		out += s
	}
	return out
}

func parseTimeArray(v any) ([]time.Time, error) {
	arr, ok := v.([]any)
	if !ok {
		return nil, fmt.Errorf("hourly.time not array")
	}
	out := make([]time.Time, 0, len(arr))
	for _, x := range arr {
		s, _ := x.(string)
		t, err := time.Parse("2006-01-02T15:04", s) // open-meteo uses ISO without seconds
		if err != nil {
			return nil, err
		}
		out = append(out, t.UTC())
	}
	return out, nil
}

func floatArray(v any) []float64 {
	arr, ok := v.([]any)
	if !ok {
		return nil
	}
	out := make([]float64, 0, len(arr))
	for _, x := range arr {
		switch n := x.(type) {
		case float64:
			out = append(out, n)
		case int:
			out = append(out, float64(n))
		default:
			// if null or unexpected, use NaN sentinel? We'll instead skip by storing nil via idx()
			out = append(out, 0)
		}
	}
	return out
}

func idx(a []float64, i int) *float64 {
	if a == nil || i < 0 || i >= len(a) {
		return nil
	}
	v := a[i]
	return &v
}