first commit

internal/providers/openmeteo.go

@@ -0,0 +1,166 @@
+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
+}