add support for barometric pressure

internal/mqttingest/barometer.go

@@ -0,0 +1,105 @@
+package mqttingest
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+type BarometerPayload struct {
+	PressureHPA float64
+}
+
+func ParseBarometer(b []byte) (*BarometerPayload, map[string]any, error) {
+	var raw map[string]any
+	if err := json.Unmarshal(b, &raw); err != nil {
+		return nil, nil, err
+	}
+
+	pressure, ok := pressureHPAFromPayload(raw)
+	if !ok {
+		return nil, raw, fmt.Errorf("barometer payload missing pressure field")
+	}
+
+	return &BarometerPayload{
+		PressureHPA: pressure,
+	}, raw, nil
+}
+
+func pressureHPAFromPayload(raw map[string]any) (float64, bool) {
+	if v, ok := findFloat(raw,
+		"pressure_hpa",
+		"pressure_mb",
+		"pressure_mbar",
+		"barometer_hpa",
+		"baro_hpa",
+		"pressure",
+	); ok {
+		return v, true
+	}
+	if v, ok := findFloat(raw, "pressure_pa"); ok {
+		return v / 100.0, true
+	}
+	if v, ok := findFloat(raw, "pressure_kpa"); ok {
+		return v * 10.0, true
+	}
+	if v, ok := findFloat(raw, "pressure_inhg", "barometer_inhg"); ok {
+		return v * 33.8638866667, true
+	}
+	return 0, false
+}
+
+func findFloat(raw map[string]any, keys ...string) (float64, bool) {
+	for _, key := range keys {
+		v, ok := raw[key]
+		if !ok {
+			continue
+		}
+		if f, ok := asFloat(v); ok {
+			return f, true
+		}
+	}
+	return 0, false
+}
+
+func asFloat(v any) (float64, bool) {
+	switch t := v.(type) {
+	case float64:
+		return t, true
+	case float32:
+		return float64(t), true
+	case int:
+		return float64(t), true
+	case int8:
+		return float64(t), true
+	case int16:
+		return float64(t), true
+	case int32:
+		return float64(t), true
+	case int64:
+		return float64(t), true
+	case uint:
+		return float64(t), true
+	case uint8:
+		return float64(t), true
+	case uint16:
+		return float64(t), true
+	case uint32:
+		return float64(t), true
+	case uint64:
+		return float64(t), true
+	case json.Number:
+		f, err := t.Float64()
+		return f, err == nil
+	case string:
+		s := strings.TrimSpace(t)
+		if s == "" {
+			return 0, false
+		}
+		f, err := strconv.ParseFloat(s, 64)
+		return f, err == nil
+	default:
+		return 0, false
+	}
+}