implement econet exporter

pkg/econet/econetmetrics/builder.go

@@ -0,0 +1,41 @@
+package econetmetrics
+
+import "go.opentelemetry.io/otel/metric"
+
+// gaugeBuilder creates observable gauges, accumulating them for a single
+// RegisterCallback and short-circuiting on the first creation error.
+//
+// Units are intentionally baked into the metric names (Prometheus idiom)
+// rather than set via metric.WithUnit — the OTEL→Prometheus exporter would
+// otherwise append a second unit suffix (e.g. econet_setpoint_fahrenheit_F).
+type gaugeBuilder struct {
+	m   metric.Meter
+	obs []metric.Observable
+	err error
+}
+
+func (b *gaugeBuilder) i64(name, desc string) metric.Int64ObservableGauge {
+	if b.err != nil {
+		return nil
+	}
+	g, err := b.m.Int64ObservableGauge(name, metric.WithDescription(desc))
+	if err != nil {
+		b.err = err
+		return nil
+	}
+	b.obs = append(b.obs, g)
+	return g
+}
+
+func (b *gaugeBuilder) f64(name, desc string) metric.Float64ObservableGauge {
+	if b.err != nil {
+		return nil
+	}
+	g, err := b.m.Float64ObservableGauge(name, metric.WithDescription(desc))
+	if err != nil {
+		b.err = err
+		return nil
+	}
+	b.obs = append(b.obs, g)
+	return g
+}