meter/handler: more idiomatic option handling

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

meter/handler/handler.go

@@ -5,6 +5,7 @@ import (
 	"context"
 
 	"github.com/unistack-org/micro/v3/codec"
+	"github.com/unistack-org/micro/v3/errors"
 	"github.com/unistack-org/micro/v3/meter"
 )
 
@@ -14,18 +15,52 @@ var (
 )
 
 type handler struct {
-	meter meter.Meter
-	opts  []meter.Option
+	opts Options
 }
 
-func NewHandler(meter meter.Meter, opts ...meter.Option) *handler {
-	return &handler{meter: meter, opts: opts}
+type Option func(*Options)
+
+type Options struct {
+	Meter        meter.Meter
+	MeterOptions []meter.Option
+	Name         string
+}
+
+func Meter(m meter.Meter) Option {
+	return func(o *Options) {
+		o.Meter = m
+	}
+}
+
+func Name(name string) Option {
+	return func(o *Options) {
+		o.Name = name
+	}
+}
+
+func MeterOptions(opts ...meter.Option) Option {
+	return func(o *Options) {
+		o.MeterOptions = append(o.MeterOptions, opts...)
+	}
+}
+
+func NewOptions(opts ...Option) Options {
+	options := Options{Meter: meter.DefaultMeter}
+	for _, o := range opts {
+		o(&options)
+	}
+	return options
+}
+
+func NewHandler(opts ...Option) *handler {
+	options := NewOptions(opts...)
+	return &handler{opts: options}
 }
 
 func (h *handler) Metrics(ctx context.Context, req *codec.Frame, rsp *codec.Frame) error {
 	buf := bytes.NewBuffer(nil)
-	if err := h.meter.Write(buf, h.opts...); err != nil {
-		return err
+	if err := h.opts.Meter.Write(buf, h.opts.MeterOptions...); err != nil {
+		return errors.InternalServerError(h.opts.Name, "%v", err)
 	}
 
 	rsp.Data = buf.Bytes()