Add internal provider

Co-authored-by: Julien Salleyron <julien.salleyron@gmail.com>

pkg/server/service/internalhandler.go

@@ -0,0 +1,89 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/containous/traefik/v2/pkg/config/runtime"
+)
+
+type serviceManager interface {
+	BuildHTTP(rootCtx context.Context, serviceName string, responseModifier func(*http.Response) error) (http.Handler, error)
+	LaunchHealthCheck()
+}
+
+// InternalHandlers is the internal HTTP handlers builder.
+type InternalHandlers struct {
+	api        http.Handler
+	dashboard  http.Handler
+	rest       http.Handler
+	prometheus http.Handler
+	ping       http.Handler
+	serviceManager
+}
+
+// NewInternalHandlers creates a new InternalHandlers.
+func NewInternalHandlers(api func(configuration *runtime.Configuration) http.Handler, configuration *runtime.Configuration, rest http.Handler, metricsHandler http.Handler, pingHandler http.Handler, dashboard http.Handler, next serviceManager) *InternalHandlers {
+	var apiHandler http.Handler
+	if api != nil {
+		apiHandler = api(configuration)
+	}
+
+	return &InternalHandlers{
+		api:            apiHandler,
+		dashboard:      dashboard,
+		rest:           rest,
+		prometheus:     metricsHandler,
+		ping:           pingHandler,
+		serviceManager: next,
+	}
+}
+
+// BuildHTTP builds an HTTP handler.
+func (m *InternalHandlers) BuildHTTP(rootCtx context.Context, serviceName string, responseModifier func(*http.Response) error) (http.Handler, error) {
+	if strings.HasSuffix(serviceName, "@internal") {
+		return m.get(serviceName)
+	}
+
+	return m.serviceManager.BuildHTTP(rootCtx, serviceName, responseModifier)
+}
+
+func (m *InternalHandlers) get(serviceName string) (http.Handler, error) {
+	switch serviceName {
+	case "api@internal":
+		if m.api == nil {
+			return nil, errors.New("api is not enabled")
+		}
+		return m.api, nil
+
+	case "dashboard@internal":
+		if m.dashboard == nil {
+			return nil, errors.New("dashboard is not enabled")
+		}
+		return m.dashboard, nil
+
+	case "rest@internal":
+		if m.rest == nil {
+			return nil, errors.New("rest is not enabled")
+		}
+		return m.rest, nil
+
+	case "ping@internal":
+		if m.ping == nil {
+			return nil, errors.New("ping is not enabled")
+		}
+		return m.ping, nil
+
+	case "prometheus@internal":
+		if m.prometheus == nil {
+			return nil, errors.New("prometheus is not enabled")
+		}
+		return m.prometheus, nil
+
+	default:
+		return nil, fmt.Errorf("unknown internal service %s", serviceName)
+	}
+}