package api

import (
	"context"
	"encoding/json"
	"net/http"

	"github.com/cpuguy83/strongerrors"
	"github.com/pkg/errors"
	stats "k8s.io/kubernetes/pkg/kubelet/apis/stats/v1alpha1"
)

// PodMetricsBackend is used in place of backend implementations to get k8s pod metrics.
type PodMetricsBackend interface {
	GetStatsSummary(context.Context) (*stats.Summary, error)
}

// PodMetricsHandlerFunc makes an HTTP handler for implementing the kubelet summary stats endpoint
func PodMetricsHandlerFunc(b PodMetricsBackend) http.HandlerFunc {
	return handleError(func(w http.ResponseWriter, req *http.Request) error {
		stats, err := b.GetStatsSummary(req.Context())
		if err != nil {
			if errors.Cause(err) == context.Canceled {
				return strongerrors.Cancelled(err)
			}
			return errors.Wrap(err, "error getting status from provider")
		}

		b, err := json.Marshal(stats)
		if err != nil {
			return strongerrors.Unknown(errors.Wrap(err, "error marshalling stats"))
		}

		if _, err := w.Write(b); err != nil {
			return strongerrors.Unknown(errors.Wrap(err, "could not write to client"))
		}
		return nil
	})
}