/*
Copyright 2016 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package registry

import (
	"context"
	"net/http"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/watch"
)

type decoratedWatcher struct {
	w         watch.Interface
	decorator ObjectFunc
	cancel    context.CancelFunc
	resultCh  chan watch.Event
}

func newDecoratedWatcher(w watch.Interface, decorator ObjectFunc) *decoratedWatcher {
	ctx, cancel := context.WithCancel(context.Background())
	d := &decoratedWatcher{
		w:         w,
		decorator: decorator,
		cancel:    cancel,
		resultCh:  make(chan watch.Event),
	}
	go d.run(ctx)
	return d
}

func (d *decoratedWatcher) run(ctx context.Context) {
	var recv, send watch.Event
	var ok bool
	for {
		select {
		case recv, ok = <-d.w.ResultChan():
			// The underlying channel may be closed after timeout.
			if !ok {
				d.cancel()
				return
			}
			switch recv.Type {
			case watch.Added, watch.Modified, watch.Deleted, watch.Bookmark:
				err := d.decorator(recv.Object)
				if err != nil {
					send = makeStatusErrorEvent(err)
					break
				}
				send = recv
			case watch.Error:
				send = recv
			}
			select {
			case d.resultCh <- send:
				if send.Type == watch.Error {
					d.cancel()
				}
			case <-ctx.Done():
			}
		case <-ctx.Done():
			d.w.Stop()
			close(d.resultCh)
			return
		}
	}
}

func (d *decoratedWatcher) Stop() {
	d.cancel()
}

func (d *decoratedWatcher) ResultChan() <-chan watch.Event {
	return d.resultCh
}

func makeStatusErrorEvent(err error) watch.Event {
	status := &metav1.Status{
		Status:  metav1.StatusFailure,
		Message: err.Error(),
		Code:    http.StatusInternalServerError,
		Reason:  metav1.StatusReasonInternalError,
	}
	return watch.Event{
		Type:   watch.Error,
		Object: status,
	}
}
