/*
Copyright 2016 The Kubernetes Authors All rights reserved.

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 pod

import (
	"fmt"
	"hash/adler32"
	"time"

	"github.com/golang/glog"

	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/api/errors"
	unversionedcore "k8s.io/kubernetes/pkg/client/typed/generated/core/unversioned"
	hashutil "k8s.io/kubernetes/pkg/util/hash"
	"k8s.io/kubernetes/pkg/util/wait"
)

func GetPodTemplateSpecHash(template api.PodTemplateSpec) uint32 {
	podTemplateSpecHasher := adler32.New()
	hashutil.DeepHashObject(podTemplateSpecHasher, template)
	return podTemplateSpecHasher.Sum32()
}

// TODO: use client library instead when it starts to support update retries
//       see https://github.com/kubernetes/kubernetes/issues/21479
type updatePodFunc func(pod *api.Pod)
type preconditionFunc func(pod *api.Pod) bool

// UpdatePodWithRetries updates a pod with given applyUpdate function, when the given precondition holds. Note that pod not found error is ignored.
// The returned bool value can be used to tell if the pod is actually updated.
func UpdatePodWithRetries(podClient unversionedcore.PodInterface, pod *api.Pod, preconditionHold preconditionFunc, applyUpdate updatePodFunc) (*api.Pod, bool, error) {
	var err error
	var podUpdated bool
	oldPod := pod
	if err = wait.Poll(10*time.Millisecond, 1*time.Minute, func() (bool, error) {
		pod, err = podClient.Get(oldPod.Name)
		if err != nil {
			return false, err
		}
		if !preconditionHold(pod) {
			glog.V(4).Infof("pod %s precondition doesn't hold, skip updating it.", pod.Name)
			return true, nil
		}
		// Apply the update, then attempt to push it to the apiserver.
		applyUpdate(pod)
		if pod, err = podClient.Update(pod); err == nil {
			// Update successful.
			return true, nil
		}
		// TODO: don't retry on perm-failed errors and handle them gracefully
		// Update could have failed due to conflict error. Try again.
		return false, nil
	}); err == nil {
		// When there's no error, we've updated this pod.
		podUpdated = true
	}

	if err == wait.ErrWaitTimeout {
		err = fmt.Errorf("timed out trying to update pod: %+v", oldPod)
	}
	if errors.IsNotFound(err) {
		glog.V(4).Infof("%s %s/%s is not found, skip updating it.", oldPod.Kind, oldPod.Namespace, oldPod.Name)
		err = nil
	}
	return pod, podUpdated, err
}