/*
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 kubectl

import (
	"bytes"
	"fmt"
	"io"

	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/api/meta"
	"k8s.io/kubernetes/pkg/api/unversioned"
	"k8s.io/kubernetes/pkg/apis/extensions"
	clientset "k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
	deploymentutil "k8s.io/kubernetes/pkg/controller/deployment/util"
	"k8s.io/kubernetes/pkg/runtime"
	sliceutil "k8s.io/kubernetes/pkg/util/slice"
)

const (
	ChangeCauseAnnotation = "kubernetes.io/change-cause"
)

// HistoryViewer provides an interface for resources have historical information.
type HistoryViewer interface {
	ViewHistory(namespace, name string, revision int64) (string, error)
}

func HistoryViewerFor(kind unversioned.GroupKind, c clientset.Interface) (HistoryViewer, error) {
	switch kind {
	case extensions.Kind("Deployment"):
		return &DeploymentHistoryViewer{c}, nil
	}
	return nil, fmt.Errorf("no history viewer has been implemented for %q", kind)
}

type DeploymentHistoryViewer struct {
	c clientset.Interface
}

// ViewHistory returns a revision-to-replicaset map as the revision history of a deployment
func (h *DeploymentHistoryViewer) ViewHistory(namespace, name string, revision int64) (string, error) {
	deployment, err := h.c.Extensions().Deployments(namespace).Get(name)
	if err != nil {
		return "", fmt.Errorf("failed to retrieve deployment %s: %v", name, err)
	}
	_, allOldRSs, newRS, err := deploymentutil.GetAllReplicaSets(deployment, h.c)
	if err != nil {
		return "", fmt.Errorf("failed to retrieve replica sets from deployment %s: %v", name, err)
	}
	allRSs := allOldRSs
	if newRS != nil {
		allRSs = append(allRSs, newRS)
	}

	historyInfo := make(map[int64]*api.PodTemplateSpec)
	for _, rs := range allRSs {
		v, err := deploymentutil.Revision(rs)
		if err != nil {
			continue
		}
		historyInfo[v] = &rs.Spec.Template
		changeCause := getChangeCause(rs)
		if historyInfo[v].Annotations == nil {
			historyInfo[v].Annotations = make(map[string]string)
		}
		if len(changeCause) > 0 {
			historyInfo[v].Annotations[ChangeCauseAnnotation] = changeCause
		}
	}

	if len(historyInfo) == 0 {
		return "No rollout history found.", nil
	}

	if revision > 0 {
		// Print details of a specific revision
		template, ok := historyInfo[revision]
		if !ok {
			return "", fmt.Errorf("unable to find the specified revision")
		}
		buf := bytes.NewBuffer([]byte{})
		DescribePodTemplate(template, buf)
		return buf.String(), nil
	}

	// Sort the revisionToChangeCause map by revision
	revisions := make([]int64, 0, len(historyInfo))
	for r := range historyInfo {
		revisions = append(revisions, r)
	}
	sliceutil.SortInts64(revisions)

	return tabbedString(func(out io.Writer) error {
		fmt.Fprintf(out, "REVISION\tCHANGE-CAUSE\n")
		for _, r := range revisions {
			// Find the change-cause of revision r
			changeCause := historyInfo[r].Annotations[ChangeCauseAnnotation]
			if len(changeCause) == 0 {
				changeCause = "<none>"
			}
			fmt.Fprintf(out, "%d\t%s\n", r, changeCause)
		}
		return nil
	})
}

// getChangeCause returns the change-cause annotation of the input object
func getChangeCause(obj runtime.Object) string {
	accessor, err := meta.Accessor(obj)
	if err != nil {
		return ""
	}
	return accessor.GetAnnotations()[ChangeCauseAnnotation]
}
