/*
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 cronjob

import (
	"fmt"
	"time"

	"github.com/robfig/cron/v3"
	"k8s.io/klog/v2"

	batchv1 "k8s.io/api/batch/v1"
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/client-go/tools/record"
)

// Utilities for dealing with Jobs and CronJobs and time.

func inActiveList(cj batchv1.CronJob, uid types.UID) bool {
	for _, j := range cj.Status.Active {
		if j.UID == uid {
			return true
		}
	}
	return false
}

func deleteFromActiveList(cj *batchv1.CronJob, uid types.UID) {
	if cj == nil {
		return
	}
	// TODO: @alpatel the memory footprint can may be reduced here by
	//  cj.Status.Active = append(cj.Status.Active[:indexToRemove], cj.Status.Active[indexToRemove:]...)
	newActive := []corev1.ObjectReference{}
	for _, j := range cj.Status.Active {
		if j.UID != uid {
			newActive = append(newActive, j)
		}
	}
	cj.Status.Active = newActive
}

// getParentUIDFromJob extracts UID of job's parent and whether it was found
func getParentUIDFromJob(j batchv1.Job) (types.UID, bool) {
	controllerRef := metav1.GetControllerOf(&j)

	if controllerRef == nil {
		return types.UID(""), false
	}

	if controllerRef.Kind != "CronJob" {
		klog.V(4).Infof("Job with non-CronJob parent, name %s namespace %s", j.Name, j.Namespace)
		return types.UID(""), false
	}

	return controllerRef.UID, true
}

// groupJobsByParent groups jobs into a map keyed by the job parent UID (e.g. cronJob).
// It has no receiver, to facilitate testing.
func groupJobsByParent(js []batchv1.Job) map[types.UID][]batchv1.Job {
	jobsByCj := make(map[types.UID][]batchv1.Job)
	for _, job := range js {
		parentUID, found := getParentUIDFromJob(job)
		if !found {
			klog.V(4).Infof("Unable to get parent uid from job %s in namespace %s", job.Name, job.Namespace)
			continue
		}
		jobsByCj[parentUID] = append(jobsByCj[parentUID], job)
	}
	return jobsByCj
}

// getRecentUnmetScheduleTimes gets a slice of times (from oldest to latest) that have passed when a Job should have started but did not.
//
// If there are too many (>100) unstarted times, just give up and return an empty slice.
// If there were missed times prior to the last known start time, then those are not returned.
func getRecentUnmetScheduleTimes(cj batchv1.CronJob, now time.Time) ([]time.Time, error) {
	starts := []time.Time{}
	sched, err := cron.ParseStandard(cj.Spec.Schedule)
	if err != nil {
		return starts, fmt.Errorf("unparseable schedule: %s : %s", cj.Spec.Schedule, err)
	}

	var earliestTime time.Time
	if cj.Status.LastScheduleTime != nil {
		earliestTime = cj.Status.LastScheduleTime.Time
	} else {
		// If none found, then this is either a recently created cronJob,
		// or the active/completed info was somehow lost (contract for status
		// in kubernetes says it may need to be recreated), or that we have
		// started a job, but have not noticed it yet (distributed systems can
		// have arbitrary delays).  In any case, use the creation time of the
		// CronJob as last known start time.
		earliestTime = cj.ObjectMeta.CreationTimestamp.Time
	}
	if cj.Spec.StartingDeadlineSeconds != nil {
		// Controller is not going to schedule anything below this point
		schedulingDeadline := now.Add(-time.Second * time.Duration(*cj.Spec.StartingDeadlineSeconds))

		if schedulingDeadline.After(earliestTime) {
			earliestTime = schedulingDeadline
		}
	}
	if earliestTime.After(now) {
		return []time.Time{}, nil
	}

	for t := sched.Next(earliestTime); !t.After(now); t = sched.Next(t) {
		starts = append(starts, t)
		// An object might miss several starts. For example, if
		// controller gets wedged on friday at 5:01pm when everyone has
		// gone home, and someone comes in on tuesday AM and discovers
		// the problem and restarts the controller, then all the hourly
		// jobs, more than 80 of them for one hourly cronJob, should
		// all start running with no further intervention (if the cronJob
		// allows concurrency and late starts).
		//
		// However, if there is a bug somewhere, or incorrect clock
		// on controller's server or apiservers (for setting creationTimestamp)
		// then there could be so many missed start times (it could be off
		// by decades or more), that it would eat up all the CPU and memory
		// of this controller. In that case, we want to not try to list
		// all the missed start times.
		//
		// I've somewhat arbitrarily picked 100, as more than 80,
		// but less than "lots".
		if len(starts) > 100 {
			// We can't get the most recent times so just return an empty slice
			return []time.Time{}, fmt.Errorf("too many missed start time (> 100). Set or decrease .spec.startingDeadlineSeconds or check clock skew")
		}
	}
	return starts, nil
}

// getNextScheduleTime gets the time of next schedule after last scheduled and before now
//  it returns nil if no unmet schedule times.
// If there are too many (>100) unstarted times, it will raise a warning and but still return
// the list of missed times.
func getNextScheduleTime(cj batchv1.CronJob, now time.Time, schedule cron.Schedule, recorder record.EventRecorder) (*time.Time, error) {
	var (
		earliestTime time.Time
	)
	if cj.Status.LastScheduleTime != nil {
		earliestTime = cj.Status.LastScheduleTime.Time
	} else {
		// If none found, then this is either a recently created cronJob,
		// or the active/completed info was somehow lost (contract for status
		// in kubernetes says it may need to be recreated), or that we have
		// started a job, but have not noticed it yet (distributed systems can
		// have arbitrary delays).  In any case, use the creation time of the
		// CronJob as last known start time.
		earliestTime = cj.ObjectMeta.CreationTimestamp.Time
	}
	if cj.Spec.StartingDeadlineSeconds != nil {
		// Controller is not going to schedule anything below this point
		schedulingDeadline := now.Add(-time.Second * time.Duration(*cj.Spec.StartingDeadlineSeconds))

		if schedulingDeadline.After(earliestTime) {
			earliestTime = schedulingDeadline
		}
	}
	if earliestTime.After(now) {
		return nil, nil
	}

	t, numberOfMissedSchedules, err := getMostRecentScheduleTime(earliestTime, now, schedule)

	if numberOfMissedSchedules > 100 {
		// An object might miss several starts. For example, if
		// controller gets wedged on friday at 5:01pm when everyone has
		// gone home, and someone comes in on tuesday AM and discovers
		// the problem and restarts the controller, then all the hourly
		// jobs, more than 80 of them for one hourly cronJob, should
		// all start running with no further intervention (if the cronJob
		// allows concurrency and late starts).
		//
		// However, if there is a bug somewhere, or incorrect clock
		// on controller's server or apiservers (for setting creationTimestamp)
		// then there could be so many missed start times (it could be off
		// by decades or more), that it would eat up all the CPU and memory
		// of this controller. In that case, we want to not try to list
		// all the missed start times.
		//
		// I've somewhat arbitrarily picked 100, as more than 80,
		// but less than "lots".
		recorder.Eventf(&cj, corev1.EventTypeWarning, "TooManyMissedTimes", "too many missed start times: %d. Set or decrease .spec.startingDeadlineSeconds or check clock skew", numberOfMissedSchedules)
		klog.InfoS("too many missed times", "cronjob", klog.KRef(cj.GetNamespace(), cj.GetName()), "missed times", numberOfMissedSchedules)
	}
	return t, err
}

// getMostRecentScheduleTime returns the latest schedule time between earliestTime and the count of number of
// schedules in between them
func getMostRecentScheduleTime(earliestTime time.Time, now time.Time, schedule cron.Schedule) (*time.Time, int64, error) {
	t1 := schedule.Next(earliestTime)
	t2 := schedule.Next(t1)

	if now.Before(t1) {
		return nil, 0, nil
	}
	if now.Before(t2) {
		return &t1, 1, nil
	}

	// It is possible for cron.ParseStandard("59 23 31 2 *") to return an invalid schedule
	// seconds - 59, minute - 23, hour - 31 (?!)  dom - 2, and dow is optional, clearly 31 is invalid
	// In this case the timeBetweenTwoSchedules will be 0, and we error out the invalid schedule
	timeBetweenTwoSchedules := int64(t2.Sub(t1).Round(time.Second).Seconds())
	if timeBetweenTwoSchedules < 1 {
		return nil, 0, fmt.Errorf("time difference between two schedules less than 1 second")
	}
	timeElapsed := int64(now.Sub(t1).Seconds())
	numberOfMissedSchedules := (timeElapsed / timeBetweenTwoSchedules) + 1
	t := time.Unix(t1.Unix()+((numberOfMissedSchedules-1)*timeBetweenTwoSchedules), 0).UTC()
	return &t, numberOfMissedSchedules, nil
}

// getJobFromTemplate makes a Job from a CronJob
func getJobFromTemplate(cj *batchv1.CronJob, scheduledTime time.Time) (*batchv1.Job, error) {
	labels := copyLabels(&cj.Spec.JobTemplate)
	annotations := copyAnnotations(&cj.Spec.JobTemplate)
	// We want job names for a given nominal start time to have a deterministic name to avoid the same job being created twice
	name := fmt.Sprintf("%s-%d", cj.Name, getTimeHash(scheduledTime))

	job := &batchv1.Job{
		ObjectMeta: metav1.ObjectMeta{
			Labels:          labels,
			Annotations:     annotations,
			Name:            name,
			OwnerReferences: []metav1.OwnerReference{*metav1.NewControllerRef(cj, controllerKind)},
		},
	}
	cj.Spec.JobTemplate.Spec.DeepCopyInto(&job.Spec)
	return job, nil
}

// getTimeHash returns Unix Epoch Time
func getTimeHash(scheduledTime time.Time) int64 {
	return scheduledTime.Unix()
}

// getJobFromTemplate2 makes a Job from a CronJob. It converts the unix time into minutes from
// epoch time and concatenates that to the job name, because the cronjob_controller v2 has the lowest
// granularity of 1 minute for scheduling job.
func getJobFromTemplate2(cj *batchv1.CronJob, scheduledTime time.Time) (*batchv1.Job, error) {
	labels := copyLabels(&cj.Spec.JobTemplate)
	annotations := copyAnnotations(&cj.Spec.JobTemplate)
	// We want job names for a given nominal start time to have a deterministic name to avoid the same job being created twice
	name := getJobName(cj, scheduledTime)

	job := &batchv1.Job{
		ObjectMeta: metav1.ObjectMeta{
			Labels:            labels,
			Annotations:       annotations,
			Name:              name,
			CreationTimestamp: metav1.Time{Time: scheduledTime},
			OwnerReferences:   []metav1.OwnerReference{*metav1.NewControllerRef(cj, controllerKind)},
		},
	}
	cj.Spec.JobTemplate.Spec.DeepCopyInto(&job.Spec)
	return job, nil
}

// getTimeHash returns Unix Epoch Time in minutes
func getTimeHashInMinutes(scheduledTime time.Time) int64 {
	return scheduledTime.Unix() / 60
}

func getFinishedStatus(j *batchv1.Job) (bool, batchv1.JobConditionType) {
	for _, c := range j.Status.Conditions {
		if (c.Type == batchv1.JobComplete || c.Type == batchv1.JobFailed) && c.Status == corev1.ConditionTrue {
			return true, c.Type
		}
	}
	return false, ""
}

// IsJobFinished returns whether or not a job has completed successfully or failed.
func IsJobFinished(j *batchv1.Job) bool {
	isFinished, _ := getFinishedStatus(j)
	return isFinished
}

// byJobStartTime sorts a list of jobs by start timestamp, using their names as a tie breaker.
type byJobStartTime []batchv1.Job

func (o byJobStartTime) Len() int      { return len(o) }
func (o byJobStartTime) Swap(i, j int) { o[i], o[j] = o[j], o[i] }

func (o byJobStartTime) Less(i, j int) bool {
	if o[i].Status.StartTime == nil && o[j].Status.StartTime != nil {
		return false
	}
	if o[i].Status.StartTime != nil && o[j].Status.StartTime == nil {
		return true
	}
	if o[i].Status.StartTime.Equal(o[j].Status.StartTime) {
		return o[i].Name < o[j].Name
	}
	return o[i].Status.StartTime.Before(o[j].Status.StartTime)
}

// byJobStartTimeStar sorts a list of jobs by start timestamp, using their names as a tie breaker.
type byJobStartTimeStar []*batchv1.Job

func (o byJobStartTimeStar) Len() int      { return len(o) }
func (o byJobStartTimeStar) Swap(i, j int) { o[i], o[j] = o[j], o[i] }

func (o byJobStartTimeStar) Less(i, j int) bool {
	if o[i].Status.StartTime == nil && o[j].Status.StartTime != nil {
		return false
	}
	if o[i].Status.StartTime != nil && o[j].Status.StartTime == nil {
		return true
	}
	if o[i].Status.StartTime.Equal(o[j].Status.StartTime) {
		return o[i].Name < o[j].Name
	}
	return o[i].Status.StartTime.Before(o[j].Status.StartTime)
}
