package scheduledscaling

import (
	"errors"
	"fmt"
	"time"

	log "github.com/sirupsen/logrus"
	v1 "github.com/zalando-incubator/kube-metrics-adapter/pkg/apis/zalando.org/v1"
	zalandov1 "github.com/zalando-incubator/kube-metrics-adapter/pkg/client/clientset/versioned/typed/zalando.org/v1"
	"golang.org/x/net/context"
	"golang.org/x/sync/errgroup"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

const (
	// The format used by v1.SchedulePeriod.StartTime. 15:04 are
	// the defined reference time in time.Format.
	hourColonMinuteLayout = "15:04"
)

var days = map[v1.ScheduleDay]time.Weekday{
	v1.SundaySchedule:    time.Sunday,
	v1.MondaySchedule:    time.Monday,
	v1.TuesdaySchedule:   time.Tuesday,
	v1.WednesdaySchedule: time.Wednesday,
	v1.ThursdaySchedule:  time.Thursday,
	v1.FridaySchedule:    time.Friday,
	v1.SaturdaySchedule:  time.Saturday,
}

var (
	// ErrNotScalingScheduleFound is returned when a item returned from
	// the ScalingScheduleCollectorPlugin.store was expected to
	// be an ScalingSchedule but the type assertion failed.
	ErrNotScalingScheduleFound = errors.New("error converting returned object to ScalingSchedule")
	// ErrInvalidScheduleDate is returned when the v1.ScheduleDate is
	// not a valid RFC3339 date. It shouldn't happen since the
	// validation is done by the CRD.
	ErrInvalidScheduleDate = errors.New("could not parse the specified schedule date, format is not RFC3339")
	// ErrInvalidScheduleStartTime is returned when the
	// v1.SchedulePeriod.StartTime is not in the format specified by
	// hourColonMinuteLayout. It shouldn't happen since the validation
	// is done by the CRD.
	ErrInvalidScheduleStartTime = errors.New("could not parse the specified schedule period start time, format is not HH:MM")
)

// Now is the function that returns a time.Time object representing the
// current moment. Its main implementation is the time.Now func in the
// std lib. It's used mainly for test/mock purposes.
type now func() time.Time

type scalingScheduleStore interface {
	List() []interface{}
}

type Controller struct {
	client                      zalandov1.ZalandoV1Interface
	scalingScheduleStore        scalingScheduleStore
	clusterScalingScheduleStore scalingScheduleStore
	now                         now
	defaultScalingWindow        time.Duration
	defaultTimeZone             string
}

func NewController(client zalandov1.ZalandoV1Interface, scalingScheduleStore, clusterScalingScheduleStore scalingScheduleStore, now now, defaultScalingWindow time.Duration, defaultTimeZone string) *Controller {
	return &Controller{
		client:                      client,
		scalingScheduleStore:        scalingScheduleStore,
		clusterScalingScheduleStore: clusterScalingScheduleStore,
		now:                         now,
		defaultScalingWindow:        defaultScalingWindow,
		defaultTimeZone:             defaultTimeZone,
	}
}

func (c *Controller) Run(ctx context.Context) {
	log.Info("Running Scaling Schedule Controller")

	ticker := time.NewTicker(time.Second * 10)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			err := c.runOnce(ctx)
			if err != nil {
				log.Errorf("failed to run scheduled scaling controller loop: %v", err)
			}
		case <-ctx.Done():
			return
		}
	}
}

func (c *Controller) runOnce(ctx context.Context) error {
	// ScalingSchedules
	var scalingGroup errgroup.Group
	scalingGroup.SetLimit(10)

	schedules := c.scalingScheduleStore.List()
	for _, scheduleInterface := range schedules {
		schedule, ok := scheduleInterface.(*v1.ScalingSchedule)
		if !ok {
			return ErrNotScalingScheduleFound
		}
		schedule = schedule.DeepCopy()

		scalingGroup.Go(func() error {
			active, err := c.scheduleActive(schedule.Spec)
			if err != nil {
				log.Errorf("Failed to check for active schedules in ScalingSchedule %s/%s: %v", schedule.Namespace, schedule.Name, err)
				return nil
			}

			if active != schedule.Status.Active {
				schedule.Status.Active = active
				_, err := c.client.ScalingSchedules(schedule.Namespace).UpdateStatus(ctx, schedule, metav1.UpdateOptions{})
				if err != nil {
					log.Errorf("Failed to update status for ScalingSchedule %s/%s: %v", schedule.Namespace, schedule.Name, err)
					return nil
				}

				status := "inactive"
				if active {
					status = "active"
				}

				log.Infof("Marked Scaling Schedule %s/%s as %s", schedule.Namespace, schedule.Name, status)
			}
			return nil
		})
	}

	err := scalingGroup.Wait()
	if err != nil {
		return fmt.Errorf("failed waiting for cluster scaling schedules: %w", err)
	}

	// ClusterScalingSchedules
	var clusterScalingGroup errgroup.Group
	clusterScalingGroup.SetLimit(10)

	clusterschedules := c.clusterScalingScheduleStore.List()
	for _, scheduleInterface := range clusterschedules {
		schedule, ok := scheduleInterface.(*v1.ClusterScalingSchedule)
		if !ok {
			return ErrNotScalingScheduleFound
		}
		schedule = schedule.DeepCopy()

		clusterScalingGroup.Go(func() error {
			active, err := c.scheduleActive(schedule.Spec)
			if err != nil {
				log.Errorf("Failed to check for active schedules in ClusterScalingSchedule %s: %v", schedule.Name, err)
				return nil
			}

			if active != schedule.Status.Active {
				schedule.Status.Active = active
				_, err := c.client.ClusterScalingSchedules().UpdateStatus(ctx, schedule, metav1.UpdateOptions{})
				if err != nil {
					log.Errorf("Failed to update status for ClusterScalingSchedule %s: %v", schedule.Name, err)
					return nil
				}

				status := "inactive"
				if active {
					status = "active"
				}

				log.Infof("Marked Cluster Scaling Schedule %s as %s", schedule.Name, status)
			}
			return nil
		})
	}

	err = clusterScalingGroup.Wait()
	if err != nil {
		return fmt.Errorf("failed waiting for cluster scaling schedules: %w", err)
	}

	return nil
}

func (c *Controller) scheduleActive(spec v1.ScalingScheduleSpec) (bool, error) {
	scalingWindowDuration := c.defaultScalingWindow
	if spec.ScalingWindowDurationMinutes != nil {
		scalingWindowDuration = time.Duration(*spec.ScalingWindowDurationMinutes) * time.Minute
	}
	if scalingWindowDuration < 0 {
		return false, fmt.Errorf("scaling window duration cannot be negative: %d", scalingWindowDuration)
	}

	for _, schedule := range spec.Schedules {
		startTime, endTime, err := ScheduleStartEnd(c.now(), schedule, c.defaultTimeZone)
		if err != nil {
			return false, err
		}

		scalingStart := startTime.Add(-scalingWindowDuration)
		scalingEnd := endTime.Add(scalingWindowDuration)

		if Between(c.now(), scalingStart, scalingEnd) {
			return true, nil
		}
	}

	return false, nil
}

func ScheduleStartEnd(now time.Time, schedule v1.Schedule, defaultTimeZone string) (time.Time, time.Time, error) {
	var startTime, endTime time.Time
	switch schedule.Type {
	case v1.RepeatingSchedule:
		location, err := time.LoadLocation(schedule.Period.Timezone)
		if schedule.Period.Timezone == "" || err != nil {
			location, err = time.LoadLocation(defaultTimeZone)
			if err != nil {
				return time.Time{}, time.Time{}, fmt.Errorf("unexpected error loading default location: %s", err.Error())
			}
		}
		nowInLocation := now.In(location)
		weekday := nowInLocation.Weekday()
		for _, day := range schedule.Period.Days {
			if days[day] == weekday {
				parsedStartTime, err := time.Parse(hourColonMinuteLayout, schedule.Period.StartTime)
				if err != nil {
					return time.Time{}, time.Time{}, ErrInvalidScheduleStartTime
				}
				startTime = time.Date(
					// v1.SchedulePeriod.StartTime can't define the
					// year, month or day, so we compute it as the
					// current date in the configured location.
					nowInLocation.Year(),
					nowInLocation.Month(),
					nowInLocation.Day(),
					// Hours and minute are configured in the
					// v1.SchedulePeriod.StartTime.
					parsedStartTime.Hour(),
					parsedStartTime.Minute(),
					parsedStartTime.Second(),
					parsedStartTime.Nanosecond(),
					location,
				)

				// If no end time was provided, set it to equal the start time
				if schedule.Period.EndTime == "" {
					endTime = startTime
				} else {
					parsedEndTime, err := time.Parse(hourColonMinuteLayout, schedule.Period.EndTime)
					if err != nil {
						return time.Time{}, time.Time{}, ErrInvalidScheduleDate
					}
					endTime = time.Date(
						// v1.SchedulePeriod.StartTime can't define the
						// year, month or day, so we compute it as the
						// current date in the configured location.
						nowInLocation.Year(),
						nowInLocation.Month(),
						nowInLocation.Day(),
						// Hours and minute are configured in the
						// v1.SchedulePeriod.StartTime.
						parsedEndTime.Hour(),
						parsedEndTime.Minute(),
						parsedEndTime.Second(),
						parsedEndTime.Nanosecond(),
						location,
					)

				}
			}
		}
	case v1.OneTimeSchedule:
		var err error
		startTime, err = time.Parse(time.RFC3339, string(*schedule.Date))
		if err != nil {
			return time.Time{}, time.Time{}, ErrInvalidScheduleDate
		}

		// If no end time was provided, set it to equal the start time
		if schedule.EndDate == nil || string(*schedule.EndDate) == "" {
			endTime = startTime
		} else {
			endTime, err = time.Parse(time.RFC3339, string(*schedule.EndDate))
			if err != nil {
				return time.Time{}, time.Time{}, ErrInvalidScheduleDate
			}
		}
	}

	// Use either the defined end time/date or the start time/date + the
	// duration, whichever is longer.
	if startTime.Add(schedule.Duration()).After(endTime) {
		endTime = startTime.Add(schedule.Duration())
	}

	return startTime, endTime, nil
}

func Between(timestamp, start, end time.Time) bool {
	if timestamp.Before(start) {
		return false
	}
	return timestamp.Before(end)
}