package scheduler

import (
	"github.com/vmware/harbor/src/common/scheduler/policy"
	"github.com/vmware/harbor/src/common/utils/log"

	"errors"
	"fmt"
	"reflect"
	"strings"
	"sync"
	"time"
)

const (
	defaultQueueSize = 10

	statSchedulePolicy   = "Schedule Policy"
	statUnSchedulePolicy = "Unschedule Policy"
	statTaskRun          = "Task Run"
	statTaskComplete     = "Task Complete"
	statTaskFail         = "Task Fail"
)

//StatItem is defined for the stat metrics.
type StatItem struct {
	//Metrics catalog
	Type string

	//The stat value
	Value uint32

	//Attach some other info
	Attachment interface{}
}

//StatSummary is used to collect some metrics of scheduler.
type StatSummary struct {
	//Count of scheduled policy
	PolicyCount uint32

	//Total count of tasks
	Tasks uint32

	//Count of successfully complete tasks
	CompletedTasks uint32

	//Count of tasks with errors
	TasksWithError uint32
}

//Configuration defines configuration of Scheduler.
type Configuration struct {
	QueueSize uint8
}

//Scheduler is designed for scheduling policies.
type Scheduler struct {
	//Mutex for sync controling.
	*sync.RWMutex

	//Related configuration options for scheduler.
	config *Configuration

	//Store to keep the references of scheduled policies.
	policies Store

	//Queue for receiving policy scheduling request
	scheduleQueue chan *Watcher

	//Queue for receiving policy unscheduling request or complete signal.
	unscheduleQueue chan *Watcher

	//Channel for receiving stat metrics.
	statChan chan *StatItem

	//Channel for terminate scheduler damon.
	terminateChan chan bool

	//The stat metrics of scheduler.
	stats *StatSummary

	//To indicate whether scheduler is running or not
	isRunning bool
}

//DefaultScheduler is a default scheduler.
var DefaultScheduler = NewScheduler(nil)

//NewScheduler is constructor for creating a scheduler.
func NewScheduler(config *Configuration) *Scheduler {
	var qSize uint8 = defaultQueueSize
	if config != nil && config.QueueSize > 0 {
		qSize = config.QueueSize
	}

	sq := make(chan *Watcher, qSize)
	usq := make(chan *Watcher, qSize)
	stChan := make(chan *StatItem, 4)
	tc := make(chan bool, 1)

	store := NewDefaultStore()
	return &Scheduler{
		RWMutex:         new(sync.RWMutex),
		config:          config,
		policies:        store,
		scheduleQueue:   sq,
		unscheduleQueue: usq,
		statChan:        stChan,
		terminateChan:   tc,
		stats: &StatSummary{
			PolicyCount:    0,
			Tasks:          0,
			CompletedTasks: 0,
			TasksWithError: 0,
		},
		isRunning: false,
	}
}

//Start the scheduler damon.
func (sch *Scheduler) Start() {
	sch.Lock()
	defer sch.Unlock()

	//If scheduler is already running
	if sch.isRunning {
		return
	}

	go func() {
		defer func() {
			if r := recover(); r != nil {
				log.Errorf("Runtime error in scheduler:%s\n", r)
			}
		}()
		defer func() {
			//Clear resources
			sch.policies.Clear()
			log.Infof("Policy scheduler stop at %s\n", time.Now().UTC().Format(time.RFC3339))
		}()
		for {
			select {
			case <-sch.terminateChan:
				//Exit
				return
			case wt := <-sch.scheduleQueue:
				//If status is stopped, no requests should be served
				if !sch.IsRunning() {
					continue
				}
				go func(watcher *Watcher) {
					if watcher != nil && watcher.p != nil {
						//Enable it.
						watcher.Start()

						//Update stats and log info.
						log.Infof("Policy %s is scheduled", watcher.p.Name())
						sch.statChan <- &StatItem{statSchedulePolicy, 1, nil}
					}
				}(wt)
			case wt := <-sch.unscheduleQueue:
				//If status is stopped, no requests should be served
				if !sch.IsRunning() {
					continue
				}
				go func(watcher *Watcher) {
					if watcher != nil && watcher.IsRunning() {
						watcher.Stop()

						//Update stats and log info.
						log.Infof("Policy %s is unscheduled", watcher.p.Name())
						sch.statChan <- &StatItem{statUnSchedulePolicy, 1, nil}
					}
				}(wt)
			case stat := <-sch.statChan:
				{
					//If status is stopped, no requests should be served
					if !sch.IsRunning() {
						continue
					}
					switch stat.Type {
					case statSchedulePolicy:
						sch.stats.PolicyCount += stat.Value
						break
					case statUnSchedulePolicy:
						sch.stats.PolicyCount -= stat.Value
						break
					case statTaskRun:
						sch.stats.Tasks += stat.Value
						break
					case statTaskComplete:
						sch.stats.CompletedTasks += stat.Value
						break
					case statTaskFail:
						sch.stats.TasksWithError += stat.Value
						break
					default:
						break
					}
					log.Infof("Policies:%d, Tasks:%d, CompletedTasks:%d, FailedTasks:%d\n",
						sch.stats.PolicyCount,
						sch.stats.Tasks,
						sch.stats.CompletedTasks,
						sch.stats.TasksWithError)

					if stat.Attachment != nil &&
						reflect.TypeOf(stat.Attachment).String() == "*errors.errorString" {
						log.Errorf("%s: %s\n", stat.Type, stat.Attachment.(error).Error())
					}
				}

			}
		}
	}()

	sch.isRunning = true
	log.Infof("Policy scheduler start at %s\n", time.Now().UTC().Format(time.RFC3339))
}

//Stop the scheduler damon.
func (sch *Scheduler) Stop() {
	//Lock for state changing
	sch.Lock()

	//Check if the scheduler is running
	if !sch.isRunning {
		sch.Unlock()
		return
	}

	sch.isRunning = false
	sch.Unlock()

	//Terminate damon to stop receiving signals.
	sch.terminateChan <- true
}

//Schedule and enable the policy.
func (sch *Scheduler) Schedule(scheduledPolicy policy.Policy) error {
	if scheduledPolicy == nil {
		return errors.New("nil is not Policy object")
	}

	if strings.TrimSpace(scheduledPolicy.Name()) == "" {
		return errors.New("Policy should be assigned a name")
	}

	tasks := scheduledPolicy.Tasks()
	if tasks == nil || len(tasks) == 0 {
		return errors.New("Policy must attach task(s)")
	}

	//Try to schedule the policy.
	//Keep the policy for future use after it's successfully scheduled.
	watcher := NewWatcher(scheduledPolicy, sch.statChan, sch.unscheduleQueue)
	if err := sch.policies.Put(scheduledPolicy.Name(), watcher); err != nil {
		return err
	}

	//Schedule the policy
	sch.scheduleQueue <- watcher

	return nil
}

//UnSchedule the specified policy from the enabled policies list.
func (sch *Scheduler) UnSchedule(policyName string) error {
	if strings.TrimSpace(policyName) == "" {
		return errors.New("Empty policy name is invalid")
	}

	//Find the watcher.
	watcher := sch.policies.Remove(policyName)
	if watcher == nil {
		return fmt.Errorf("Policy %s is not existing", policyName)
	}

	//Unschedule the policy.
	sch.unscheduleQueue <- watcher

	return nil
}

//IsRunning to indicate whether the scheduler is running.
func (sch *Scheduler) IsRunning() bool {
	sch.RLock()
	defer sch.RUnlock()

	return sch.isRunning
}

//HasScheduled is to check whether the given policy has been scheduled or not.
func (sch *Scheduler) HasScheduled(policyName string) bool {
	return sch.policies.Exists(policyName)
}

//GetPolicy is used to get related policy reference by its name.
func (sch *Scheduler) GetPolicy(policyName string) policy.Policy {
	wk := sch.policies.Get(policyName)
	if wk != nil {
		return wk.p
	}

	return nil
}

//PolicyCount returns the count of currently scheduled policies in the scheduler.
func (sch *Scheduler) PolicyCount() uint32 {
	return sch.policies.Size()
}