package gocron

import (
	"sort"
	"time"
)

// Scheduler struct, the only data member is the list of jobs.
// - implements the sort.Interface{} for sorting jobs, by the time nextRun
type Scheduler struct {
	jobs [MAXJOBNUM]*Job // Array store jobs
	size int             // Size of jobs which jobs holding.
	loc  *time.Location  // Location to use when scheduling jobs with specified times
}

var (
	defaultScheduler = NewScheduler()
)

// NewScheduler creates a new scheduler
func NewScheduler() *Scheduler {
	return &Scheduler{
		jobs: [MAXJOBNUM]*Job{},
		size: 0,
		loc:  loc,
	}
}

// Jobs returns the list of Jobs from the Scheduler
func (s *Scheduler) Jobs() []*Job {
	return s.jobs[:s.size]
}

func (s *Scheduler) Len() int {
	return s.size
}

func (s *Scheduler) Swap(i, j int) {
	s.jobs[i], s.jobs[j] = s.jobs[j], s.jobs[i]
}

func (s *Scheduler) Less(i, j int) bool {
	return s.jobs[j].nextRun.Unix() >= s.jobs[i].nextRun.Unix()
}

// ChangeLoc changes the default time location
func (s *Scheduler) ChangeLoc(newLocation *time.Location) {
	s.loc = newLocation
}

// Get the current runnable jobs, which shouldRun is True
func (s *Scheduler) getRunnableJobs() (runningJobs [MAXJOBNUM]*Job, n int) {
	runnableJobs := [MAXJOBNUM]*Job{}
	n = 0
	sort.Sort(s)
	for i := 0; i < s.size; i++ {
		if s.jobs[i].shouldRun() {
			runnableJobs[n] = s.jobs[i]
			n++
		} else {
			break
		}
	}
	return runnableJobs, n
}

// NextRun datetime when the next job should run.
func (s *Scheduler) NextRun() (*Job, time.Time) {
	if s.size <= 0 {
		return nil, time.Now()
	}
	sort.Sort(s)
	return s.jobs[0], s.jobs[0].nextRun
}

// Every schedule a new periodic job with interval
func (s *Scheduler) Every(interval uint64) *Job {
	job := NewJob(interval).Loc(s.loc)
	s.jobs[s.size] = job
	s.size++
	return job
}

// RunPending runs all the jobs that are scheduled to run.
func (s *Scheduler) RunPending() {
	runnableJobs, n := s.getRunnableJobs()

	if n != 0 {
		for i := 0; i < n; i++ {
			go runnableJobs[i].run()
			runnableJobs[i].lastRun = time.Now()
			runnableJobs[i].scheduleNextRun()
		}
	}
}

// RunAll run all jobs regardless if they are scheduled to run or not
func (s *Scheduler) RunAll() {
	s.RunAllwithDelay(0)
}

// RunAllwithDelay runs all jobs with delay seconds
func (s *Scheduler) RunAllwithDelay(d int) {
	for i := 0; i < s.size; i++ {
		go s.jobs[i].run()
		if 0 != d {
			time.Sleep(time.Duration(d))
		}
	}
}

// Remove specific job j by function
func (s *Scheduler) Remove(j interface{}) {
	s.removeByCondition(func(someJob *Job) bool {
		return someJob.jobFunc == getFunctionName(j)
	})
}

// RemoveByRef removes specific job j by reference
func (s *Scheduler) RemoveByRef(j *Job) {
	s.removeByCondition(func(someJob *Job) bool {
		return someJob == j
	})
}

func (s *Scheduler) removeByCondition(shouldRemove func(*Job) bool) {
	i := 0

	// keep deleting until no more jobs match the criteria
	for {
		found := false

		for ; i < s.size; i++ {
			if shouldRemove(s.jobs[i]) {
				found = true
				break
			}
		}

		if !found {
			return
		}

		for j := (i + 1); j < s.size; j++ {
			s.jobs[i] = s.jobs[j]
			i++
		}
		s.size--
		s.jobs[s.size] = nil
	}
}

// Scheduled checks if specific job j was already added
func (s *Scheduler) Scheduled(j interface{}) bool {
	for _, job := range s.jobs {
		if job.jobFunc == getFunctionName(j) {
			return true
		}
	}
	return false
}

// Clear delete all scheduled jobs
func (s *Scheduler) Clear() {
	for i := 0; i < s.size; i++ {
		s.jobs[i] = nil
	}
	s.size = 0
}

// Start all the pending jobs
// Add seconds ticker
func (s *Scheduler) Start() chan bool {
	stopped := make(chan bool, 1)
	ticker := time.NewTicker(1 * time.Second)

	go func() {
		for {
			select {
			case <-ticker.C:
				s.RunPending()
			case <-stopped:
				ticker.Stop()
				return
			}
		}
	}()

	return stopped
}

// The following methods are shortcuts for not having to
// create a Scheduler instance

// Every schedules a new periodic job running in specific interval
func Every(interval uint64) *Job {
	return defaultScheduler.Every(interval)
}

// RunPending run all jobs that are scheduled to run
//
// Please note that it is *intended behavior that run_pending()
// does not run missed jobs*. For example, if you've registered a job
// that should run every minute and you only call run_pending()
// in one hour increments then your job won't be run 60 times in
// between but only once.
func RunPending() {
	defaultScheduler.RunPending()
}

// RunAll run all jobs regardless if they are scheduled to run or not.
func RunAll() {
	defaultScheduler.RunAll()
}

// RunAllwithDelay run all the jobs with a delay in seconds
//
// A delay of `delay` seconds is added between each job. This can help
// to distribute the system load generated by the jobs more evenly over
// time.
func RunAllwithDelay(d int) {
	defaultScheduler.RunAllwithDelay(d)
}

// Start run all jobs that are scheduled to run
func Start() chan bool {
	return defaultScheduler.Start()
}

// Clear all scheduled jobs
func Clear() {
	defaultScheduler.Clear()
}

// Remove a specific job
func Remove(j interface{}) {
	defaultScheduler.Remove(j)
}

// Scheduled checks if specific job j was already added
func Scheduled(j interface{}) bool {
	for _, job := range defaultScheduler.jobs {
		if job.jobFunc == getFunctionName(j) {
			return true
		}
	}
	return false
}

// NextRun gets the next running time
func NextRun() (job *Job, time time.Time) {
	return defaultScheduler.NextRun()
}