package scheduler

import (
	"fmt"
	"local/firestormy/config"
	"local/firestormy/logger"
	"time"

	cron "github.com/robfig/cron/v3"
)

type Scheduler struct {
	cron    *cron.Cron
	running map[string]cron.EntryID
}

func New() *Scheduler {
	l := logger.New()
	c := cron.New(
		cron.WithLocation(time.Local),
		cron.WithLogger(l),
		cron.WithChain(
			cron.SkipIfStillRunning(l),
			cron.Recover(l),
		),
	)
	return &Scheduler{
		cron:    c,
		running: make(map[string]cron.EntryID),
	}
}

func (s *Scheduler) Start() error {
	jobs, err := s.List()
	if err != nil {
		return err
	}
	for i := range jobs {
		if err := s.Add(jobs[i]); err != nil && err != ErrDuplicateJob {
			return err
		}
	}
	s.cron.Start()
	return nil
}

func (s *Scheduler) Stop() error {
	ctx := s.cron.Stop()
	<-ctx.Done()
	return nil
}

func (s *Scheduler) List() ([]*Job, error) {
	entries, err := config.Store.List(nil)
	if err != nil {
		return nil, err
	}
	errors := []error{}
	jobs := []*Job{}
	for _, k := range entries {
		j, err := s.loadJobFromStore(k)
		if err != nil {
			errors = append(errors, err)
		} else {
			jobs = append(jobs, j)
		}
	}
	err = nil
	if len(errors) > 0 {
		err = fmt.Errorf("errors listing jobs: %v", errors)
	}
	return jobs, err
}

func (s *Scheduler) loadJobFromStore(k string) (*Job, error) {
	b, err := config.Store.Get(k)
	if err != nil {
		return nil, err
	}
	j := &Job{}
	err = j.Decode(b)
	return j, err
}

func (s *Scheduler) Add(j *Job) error {
	if _, ok := s.getEntry(j); ok {
		return ErrDuplicateJob
	}
	b, err := j.Encode()
	if err != nil {
		return err
	}
	if err := config.Store.Set(j.Name, b); err != nil {
		return err
	}
	entryID, err := s.cron.AddJob(j.Schedule, j)
	if err != nil {
		return err
	}
	s.running[j.Name] = entryID
	return nil
}

func (s *Scheduler) Remove(j *Job) error {
	entryID, ok := s.getEntry(j)
	if !ok {
		return ErrJobNotFound
	}
	was := len(s.cron.Entries())
	s.cron.Remove(entryID)
	is := len(s.cron.Entries())
	if was == is {
		return ErrJobNotFound
	}
	return config.Store.Set(j.Name, nil)
}

func (s *Scheduler) getEntry(j *Job) (cron.EntryID, bool) {
	entryID, ok := s.running[j.Name]
	return entryID, ok
}