manager.go

package jobqueue

import (
	"fmt"
	"github.com/robfig/cron/v3"
	"gorm.io/gorm"
	"sync"
	"time"
)

type ManagerState int

const (
	ManagerStateStopped = iota
	ManagerStateRunning
)

type Manager struct {
	state ManagerState

	queue     *Queue
	workerMap map[WorkerID]Worker
	eventBus  *EventBus

	activeJobs map[JobID]GenericJob

	jobEventCh chan interface{}

	cronInstance *cron.Cron
	logger       Logger

	database *gorm.DB
	dbSaver  *DBSaver

	mu sync.Mutex
}

// NewManager initializes a new Manager
func NewManager() *Manager {

	eventBus := NewEventBus()

	mng := &Manager{
		state:      ManagerStateStopped,
		queue:      NewQueue(eventBus),
		workerMap:  make(map[WorkerID]Worker),
		eventBus:   eventBus,
		activeJobs: make(map[JobID]GenericJob),
	}

	return mng

}

func (m *Manager) GetEventBus() *EventBus {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.eventBus
}

func (m *Manager) SetCronInstance(cronInstance *cron.Cron) *Manager {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.cronInstance = cronInstance
	return m
}

func (m *Manager) GetCronInstance() *cron.Cron {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.cronInstance
}

func (m *Manager) NewCronScheduler(spec string) *CronScheduler {
	return &CronScheduler{
		Spec: spec,
		cron: m.GetCronInstance(),
	}
}

func (m *Manager) NewInstantScheduler() *InstantScheduler {
	return &InstantScheduler{}
}

func (m *Manager) NewIntervalScheduler(interval time.Duration) *IntervalScheduler {
	return &IntervalScheduler{
		Interval: interval,
	}
}

func (m *Manager) NewDelayScheduler(delay time.Duration) *DelayScheduler {
	return &DelayScheduler{
		Delay: delay,
	}
}

func (m *Manager) NewEventScheduler(event EventName) *EventScheduler {
	return &EventScheduler{
		Event: event,
	}
}

func (m *Manager) SetDB(db *gorm.DB) *Manager {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.database = db

	if m.dbSaver != nil {
		return m
	}

	m.dbSaver = NewDBSaver()
	m.dbSaver.SetManager(m)

	return m
}

// GetDB returns the database connection
func (m *Manager) GetDB() *gorm.DB {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.database
}

// GetQueue returns the queue
func (m *Manager) checkAndSetRunningState() error {

	m.state = ManagerStateStopped

	if m.workerMap == nil {
		return ErrNoWorkers
	}

	if len(m.workerMap) == 0 {
		return ErrNoWorkers
	}

	for _, worker := range m.workerMap {
		if worker.Status() == WorkerStatusRunning {
			m.state = ManagerStateRunning
			return nil
		}
	}

	return nil
}

// AddWorker adds a worker to the manager
func (m *Manager) AddWorker(worker Worker) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	// check if worker is already added
	if _, ok := m.workerMap[worker.GetID()]; ok {
		return ErrWorkerAlreadyAdded
	}

	// check if state of worker is not running
	if worker.Status() != WorkerStatusStopped {
		return ErrWorkerAlreadyRunning
	}

	if m.state == ManagerStateRunning {
		err := worker.Start()
		if err != nil {
			return err
		}
	}

	// add worker to workerMap
	m.workerMap[worker.GetID()] = worker
	worker.SetManager(m)

	return m.checkAndSetRunningState()
}

// RemoveWorker removes a worker from the manager
func (m *Manager) RemoveWorker(worker Worker) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	// check if worker is added
	if _, ok := m.workerMap[worker.GetID()]; !ok {
		return ErrWorkerNotAdded
	}

	// check if state of worker is not running
	if worker.Status() != WorkerStatusStopped {
		err := worker.Stop()
		if err != nil {
			return err
		}
	}

	// remove worker from workerMap
	delete(m.workerMap, worker.GetID())
	err := m.checkAndSetRunningState()

	if err != nil && err != ErrNoWorkers {
		return err
	}

	return nil

}

// Start starts the manager
func (m *Manager) Start() error {
	var err error

	m.mu.Lock()
	defer m.mu.Unlock()

	if m.state == ManagerStateRunning {
		return ErrManagerAlreadyRunning
	}

	if m.dbSaver != nil {
		err = m.dbSaver.Start()
		if err != nil {
			if m.logger != nil {
				m.logger.Error("Error while starting db saver", "error", err)
			}
		}
	}

	if len(m.workerMap) == 0 {
		return ErrNoWorkers
	}

	var wrappedErr error

	for _, worker := range m.workerMap {
		err := worker.Start()
		if err != nil && err != ErrWorkerAlreadyRunning {
			if wrappedErr == nil {
				wrappedErr = fmt.Errorf("Error: ")
			}

			wrappedErr = fmt.Errorf("%w\n%s", wrappedErr, err.Error())
		}
	}

	// check if we have one worker
	for _, worker := range m.workerMap {
		if worker.Status() == WorkerStatusRunning {
			m.state = ManagerStateRunning
			break
		}
	}

	m.jobEventCh = make(chan interface{}, 100)

	m.eventBus.Subscribe(QueueJob, m.jobEventCh)
	m.eventBus.Subscribe(JobReady, m.jobEventCh)

	go m.handleJobEvents()

	err = m.checkAndSetRunningState()

	if err != nil {
		wrappedErr = fmt.Errorf("%w\n%s", wrappedErr, err.Error())
	}

	if m.cronInstance != nil {
		m.cronInstance.Start()
	}

	return wrappedErr

}

// Stop stops the manager
func (m *Manager) Stop() error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if m.state == ManagerStateStopped {
		return ErrManagerAlreadyStopped
	}

	m.eventBus.Unsubscribe(QueueJob, m.jobEventCh)
	m.eventBus.Unsubscribe(JobReady, m.jobEventCh)

	close(m.jobEventCh)

	var wrappedErr error

	for _, worker := range m.workerMap {
		err := worker.Stop()
		if err != nil && err != ErrWorkerAlreadyStopped {
			if wrappedErr == nil {
				wrappedErr = fmt.Errorf("Error: ")
			}

			wrappedErr = fmt.Errorf("%w\n%s", wrappedErr, err.Error())
		}
	}

	err := m.checkAndSetRunningState()

	if err != nil {
		wrappedErr = fmt.Errorf("%w\n%s", wrappedErr, err.Error())
	}

	if m.cronInstance != nil {
		m.cronInstance.Stop()
	}

	if m.dbSaver != nil {
		m.dbSaver.Stop()
	}

	return wrappedErr
}

func (m *Manager) SetLogger(logger Logger) *Manager {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.logger = logger
	return m
}

func (m *Manager) GetLogger() Logger {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.logger
}

// handleJobEvents handles job events
func (m *Manager) handleJobEvents() {

	for event := range m.jobEventCh {
		switch event := event.(type) {
		case Event:

			if m.logger != nil {
				m.logger.Info("Event received", "event", event.Name, "data", event.Data, "message_id", event.MessageID)
			}

			switch event.Name {
			case QueueJob:

				if m.logger != nil {
					m.logger.Info("Job queued", "job_id", event.Data.(GenericJob).GetID())
				}

				job := event.Data.(GenericJob)
				err := m.queue.Enqueue(job)
				if err != nil && err != ErrJobAlreadyExists {
					if m.logger != nil {
						m.logger.Error("Error while queueing job", "error", err)
					}
				}

			case JobReady:
				for {

					nextJob, err := m.queue.Dequeue()
					if err != nil {
						break
					}

					if m.logger != nil {
						m.logger.Info("Job ready", "job_id", nextJob.GetID())
					}

					assigned := false
					maxTries := 10

					for maxTries > 0 {
						maxTries--

						for _, worker := range m.workerMap {
							if err := worker.AssignJob(nextJob); err == nil {
								assigned = true
								break
							}
						}

						if assigned == true {
							break
						}

						time.Sleep(1 * time.Second)
					}

					if !assigned {
						if m.logger != nil {
							m.logger.Info("No worker available for job", "job_id", nextJob.GetID())
						}
					} else {

						if nextJob.GetScheduler() != nil {
							if nextJob.GetScheduler().IsAdHoc() {
								eventBus := m.GetEventBus()
								eventBus.Publish(JobFinished, nextJob)
							}

						}

					}
				}

			case JobFinished:
				// job is finished and should be archived

				job := event.Data.(GenericJob)
				_ = job

				err := m.CancelJobSchedule(job.GetID())
				if err != nil {
					if m.logger != nil {
						m.logger.Error("Error while canceling job schedule", "error", err)
					}
				}
			}
		}
	}
}

// ScheduleJob schedules a job
func (m *Manager) ScheduleJob(job GenericJob, scheduler Scheduler) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if scheduler == nil {
		return ErrSchedulerNotSet
	}

	if m.state != ManagerStateRunning {
		return ErrManagerNotRunning
	}

	if job.GetScheduler() != nil {
		return ErrJobAlreadyScheduled
	}

	if _, ok := m.activeJobs[job.GetID()]; ok {
		return ErrJobAlreadyActive
	}

	job.SetScheduler(scheduler)
	err := scheduler.Schedule(job, m.eventBus)
	if err != nil {
		return err
	}

	m.activeJobs[job.GetID()] = job
	return nil

}

func (m *Manager) CancelJobSchedule(id JobID) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if m.state != ManagerStateRunning {
		return ErrManagerNotRunning
	}

	job, ok := m.activeJobs[id]
	if !ok {
		return ErrJobNotActive
	}

	if job.GetScheduler() == nil {
		return ErrJobNotScheduled
	}

	scheduler := job.GetScheduler()

	err := scheduler.Cancel(job.GetID())
	if err != nil {
		return err
	}

	job.SetScheduler(nil)
	delete(m.activeJobs, job.GetID())

	return nil
}