ersteller/queue/general_queue.go

package queue

import (
	"context"
	"fmt"
	"log"
	"sync"
	"time"

	. "git.gorlug.de/code/ersteller"
	"git.gorlug.de/code/ersteller/schema/ent"
	"git.gorlug.de/code/ersteller/schema/ent/generalqueue"
	"git.gorlug.de/code/ersteller/schema/ent/generalqueuestate"
)

type GeneralQueueStatus string

const (
	GeneralQueueStatusPending    GeneralQueueStatus = "pending"
	GeneralQueueStatusInProgress GeneralQueueStatus = "in_progress"
	GeneralQueueStatusCompleted  GeneralQueueStatus = "completed"
	GeneralQueueStatusFailed     GeneralQueueStatus = "failed"
)

type GeneralQueueJob struct {
	ID             int
	CreatedAt      time.Time
	NumberOfTries  int
	Payload        map[string]interface{}
	Status         GeneralQueueStatus
	FailurePayload map[string]interface{}
	ResultPayload  map[string]interface{}
}

type GeneralQueueHandlerResult struct {
	ResultPayload  map[string]interface{}
	FailurePayload map[string]interface{}
}

type GeneralQueueHandler func(ctx context.Context, job GeneralQueueJob) (GeneralQueueHandlerResult, error)

type GeneralQueue struct {
	Name         string
	client       *ent.Client
	running      bool
	handler      GeneralQueueHandler
	workerCount  int
	pollInterval time.Duration
	cancel       context.CancelFunc
	startCtx     context.Context
	wg           sync.WaitGroup
}

// NewGeneralQueue creates a new general queue instance
func NewGeneralQueue(name string, client *ent.Client, handler GeneralQueueHandler, processors int) *GeneralQueue {
	if processors <= 0 {
		processors = 1
	}
	return &GeneralQueue{
		Name:         name,
		client:       client,
		running:      false,
		handler:      handler,
		workerCount:  processors,
		pollInterval: 5 * time.Second,
	}
}

// SetRunning persists the running state of the queue to the database
func (q *GeneralQueue) SetRunning(ctx context.Context, running bool) error {
	now := time.Now()

	// Try to find existing state
	existing, err := q.client.GeneralQueueState.Query().
		Where(generalqueuestate.NameEQ(q.Name)).
		First(ctx)

	if err != nil && !ent.IsNotFound(err) {
		return fmt.Errorf("failed to query queue state: %w", err)
	}

	if existing != nil {
		// Update existing
		err = q.client.GeneralQueueState.UpdateOne(existing).
			SetRunning(running).
			SetUpdatedAt(now).
			Exec(ctx)
		if err != nil {
			return fmt.Errorf("failed to update queue running state: %w", err)
		}
	} else {
		// Create new
		_, err = q.client.GeneralQueueState.Create().
			SetName(q.Name).
			SetRunning(running).
			SetUpdatedAt(now).
			Save(ctx)
		if err != nil {
			return fmt.Errorf("failed to create queue running state: %w", err)
		}
	}

	return nil
}

// IsRunning returns the persisted running state of the queue from the database
func (q *GeneralQueue) IsRunning(ctx context.Context) (bool, error) {
	state, err := q.client.GeneralQueueState.Query().
		Where(generalqueuestate.NameEQ(q.Name)).
		First(ctx)

	if err != nil {
		if ent.IsNotFound(err) {
			return false, nil // No state record means not running
		}
		return false, fmt.Errorf("failed to get queue running state: %w", err)
	}

	return state.Running, nil
}

// Start begins processing jobs from the queue in a background goroutine
func (q *GeneralQueue) Start(ctx context.Context) error {
	if q.running {
		return nil
	}
	q.running = true
	if err := q.SetRunning(ctx, true); err != nil {
		Error("Failed to persist queue running state (start):", err)
		return err
	}
	// create a cancellable context used by workers
	q.startCtx, q.cancel = context.WithCancel(ctx)
	// start workers
	workers := q.workerCount
	if workers <= 0 {
		workers = 1
	}
	for i := 0; i < workers; i++ {
		q.wg.Add(1)
		go q.workerLoop(q.startCtx, q.handler)
	}
	// Auto-stop persistence: when all workers finish (e.g., no more jobs),
	// mark queue as not running in DB and in memory, mirroring previous behavior.
	go func(name string) {
		q.wg.Wait()
		q.running = false
		if err := q.SetRunning(context.Background(), false); err != nil {
			LogError("Failed to persist queue running state (auto-stop):", err)
		}
		LogDebug("Queue '%s' completed. Auto-stopping.", name)
	}(q.Name)
	LogDebug("Queue '%s' started with %d processors", q.Name, workers)
	return nil
}

// Stop stops the queue from processing new jobs
func (q *GeneralQueue) Stop(ctx context.Context) error {
	if !q.running {
		return nil
	}
	if q.cancel != nil {
		q.cancel()
	}
	q.wg.Wait()
	q.running = false
	if err := q.SetRunning(ctx, false); err != nil {
		Error("Failed to persist queue running state (stop):", err)
		return err
	}
	LogDebug("Queue '%s' stopped", q.Name)
	return nil
}

// loop processes jobs continuously until stopped
func (q *GeneralQueue) workerLoop(ctx context.Context, handler GeneralQueueHandler) {
	defer q.wg.Done()
	ticker := time.NewTicker(q.pollInterval)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			// Process at most one job per tick per worker
			processed, err := q.processNext(ctx, handler)
			if err != nil {
				LogError("Queue '%s' processing error:", q.Name, err)
			}
			// If no job was processed, initiate auto-stop (match previous behavior)
			if err == nil && !processed {
				if q.cancel != nil {
					q.cancel()
				}
				return
			}
		}
	}
}

// processNext processes the next pending job and returns true if a job was processed
func (q *GeneralQueue) processNext(ctx context.Context, handler GeneralQueueHandler) (bool, error) {
	job, err := q.claimNextPendingJob(ctx)
	if err != nil {
		return false, err
	}
	if job == nil {
		return false, nil // No pending jobs
	}

	// Create job struct for handler
	queueJob := GeneralQueueJob{
		ID:             job.ID,
		CreatedAt:      job.CreatedAt,
		NumberOfTries:  job.NumberOfTries,
		Payload:        job.Payload,
		Status:         GeneralQueueStatus(job.Status),
		FailurePayload: job.FailurePayload,
	}

	// Create a context with 15-minute timeout for job processing
	jobCtx, cancel := context.WithTimeout(ctx, 15*time.Minute)
	defer cancel()

	// Process the job with timeout
	type handlerResult struct {
		err           error
		resultPayload any
		errPayload    any
	}
	resultChan := make(chan handlerResult, 1)

	go func() {
		//handlerErr, handlerResultPayload, handlerErrPayload := handler(jobCtx, queueJob)
		result, err := handler(jobCtx, queueJob)
		resultChan <- handlerResult{err: err, resultPayload: result.ResultPayload, errPayload: result.FailurePayload}
	}()

	var handlerErr error
	var resultPayload any
	var errPayload any

	select {
	case result := <-resultChan:
		handlerErr = result.err
		resultPayload = result.resultPayload
		errPayload = result.errPayload
	case <-jobCtx.Done():
		// Timeout occurred
		handlerErr = fmt.Errorf("job processing timeout after 15 minutes")
		resultPayload = nil
		errPayload = nil
	}

	// Process the job
	err = handlerErr
	if err != nil {
		// Increment tries
		if incrementErr := q.IncrementTries(ctx, job.ID, job.NumberOfTries); incrementErr != nil {
			log.Printf("Failed to increment tries for job %d: %v", job.ID, incrementErr)
		}

		// Check if we should retry or fail
		if job.NumberOfTries+1 >= job.MaxRetries {
			errPayloadMap, mapErr := StructToMap(errPayload)
			if mapErr != nil {
				Error("failed to convert error payload to map:", mapErr)
				errPayloadMap = map[string]interface{}{}
			}

			// Max retries reached, mark as failed
			failurePayload := map[string]interface{}{
				"error":        err.Error(),
				"errorPayload": errPayloadMap,
			}
			if updateErr := q.UpdateJobStatus(ctx, job.ID, generalqueue.StatusFailed, err.Error(), failurePayload, nil); updateErr != nil {
				log.Printf("Failed to mark job %d as failed: %v", job.ID, updateErr)
			}
		} else {
			// Retry - mark as pending again
			if updateErr := q.UpdateJobStatus(ctx, job.ID, generalqueue.StatusPending, err.Error(), nil, nil); updateErr != nil {
				log.Printf("Failed to mark job %d as pending for retry: %v", job.ID, updateErr)
			}
		}
		return true, err
	}

	// Job succeeded, mark as completed
	resultPayloadMap, mapErr := StructToMap(resultPayload)
	if mapErr != nil {
		Error("failed to convert result payload to map:", mapErr)
		resultPayloadMap = map[string]interface{}{}
	}

	err = q.UpdateJobStatus(ctx, job.ID, generalqueue.StatusCompleted, "", nil, resultPayloadMap)
	if err != nil {
		log.Printf("Failed to mark job %d as completed: %v", job.ID, err)
	}

	return true, nil
}

// claimNextPendingJob atomically claims the next pending job by setting it to in_progress.
// It avoids races when multiple workers attempt to pick the same job.
func (q *GeneralQueue) claimNextPendingJob(ctx context.Context) (*ent.GeneralQueue, error) {
	// Try a few times in case of races with other workers
	for attempts := 0; attempts < 3; attempts++ {
		job, err := q.GetNextPendingJob(ctx)
		if err != nil {
			return nil, err
		}
		if job == nil {
			return nil, nil
		}

		// Attempt to move to in_progress only if it's still pending
		updated, err := q.client.GeneralQueue.UpdateOneID(job.ID).
			Where(generalqueue.StatusEQ(generalqueue.StatusPending)).
			SetStatus(generalqueue.StatusInProgress).
			SetUpdatedAt(time.Now()).
			Save(ctx)
		if err != nil {
			if ent.IsNotFound(err) {
				// Lost the race; retry
				continue
			}
			return nil, fmt.Errorf("failed to claim pending job: %w", err)
		}
		return updated, nil
	}
	return nil, nil
}

// Enqueue adds a new job to the queue
func (q *GeneralQueue) Enqueue(ctx context.Context, payload any, maxRetries int, userId int) (*ent.GeneralQueue, error) {
	now := time.Now()

	payloadMap, err := StructToMap(payload)
	if err != nil {
		Error("failed to convert payload to map:", err)
		return nil, fmt.Errorf("failed to convert payload to map: %w", err)
	}

	create := q.client.GeneralQueue.Create().
		SetName(q.Name).
		SetPayload(payloadMap).
		SetStatus(generalqueue.StatusPending).
		SetNumberOfTries(0).
		SetMaxRetries(maxRetries).
		SetCreatedAt(now).
		SetUpdatedAt(now).
		SetUserID(userId)

	job, err := create.Save(ctx)

	if err != nil {
		return nil, fmt.Errorf("failed to enqueue job: %w", err)
	}

	return job, nil
}

// GetNextPendingJob retrieves the next pending job from the queue
func (q *GeneralQueue) GetNextPendingJob(ctx context.Context) (*ent.GeneralQueue, error) {
	job, err := q.client.GeneralQueue.Query().
		Where(
			generalqueue.NameEQ(q.Name),
			generalqueue.StatusEQ(generalqueue.StatusPending),
		).
		Order(ent.Asc(generalqueue.FieldCreatedAt)).
		First(ctx)

	if err != nil {
		if ent.IsNotFound(err) {
			return nil, nil // No pending jobs
		}
		return nil, fmt.Errorf("failed to get next pending job: %w", err)
	}

	return job, nil
}

// UpdateJobStatus updates the status of a job
func (q *GeneralQueue) UpdateJobStatus(ctx context.Context, jobID int, status generalqueue.Status, errorMessage string, failurePayload map[string]interface{}, resultPayload map[string]interface{}) error {
	update := q.client.GeneralQueue.UpdateOneID(jobID).
		SetStatus(status).
		SetUpdatedAt(time.Now())

	if status == generalqueue.StatusCompleted || status == generalqueue.StatusFailed {
		update = update.SetProcessedAt(time.Now())
	}

	if errorMessage != "" {
		update = update.SetErrorMessage(errorMessage)
	}

	if failurePayload != nil {
		update = update.SetFailurePayload(failurePayload)
	}

	if resultPayload != nil {
		update = update.SetResultPayload(resultPayload)
	}

	_, err := update.Save(ctx)
	if err != nil {
		return fmt.Errorf("failed to update job status: %w", err)
	}

	return nil
}

// IncrementTries increments the number of tries for a job
func (q *GeneralQueue) IncrementTries(ctx context.Context, jobID int, currentTries int) error {
	_, err := q.client.GeneralQueue.UpdateOneID(jobID).
		SetNumberOfTries(currentTries + 1).
		SetUpdatedAt(time.Now()).
		Save(ctx)

	if err != nil {
		return fmt.Errorf("failed to increment tries: %w", err)
	}

	return nil
}

func (q *GeneralQueue) Resume(ctx context.Context) error {
	// Check if queue should auto-start
	if isRunning, err := q.IsRunning(ctx); err != nil {
		Error("Failed to check ", q.Name, " queue state:", err)
	} else if isRunning {
		Debug("restarting ", q.Name, " queue")
		err := q.Start(ctx)
		if err != nil {
			Error("Failed to restart ", q.Name, " queue:", err)
			return err
		} else {
			Debug(q.Name, " queue auto-started")
		}
	} else {
		Debug(q.Name, " queue not running")
	}
	return nil
}