Refactor: improve code quality and worker flow

Backend/internal/worker/runner.go

@@ -0,0 +1,118 @@
+package worker
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"strings"
+	"time"
+
+	"moku-backend/internal/jobs"
+)
+
+type JobStore interface {
+	ClaimNext(ctx context.Context) (*jobs.Job, error)
+	MarkSucceeded(ctx context.Context, jobID string) error
+	MarkFailed(ctx context.Context, jobID, failure string) error
+}
+
+type Handler func(ctx context.Context, job jobs.Job) error
+
+type Runner struct {
+	store        JobStore
+	logger       *slog.Logger
+	pollInterval time.Duration
+	handlers     map[string]Handler
+}
+
+func NewRunner(store JobStore, logger *slog.Logger, pollInterval time.Duration) *Runner {
+	interval := pollInterval
+	if interval <= 0 {
+		interval = time.Second
+	}
+
+	return &Runner{
+		store:        store,
+		logger:       logger,
+		pollInterval: interval,
+		handlers:     make(map[string]Handler),
+	}
+}
+
+func (runner *Runner) Register(kind string, handler Handler) {
+	runner.handlers[strings.TrimSpace(kind)] = handler
+}
+
+func (runner *Runner) Run(ctx context.Context) error {
+	for {
+		select {
+		case <-ctx.Done():
+			return nil
+		default:
+		}
+
+		job, err := runner.store.ClaimNext(ctx)
+		if err != nil {
+			if ctx.Err() != nil {
+				return nil
+			}
+
+			return err
+		}
+
+		if job == nil {
+			if err := waitForNextPoll(ctx, runner.pollInterval); err != nil {
+				return nil
+			}
+
+			continue
+		}
+
+		handler, ok := runner.handlers[job.Kind]
+		if !ok {
+			failure := fmt.Sprintf("no handler registered for job kind %q", job.Kind)
+			if err := runner.store.MarkFailed(ctx, job.ID, failure); err != nil {
+				return err
+			}
+
+			runner.logger.Error("worker job failed", "jobID", job.ID, "kind", job.Kind, "error", failure)
+			continue
+		}
+
+		if err := handler(ctx, *job); err != nil {
+			if ctx.Err() != nil {
+				return nil
+			}
+
+			failure := strings.TrimSpace(err.Error())
+			if failure == "" {
+				failure = "job handler returned an empty error"
+			}
+
+			if markErr := runner.store.MarkFailed(ctx, job.ID, failure); markErr != nil {
+				return markErr
+			}
+
+			runner.logger.Error("worker job failed", "jobID", job.ID, "kind", job.Kind, "error", failure)
+			continue
+		}
+
+		if err := runner.store.MarkSucceeded(ctx, job.ID); err != nil {
+			return err
+		}
+
+		runner.logger.Info("worker job succeeded", "jobID", job.ID, "kind", job.Kind)
+	}
+}
+
+func waitForNextPoll(ctx context.Context, interval time.Duration) error {
+	timer := time.NewTimer(interval)
+	defer timer.Stop()
+
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-timer.C:
+		return nil
+	}
+}