Initial implementation of cron scheduler

internal/cron/cron.go

@@ -0,0 +1,68 @@
+package cron
+
+import (
+	"fmt"
+
+	"github.com/go-co-op/gocron/v2"
+	"github.com/google/uuid"
+)
+
+// Cron is a wrapper around the gocron.Scheduler with the specific
+// configuration for the project.
+type Cron struct {
+	scheduler gocron.Scheduler
+}
+
+// New creates a new instance of the Cron struct.
+func New() (*Cron, error) {
+	scheduler, err := gocron.NewScheduler()
+	if err != nil {
+		return nil, err
+	}
+
+	return &Cron{
+		scheduler: scheduler,
+	}, nil
+}
+
+// UpsertJob adds a new job to the scheduler and it deletes the job first if
+// it already exists.
+func (c *Cron) UpsertJob(
+	id uuid.UUID, timeZone string, cronExpression string, job func(),
+) error {
+	if err := c.RemoveJob(id); err != nil {
+		return err
+	}
+
+	exp := fmt.Sprintf("CRON_TZ=%s %s", timeZone, cronExpression)
+	_, err := c.scheduler.NewJob(
+		gocron.CronJob(exp, false),
+		gocron.NewTask(job),
+		gocron.WithIdentifier(id),
+		gocron.WithSingletonMode(gocron.LimitModeReschedule),
+	)
+
+	return err
+}
+
+// RemoveJob removes a job from the scheduler only if it exists.
+func (c *Cron) RemoveJob(id uuid.UUID) error {
+	jobs := c.scheduler.Jobs()
+	for _, job := range jobs {
+		if job.ID() == id {
+			return c.scheduler.RemoveJob(id)
+		}
+	}
+
+	return nil
+}
+
+// Start starts the scheduler.
+func (c *Cron) Start() {
+	c.scheduler.Start()
+}
+
+// Shutdown stops the scheduler.
+func (c *Cron) Shutdown() error {
+	return c.scheduler.Shutdown()
+}