Add basic cron concept for periodic commands

Author: theandrew168

backend/cron/cron.go

@@ -0,0 +1,69 @@
+package cron
+
+import (
+	"context"
+	"log/slog"
+	"sync"
+	"time"
+
+	"github.com/theandrew168/bloggulus/backend/command"
+)
+
+type Cron struct {
+	cmd *command.Command
+}
+
+type Job struct {
+	Interval time.Duration
+	RunNow   bool
+	Run      func(cmd *command.Command) error
+}
+
+func NewCron(cmd *command.Command) *Cron {
+	c := Cron{
+		cmd: cmd,
+	}
+	return &c
+}
+func (c *Cron) Run(ctx context.Context, jobs []Job) error {
+	var wg sync.WaitGroup
+
+	for _, job := range jobs {
+		// If the job is set to run immediately, run it now.
+		if job.RunNow {
+			err := job.Run(c.cmd)
+			if err != nil {
+				slog.Error("error running job",
+					"error", err.Error(),
+				)
+			}
+		}
+
+		// Start the job in a goroutine that runs on the specified interval.
+		wg.Add(1)
+		go func(j Job) {
+			defer wg.Done()
+
+			ticker := time.NewTicker(j.Interval)
+			defer ticker.Stop()
+
+			for {
+				select {
+				case <-ctx.Done():
+					return
+				case <-ticker.C:
+					err := j.Run(c.cmd)
+					if err != nil {
+						slog.Error("error running job",
+							"error", err.Error(),
+						)
+					}
+				}
+			}
+		}(job)
+	}
+
+	// Block until all jobs are done.
+	wg.Wait()
+	return nil
+}