From b25d7be29d01322c62fd68924063ce9a0e8f3984 Mon Sep 17 00:00:00 2001
From: Ruidy <ruidy.nemausat@gmail.com>
Date: Sun, 30 Jun 2024 12:49:26 +0200
Subject: [PATCH] basic task scheduler

---
 Makefile                    |  2 +
 cmd/cron/main.go            | 48 ++++++++++++++++++++
 internal/cron/cron.go       | 88 +++++++++++++++++++++++++++++++++++++
 internal/cron/job_report.go | 16 +++++++
 4 files changed, 154 insertions(+)
 create mode 100644 cmd/cron/main.go
 create mode 100644 internal/cron/cron.go
 create mode 100644 internal/cron/job_report.go

diff --git a/Makefile b/Makefile
index 86eeb8a..a865ab0 100644
--- a/Makefile
+++ b/Makefile
@@ -9,6 +9,8 @@ run: build
 	@docker run -p ${PORT}:${PORT} -e DATABASE_URL="host=docker.for.mac.host.internal user=${DB_USER} database=${DB_NAME}" -e PORT=${PORT} ${NAME}
 dev: templ
 	@air cmd/main.go
+cron:
+	@go run cmd/cron/main.go
 templ:
 	@templ generate --watch --proxy=http://localhost:${PORT} &
 format:
diff --git a/cmd/cron/main.go b/cmd/cron/main.go
new file mode 100644
index 0000000..137598d
--- /dev/null
+++ b/cmd/cron/main.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/rjNemo/rentease/internal/cron"
+)
+
+func main() {
+	scheduler := cron.New()
+
+	scheduler.AddJob(cron.Job{
+		Name:     "Monthly Booking Report",
+		Schedule: "minute",
+		//Schedule: "monthly",
+		Action: cron.JobMonthlyBookingReport,
+	})
+
+	go scheduler.Start()
+
+	go func() {
+		for {
+			select {
+			case err := <-scheduler.ErrChan:
+				if err != nil {
+					log.Println("Error:", err)
+				}
+			case msg := <-scheduler.SuccessChan:
+				log.Print(msg)
+			}
+		}
+	}()
+
+	// Capture termination signals for graceful shutdown
+	sigChan := make(chan os.Signal, 1)
+	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+
+	// Wait for termination signal
+	<-sigChan
+	log.Println("Received termination signal, shutting down...")
+
+	// Stop the task manager and close channels
+	scheduler.Stop()
+	log.Println("All tasks stopped, exiting.")
+}
diff --git a/internal/cron/cron.go b/internal/cron/cron.go
new file mode 100644
index 0000000..637276f
--- /dev/null
+++ b/internal/cron/cron.go
@@ -0,0 +1,88 @@
+package cron
+
+import (
+	"fmt"
+	"log"
+	"time"
+)
+
+// Cron handles jobs scheduling and execution
+type Cron struct {
+	jobs        []Job
+	ErrChan     chan error
+	DoneChan    chan struct{}
+	SuccessChan chan string
+}
+
+// Job is a type that holds the details for each job.
+type Job struct {
+	Name     string
+	Schedule string
+	Action   JobFunc
+}
+
+type JobFunc func() error
+
+func New() *Cron {
+	return &Cron{
+		jobs:        make([]Job, 0),
+		ErrChan:     make(chan error),
+		SuccessChan: make(chan string),
+		DoneChan:    make(chan struct{}),
+	}
+}
+
+func (c *Cron) AddJob(job Job) {
+	c.jobs = append(c.jobs, job)
+}
+
+func (c *Cron) Start() {
+	for _, j := range c.jobs {
+		go c.scheduleJob(j)
+	}
+}
+
+func (c *Cron) Stop() {
+	close(c.DoneChan)
+	close(c.SuccessChan)
+	close(c.ErrChan)
+}
+
+// scheduleJob adds a task to the Cron schedule based on its schedule
+func (c *Cron) scheduleJob(j Job) {
+	for {
+		select {
+		case <-c.DoneChan:
+			log.Printf("stopping job %s", j.Name)
+			return
+		default:
+			now := time.Now()
+
+			var next time.Time
+			switch j.Schedule {
+			case "minute":
+				next = now.Add(10 * time.Second)
+			case "daily":
+				next = now.AddDate(0, 0, 1).Truncate(24 * time.Hour)
+			case "weekly":
+				next = now.AddDate(0, 0, 7).Truncate(24 * time.Hour)
+			case "monthly":
+				nextMonth := now.AddDate(0, 1, 0)
+				next = time.Date(nextMonth.Year(), nextMonth.Month(), 1, 0, 0, 0, 0, nextMonth.Location())
+			default:
+				log.Printf("Unknown schedule %q for job %q", j.Schedule, j.Name)
+				return
+			}
+
+			sleepDuration := time.Until(next)
+			log.Printf("Job %q will run in %s", j.Name, sleepDuration.String())
+			time.Sleep(sleepDuration)
+
+			if err := j.Action(); err != nil {
+				c.ErrChan <- fmt.Errorf("job %s failed: %w", j.Name, err)
+			} else {
+				c.SuccessChan <- fmt.Sprintf("job %s completed successfully", j.Name)
+			}
+		}
+	}
+}
diff --git a/internal/cron/job_report.go b/internal/cron/job_report.go
new file mode 100644
index 0000000..c368ad1
--- /dev/null
+++ b/internal/cron/job_report.go
@@ -0,0 +1,16 @@
+package cron
+
+import (
+	"errors"
+	"log"
+	"time"
+)
+
+func JobMonthlyBookingReport() error {
+	now := time.Now()
+	log.Println("Start Monthly Booking Report job at:", now)
+	//err := booking.NewService().BuildReport("monthly", int(now.Month()), now.Year())
+	err := errors.New("test")
+	log.Printf("Executed Monthly Booking Report job at %v with errors: %s:", time.Now().Format(time.DateTime), err)
+	return err
+}