package main

import (
	"context"
	"fmt"
	"github.com/multiplay/go-slack/chat"
	"github.com/multiplay/go-slack/webhook"
	"github.com/robfig/cron"
	"gopkg.in/alecthomas/kingpin.v2"
	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	"os"
	"os/signal"
	"syscall"
	"time"
)

func main() {
	slackUrl := kingpin.Flag("slack-url", "The Slack Webhook URL").Envar("SLACK_URL").Required().String()
	kingpin.Parse()

	config, err := rest.InClusterConfig()
	if err != nil {
		panic(err.Error())
	}
	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		panic(err.Error())
	}

	slack := webhook.New(*slackUrl)

	parser := cron.NewParser(cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow)

	ic := make(chan os.Signal, 1)
	signal.Notify(ic, os.Interrupt, syscall.SIGTERM)

	for {
		select {
		case <-ic:
			fmt.Printf("Got SIGTERM signal, exiting\n")
			break
		default:
			cronjobs, err := clientset.BatchV1beta1().CronJobs("").List(context.Background(), v1.ListOptions{})
			if err != nil {
				fmt.Printf("Error getting cronjobs: %s", err)
				os.Exit(1)
			}
			limit := time.Now().Add(-120 * time.Second)
			for _, c := range cronjobs.Items {
				if c.Spec.Suspend == nil || !*c.Spec.Suspend {
					since := c.CreationTimestamp
					if c.Status.LastScheduleTime != nil {
						since = *c.Status.LastScheduleTime
					}
					schedule, err := parser.Parse(c.Spec.Schedule)
					if err != nil {
						fmt.Printf("Error parsing schedule of %s/%s (%s): %s", c.Namespace, c.Name, c.Spec.Schedule, err)
						os.Exit(1)
					}
					next := schedule.Next(since.Time)
					fmt.Printf("Checking %s/%s since %s, next schedule %s, limit %s.\n", c.Namespace, c.Name, since.Format(time.RFC3339), next.Format(time.RFC3339), limit.Format(time.RFC3339))
					if next.Before(limit) {
						fmt.Printf("%s was not scheduled. Sending Slack notification.\n", c.Name)
						m := &chat.Message{
							Text:     fmt.Sprintf("Cronjob %s/%s is not running according to schedule (%s). Last scheduled: %s", c.Namespace, c.Name, c.Spec.Schedule, since.Format(time.RFC3339)),
							Username: "cron-checker",
						}
						resp, err := m.Send(slack)
						if err != nil {
							fmt.Printf("Unable to send Slack notification: %s", err)
						}
						if !resp.OK {
							fmt.Printf("Unable to send Slack notification: %s", resp.Error)
						}
					}
				}
			}
			time.Sleep(60 * time.Second)
		}
	}
}