/*
 Copyright 2019 Adrien Waksberg

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     https://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
*/

package main

import (
	"fmt"
	"flag"
	"os"
	"os/exec"
	"strings"
	"time"
)

// Option to parse
var (
  HELP     = flag.Bool("help", false, "print the help message")
  SERVICE  = flag.String("service", "", "service name")
  LIFETIME = flag.Int("lifetime", 60, "minimum life time in second")
)

func init() {
  flag.Parse()

  if *HELP {
    flag.PrintDefaults()
    os.Exit(3)
  }

  if *SERVICE == "" {
    Critical("Please set service name")
  }
}

// Critical print a message and exit with code 2
func Critical(msg string) {
  fmt.Println(fmt.Sprintf("CRITICAL - %s", msg))
  os.Exit(2)
}

// Warning print a message and exit with code 1
func Warning(msg string) {
  fmt.Println(fmt.Sprintf("WARNING - %s", msg))
  os.Exit(1)
}

// Ok print a message and exit with code 0
func Ok(msg string) {
  fmt.Println(fmt.Sprintf("OK - %s", msg))
  os.Exit(0)
}

// ServiceStatus check if the service is started
func ServiceStatus() error {
	cmd := exec.Command("systemctl", "is-active", *SERVICE)
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("the service is inactive")
	}

	output, err := exec.Command("systemctl", "show", *SERVICE, "-p", "ExecMainStartTimestamp", "--value").Output()
	if err != nil {
		return err
	}

	startDate, err  := time.Parse("Mon 2006-01-02 15:04:05 MST", strings.Trim(string(output), "\n"))
	if err != nil {
		return err
	}

	if startDate.Unix() > time.Now().Add(- time.Duration(*LIFETIME) * time.Second).Unix() {
		return fmt.Errorf("the service has started for less than %d seconds", *LIFETIME)
	}

	return nil
}

func main() {
  err := ServiceStatus()
  if err != nil {
    Critical(fmt.Sprintf("%v", err))
  }

  Ok("the service is active")
}