package main

import (
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"time"

	"github.com/djherbis/atime"
)

var durations = []time.Duration{
	time.Nanosecond,
	time.Microsecond,
	time.Millisecond,
}

func main() {
	var errCounts = make([]int, len(durations))
	var succCounts = make([]int, len(durations))
	for j := 0; j < 3; j++ {
		for i := 1; i <= 100; i++ {
			err := checkAtimeSupport("/home/harsha", time.Duration(i)*durations[j])
			if err != nil {
				errCounts[j]++
			} else {
				succCounts[j]++
			}
		}
	}
	for j := 0; j < 3; j++ {
		fmt.Println("Errors:", errCounts[j], "Success:", succCounts[j], "Duration:", durations[j])
	}
}

// Return error if Atime is disabled on the O/S
func checkAtimeSupport(dir string, delay time.Duration) (err error) {
	file, err := ioutil.TempFile(dir, "prefix")
	if err != nil {
		return err
	}

	fname := file.Name()
	defer os.Remove(fname)

	finfo1, err := os.Stat(fname)
	if err != nil {
		file.Close()
		return err
	}
	file.Close()

	time.Sleep(delay)
	if _, err = ioutil.ReadFile(fname); err != nil {
		return err
	}

	finfo2, err := os.Stat(fname)
	if atime.Get(finfo2).Equal(atime.Get(finfo1)) {
		return errors.New("Atime not supported")
	}
	return
}