package main

import (
	"net"
	"os/exec"
	"strconv"
	"strings"
)

// Ping sends one ICMP echo packet to the given IP and times how long
// it takes to get a response, in milleseconds.  Returns -1 if no
// response is received.
func Ping(ip net.IP) float64 {
	cmd := exec.Command("ping",
		"-n", // numeric
		"-q", // quiet
		"-c", "1",
		ip.String())
	_output, _ := cmd.CombinedOutput()
	output := string(_output)
	for _, line := range strings.Split(output, "\n") {
		if !strings.HasPrefix(line, "rtt min/avg/max/mdev = ") {
			continue
		}
		values := strings.TrimPrefix(line, "rtt min/avg/max/mdev = ")
		value, err := strconv.ParseFloat(strings.Split(values, "/")[0], 64)
		if err != nil {
			continue
		}
		return value
	}
	return -1
}