isitup/main.go

package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"net/http"
	"net/url"
	"os"
	"strings"

	"github.com/fatih/color"
)

var Version = "develop"

func main() {
	fs := flag.NewFlagSet("isitup", flag.ExitOnError)
	versionFlag := fs.Bool("version", false, "Display version and exit")
	fs.BoolVar(versionFlag, "v", *versionFlag, "--version")
	if err := fs.Parse(os.Args[1:]); err != nil {
		fmt.Println(err)
		return
	}

	if *versionFlag {
		fmt.Printf("isitup %s\n", Version)
		return
	}

	if fs.NArg() < 1 {
		fmt.Println("isitup requires a host to check")
		return
	}
	host := fs.Arg(0)

	r, err := Check(host)
	if err != nil {
		fmt.Println(err)
		return
	}

	var status string
	switch r.StatusCode {
	case 1:
		status = color.GreenString("up")
	case 2:
		status = color.RedString("down")
	case 3:
		status = color.BlackString("an invalid domain")
	default:
		fmt.Printf("isitup returned an invalid status %d\n", r.StatusCode)
		return
	}

	fmt.Printf("%s is %s!\n", color.YellowString(host), status)
}

// Response is a response from the API
type Response struct {
	Domain       string  `json:"domain"`
	Port         int     `json:"port"`
	StatusCode   int     `json:"status_code"`
	ResponseIP   string  `json:"response_ip"`
	ResponseCode int     `json:"response_code"`
	ResponseTime float64 `json:"response_time"`
}

// Check checks a given host
func Check(host string) (*Response, error) {
	u, err := url.Parse(host)
	if err != nil {
		return nil, fmt.Errorf("could not parse host %q: %w", host, err)
	}

	var h string
	switch {
	case u.Scheme != "":
		h = u.Hostname()
	case u.Path != "":
		p := strings.TrimPrefix(u.Path, "/")
		h = strings.Split(p, "/")[0]
	default:
		return nil, fmt.Errorf("could not derive host from %q", host)
	}

	res, err := http.Get(fmt.Sprintf("https://isitup.org/%s.json", h))
	if err != nil {
		return nil, fmt.Errorf("could not get from API: %w", err)
	}

	var r Response
	if err := json.NewDecoder(res.Body).Decode(&r); err != nil {
		return nil, fmt.Errorf("could not decode response body: %w", err)
	}

	return &r, nil
}