country-geo-locations/pkg/downloader/downloader.go

package downloader

import (
	"errors"
	"fmt"
	"io"
	"os"
	"strings"

	req "github.com/levigross/grequests"
	"github.com/schollz/progressbar/v3"
)

func handleError(err error) {
	fmt.Println(err.Error())
	os.Exit(0)
}

func DownloadFile(path, url string) {
	resp, err := req.Head(url, nil)
	if err != nil {
		if strings.Contains(err.Error(), "no such host") {
			handleError(errors.New("invalid url"))
		} else if strings.Contains(err.Error(), "certificate signed by unknown authority") {
			handleError(errors.New("certificate from unknown authority"))
		}
		handleError(err)
	}
	defer resp.Close()
	if resp.StatusCode == 404 {
		handleError(errors.New("invalid url"))
	} else if resp.StatusCode == 401 {
		handleError(errors.New("restricted access (credentials required)"))
	} else if resp.StatusCode != 200 {
		handleError(errors.New(resp.RawResponse.Status))
	}
	resp.Close()

	resp, err = req.Get(url, nil)
	if err != nil {
		handleError(err)
	}

	var filesize int64
	if resp.RawResponse.ContentLength > -1 {
		filesize = resp.RawResponse.ContentLength
	}

	destFile, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		handleError(err)
	}
	defer destFile.Close()

	bar := progressbar.DefaultBytes(
		filesize,
		"downloading",
	)

	_, err = io.Copy(io.MultiWriter(destFile, bar), resp.RawResponse.Body)
	if err != nil {
		handleError(err)
	}

	fmt.Println("Saved file to", path)
}

func FileExists(path string) bool {
	_, err := os.Stat(path)
	return !errors.Is(err, os.ErrNotExist)
}