file-downloader

file-downloader.go

package main

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/dustin/go-humanize"
)

type WriteCounter struct {
	Total uint64
}

func (wc *WriteCounter) Write(p []byte) (int, error) {
	n := len(p)
	wc.Total += uint64(n)
	wc.PrintProgress()
	return n, nil
}

// PrintProgress prints the progress of a file write
func (wc WriteCounter) PrintProgress() {
	// Clear the line by using a character return to go back to the start and remove
	// the remaining characters by filling it with spaces
	fmt.Printf("\r%s", strings.Repeat(" ", 50))

	// Return again and print current status of download
	// We use the humanize package to print the bytes in a meaningful way (e.g. 10 MB)
	fmt.Printf("\rDownloading... %s complete", humanize.Bytes(wc.Total))
}

func DownloadFile(url string, filepath string) error {
	h := http.Client{Timeout: 30 * time.Second}
	out, err := os.Create(filepath + ".tmp")
	if err != nil {
		return err
	}
	defer out.Close()

	req, err := http.NewRequest(http.MethodGet, url, nil)
	if err != nil {
		return err
	}

	res, err := h.Do(req)

	if err != nil {
		return err
	}

	defer res.Body.Close()

	_, err = io.Copy(out, io.TeeReader(res.Body, &WriteCounter{}))
	if err != nil {
		return err
	}

	fmt.Println()

	err = os.Rename(filepath+".tmp", filepath)
	if err != nil {
		return err
	}

	return nil
}

func main() {
	
	err := DownloadFile("url", "my_file.pdf")
	if err != nil {
		panic(err)
	}

}