Dwango@5

dwango5.go

package main

import (
	"os"
	"net/http"
	"io"
	"path/filepath"
	"sync"
	"github.com/codegangsta/cli"
	"runtime"
)

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU())

	app := cli.NewApp()
	app.Name = "downloader"
	app.Usage = "hogehoge"
	app.Action = func(c *cli.Context) {
		var waitGroup sync.WaitGroup
		for _, url := range c.Args() {
			waitGroup.Add(1)
			go Download(url, &waitGroup)
		}
		waitGroup.Wait()
	}
	app.Run(os.Args)
}

func Download(url string, waitGroup *sync.WaitGroup) {
	defer waitGroup.Done()

	_, fileName := filepath.Split(url)
	downloader := NewDownloader(url, "/tmp/"+fileName)
	downloader.Download()
}

type Downloader struct {
	Uri        string
	SavePath   string
}

func NewDownloader(uri string, savePath string) *Downloader {
	return &Downloader{Uri: uri, SavePath: savePath}
}

func (d *Downloader) Download() error {
	tmpFile, err := d.createTmpFile(d.SavePath)
	if err != nil {
		return err
	}
	defer tmpFile.Close()
	response, err := d.request()
	if err != nil {
		return err
	}
	defer response.Body.Close()
	return d.copyResponseToTmpFile(tmpFile, response)
}

func (d *Downloader) createTmpFile(path string) (*os.File, error) {
	file, err := os.Create(path)
	if err != nil {
		return nil, err
	}
	return file, nil
}

func (d *Downloader) request() (*http.Response, error) {
	response, err := http.Get(d.Uri)
	if err != nil {
		return nil, err
	}
	return response, err
}

func (d *Downloader) copyResponseToTmpFile(tmpFile *os.File, response *http.Response) (error) {
	_, err := io.Copy(tmpFile, response.Body)
	return err
}