fetch.go

package main

import (
	"crypto/sha1"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
	"sync"

	"github.com/PuerkitoBio/goquery"
	"github.com/cryptix/go/logging"
)

var (
	log    = logging.Logger("linkExt")
	hashes *os.File
)

const url = `http://www.spiegel.de/international/germany/inside-the-nsa-s-war-on-internet-security-a-1010361.html`

func main() {
	var wg sync.WaitGroup

	doc, err := goquery.NewDocument(url)
	logging.CheckFatal(err)

	hashes, err = os.Create("hashes")
	logging.CheckFatal(err)
	defer hashes.Close()

	doc.Find("a").Each(func(i int, s *goquery.Selection) {
		link, found := s.Attr("href")
		title, _ := s.Attr("title")
		if found && strings.HasSuffix(link, ".pdf") {

			wg.Add(1)
			go fetchPDF(&wg, link, title)
		}

	})

	wg.Wait()
	log.Notice("Done")
}

func fetchPDF(wg *sync.WaitGroup, l, t string) (err error) {
	s := sha1.New()

	fname := l[7:len(l)-4] + "-" + strings.TrimSpace(t) + ".pdf"
	fname = strings.Replace(fname, "/", "-", -1)
	fname = "pdfs/" + fname
	log.Noticef("fetching: %s", fname)

	defer func() {
		if err != nil {
			fetchPDF(wg, l, t)
		} else {
			fmt.Fprintf(hashes, "%x %s\n", s.Sum(nil), fname)
			wg.Done()
		}
	}()

	resp, err := http.Get("https://www.spiegel.de/" + l)
	if err != nil {
		log.Critical(err)
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		log.Criticalf("http.Get %q", resp.Status)
		return
	}

	f, err := os.Create(fname)
	if err != nil {
		log.Critical(err)
		return
	}

	multi := io.MultiWriter(s, f)
	_, err = io.Copy(multi, resp.Body)
	if err != nil {
		log.Critical(err)
		os.Remove(fname)
		return err
	}
	log.Noticef("Saved: %s", fname)

	return nil
}