Use http.ServeContet to be able to continue downloads

- Closes: #59

lib/storage/storage.go

@@ -15,6 +15,7 @@ type Store interface {
 type File interface {
 	io.ReadCloser
 	io.ReaderAt
+	io.Seeker
 	Stat() (fi os.FileInfo, err error)
 }
 

lib/trantor.go

@@ -1,12 +1,9 @@
 package trantor
 
 import (
-	"time"
-
 	log "github.com/cihub/seelog"
 
 	"fmt"
-	"io"
 	"net/http"
 	"path"
 	"strings"
@@ -115,14 +112,8 @@ func downloadHandler(h handler) {
 	}
 	defer f.Close()
 
-	headers := h.w.Header()
-	headers["Content-Type"] = []string{"application/epub+zip"}
-	headers["Content-Disposition"] = []string{fmt.Sprintf("attachment; filename=\"%s - %s.epub\"", strings.Join(book.Authors, ", "), book.Title)}
-	headers["Content-Length"] = []string{fmt.Sprint(book.FileSize)}
-	headers["Last-Modified"] = []string{fmt.Sprint(book.UploadDate.Format(time.RFC1123))}
 	addCacheControlHeader(h.w, false)
-
-	io.Copy(h.w, f)
+	http.ServeContent(h.w, h.r, fmt.Sprintf("%s - %s.epub", strings.Join(book.Authors, ", "), book.Title), book.UploadDate, f)
 }
 
 type indexData struct {