Switch to using zipstream-ng to generate and stream zip files

- Fixes zip downloads failing when zipping enough data that Zip64
   extensions are required by automatically enabling them if needed.
 - Fixes zip downloads failing when a file has a datestamp that zipfiles
   cannot store (pre-1980 or post-2108) by clamping them within the
   supported range.
 - Massively speeds up zip downloads by disabling compression (audio
   files generally don't compress well anyway)
 - Computes the total size of a generated zip file before streaming it
   and sets the `Content-Length` header. This allows clients to show a
   final size and progress bar while downloading, as well as detect if
   the download fails.
 - Adds a check to prevent sending an empty zip file to the client if
   there was no content to download (will error out instead).

setup.py

@@ -18,7 +18,7 @@ reqs = [
     "requests>=1.0.0",
     "mediafile",
     "watchdog>=0.8.0",
-    "zipstream",
+    "zipstream-ng>=1.1.0,<2.0.0",
 ]
 
 setup(

supysonic/api/media.py

@@ -22,8 +22,7 @@ from flask import current_app
 from PIL import Image
 from pony.orm import ObjectNotFound
 from xml.etree import ElementTree
-from zipfile import ZIP_DEFLATED
-from zipstream import ZipFile
+from zipstream import ZipStream
 
 from ..cache import CacheMiss
 from ..db import Track, Album, Folder, now
@@ -251,16 +250,20 @@ def download_media():
             raise NotFound("Folder")
 
     # Stream a zip of the tracks + cover art to the client
-    z = ZipFile(compression=ZIP_DEFLATED)
+    z = ZipStream(sized=True)
     for track in rv.tracks:
-        z.write(track.path, os.path.basename(track.path))
+        z.add_path(track.path)
 
     cover_path = _cover_from_collection(rv, extract=False)
     if cover_path:
-        z.write(cover_path, os.path.basename(cover_path))
+        z.add_path(cover_path)
+
+    if not z:
+        raise GenericError("Nothing to download")
 
     resp = Response(z, mimetype="application/zip")
     resp.headers["Content-Disposition"] = "attachment; filename={}.zip".format(rv.name)
+    resp.headers["Content-Length"] = len(z)
     return resp