games/fetch-itch: Allow to pass a version

So far we had a similar "experience" with itch.io as we had with
humblebundle having upstream URLs being updated in-place and thus
whenever we're trying to get an earlier revision than the latest one,
our fetcher would fail.

However, itch.io has build IDs which even contain version string that we
can actually use in our packages as-is and they directly map to a build
ID.

This commit implements just that, so that whenever a version attribute
is passed to fetchItch, an explicit version is selected. If such a
version couldn't be found, a list of the most recent versions is
displayed, which should also make it easier for updating packages.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

1 files changed, 30 insertions, 4 deletions

diff --git a/pkgs/games/itch/fetch-itch/default.nix b/pkgs/games/itch/fetch-itch/default.nix
index ed1ac7f6..3700f5c6 100644
--- a/pkgs/games/itch/fetch-itch/default.nix
+++ b/pkgs/games/itch/fetch-itch/default.nix
@@ -3,7 +3,7 @@
 , apiKey
 }:
 
-{ name, gameId, uploadId, sha256 }:
+{ name, gameId, uploadId, sha256, version ? null }:
 
 let
   cafile = "${cacert}/etc/ssl/certs/ca-bundle.crt";
@@ -21,15 +21,41 @@ let
     NAME = os.getenv('name')
     GAME_ID = int(os.getenv('gameId'))
     UPLOAD_ID = int(os.getenv('uploadId'))
+    VERSION = os.getenv('version', None)
 
     def request(path):
       with urlopen(urljoin(API_BASE, path)) as u:
         return json.loads(u.read())
 
+    def get_versions(key):
+      url = 'upload/{}/builds'.format(UPLOAD_ID)
+      return request(url + '?download_key_id=' + str(key))['builds']
+
+    def print_download_url(key):
+      if VERSION is not None:
+        versions = get_versions(key)
+        wanted = [ver for ver in versions if ver['user_version'] == VERSION]
+        if len(wanted) == 1:
+          url = 'upload/{}/download/builds/{}?download_key_id={}'.format(
+            UPLOAD_ID, wanted[0]['id'], key
+          )
+          sys.stdout.write(request(url)['archive']['url'] + '\n')
+          return
+        else:
+          msg = 'Unknown version {}, recent versions are:\n'.format(VERSION)
+          sys.stderr.write(msg)
+          for ver in versions[:20]:
+            sys.stderr.write('Update date: {}, version: {}\n'.format(
+              ver['updated_at'], ver['user_version']
+            ))
+          raise SystemExit(1)
+
+      url = 'download-key/{}/download/{}'.format(key, UPLOAD_ID)
+      sys.stdout.write(request(url)['url'] + '\n')
+
     for key in request('my-owned-keys')['owned_keys']:
       if key['game']['id'] == GAME_ID:
-        url = 'download-key/{}/download/{}'.format(key['id'], UPLOAD_ID)
-        sys.stdout.write(request(url)['url'] + '\n')
+        print_download_url(key['id'])
         raise SystemExit(0)
 
     sys.stderr.write('Unable to find download for game {}!'.format(NAME))
@@ -37,7 +63,7 @@ let
   '';
 
 in stdenv.mkDerivation {
-  inherit name apiKey gameId uploadId;
+  inherit name apiKey gameId uploadId version;
   outputHashAlgo = "sha256";
   outputHash = sha256;