automate nix package updates

contrib/package/nix/copyparty/default.nix

@@ -2,6 +2,7 @@
 , pyvips, pyftpdlib, pyopenssl, impacket, ffmpeg }:
 
 let
+  pinData = lib.importJSON ./pin.json;
   pyEnv = python.withPackages (ps:
     with ps; [
       # mandatory
@@ -21,11 +22,10 @@ let
     ]);
 in stdenv.mkDerivation rec {
   pname = "copyparty";
-  version = "1.6.11";
+  version = pinData.version;
   src = fetchurl {
-    url =
-      "https://github.com/9001/copyparty/releases/download/v${version}/copyparty-sfx.py";
-    hash = "sha256-0JbjOrZm70UhOJndOhBzX2K1RBM5y3N0+TsjLQtsjTQ=";
+    url = pinData.url;
+    hash = pinData.hash;
   };
   buildInputs = [ makeWrapper ];
   dontUnpack = true;

contrib/package/nix/copyparty/pin.json

@@ -0,0 +1,5 @@
+{
+    "url": "https://github.com/9001/copyparty/releases/download/v1.6.11/copyparty-sfx.py",
+    "version": "1.6.11",
+    "hash": "sha256-0JbjOrZm70UhOJndOhBzX2K1RBM5y3N0+TsjLQtsjTQ="
+}

contrib/package/nix/copyparty/update.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+
+# Update the Nix package pin
+#
+# Usage: ./update.sh [PATH]
+# When the [PATH] is not set, it will fetch the latest release from the repo.
+# With [PATH] set, it will hash the given file and generate the URL,
+# base on the version contained within the file
+
+import base64
+import json
+import hashlib
+import sys
+import re
+from pathlib import Path
+
+OUTPUT_FILE = Path("pin.json")
+TARGET_ASSET = "copyparty-sfx.py"
+HASH_TYPE = "sha256"
+LATEST_RELEASE_URL = "https://api.github.com/repos/9001/copyparty/releases/latest"
+DOWNLOAD_URL = lambda version: f"https://github.com/9001/copyparty/releases/download/v{version}/{TARGET_ASSET}"
+
+
+def get_formatted_hash(binary):
+    hasher = hashlib.new("sha256")
+    hasher.update(binary)
+    asset_hash = hasher.digest()
+    encoded_hash = base64.b64encode(asset_hash).decode("ascii")
+    return f"{HASH_TYPE}-{encoded_hash}"
+
+
+def version_from_sfx(binary):
+    result = re.search(b'^VER = "(.*)"$', binary, re.MULTILINE)
+    if result:
+        return result.groups(1)[0].decode("ascii")
+
+    raise ValueError("version not found in provided file")
+
+
+def remote_release_pin():
+    import requests
+
+    response = requests.get(LATEST_RELEASE_URL).json()
+    version = response["tag_name"].lstrip("v")
+    asset_info = [a for a in response["assets"] if a["name"] == TARGET_ASSET][0]
+    download_url = asset_info["browser_download_url"]
+    asset = requests.get(download_url)
+    formatted_hash = get_formatted_hash(asset.content)
+
+    result = {"url": download_url, "version": version, "hash": formatted_hash}
+    return result
+
+
+def local_release_pin(path):
+    asset = path.read_bytes()
+    version = version_from_sfx(asset)
+    download_url = DOWNLOAD_URL(version)
+    formatted_hash = get_formatted_hash(asset)
+
+    result = {"url": download_url, "version": version, "hash": formatted_hash}
+    return result
+
+
+def main():
+    if len(sys.argv) > 1:
+        asset_path = Path(sys.argv[1])
+        result = local_release_pin(asset_path)
+    else:
+        result = remote_release_pin()
+
+    print(result)
+    json_result = json.dumps(result, indent=4)
+    OUTPUT_FILE.write_text(json_result)
+
+
+if __name__ == "__main__":
+    main()