convert caddy to nixos builtin

nix/packages/caddy-static-prepare/default.nix

@@ -0,0 +1,13 @@
+{ pkgs, lib, name, src ? null, ... }: pkgs.stdenv.mkDerivation {
+  inherit name src;
+
+  buildInputs = with pkgs; [ python311 python311Packages.zstandard python311Packages.brotli ];
+
+  buildPhase = ''
+    mkdir -p $out
+    cp -r $src/* $out/
+    chmod -R +w $out
+    ${lib.getExe pkgs.python311} ${./prepare.py} $out
+    chmod -R -w $out
+  '';
+}

nix/packages/caddy-static-prepare/prepare.py

@@ -0,0 +1,60 @@
+import os
+import sys
+import gzip
+import brotli
+import zstandard
+import hashlib
+
+
+def usage():
+    print("usage: prepare.py [SRC]")
+
+
+def write_etag(path, content):
+    shasum = hashlib.sha256(content)
+    etag_path = path+".sha256"
+    with open(etag_path, "w") as f:
+        print(f"Writing ETag {etag_path}")
+        f.write(f'"{shasum.hexdigest()}"')
+
+
+def main():
+    if len(sys.argv) < 2:
+        usage()
+        exit(1)
+
+    src_dir = sys.argv[1]
+
+    for root, dirs, files in os.walk(src_dir):
+        for file in files:
+            path = os.path.join(root, file)
+
+            # Ignore etags
+            if path.endswith(".sha256") or path.endswith(".b3sum"):
+                continue
+
+            # Ignore already compressed files        
+            if path.endswith(".gz") or path.endswith(".zst") or path.endswith(".br"):
+                continue
+
+            with open(path, "rb") as f:
+                content = f.read()
+
+            compressions = [
+                (".gz", gzip),
+                (".zst", zstandard),
+                (".br", brotli),
+            ]
+
+            for ext, alg in compressions:
+                new_path = path+ext
+                with open(new_path, "wb") as out:
+                    print(f"Writing {new_path}")
+                    compressed = alg.compress(content)
+                    out.write(compressed)
+                    write_etag(new_path, compressed)
+
+            write_etag(path, content)
+
+if __name__ == "__main__":
+    main()