Add derivation for static website

.gitignore

@@ -18,3 +18,4 @@ devenv.local.nix
 .pre-commit-config.yaml
 
 .jekyll-cache/
+result

flake.lock

@@ -0,0 +1,61 @@
+{
+  "nodes": {
+    "flutils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1710146030,
+        "narHash": "sha256-SZ5L6eA7HJ/nmkzGG7/ISclqe6oZdOZTNoesiInkXPQ=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "b1d9ab70662946ef0850d488da1c9019f3a9752a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1714076141,
+        "narHash": "sha256-Drmja/f5MRHZCskS6mvzFqxEaZMeciScCTFxWVLqWEY=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "7bb2ccd8cdc44c91edba16c48d2c8f331fb3d856",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flutils": "flutils",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -3,13 +3,46 @@
 
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+    flutils.url = "github:numtide/flake-utils";
   };
 
-  outputs = { self, nixpkgs }: {
-
-    packages.x86_64-linux.hello = nixpkgs.legacyPackages.x86_64-linux.hello;
-
-    packages.x86_64-linux.default = self.packages.x86_64-linux.hello;
+  outputs = { self, nixpkgs, flutils }: flutils.lib.eachDefaultSystem (system:
+    let
+      pkgs = nixpkgs.legacyPackages.${system};
 
+      gems = pkgs.bundlerEnv {
+        name = "blog-pim";
+        gemdir = ./src;
       };
+
+      patch-feed-date = pkgs.stdenv.mkDerivation {
+        name = "path-feed-date";
+        propagatedBuildInputs = [ pkgs.python3 ];
+        dontUnpack = true;
+        installPhase = "install -Dm755 ${./patch-feed-date.py} $out/bin/patch-feed-date";
+      };
+    in
+    {
+      packages.website = pkgs.stdenv.mkDerivation {
+        name = "blog-pim";
+        src = ./src;
+        sourceRoot = "src";
+
+        buildInputs = [
+          gems
+          gems.wrappedRuby
+          patch-feed-date
+        ];
+
+        buildPhase = ''
+          bundle exec jekyll build
+        '';
+
+        installPhase = ''
+          mkdir -p $out
+          cp -r _site/* $out/
+          patch-feed-date --file _site/feed.xml > $out/feed.xml
+        '';
+      };
+    });
 }

patch-feed-date.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+
+import argparse
+import re
+from datetime import datetime
+
+updated_pattern = r"<updated>(?P<datetime>.{25})</updated>"
+datetime_pattern = "%Y-%m-%dT%H:%M:%S%z"
+
+
+def get_post_datetimes(feed):
+    regex = re.compile(updated_pattern)
+
+    datetimes = list()
+    first_skipped = False
+
+    for match in regex.finditer(feed):
+        # Skip first found datetime, as this is what we want to replace.
+        if not first_skipped:
+            first_skipped = True
+            continue
+        dt = datetime.strptime(match.group("datetime"), datetime_pattern)
+        datetimes.append(dt)
+
+    return datetimes
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Patch the updated date field on an Atom feed."
+    )
+
+    parser.add_argument(
+        "--file", "-f", type=str, required=True, help="Path to the Atom feed file."
+    )
+
+    args = parser.parse_args()
+    with open(args.file, "r") as f:
+        feed = f.read()
+
+    datetimes = get_post_datetimes(feed)
+    newest_datetime = max(datetimes)
+
+    print(
+        re.sub(
+            updated_pattern,
+            f"<updated>{newest_datetime.strftime(datetime_pattern)}</updated>",
+            feed,
+            count=1,
+        ),
+        end="",
+    )
+
+
+if __name__ == "__main__":
+    main()