nixos/foswiki: basic working service definition

Activation is as simple as:
  services.httpd = {
    enable = true;
    adminAddr = "nobody@example.com";
    extraSubservices = [ {
      serviceType = "foswiki";
    } ];
  };

nixos/modules/services/web-servers/apache-httpd/foswiki.nix

@@ -0,0 +1,78 @@
+{ config, pkgs, lib, serverInfo, ... }:
+let
+  inherit (pkgs) foswiki;
+  inherit (serverInfo.serverConfig) user group;
+  inherit (config) vardir;
+in
+{
+  options.vardir = lib.mkOption {
+    type = lib.types.path;
+    default = "/var/www/foswiki";
+    description = "The directory where variable foswiki data will be stored and served from.";
+  };
+
+  # TODO: this will probably need to be better customizable
+  extraConfig =
+    let httpd-conf = pkgs.runCommand "foswiki-httpd.conf"
+      { preferLocalBuild = true; }
+      ''
+        substitute '${foswiki}/foswiki_httpd_conf.txt' "$out" \
+          --replace /var/www/foswiki/ "${vardir}/"
+      '';
+    in
+      ''
+        RewriteEngine on
+        RewriteRule /foswiki/(.*) ${vardir}/$1
+
+        <Directory "${vardir}">
+          Require all granted
+        </Directory>
+
+        Include ${httpd-conf}
+        <Directory "${vardir}/pub">
+          Options FollowSymlinks
+        </Directory>
+      '';
+
+  /** This handles initial setup and updates.
+      It will probably need some tweaking, maybe per-site.  */
+  startupScript = pkgs.writeScript "foswiki_startup.sh" (
+    let storeLink = "${vardir}/package"; in
+    ''
+      [ -e '${storeLink}' ] || needs_setup=1
+      mkdir -p '${vardir}'
+      cd '${vardir}'
+      ln -sf -T '${foswiki}' '${storeLink}'
+
+      if [ -n "$needs_setup" ]; then # do initial setup
+        mkdir -p bin lib
+        # setup most of data/ as copies only
+        cp -r '${foswiki}'/data '${vardir}/'
+        rm -r '${vardir}'/data/{System,mime.types}
+        ln -sr -t '${vardir}/data/' '${storeLink}'/data/{System,mime.types}
+
+        ln -sr '${storeLink}/locale' .
+
+        mkdir pub
+        ln -sr '${storeLink}/pub/System' pub/
+
+        mkdir templates
+        ln -sr '${storeLink}'/templates/* templates/
+
+        ln -sr '${storeLink}/tools' .
+
+        mkdir -p '${vardir}'/working/{logs,tmp}
+        ln -sr '${storeLink}/working/README' working/ # used to check dir validity
+
+        chown -R '${user}:${group}' .
+        chmod +w -R .
+      fi
+
+      # bin/* and lib/* shall always be overwritten, in case files are added
+      ln -srf '${storeLink}'/bin/* '${vardir}/bin/'
+      ln -srf '${storeLink}'/lib/* '${vardir}/lib/'
+    ''
+    /* Symlinking bin/ one-by-one ensures that ${vardir}/lib/LocalSite.cfg
+        is used instead of ${foswiki}/... */
+  );
+}