overview: implement the whole project list using modules

overview/content-types/project-list-item.nix

@@ -41,6 +41,7 @@ in
     };
     __toString = mkOption {
       type = with types; functionTo str;
+      readOnly = true;
       default =
         self: with lib; ''
           <article class="project">

overview/content-types/project-list.nix

@@ -0,0 +1,76 @@
+# The top-level overview for all projects
+{ config, lib, ... }:
+let
+  inherit (lib)
+    mkOption
+    types
+    concatMapStringsSep
+    attrValues
+    ;
+  inherit (types)
+    listOf
+    nullOr
+    functionTo
+    str
+    submodule
+    ;
+in
+{
+  options = {
+    projects = mkOption {
+      type = listOf (submodule ./project-list-item.nix);
+    };
+    version = mkOption {
+      type = nullOr str;
+    };
+    lastModified = mkOption {
+      type = nullOr str;
+    };
+    __toString = mkOption {
+      type = functionTo str;
+      readOnly = true;
+      default = self: ''
+        <section class="page-width">
+          <h1>NGIpkgs</h1>
+
+          <p>
+            NGIpkgs is collection of software applications funded by the <a href="https://www.ngi.eu/ngi-projects/ngi-zero/">Next Generation Internet</a> initiative and packaged for <a href="https://nixos.org">NixOS</a>.
+          </p>
+
+          <p>
+            This service is still <strong>experimental</strong> and under active development.
+            Don't expect anything specific to work yet:
+          </p>
+
+          <ul>
+            <li>The package collection is far incomplete</li>
+            <li>Many packages lack crucial components</li>
+            <li>There are no instructions for getting started</li>
+            <li>How software and the corresponding Nix expressions are exposed is subject to change</li>
+          </ul>
+
+          <p>
+            More information about the project:
+          </p>
+
+          <ul>
+            <li>
+              <a href="https://github.com/ngi-nix/ngipkgs">Source code</a>
+            </li>
+            <li>
+              <a href="https://github.com/ngi-nix/summer-of-nix/issues/41">Issue tracker</a>
+            </li>
+            <li>
+              <a href="https://nixos.org/community/teams/ngi/">Nix@NGI team</a>
+            </li>
+          </ul>
+
+        ${concatMapStringsSep "\n" toString (self.projects)}
+
+        </section>
+
+        <footer>Version: ${self.version}, Last Modified: ${self.lastModified}</footer>
+      '';
+    };
+  };
+}

overview/default.nix

@@ -239,30 +239,6 @@ let
       </article>
     '';
 
-    # The snippets for each project that are rendered on https://ngi.nixos.org
-    projectSnippets =
-      projects:
-      eval {
-        options = {
-          projects = mkOption {
-            type = with types; attrsOf (submodule ./content-types/project-list-item.nix);
-            default = lib.mapAttrs (name: project: {
-              inherit name;
-              description = project.metadata.summary or null;
-              deliverables = {
-                service = project.nixos.modules ? services && project.nixos.modules.services != { };
-                program = project.nixos.modules ? programs && project.nixos.modules.programs != { };
-                demo = project.nixos.examples ? demo;
-              };
-            }) projects;
-          };
-          __toString = mkOption {
-            type = with types; functionTo str;
-            default = self: with lib; concatMapStringsSep "\n" toString (attrValues self.projects);
-          };
-        };
-      };
-
     demoGlue.one = exampleText: ''
       # default.nix
       {
@@ -331,50 +307,6 @@ let
       '';
   };
 
-  # The top-level overview for all projects
-  index = ''
-    <section class="page-width">
-      ${heading 1 null "NGIpkgs"}
-
-      <p>
-        NGIpkgs is collection of software applications funded by the <a href="https://www.ngi.eu/ngi-projects/ngi-zero/">Next Generation Internet</a> initiative and packaged for <a href="https://nixos.org">NixOS</a>.
-      </p>
-
-      <p>
-        This service is still <strong>experimental</strong> and under active development.
-        Don't expect anything specific to work yet:
-      </p>
-
-      <ul>
-        <li>The package collection is far incomplete</li>
-        <li>Many packages lack crucial components</li>
-        <li>There are no instructions for getting started</li>
-        <li>How software and the corresponding Nix expressions are exposed is subject to change</li>
-      </ul>
-
-      <p>
-        More information about the project:
-      </p>
-
-      <ul>
-        <li>
-          <a href="https://github.com/ngi-nix/ngipkgs">Source code</a>
-        </li>
-        <li>
-          <a href="https://github.com/ngi-nix/summer-of-nix/issues/41">Issue tracker</a>
-        </li>
-        <li>
-          <a href="https://nixos.org/community/teams/ngi/">Nix@NGI team</a>
-        </li>
-      </ul>
-
-    ${render.projectSnippets projects}
-
-    </section>
-
-    <footer>Version: ${version}, Last Modified: ${lastModified}</footer>
-  '';
-
   # HTML project pages
   projectPages = mapAttrs' (
     name: project:
@@ -390,6 +322,22 @@ let
     }
   ) projects;
 
+  index = eval {
+    imports = [ ./content-types/project-list.nix ];
+
+    projects = lib.mapAttrsToList (name: project: {
+      inherit name;
+      description = project.metadata.summary or null;
+      deliverables = {
+        service = project.nixos.modules ? services && project.nixos.modules.services != { };
+        program = project.nixos.modules ? programs && project.nixos.modules.programs != { };
+        demo = project.nixos.examples ? demo;
+      };
+    }) projects;
+    inherit version;
+    inherit lastModified;
+  };
+
   # The summary page at the overview root
   indexPage = {
     pagetitle = "NGIpkgs software repository";