Multitype posts in db

lib/DB.rakumod

@@ -73,24 +73,36 @@ class MarkdownPost does Post is json {
     }
 }
 
-# #| A literate idris post in markdown format
-# class IdrisPost does Post {
 
-#     method title(--> Str:D) {
+#| A plain markdown post
-#         markdown-title($!source)
+class IdrisPost does Post is json {
-#     }
+    #| Marker for disambiguation between post types in json representation, the
-# }
+    #| cheaty way
+    has Bool:D $.idris = True;
+
+    method title(--> Str:D) {
+        markdown-title($!source)
+    }
+}
+
+class Posts is json(:dictionary(:keyof(Int:D), MarkdownPost:D, IdrisPost:D)) {}
+
+subset PostTypes where MarkdownPost:D | IdrisPost:D;
 
 #| The top level posts database
 class PostDB is json(:pretty) {
    #| The metadat for the blog
    has BlogMeta:D $.meta is required;
    #| A mapping from post ids to posts
-   has %.posts{Int:D} of MarkdownPost:D = %();
+   has %.posts is Posts;
+
+   method TWEAK() {
+       %!posts := Posts.new unless %!posts;
+   }
 
    #| Get the next unused post ID
    method next-post-id(--> Int) {
-       if %!posts {
+       if %!posts.elems > 0 {
            %!posts.keys.max + 1
        } else {
            0
@@ -98,7 +110,7 @@ class PostDB is json(:pretty) {
    }
 
    #| Insert a new post to the DB, returning its id
-   method insert-post(Post:D $post --> Int) {
+   method insert-post(PostTypes $post --> Int) {
        my $id = self.next-post-id;
        %!posts{$id} = $post;
        $id