WIP: implement the DOM

presentation/dom.nix

@@ -0,0 +1,178 @@
+/**
+  A strongly typed module system implementation of the Document Object Model (DOM)
+
+  Based on the WHATWG's HTML Living Standard https://html.spec.whatwg.org (CC-BY 4.0)
+  Inspired by https://github.com/knupfer/type-of-html by @knupfer (BSD-3-Clause)
+  Similar work from the OCaml ecosystem: https://github.com/ocsigen/tyxml
+*/
+{ lib, ... }:
+let
+  # https://html.spec.whatwg.org/multipage/dom.html#content-models
+  # https://html.spec.whatwg.org/multipage/dom.html#kinds-of-content
+  content-categories = [
+    "none" # https://html.spec.whatwg.org/multipage/dom.html#the-nothing-content-model
+    "text" # https://html.spec.whatwg.org/multipage/dom.html#text-content
+    "metadata" # https://html.spec.whatwg.org/multipage/dom.html#metadata-content
+    "flow" # https://html.spec.whatwg.org/multipage/dom.html#flow-content
+    "sectioning" # https://html.spec.whatwg.org/multipage/dom.html#sectioning-content
+    "heading" # https://html.spec.whatwg.org/multipage/dom.html#heading-content
+    "phrasing" # https://html.spec.whatwg.org/multipage/dom.html#phrasing-content
+    "embedded" # https://html.spec.whatwg.org/multipage/dom.html#embedded-content-2
+    "interactive" # https://html.spec.whatwg.org/multipage/dom.html#interactive-content
+    "palpable" # https://html.spec.whatwg.org/multipage/dom.html#palpable-content
+    "scripting" # https://html.spec.whatwg.org/multipage/dom.html#script-supporting-elements
+  ];
+
+  # base type for all DOM elements
+  element = { name, config, ... }: {
+    options = with lib; {
+      attrs = mkAttrs { };
+      categories = mkOption {
+        type = types.listOfUnique (types.enum content-categories);
+      };
+      __toString = mkOption {
+        internal = true;
+        type = with types; functionTo str;
+      };
+    };
+  };
+
+  # options with types for all the defined DOM elements
+  element-types = lib.mapAttrs
+    (name: value: mkOption { type = types.submodule e; })
+    elements;
+
+  # attrset of categories, where values are module options with the type of the
+  # elements that belong to these categories
+  categories = with lib;
+    genAttrs
+      content-categories
+      (category:
+        (mapAttrs (_: e: mkOption { type = types.submodule e; })
+          # HACK: don't evaluate the submodule types, just grab the config directly
+          (filterAttrs (_: e: elem category (e { name = "dummy"; }).config.categories) elements))
+      );
+
+  global-attrs =
+    let
+      inherit (lib) mkOption types;
+    in
+    {
+      class = mkOption {
+        type = with types; listOf nonEmptyStr;
+      };
+      hidden = mkOption {
+        type = types.bool;
+      };
+      id = mkOption {
+        type = types.nonEmptyStr;
+      };
+      lang = mkOption {
+        # TODO: https://www.rfc-editor.org/rfc/rfc5646.html
+        type = types.str;
+      };
+      style = mkOption {
+        # TODO: CSS type ;..)
+        type = types.str;
+      };
+      title = mkOption {
+        type = types.lines;
+      };
+      # TODO: more global attributes
+      # https://html.spec.whatwg.org/#global-attributes
+      # https://html.spec.whatwg.org/#attr-aria-*
+      # https://html.spec.whatwg.org/multipage/microdata.html#encoding-microdata
+    };
+
+  mkAttrs = attrs: with lib; mkOption {
+    type = types.submodule {
+      options = global-attrs // attrs;
+    };
+    default = { };
+  };
+
+  print-element = name: attrs: content:
+    with lib;
+    let
+      attributes = join " " (mapAttrsToList
+        # TODO: this needs to be smarter for boolean attributes
+        #       where the value must be written out explicitly.
+        #       probably the attribute itself should have its own `__toString`.
+        (name: value: if isBool value then name else "${name}=${value}")
+        attrs);
+    in
+    lib.squash ''
+      <${name}${optionalString (stringLength attributes > 0) " ${attributes}"}>
+         ${lib.indent "  " content}
+      </${name}>
+    '';
+
+  elements = rec {
+    document = { ... }: {
+      imports = [ element ];
+      options = {
+        inherit (element-types) html;
+      };
+
+      config.categories = [ ];
+      config.__toString = self: ''
+        <!DOCTYPE HTML>
+        ${self.html}
+      '';
+    };
+
+    html = { name, ... }: {
+      imports = [ element ];
+      options = {
+        inherit (element-types) head body;
+      };
+
+      config.categories = [ ];
+      config.__toString = self: print-element name self.attrs ''
+        ${self.head}
+        ${self.body}
+      '';
+    };
+
+    head = { name, ... }: {
+      imports = [ element ];
+      options = with lib; {
+        # https://html.spec.whatwg.org/multipage/semantics.html#the-head-element:concept-element-content-model
+        # XXX: this doesn't implement the iframe srcdoc semantics
+        #      as those have questionable value and would complicate things a bit.
+        #      it should be possible though, by passing a flag via module arguments.
+        inherit (element-types) title;
+        base = mkOption {
+          type = with types; nullOr (submodule base);
+          default = null;
+        };
+        content = with types;
+          listOf (attrTag (
+            removeAttrs categories.metadata [ "title" "base" ]
+          ));
+      };
+
+      config.categories = [ ];
+      config.__toString = self: print-element name self.attrs ''
+        ${self.title}
+        ${with lib; optionalString (!isNull self.base) self.base}
+        ${join "\n" (map (s: "${s}") self.content)}
+      '';
+    };
+
+    title = { name, ... }: {
+      # TODO
+      config.categories = [ "metadata" ];
+
+    };
+    base = { name, ... }: {
+      # TODO
+      config.categories = [ "metadata" ];
+    };
+
+    body = { name, ... }: {
+      # TODO
+    };
+  };
+in
+elements