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+# Copyright © 2021 sterni
+# SPDX-License-Identifier: MIT
+#
+# This file provides a cursed HTML DSL for nix which works by overloading
+# the NIX_PATH lookup operation via angle bracket operations, e. g. `<nixpkgs>`.
+
+{ ... }:
+
+let
+  /* Escape everything we have to escape in an HTML document if either
+     in a normal context or an attribute string (`<>&"'`).
+
+     A shorthand for this function called `esc` is also provided.
+
+     Type: string -> string
+
+     Example:
+
+     escapeMinimal "<hello>"
+     => "&lt;hello&gt;"
+  */
+  escapeMinimal = builtins.replaceStrings
+    [ "<"    ">"    "&"     "\""     "'"      ]
+    [ "&lt;" "&gt;" "&amp;" "&quot;" "&#039;" ];
+
+  /* Return a string with a correctly rendered tag of the given name,
+     with the given attributes which are automatically escaped.
+
+     If the content argument is `null`, the tag will have no children nor a
+     closing element. If the content argument is a string it is used as the
+     content as is (unescaped). If the content argument is a list, its
+     elements are concatenated.
+
+     `renderTag` is only an internal function which is reexposed as `__findFile`
+     to allow for much neater syntax than calling `renderTag` everywhere:
+
+     ```nix
+     { depot, ... }:
+     let
+       inherit (depot.users.sterni.nix.html) __findFile esc;
+     in
+
+     <html> {} [
+       (<head> {} (<title> {} (esc "hello world")))
+       (<body> {} [
+         (<h1> {} (esc "hello world"))
+         (<p> {} (esc "foo bar"))
+       ])
+     ]
+
+     ```
+
+     As you can see, the need to call a function disappears, instead the
+     `NIX_PATH` lookup operation via `<foo>` is overloaded, so it becomes
+     `renderTag "foo"` automatically.
+
+     Since the content argument may contain the result of other `renderTag`
+     calls, we can't escape it automatically. Instead this must be done manually
+     using `esc`.
+
+     Type: string -> attrs<string> -> (list<string> | string | null) -> string
+
+     Example:
+
+     <link> {
+       rel = "stylesheet";
+       href = "/css/main.css";
+       type = "text/css";
+     } null
+
+     renderTag "link" {
+       rel = "stylesheet";
+       href = "/css/main.css";
+       type = "text/css";
+     } null
+
+     => "<link href=\"/css/main.css\" rel=\"stylesheet\" type=\"text/css\"/>"
+
+     <p> {} [
+       "foo "
+       (<strong> {} "bar")
+     ]
+
+     renderTag "p" {} "foo <strong>bar</strong>"
+     => "<p>foo <strong>bar</strong></p>"
+  */
+  renderTag = tag: attrs: content:
+    let
+      attrs' = builtins.concatStringsSep "" (
+        builtins.map (n:
+          " ${escapeMinimal n}=\"${escapeMinimal (toString attrs.${n})}\""
+        ) (builtins.attrNames attrs)
+      );
+      content' =
+        if builtins.isList content
+        then builtins.concatStringsSep "" content
+        else content;
+    in
+      if content == null
+      then "<${tag}${attrs'}/>"
+      else "<${tag}${attrs'}>${content'}</${tag}>";
+
+  /* Prepend "<!DOCTYPE html>" to a string.
+
+     Type: string -> string
+
+     Example:
+
+     withDoctype (<body> {} (esc "hello"))
+     => "<!DOCTYPE html><body>hello</body>"
+  */
+  withDoctype = doc: "<!DOCTYPE html>" + doc;
+
+in {
+  inherit escapeMinimal renderTag withDoctype;
+
+  __findFile = _: renderTag;
+  esc = escapeMinimal;
+}