{ lib, ... }:
let
  inherit (lib)
    mkOption
    types
    ;
in
{
  content-types.document = { name, config, link, ... }: {
    config._module.args.link = config.link;
    options = {
      name = mkOption {
        description = "Symbolic name, used as a human-readable identifier";
        type = types.str;
        default = name;
      };
      # TODO: reconsider using `page.outPath` and what to put into `locations`.
      #       maybe we can avoid having ".html" suffixes there.
      #       since templates can output multiple files, `html` is merely one of many things we *could* produce.
      # TODO: make `apply` configurable so one can programmatically modify locations
      locations = mkOption {
        description = ''
          List of historic output locations for the resulting file

          The first element is the canonical location.
          All other elements are used to create redirects to the canonical location.
        '';
        type = with types; nonEmptyListOf str;
      };
      link = mkOption {
        description = "Helper function for transparent linking to other pages";
        type = with types; functionTo str;
        default = target: with lib; relativePath (head config.locations) (head target.locations);
      };
      # TODO: may not need it when using `link`; could repurpose it to render the default template
      outPath = mkOption {
        description = ''
          Location of the page, used for transparently creating links
        '';
        type = types.str;
        default = lib.head config.locations;
      };
      outputs = mkOption {
        description = ''
          Representations of the document in different formats
        '';
        type = with types; attrsOf str;
      };
    };
  };
}