lix-releng-staging/doc/manual/generate-manpage.nix

let
  inherit (builtins)
    attrNames
    attrValues
    fromJSON
    listToAttrs
    mapAttrs
    concatStringsSep
    concatMap
    length
    lessThan
    replaceStrings
    sort
    ;
  inherit (import ./utils.nix)
    concatStrings
    optionalString
    filterAttrs
    trim
    squash
    unique
    showSettings
    ;
in

inlineHTML: commandDump:

let

  commandInfo = fromJSON commandDump;

  showCommand =
    {
      command,
      details,
      filename,
      toplevel,
    }:
    let

      result = ''
        > **Warning** \
        > This program is
        > [**experimental**](@docroot@/contributing/experimental-features.md#xp-feature-nix-command)
        > and its interface is subject to change.

        # Name

        `${command}` - ${details.description}

        # Synopsis

        ${showSynopsis command details.args}

        ${maybeSubcommands}

        ${maybeStoreDocs}

        ${maybeOptions}
      '';

      showSynopsis =
        command: args:
        let
          showArgument = arg: "*${arg.label}*" + optionalString (!arg ? arity) "...";
          arguments = concatStringsSep " " (map showArgument args);
        in
        ''
          `${command}` [*option*...] ${arguments}
        '';

      maybeSubcommands = optionalString (details ? commands && details.commands != { }) ''
        where *subcommand* is one of the following:

        ${subcommands}
      '';

      subcommands = if length categories > 1 then listCategories else listSubcommands details.commands;

      categories = sort (x: y: x.id < y.id) (
        unique (map (cmd: cmd.category) (attrValues details.commands))
      );

      listCategories = concatStrings (map showCategory categories);

      showCategory = cat: ''
        **${toString cat.description}:**

        ${listSubcommands (filterAttrs (n: v: v.category == cat) details.commands)}
      '';

      listSubcommands = cmds: concatStrings (attrValues (mapAttrs showSubcommand cmds));

      showSubcommand = name: subcmd: ''
        * [`${command} ${name}`](./${appendName filename name}.md) - ${subcmd.description}
      '';

      # TODO: move this confusing special case out of here when implementing #8496
      maybeStoreDocs = optionalString (details ? doc) (
        replaceStrings [ "@stores@" ] [ storeDocs ] details.doc
      );

      maybeOptions = optionalString (details.flags != { }) ''
        # Options

        ${showOptions details.flags toplevel.flags}

        > **Note**
        >
        > See [`man nix.conf`](@docroot@/command-ref/conf-file.md#command-line-flags) for overriding configuration settings with command line flags.
      '';

      showOptions =
        options: commonOptions:
        let
          allOptions = options // commonOptions;
          showCategory = cat: ''
            ${optionalString (cat != "") "**${cat}:**"}

            ${listOptions (filterAttrs (n: v: v.category == cat) allOptions)}
          '';
          listOptions = opts: concatStringsSep "\n" (attrValues (mapAttrs showOption opts));
          showOption =
            name: option:
            let
              result = trim ''
                - ${item}
                  ${option.description}
              '';
              item =
                if inlineHTML then
                  ''<span id="opt-${name}">[`--${name}`](#opt-${name})</span> ${shortName} ${labels}''
                else
                  "`--${name}` ${shortName} ${labels}";
              shortName = optionalString (option ? shortName) ("/ `-${option.shortName}`");
              labels = optionalString (option ? labels) (concatStringsSep " " (map (s: "*${s}*") option.labels));
            in
            result;
          categories = sort lessThan (unique (map (cmd: cmd.category) (attrValues allOptions)));
        in
        concatStrings (map showCategory categories);
    in
    squash result;

  appendName = filename: name: (if filename == "nix" then "nix3" else filename) + "-" + name;

  processCommand =
    {
      command,
      details,
      filename,
      toplevel,
    }:
    let
      cmd = {
        inherit command;
        name = filename + ".md";
        value = showCommand {
          inherit
            command
            details
            filename
            toplevel
            ;
        };
      };
      subcommand =
        subCmd:
        processCommand {
          command = command + " " + subCmd;
          details = details.commands.${subCmd};
          filename = appendName filename subCmd;
          inherit toplevel;
        };
    in
    [ cmd ] ++ concatMap subcommand (attrNames details.commands or { });

  manpages = processCommand {
    command = "nix";
    details = commandInfo.args;
    filename = "nix";
    toplevel = commandInfo.args;
  };

  storeDocs =
    let
      showStore =
        name:
        {
          settings,
          doc,
          experimentalFeature,
        }:
        let
          experimentalFeatureNote = optionalString (experimentalFeature != null) ''
            > **Warning**
            > This store is part of an
            > [experimental feature](@docroot@/contributing/experimental-features.md).

            To use this store, you need to make sure the corresponding experimental feature,
            [`${experimentalFeature}`](@docroot@/contributing/experimental-features.md#xp-feature-${experimentalFeature}),
            is enabled.
            For example, include the following in [`nix.conf`](@docroot@/command-ref/conf-file.md):

            ```
            extra-experimental-features = ${experimentalFeature}
            ```
          '';
        in
        ''
          ## ${name}

          ${doc}

          ${experimentalFeatureNote}

          **Settings**:

          ${showSettings { inherit inlineHTML; } settings}
        '';
    in
    concatStrings (attrValues (mapAttrs showStore commandInfo.stores));
in
listToAttrs manpages