gen-docs.nix

with import ./. {};

let

    extraSources = [];
    lib = pkgs.lib;

    optionsListVisible =
        lib.filter (opt: opt.visible && !opt.internal)
        (lib.optionAttrSetToDocList options);

    # Replace functions by the string <function>
    substFunction = x:
        if builtins.isAttrs x then lib.mapAttrs (name: substFunction) x
        else if builtins.isList x then map substFunction x
        else if lib.isFunction x then "<function>"
        else if isPath x then toString x
        else x;

    isPath = x: (builtins.typeOf x) == "path";

    optionsListDesc = lib.flip map optionsListVisible (opt: opt // {
        description = let attempt = builtins.tryEval opt.description; in
            if attempt.success then attempt.value else "N/A";
        declarations = map stripAnyPrefixes opt.declarations;
        }
        // lib.optionalAttrs (opt ? example) {
            example = substFunction opt.example; }
        // lib.optionalAttrs (opt ? default) {
            default = substFunction opt.default; }
        // lib.optionalAttrs (opt ? type) {
            type = substFunction opt.type; }
        // lib.optionalAttrs
            (opt ? relatedPackages && opt.relatedPackages != []) {
                relatedPackages = genRelatedPackages opt.relatedPackages; }
        );

    genRelatedPackages = packages: let
        unpack = p: if lib.isString p then { name = p; }
                    else if lib.isList p then { path = p; }
                    else p;
        describe = args: let
            title = args.title or null;
            name = args.name or (lib.concatStringsSep "." args.path);
            path = args.path or [ args.name ];
            package = args.package or (lib.attrByPath path (throw
                "Invalid package attribute path '${toString path}'") pkgs);
            in "<listitem>"
            + "<para><literal>${lib.optionalString (title != null)
                "${title} aka "}pkgs.${name} (${package.meta.name})</literal>"
            + lib.optionalString (!package.meta.available)
                " <emphasis>[UNAVAILABLE]</emphasis>"
            + ": ${package.meta.description or "???"}.</para>"
            + lib.optionalString (args ? comment)
                "\n<para>${args.comment}</para>"
            + lib.optionalString (package.meta ? longDescription)
                "\n<programlisting>${package.meta.longDescription}"
                + "</programlisting>"
            + "</listitem>";
        in "<itemizedlist>${lib.concatStringsSep "\n" (map (p:
            describe (unpack p)) packages)}</itemizedlist>";

    optionLess = a: b:
        let
        ise = lib.hasPrefix "enable";
        isp = lib.hasPrefix "package";
        cmp = lib.splitByAndCompare ise lib.compare
            (lib.splitByAndCompare isp lib.compare lib.compare);
        in lib.compareLists cmp a.loc b.loc < 0;


    prefixesToStrip = map (p: "${toString p}/") ([ ../../.. ] ++ extraSources);
    stripAnyPrefixes = lib.flip (lib.fold lib.removePrefix) prefixesToStrip;

###############################################################################

    # This is the REAL meat of what we were after.
    # Output this however you want.
    optionsList = lib.sort optionLess optionsListDesc;

    optionsJSON = builtins.unsafeDiscardStringContext (builtins.toJSON
        (builtins.listToAttrs (map (o: {
            name = o.name;
            value = removeAttrs o [
            # Select the fields you want to drop here:
                "name" "visible" "internal" "loc" "readOnly" ];
        }) optionsList)));

in

    pkgs.writeText "options.json" optionsJSON