-module(pig@skill).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/pig/skill.gleam").
-export([parse_frontmatter/1, load/1, skill_to_system_fragment/1]).
-export_type([skill/0, skill_error/0, frontmatter/0]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC(
    " Skill loading and parsing.\n"
    "\n"
    " A Skill is a directory on disk containing a `SKILL.md` file with\n"
    " YAML frontmatter (name + description) and a markdown body.\n"
    "\n"
    " Frontmatter parsing is deliberately simple: split on `---` delimiters,\n"
    " extract `name` and `description` fields from the YAML-like block.\n"
    " No full YAML parser needed.\n"
).

-type skill() :: {skill, binary(), binary(), binary(), list(binary())}.

-type skill_error() :: skill_not_found | invalid_frontmatter.

-type frontmatter() :: {frontmatter, binary(), binary(), binary()}.

-file("src/pig/skill.gleam", 126).
?DOC(
    " List supplementary files in a skill directory (excluding SKILL.md).\n"
    " Returns relative paths from the skill directory.\n"
).
-spec list_files(binary()) -> list(binary()).
list_files(Path) ->
    case simplifile_erl:read_directory(Path) of
        {ok, Entries} ->
            _pipe = Entries,
            _pipe@1 = gleam@list:filter(
                _pipe,
                fun(E) -> E /= <<"SKILL.md"/utf8>> end
            ),
            gleam@list:filter(
                _pipe@1,
                fun(E@1) ->
                    Full = <<<<Path/binary, "/"/utf8>>/binary, E@1/binary>>,
                    case simplifile_erl:is_file(Full) of
                        {ok, true} ->
                            true;

                        _ ->
                            false
                    end
                end
            );

        {error, _} ->
            []
    end.

-file("src/pig/skill.gleam", 69).
?DOC(" Walk frontmatter lines collecting name/description accumulators.\n").
-spec parse_lines(list(binary()), binary(), binary(), boolean()) -> {ok,
        frontmatter()} |
    {error, skill_error()}.
parse_lines(Lines, Acc_name, Acc_desc, In_fm) ->
    case Lines of
        [] ->
            {error, invalid_frontmatter};

        [<<"---"/utf8>> | Rest] when In_fm ->
            Body = gleam@string:join(Rest, <<"\n"/utf8>>),
            case {Acc_name, Acc_desc} of
                {<<""/utf8>>, _} ->
                    {error, invalid_frontmatter};

                {_, <<""/utf8>>} ->
                    {error, invalid_frontmatter};

                {_, _} ->
                    {ok,
                        {frontmatter,
                            gleam@string:trim(Acc_name),
                            gleam@string:trim(Acc_desc),
                            Body}}
            end;

        [Line | Rest@1] when In_fm ->
            Parts = gleam@string:split(Line, <<": "/utf8>>),
            case Parts of
                [Key, Value] ->
                    New_name = case Key of
                        <<"name"/utf8>> ->
                            Value;

                        _ ->
                            Acc_name
                    end,
                    New_desc = case Key of
                        <<"description"/utf8>> ->
                            Value;

                        _ ->
                            Acc_desc
                    end,
                    parse_lines(Rest@1, New_name, New_desc, true);

                _ ->
                    parse_lines(Rest@1, Acc_name, Acc_desc, true)
            end;

        _ ->
            {error, invalid_frontmatter}
    end.

-file("src/pig/skill.gleam", 61).
?DOC(
    " Parse frontmatter from a SKILL.md content string.\n"
    "\n"
    " Expects `---\\n` at start, content between delimiters, and closing `---\\n`.\n"
    " Extracts `name:` and `description:` fields. Returns remaining body after\n"
    " the closing delimiter.\n"
    "\n"
    " This is a simple parser — not a full YAML parser. It handles:\n"
    " - `key: value` lines\n"
).
-spec parse_frontmatter(binary()) -> {ok, frontmatter()} |
    {error, skill_error()}.
parse_frontmatter(Raw) ->
    case gleam@string:split(Raw, <<"\n"/utf8>>) of
        [<<"---"/utf8>> | Rest] ->
            parse_lines(Rest, <<""/utf8>>, <<""/utf8>>, true);

        _ ->
            {error, invalid_frontmatter}
    end.

-file("src/pig/skill.gleam", 34).
?DOC(
    " Load a skill from a directory path.\n"
    "\n"
    " Reads `SKILL.md` from the directory, parses frontmatter for name/description,\n"
    " and lists supplementary files (everything except `SKILL.md`).\n"
).
-spec load(binary()) -> {ok, skill()} | {error, skill_error()}.
load(Path) ->
    Skill_md_path = <<Path/binary, "/SKILL.md"/utf8>>,
    case simplifile:read(Skill_md_path) of
        {ok, Content} ->
            case parse_frontmatter(Content) of
                {ok, Fm} ->
                    {ok,
                        {skill,
                            erlang:element(2, Fm),
                            erlang:element(3, Fm),
                            Path,
                            list_files(Path)}};

                {error, E} ->
                    {error, E}
            end;

        {error, _} ->
            {error, skill_not_found}
    end.

-file("src/pig/skill.gleam", 114).
?DOC(
    " Generate a system prompt fragment from a skill.\n"
    "\n"
    " Used to inject skill descriptions into the system prompt so the agent\n"
    " knows what skills are available.\n"
).
-spec skill_to_system_fragment(skill()) -> binary().
skill_to_system_fragment(Skill) ->
    <<<<<<<<<<<<"Skill: "/utf8, (erlang:element(2, Skill))/binary>>/binary,
                        "\nDescription: "/utf8>>/binary,
                    (erlang:element(3, Skill))/binary>>/binary,
                "\nPath: "/utf8>>/binary,
            (erlang:element(4, Skill))/binary>>/binary,
        "\n"/utf8>>.