-module(facet).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([parse/1]).
-export_type([error/0, frontmatter/0, document/0]).

-type error() :: empty | {parse_error, binary()}.

-type frontmatter() :: {toml, binary()} | {json, binary()} | {yaml, binary()}.

-type document() :: {document, gleam@option:option(frontmatter()), binary()}.

-file("/home/blu/git/ssg/facet/src/facet.gleam", 22).
-spec grab_frontmatter(
    list(binary()),
    list(binary()),
    fun((binary()) -> frontmatter()),
    binary()
) -> {ok, document()} | {error, error()}.
grab_frontmatter(Input, Frontmatter, Format_constructor, Delimiter) ->
    case Input of
        [] ->
            {error, {parse_error, <<"expected ending delimitor"/utf8>>}};

        [Line | Rest] when Line =:= Delimiter ->
            Final_content = case Delimiter of
                <<"}"/utf8>> ->
                    gleam@string:join(
                        lists:append(Frontmatter, [<<"}"/utf8>>]),
                        <<"\n"/utf8>>
                    );

                _ ->
                    gleam@string:join(Frontmatter, <<"\n"/utf8>>)
            end,
            {ok,
                {document,
                    {some, Format_constructor(Final_content)},
                    gleam@string:join(Rest, <<"\n"/utf8>>)}};

        [Line@1 | Rest@1] ->
            grab_frontmatter(
                Rest@1,
                lists:append(Frontmatter, [Line@1]),
                Format_constructor,
                Delimiter
            )
    end.

-file("/home/blu/git/ssg/facet/src/facet.gleam", 55).
-spec parse(binary()) -> {ok, document()} | {error, error()}.
parse(In) ->
    Lines = begin
        _pipe = In,
        gleam@string:split(_pipe, <<"\n"/utf8>>)
    end,
    case Lines of
        [] ->
            {error, empty};

        [<<"+++"/utf8>> | Rest] ->
            grab_frontmatter(
                Rest,
                [],
                fun(Field@0) -> {toml, Field@0} end,
                <<"+++"/utf8>>
            );

        [<<"{"/utf8>> | Rest@1] ->
            grab_frontmatter(
                Rest@1,
                [<<"{"/utf8>>],
                fun(Field@0) -> {json, Field@0} end,
                <<"}"/utf8>>
            );

        [<<"---"/utf8>> | Rest@2] ->
            grab_frontmatter(
                Rest@2,
                [],
                fun(Field@0) -> {yaml, Field@0} end,
                <<"---"/utf8>>
            );

        Rest@3 ->
            {ok, {document, none, gleam@string:join(Rest@3, <<"\n"/utf8>>)}}
    end.