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

-export([syntax_highlighter/1, line_class/2, block_class/2, syntax_highlight/2]).
-export_type([config/0, syntax_highlighting_error/0, highlight_event/0]).

-opaque config() :: {config, binary(), binary(), binary()}.

-type syntax_highlighting_error() :: {unsupported_language, binary()} |
    tree_sitter_error |
    unmatched_highlight_events.

-type highlight_event() :: {highlight_start, integer()} |
    {source, integer(), integer()} |
    highlight_end.

-spec syntax_highlighter(binary()) -> config().
syntax_highlighter(Language) ->
    {config, Language, <<"line"/utf8>>, <<""/utf8>>}.

-spec line_class(config(), binary()) -> config().
line_class(Config, Class) ->
    erlang:setelement(3, Config, Class).

-spec block_class(config(), binary()) -> config().
block_class(Config, Class) ->
    erlang:setelement(4, Config, Class).

-spec parse_highlights(list(integer())) -> {binary(), list(integer())}.
parse_highlights(Highlights) ->
    case Highlights of
        [Highlight | Rest_of_highlights] ->
            {libglimra:get_highlight_name(Highlight), Rest_of_highlights};

        [] ->
            {<<""/utf8>>, []}
    end.

-spec prepend_with_snippet(
    list(lustre@internals@vdom:element(nil)),
    binary(),
    binary()
) -> list(lustre@internals@vdom:element(nil)).
prepend_with_snippet(Siblings, Highlight_name, Snippet) ->
    case gleam@string:is_empty(Snippet) of
        true ->
            Siblings;

        false ->
            [lustre@element@html:span(
                    [lustre@attribute:class(Highlight_name)],
                    [lustre@element@html:text(Snippet)]
                ) |
                Siblings]
    end.

-spec prepend_with_linebreak(
    config(),
    list(lustre@internals@vdom:element(nil)),
    list(lustre@internals@vdom:element(nil))
) -> list(lustre@internals@vdom:element(nil)).
prepend_with_linebreak(Config, Siblings, Children) ->
    [lustre@element@html:span(
            [lustre@attribute:class(erlang:element(3, Config))],
            lists:reverse(Children)
        ) |
        Siblings].

-spec do_syntax_highlight(
    binary(),
    list(highlight_event()),
    config(),
    list(lustre@internals@vdom:element(nil)),
    list(lustre@internals@vdom:element(nil)),
    list(integer()),
    binary()
) -> {ok, list(lustre@internals@vdom:element(nil))} |
    {error, syntax_highlighting_error()}.
do_syntax_highlight(
    Source,
    Events,
    Config,
    Code_block,
    Code_row,
    Highlights,
    Snippet
) ->
    {Highlight_name, Rest_of_highlights} = parse_highlights(Highlights),
    case Events of
        [Event | Rest] ->
            case Event of
                {highlight_start, Highlight_type} ->
                    case Snippet of
                        <<""/utf8>> ->
                            do_syntax_highlight(
                                Source,
                                Rest,
                                Config,
                                Code_block,
                                Code_row,
                                [Highlight_type | Highlights],
                                Snippet
                            );

                        _ ->
                            do_syntax_highlight(
                                Source,
                                Rest,
                                Config,
                                Code_block,
                                prepend_with_snippet(
                                    Code_row,
                                    Highlight_name,
                                    Snippet
                                ),
                                [Highlight_type | Highlights],
                                <<""/utf8>>
                            )
                    end;

                highlight_end ->
                    case gleam@string:is_empty(Highlight_name) andalso gleam@list:is_empty(
                        Rest_of_highlights
                    ) of
                        true ->
                            {error, unmatched_highlight_events};

                        false ->
                            do_syntax_highlight(
                                Source,
                                Rest,
                                Config,
                                Code_block,
                                prepend_with_snippet(
                                    Code_row,
                                    Highlight_name,
                                    Snippet
                                ),
                                Rest_of_highlights,
                                <<""/utf8>>
                            )
                    end;

                {source, Start, End} ->
                    New_snippet = gleam@string:slice(Source, Start, End - Start),
                    case gleam_stdlib:contains_string(
                        New_snippet,
                        <<"\n"/utf8>>
                    ) of
                        true ->
                            _assert_subject = gleam@string:split_once(
                                New_snippet,
                                <<"\n"/utf8>>
                            ),
                            {ok, {Before_linebreak, After_linebreak}} = case _assert_subject of
                                {ok, {_, _}} -> _assert_subject;
                                _assert_fail ->
                                    erlang:error(#{gleam_error => let_assert,
                                                message => <<"Assertion pattern match failed"/utf8>>,
                                                value => _assert_fail,
                                                module => <<"glimra"/utf8>>,
                                                function => <<"do_syntax_highlight"/utf8>>,
                                                line => 183})
                            end,
                            do_syntax_highlight(
                                Source,
                                Rest,
                                Config,
                                prepend_with_linebreak(
                                    Config,
                                    Code_block,
                                    prepend_with_snippet(
                                        Code_row,
                                        Highlight_name,
                                        <<Snippet/binary,
                                            Before_linebreak/binary>>
                                    )
                                ),
                                prepend_with_snippet(
                                    [],
                                    Highlight_name,
                                    After_linebreak
                                ),
                                Highlights,
                                <<""/utf8>>
                            );

                        false ->
                            do_syntax_highlight(
                                Source,
                                Rest,
                                Config,
                                Code_block,
                                Code_row,
                                Highlights,
                                <<Snippet/binary, New_snippet/binary>>
                            )
                    end
            end;

        [] ->
            {ok,
                prepend_with_linebreak(
                    Config,
                    Code_block,
                    prepend_with_snippet(Code_row, Highlight_name, Snippet)
                )}
    end.

-spec syntax_highlight(config(), binary()) -> {ok,
        lustre@internals@vdom:element(nil)} |
    {error, syntax_highlighting_error()}.
syntax_highlight(Config, Source) ->
    Language = gleam@string:lowercase(erlang:element(2, Config)),
    Language_supported = gleam@list:contains(
        libglimra:get_supported_languages(),
        Language
    ),
    gleam@bool:guard(
        not Language_supported,
        {error, {unsupported_language, Language}},
        fun() ->
            gleam@result:'try'(
                begin
                    _pipe = libglimra:get_highlight_events(Source, Language),
                    gleam@result:replace_error(_pipe, tree_sitter_error)
                end,
                fun(Events) ->
                    gleam@result:'try'(
                        do_syntax_highlight(
                            Source,
                            Events,
                            Config,
                            [],
                            [],
                            [],
                            <<""/utf8>>
                        ),
                        fun(Reversed_lines) ->
                            {ok,
                                lustre@element@html:code(
                                    [lustre@attribute:class(
                                            erlang:element(4, Config)
                                        )],
                                    lists:reverse(Reversed_lines)
                                )}
                        end
                    )
                end
            )
        end
    ).