-module(gap).
-compile(no_auto_import).

-export([to_styled/1, compare_strings/2, compare_lists/2]).
-export_type([score/1]).

-type score(FFC) :: {score, integer(), gleam@option:option(FFC)}.

-spec to_styled(gap@comparison:comparison(any())) -> gap@styled_comparison:styled_comparison().
to_styled(Comparison) ->
    _pipe = Comparison,
    _pipe@1 = gap@styling:from_comparison(_pipe),
    _pipe@2 = gap@styling:highlight(
        _pipe@1,
        fun gap@styling:first_highlight_default/1,
        fun gap@styling:second_highlight_default/1,
        fun gap@styling:no_highlight/1
    ),
    gap@styling:to_styled_comparison(_pipe@2).

-spec compare_strings(binary(), binary()) -> gap@comparison:comparison(binary()).
compare_strings(First, Second) ->
    Comparison = compare_lists(
        gleam@string:to_graphemes(First),
        gleam@string:to_graphemes(Second)
    ),
    case Comparison of
        {list_comparison, First@1, Second@1} ->
            {string_comparison, First@1, Second@1};

        {string_comparison, First@2, Second@2} ->
            {string_comparison, First@2, Second@2}
    end.

-spec compare_lists(list(FFM), list(FFM)) -> gap@comparison:comparison(FFM).
compare_lists(First_sequence, Second_sequence) ->
    Diff_map@2 = begin
        _pipe = Second_sequence,
        gleam@list:index_fold(
            _pipe,
            gleam@map:new(),
            fun(Diff_map, Item_second, Index_second) ->
                _pipe@1 = First_sequence,
                gleam@list:index_fold(
                    _pipe@1,
                    Diff_map,
                    fun(Diff_map@1, Item_first, Index_first) ->
                        build_diff_map(
                            Item_first,
                            Index_first,
                            Item_second,
                            Index_second,
                            Diff_map@1
                        )
                    end
                )
            end
        )
    end,
    Tracking = begin
        _pipe@2 = back_track(
            Diff_map@2,
            gleam@list:length(First_sequence)
            - 1,
            gleam@list:length(Second_sequence)
            - 1,
            []
        ),
        gleam@map:from_list(_pipe@2)
    end,
    First_segments = collect_matches(
        Tracking,
        First_sequence,
        fun(Key) ->
            {First, _} = Key,
            First
        end
    ),
    Second_segments = collect_matches(
        Tracking,
        Second_sequence,
        fun(Key@1) ->
            {_, Second} = Key@1,
            Second
        end
    ),
    {list_comparison, First_segments, Second_segments}.

-spec collect_matches(
    gleam@map:map_({integer(), integer()}, any()),
    list(FFR),
    fun(({integer(), integer()}) -> integer())
) -> list(gap@comparison:match(list(FFR))).
collect_matches(Tracking, Str, Extract_fun) ->
    Matching_indexes = begin
        _pipe = gleam@map:keys(Tracking),
        _pipe@1 = gleam@list:map(_pipe, Extract_fun),
        gleam@set:from_list(_pipe@1)
    end,
    Matches = begin
        _pipe@2 = Str,
        gleam@list:index_map(
            _pipe@2,
            fun(Index, Item) ->
                case gleam@set:contains(Matching_indexes, Index) of
                    true ->
                        {match, Item};

                    false ->
                        {no_match, Item}
                end
            end
        )
    end,
    _pipe@3 = Matches,
    _pipe@4 = gleam@list:chunk(_pipe@3, fun(Match) -> case Match of
                {match, _} ->
                    true;

                {no_match, _} ->
                    false
            end end),
    gleam@list:map(_pipe@4, fun(Match_list) -> case Match_list of
                [{match, _} | _] ->
                    {match,
                        gleam@list:filter_map(
                            Match_list,
                            fun(Match@1) -> case Match@1 of
                                    {match, Item@1} ->
                                        {ok, Item@1};

                                    {no_match, _} ->
                                        {error, nil}
                                end end
                        )};

                [{no_match, _} | _] ->
                    {no_match,
                        gleam@list:filter_map(
                            Match_list,
                            fun(Match@2) -> case Match@2 of
                                    {no_match, Item@2} ->
                                        {ok, Item@2};

                                    {match, _} ->
                                        {error, nil}
                                end end
                        )}
            end end).

-spec back_track(
    gleam@map:map_({integer(), integer()}, score(FFV)),
    integer(),
    integer(),
    list({{integer(), integer()}, FFV})
) -> list({{integer(), integer()}, FFV}).
back_track(Diff_map, First_index, Second_index, Stack) ->
    case (First_index =:= 0) orelse (Second_index =:= 0) of
        true ->
            This_score = begin
                _pipe = gleam@map:get(Diff_map, {First_index, Second_index}),
                gleam@result:unwrap(_pipe, {score, 0, none})
            end,
            case This_score of
                {score, _, {some, Item}} ->
                    [{{First_index, Second_index}, Item} | Stack];

                _ ->
                    case {First_index, Second_index} of
                        {0, A} when A > 0 ->
                            back_track(
                                Diff_map,
                                First_index,
                                Second_index
                                - 1,
                                Stack
                            );

                        {A@1, 0} when A@1 > 0 ->
                            back_track(
                                Diff_map,
                                First_index
                                - 1,
                                Second_index,
                                Stack
                            );

                        {0, 0} ->
                            Stack;

                        {_, _} ->
                            back_track(
                                Diff_map,
                                First_index
                                - 1,
                                Second_index,
                                Stack
                            )
                    end
            end;

        false ->
            This_score@1 = begin
                _pipe@1 = gleam@map:get(Diff_map, {First_index, Second_index}),
                gleam@result:unwrap(_pipe@1, {score, 0, none})
            end,
            case This_score@1 of
                {score, _, {some, Item@1}} ->
                    back_track(
                        Diff_map,
                        First_index
                        - 1,
                        Second_index
                        - 1,
                        [{{First_index, Second_index}, Item@1} | Stack]
                    );

                {score, _, none} ->
                    Up = begin
                        _pipe@2 = gleam@map:get(
                            Diff_map,
                            {First_index, Second_index - 1}
                        ),
                        gleam@result:unwrap(_pipe@2, {score, 0, none})
                    end,
                    Back = begin
                        _pipe@3 = gleam@map:get(
                            Diff_map,
                            {First_index - 1, Second_index}
                        ),
                        gleam@result:unwrap(_pipe@3, {score, 0, none})
                    end,
                    case gleam@int:compare(
                        erlang:element(2, Up),
                        erlang:element(2, Back)
                    ) of
                        gt ->
                            back_track(
                                Diff_map,
                                First_index,
                                Second_index
                                - 1,
                                Stack
                            );

                        lt ->
                            back_track(
                                Diff_map,
                                First_index
                                - 1,
                                Second_index,
                                Stack
                            );

                        eq ->
                            case {First_index, Second_index} of
                                {0, A@2} when A@2 > 0 ->
                                    back_track(
                                        Diff_map,
                                        First_index,
                                        Second_index
                                        - 1,
                                        Stack
                                    );

                                {A@3, 0} when A@3 > 0 ->
                                    back_track(
                                        Diff_map,
                                        First_index
                                        - 1,
                                        Second_index,
                                        Stack
                                    );

                                {0, 0} ->
                                    Stack;

                                {_, _} ->
                                    back_track(
                                        Diff_map,
                                        First_index
                                        - 1,
                                        Second_index,
                                        Stack
                                    )
                            end
                    end
            end
    end.

-spec build_diff_map(
    FGB,
    integer(),
    FGB,
    integer(),
    gleam@map:map_({integer(), integer()}, score(FGB))
) -> gleam@map:map_({integer(), integer()}, score(FGB)).
build_diff_map(First_item, First_index, Second_item, Second_index, Diff_map) ->
    Prev_score = begin
        _pipe = gleam@map:get(Diff_map, {First_index - 1, Second_index - 1}),
        gleam@result:unwrap(_pipe, {score, 0, none})
    end,
    Derived_score_up = begin
        _pipe@1 = Diff_map,
        _pipe@2 = gleam@map:get(_pipe@1, {First_index, Second_index - 1}),
        gleam@result:unwrap(_pipe@2, {score, 0, none})
    end,
    Derived_score_back = begin
        _pipe@3 = Diff_map,
        _pipe@4 = gleam@map:get(_pipe@3, {First_index - 1, Second_index}),
        gleam@result:unwrap(_pipe@4, {score, 0, none})
    end,
    Derived_score = gleam@int:max(
        erlang:element(2, Derived_score_up),
        erlang:element(2, Derived_score_back)
    ),
    This_score = case First_item =:= Second_item of
        true ->
            {score, erlang:element(2, Prev_score) + 1, {some, First_item}};

        false ->
            {score, Derived_score, none}
    end,
    _pipe@5 = Diff_map,
    gleam@map:insert(_pipe@5, {First_index, Second_index}, This_score).