-module(mongo@cursor).
-compile([no_auto_import, nowarn_unused_vars]).

-export([new/3, next/1, to_list/1]).
-export_type([cursor/0]).

-opaque cursor() :: {cursor,
        mongo@client:collection(),
        integer(),
        integer(),
        gleam@iterator:iterator(bson@value:value())}.

-spec new(mongo@client:collection(), integer(), list(bson@value:value())) -> cursor().
new(Collection, Id, Batch) ->
    {cursor,
        Collection,
        Id,
        gleam@list:length(Batch),
        gleam@iterator:from_list(Batch)}.

-spec get_more(cursor()) -> {ok, cursor()} | {error, mongo@utils:mongo_error()}.
get_more(Cursor) ->
    case mongo@client:get_more(
        erlang:element(2, Cursor),
        erlang:element(3, Cursor),
        erlang:element(4, Cursor)
    ) of
        {ok, Result} ->
            [{<<"cursor"/utf8>>, {document, Result@1}}, {<<"ok"/utf8>>, Ok}] = Result,
            _assert_subject = gleam@list:key_find(Result@1, <<"id"/utf8>>),
            {ok, {int64, Id}} = case _assert_subject of
                {ok, {int64, _}} -> _assert_subject;
                _assert_fail ->
                    erlang:error(#{gleam_error => let_assert,
                                message => <<"Assertion pattern match failed"/utf8>>,
                                value => _assert_fail,
                                module => <<"mongo/cursor"/utf8>>,
                                function => <<"get_more"/utf8>>,
                                line => 76})
            end,
            _assert_subject@1 = gleam@list:key_find(
                Result@1,
                <<"nextBatch"/utf8>>
            ),
            {ok, {array, Batch}} = case _assert_subject@1 of
                {ok, {array, _}} -> _assert_subject@1;
                _assert_fail@1 ->
                    erlang:error(#{gleam_error => let_assert,
                                message => <<"Assertion pattern match failed"/utf8>>,
                                value => _assert_fail@1,
                                module => <<"mongo/cursor"/utf8>>,
                                function => <<"get_more"/utf8>>,
                                line => 77})
            end,
            case Ok of
                {double, 1.0} ->
                    _pipe = new(erlang:element(2, Cursor), Id, Batch),
                    {ok, _pipe};

                _ ->
                    {error, {mongo_error, -16, <<""/utf8>>, null}}
            end;

        {error, {Code, Msg}} ->
            {error, {mongo_error, Code, Msg, null}}
    end.

-spec next(cursor()) -> {gleam@option:option(bson@value:value()), cursor()}.
next(Cursor) ->
    case gleam@iterator:step(erlang:element(5, Cursor)) of
        {next, Doc, Rest} ->
            {{some, Doc},
                {cursor,
                    erlang:element(2, Cursor),
                    erlang:element(3, Cursor),
                    erlang:element(4, Cursor),
                    Rest}};

        done ->
            case erlang:element(3, Cursor) of
                0 ->
                    {none,
                        {cursor,
                            erlang:element(2, Cursor),
                            0,
                            erlang:element(4, Cursor),
                            gleam@iterator:empty()}};

                _ ->
                    _assert_subject = get_more(Cursor),
                    {ok, New_cursor} = 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 => <<"mongo/cursor"/utf8>>,
                                        function => <<"next"/utf8>>,
                                        line => 34})
                    end,
                    case gleam@iterator:step(erlang:element(5, New_cursor)) of
                        {next, Doc@1, Rest@1} ->
                            {{some, Doc@1},
                                {cursor,
                                    erlang:element(2, Cursor),
                                    erlang:element(3, New_cursor),
                                    erlang:element(4, New_cursor),
                                    Rest@1}};

                        done ->
                            {none,
                                {cursor,
                                    erlang:element(2, Cursor),
                                    erlang:element(3, New_cursor),
                                    erlang:element(4, New_cursor),
                                    gleam@iterator:empty()}}
                    end
            end
    end.

-spec to_list_internal(cursor(), list(bson@value:value())) -> list(bson@value:value()).
to_list_internal(Cursor, Storage) ->
    case next(Cursor) of
        {{some, Next}, New_cursor} ->
            to_list_internal(New_cursor, gleam@list:append(Storage, [Next]));

        {none, _} ->
            Storage
    end.

-spec to_list(cursor()) -> list(bson@value:value()).
to_list(Cursor) ->
    to_list_internal(Cursor, []).