-module(gleam@iterator).
-compile(no_auto_import).

-export([unfold/2, repeatedly/1, repeat/1, from_list/1, fold/3, run/1, to_list/1, step/1, take/2, drop/2, map/2, append/2, flatten/1, flat_map/2, filter/2, cycle/1, range/2, find/2, index/1, iterate/2, take_while/2, drop_while/2, scan/3, zip/2, chunk/2, sized_chunk/2, intersperse/2, any/2, all/2, group/2, reduce/2, last/1, empty/0, once/1, single/1, interleave/2, fold_until/3, try_fold/3, first/1, at/2]).
-export_type([action/1, iterator/1, step/2, chunk/2, sized_chunk/1]).

-type action(BIV) :: stop | {continue, BIV, fun(() -> action(BIV))}.

-opaque iterator(BIW) :: {iterator, fun(() -> action(BIW))}.

-type step(BIX, BIY) :: {next, BIX, BIY} | done.

-type chunk(BIZ, BJA) :: {another_by,
                          list(BIZ),
                          BJA,
                          BIZ,
                          fun(() -> action(BIZ))} |
    {last_by, list(BIZ)}.

-type sized_chunk(BJB) :: {another, list(BJB), fun(() -> action(BJB))} |
    {last, list(BJB)} |
    no_more.

-spec stop() -> action(any()).
stop() ->
    stop.

-spec do_unfold(BJG, fun((BJG) -> step(BJH, BJG))) -> fun(() -> action(BJH)).
do_unfold(Initial, F) ->
    fun() -> case F(Initial) of
            {next, X, Acc} ->
                {continue, X, do_unfold(Acc, F)};

            done ->
                stop
        end end.

-spec unfold(BJL, fun((BJL) -> step(BJM, BJL))) -> iterator(BJM).
unfold(Initial, F) ->
    _pipe = Initial,
    _pipe@1 = do_unfold(_pipe, F),
    {iterator, _pipe@1}.

-spec repeatedly(fun(() -> BJQ)) -> iterator(BJQ).
repeatedly(F) ->
    unfold(nil, fun(_) -> {next, F(), nil} end).

-spec repeat(BJS) -> iterator(BJS).
repeat(X) ->
    repeatedly(fun() -> X end).

-spec from_list(list(BJU)) -> iterator(BJU).
from_list(List) ->
    Yield = fun(Acc) -> case Acc of
            [] ->
                done;

            [Head | Tail] ->
                {next, Head, Tail}
        end end,
    unfold(List, Yield).

-spec do_fold(fun(() -> action(BJX)), fun((BJZ, BJX) -> BJZ), BJZ) -> BJZ.
do_fold(Continuation, F, Accumulator) ->
    case Continuation() of
        {continue, Elem, Next} ->
            do_fold(Next, F, F(Accumulator, Elem));

        stop ->
            Accumulator
    end.

-spec fold(iterator(BKA), BKC, fun((BKC, BKA) -> BKC)) -> BKC.
fold(Iterator, Initial, F) ->
    _pipe = erlang:element(2, Iterator),
    do_fold(_pipe, F, Initial).

-spec run(iterator(any())) -> nil.
run(Iterator) ->
    fold(Iterator, nil, fun(_, _) -> nil end).

-spec to_list(iterator(BKF)) -> list(BKF).
to_list(Iterator) ->
    _pipe = Iterator,
    _pipe@1 = fold(_pipe, [], fun(Acc, E) -> [E | Acc] end),
    gleam@list:reverse(_pipe@1).

-spec step(iterator(BKI)) -> step(BKI, iterator(BKI)).
step(Iterator) ->
    case (erlang:element(2, Iterator))() of
        stop ->
            done;

        {continue, E, A} ->
            {next, E, {iterator, A}}
    end.

-spec do_take(fun(() -> action(BKN)), integer()) -> fun(() -> action(BKN)).
do_take(Continuation, Desired) ->
    fun() -> case Desired > 0 of
            false ->
                stop;

            true ->
                case Continuation() of
                    stop ->
                        stop;

                    {continue, E, Next} ->
                        {continue, E, do_take(Next, Desired - 1)}
                end
        end end.

-spec take(iterator(BKQ), integer()) -> iterator(BKQ).
take(Iterator, Desired) ->
    _pipe = erlang:element(2, Iterator),
    _pipe@1 = do_take(_pipe, Desired),
    {iterator, _pipe@1}.

-spec do_drop(fun(() -> action(BKT)), integer()) -> action(BKT).
do_drop(Continuation, Desired) ->
    case Continuation() of
        stop ->
            stop;

        {continue, E, Next} ->
            case Desired > 0 of
                true ->
                    do_drop(Next, Desired - 1);

                false ->
                    {continue, E, Next}
            end
    end.

-spec drop(iterator(BKW), integer()) -> iterator(BKW).
drop(Iterator, Desired) ->
    _pipe = fun() -> do_drop(erlang:element(2, Iterator), Desired) end,
    {iterator, _pipe}.

-spec do_map(fun(() -> action(BKZ)), fun((BKZ) -> BLB)) -> fun(() -> action(BLB)).
do_map(Continuation, F) ->
    fun() -> case Continuation() of
            stop ->
                stop;

            {continue, E, Continuation@1} ->
                {continue, F(E), do_map(Continuation@1, F)}
        end end.

-spec map(iterator(BLD), fun((BLD) -> BLF)) -> iterator(BLF).
map(Iterator, F) ->
    _pipe = erlang:element(2, Iterator),
    _pipe@1 = do_map(_pipe, F),
    {iterator, _pipe@1}.

-spec do_append(fun(() -> action(BLH)), fun(() -> action(BLH))) -> action(BLH).
do_append(First, Second) ->
    case First() of
        {continue, E, First@1} ->
            {continue, E, fun() -> do_append(First@1, Second) end};

        stop ->
            Second()
    end.

-spec append(iterator(BLL), iterator(BLL)) -> iterator(BLL).
append(First, Second) ->
    _pipe = fun() ->
        do_append(erlang:element(2, First), erlang:element(2, Second))
    end,
    {iterator, _pipe}.

-spec do_flatten(fun(() -> action(iterator(BLP)))) -> action(BLP).
do_flatten(Flattened) ->
    case Flattened() of
        stop ->
            stop;

        {continue, It, Next_iterator} ->
            do_append(
                erlang:element(2, It),
                fun() -> do_flatten(Next_iterator) end
            )
    end.

-spec flatten(iterator(iterator(BLT))) -> iterator(BLT).
flatten(Iterator) ->
    _pipe = fun() -> do_flatten(erlang:element(2, Iterator)) end,
    {iterator, _pipe}.

-spec flat_map(iterator(BLX), fun((BLX) -> iterator(BLZ))) -> iterator(BLZ).
flat_map(Iterator, F) ->
    _pipe = Iterator,
    _pipe@1 = map(_pipe, F),
    flatten(_pipe@1).

-spec do_filter(fun(() -> action(BMC)), fun((BMC) -> boolean())) -> action(BMC).
do_filter(Continuation, Predicate) ->
    case Continuation() of
        stop ->
            stop;

        {continue, E, Iterator} ->
            case Predicate(E) of
                true ->
                    {continue, E, fun() -> do_filter(Iterator, Predicate) end};

                false ->
                    do_filter(Iterator, Predicate)
            end
    end.

-spec filter(iterator(BMF), fun((BMF) -> boolean())) -> iterator(BMF).
filter(Iterator, Predicate) ->
    _pipe = fun() -> do_filter(erlang:element(2, Iterator), Predicate) end,
    {iterator, _pipe}.

-spec cycle(iterator(BMI)) -> iterator(BMI).
cycle(Iterator) ->
    _pipe = repeat(Iterator),
    flatten(_pipe).

-spec range(integer(), integer()) -> iterator(integer()).
range(Start, Stop) ->
    case gleam@int:compare(Start, Stop) of
        eq ->
            once(fun() -> Start end);

        gt ->
            unfold(Start, fun(Current) -> case Current < Stop of
                        false ->
                            {next, Current, Current - 1};

                        true ->
                            done
                    end end);

        lt ->
            unfold(Start, fun(Current@1) -> case Current@1 > Stop of
                        false ->
                            {next, Current@1, Current@1 + 1};

                        true ->
                            done
                    end end)
    end.

-spec do_find(fun(() -> action(BMM)), fun((BMM) -> boolean())) -> {ok, BMM} |
    {error, nil}.
do_find(Continuation, F) ->
    case Continuation() of
        stop ->
            {error, nil};

        {continue, E, Next} ->
            case F(E) of
                true ->
                    {ok, E};

                false ->
                    do_find(Next, F)
            end
    end.

-spec find(iterator(BMQ), fun((BMQ) -> boolean())) -> {ok, BMQ} | {error, nil}.
find(Haystack, Is_desired) ->
    _pipe = erlang:element(2, Haystack),
    do_find(_pipe, Is_desired).

-spec do_index(fun(() -> action(BMU)), integer()) -> fun(() -> action({integer(),
                                                                       BMU})).
do_index(Continuation, Next) ->
    fun() -> case Continuation() of
            stop ->
                stop;

            {continue, E, Continuation@1} ->
                {continue, {Next, E}, do_index(Continuation@1, Next + 1)}
        end end.

-spec index(iterator(BMX)) -> iterator({integer(), BMX}).
index(Iterator) ->
    _pipe = erlang:element(2, Iterator),
    _pipe@1 = do_index(_pipe, 0),
    {iterator, _pipe@1}.

-spec iterate(BNA, fun((BNA) -> BNA)) -> iterator(BNA).
iterate(Initial, F) ->
    unfold(Initial, fun(Element) -> {next, Element, F(Element)} end).

-spec do_take_while(fun(() -> action(BNC)), fun((BNC) -> boolean())) -> fun(() -> action(BNC)).
do_take_while(Continuation, Predicate) ->
    fun() -> case Continuation() of
            stop ->
                stop;

            {continue, E, Next} ->
                case Predicate(E) of
                    false ->
                        stop;

                    true ->
                        {continue, E, do_take_while(Next, Predicate)}
                end
        end end.

-spec take_while(iterator(BNF), fun((BNF) -> boolean())) -> iterator(BNF).
take_while(Iterator, Predicate) ->
    _pipe = erlang:element(2, Iterator),
    _pipe@1 = do_take_while(_pipe, Predicate),
    {iterator, _pipe@1}.

-spec do_drop_while(fun(() -> action(BNI)), fun((BNI) -> boolean())) -> action(BNI).
do_drop_while(Continuation, Predicate) ->
    case Continuation() of
        stop ->
            stop;

        {continue, E, Next} ->
            case Predicate(E) of
                false ->
                    {continue, E, Next};

                true ->
                    do_drop_while(Next, Predicate)
            end
    end.

-spec drop_while(iterator(BNL), fun((BNL) -> boolean())) -> iterator(BNL).
drop_while(Iterator, Predicate) ->
    _pipe = fun() -> do_drop_while(erlang:element(2, Iterator), Predicate) end,
    {iterator, _pipe}.

-spec do_scan(fun(() -> action(BNO)), fun((BNQ, BNO) -> BNQ), BNQ) -> fun(() -> action(BNQ)).
do_scan(Continuation, F, Accumulator) ->
    fun() -> case Continuation() of
            stop ->
                stop;

            {continue, El, Next} ->
                Accumulated = F(Accumulator, El),
                {continue, Accumulated, do_scan(Next, F, Accumulated)}
        end end.

-spec scan(iterator(BNS), BNU, fun((BNU, BNS) -> BNU)) -> iterator(BNU).
scan(Iterator, Initial, F) ->
    _pipe = erlang:element(2, Iterator),
    _pipe@1 = do_scan(_pipe, F, Initial),
    {iterator, _pipe@1}.

-spec do_zip(fun(() -> action(BNW)), fun(() -> action(BNY))) -> fun(() -> action({BNW,
                                                                                  BNY})).
do_zip(Left, Right) ->
    fun() -> case Left() of
            stop ->
                stop;

            {continue, El_left, Next_left} ->
                case Right() of
                    stop ->
                        stop;

                    {continue, El_right, Next_right} ->
                        {continue,
                         {El_left, El_right},
                         do_zip(Next_left, Next_right)}
                end
        end end.

-spec zip(iterator(BOB), iterator(BOD)) -> iterator({BOB, BOD}).
zip(Left, Right) ->
    _pipe = do_zip(erlang:element(2, Left), erlang:element(2, Right)),
    {iterator, _pipe}.

-spec next_chunk(fun(() -> action(BOJ)), fun((BOJ) -> BOL), BOL, list(BOJ)) -> chunk(BOJ, BOL).
next_chunk(Continuation, F, Previous_key, Current_chunk) ->
    case Continuation() of
        stop ->
            {last_by, gleam@list:reverse(Current_chunk)};

        {continue, E, Next} ->
            Key = F(E),
            case Key =:= Previous_key of
                true ->
                    next_chunk(Next, F, Key, [E | Current_chunk]);

                false ->
                    {another_by,
                     gleam@list:reverse(Current_chunk),
                     Key,
                     E,
                     Next}
            end
    end.

-spec do_chunk(fun(() -> action(BOP)), fun((BOP) -> BOR), BOR, BOP) -> action(list(BOP)).
do_chunk(Continuation, F, Previous_key, Previous_element) ->
    case next_chunk(Continuation, F, Previous_key, [Previous_element]) of
        {last_by, Chunk} ->
            {continue, Chunk, fun stop/0};

        {another_by, Chunk@1, Key, El, Next} ->
            {continue, Chunk@1, fun() -> do_chunk(Next, F, Key, El) end}
    end.

-spec chunk(iterator(BOU), fun((BOU) -> any())) -> iterator(list(BOU)).
chunk(Iterator, F) ->
    _pipe = fun() -> case (erlang:element(2, Iterator))() of
            stop ->
                stop;

            {continue, E, Next} ->
                do_chunk(Next, F, F(E), E)
        end end,
    {iterator, _pipe}.

-spec next_sized_chunk(fun(() -> action(BPC)), integer(), list(BPC)) -> sized_chunk(BPC).
next_sized_chunk(Continuation, Left, Current_chunk) ->
    case Continuation() of
        stop ->
            case Current_chunk of
                [] ->
                    no_more;

                Remaining ->
                    {last, gleam@list:reverse(Remaining)}
            end;

        {continue, E, Next} ->
            Chunk = [E | Current_chunk],
            case Left > 1 of
                false ->
                    {another, gleam@list:reverse(Chunk), Next};

                true ->
                    next_sized_chunk(Next, Left - 1, Chunk)
            end
    end.

-spec do_sized_chunk(fun(() -> action(BPG)), integer()) -> fun(() -> action(list(BPG))).
do_sized_chunk(Continuation, Count) ->
    fun() -> case next_sized_chunk(Continuation, Count, []) of
            no_more ->
                stop;

            {last, Chunk} ->
                {continue, Chunk, fun stop/0};

            {another, Chunk@1, Next_element} ->
                {continue, Chunk@1, do_sized_chunk(Next_element, Count)}
        end end.

-spec sized_chunk(iterator(BPK), integer()) -> iterator(list(BPK)).
sized_chunk(Iterator, Count) ->
    _pipe = erlang:element(2, Iterator),
    _pipe@1 = do_sized_chunk(_pipe, Count),
    {iterator, _pipe@1}.

-spec do_intersperse(fun(() -> action(BPO)), BPO) -> action(BPO).
do_intersperse(Continuation, Separator) ->
    case Continuation() of
        stop ->
            stop;

        {continue, E, Next} ->
            Next_interspersed = fun() -> do_intersperse(Next, Separator) end,
            {continue, Separator, fun() -> {continue, E, Next_interspersed} end}
    end.

-spec intersperse(iterator(BPR), BPR) -> iterator(BPR).
intersperse(Iterator, Elem) ->
    _pipe = fun() -> case (erlang:element(2, Iterator))() of
            stop ->
                stop;

            {continue, E, Next} ->
                {continue, E, fun() -> do_intersperse(Next, Elem) end}
        end end,
    {iterator, _pipe}.

-spec do_any(fun(() -> action(BPU)), fun((BPU) -> boolean())) -> boolean().
do_any(Continuation, Predicate) ->
    case Continuation() of
        stop ->
            false;

        {continue, E, Next} ->
            Predicate(E) orelse do_any(Next, Predicate)
    end.

-spec any(iterator(BPW), fun((BPW) -> boolean())) -> boolean().
any(Iterator, Predicate) ->
    _pipe = erlang:element(2, Iterator),
    do_any(_pipe, Predicate).

-spec do_all(fun(() -> action(BPY)), fun((BPY) -> boolean())) -> boolean().
do_all(Continuation, Predicate) ->
    case Continuation() of
        stop ->
            true;

        {continue, E, Next} ->
            Predicate(E) andalso do_all(Next, Predicate)
    end.

-spec all(iterator(BQA), fun((BQA) -> boolean())) -> boolean().
all(Iterator, Predicate) ->
    _pipe = erlang:element(2, Iterator),
    do_all(_pipe, Predicate).

-spec update_group_with(BQC) -> fun((gleam@option:option(list(BQC))) -> list(BQC)).
update_group_with(El) ->
    fun(Maybe_group) -> case Maybe_group of
            {some, Group} ->
                [El | Group];

            none ->
                [El]
        end end.

-spec group_updater(fun((BQG) -> BQH)) -> fun((gleam@map:map_(BQH, list(BQG)), BQG) -> gleam@map:map_(BQH, list(BQG))).
group_updater(F) ->
    fun(Groups, Elem) ->
        _pipe = Groups,
        gleam@map:update(_pipe, F(Elem), update_group_with(Elem))
    end.

-spec group(iterator(BQO), fun((BQO) -> BQQ)) -> gleam@map:map_(BQQ, list(BQO)).
group(Iterator, Key) ->
    _pipe = Iterator,
    _pipe@1 = fold(_pipe, gleam@map:new(), group_updater(Key)),
    gleam@map:map_values(
        _pipe@1,
        fun(_, Group) -> gleam@list:reverse(Group) end
    ).

-spec reduce(iterator(BQU), fun((BQU, BQU) -> BQU)) -> {ok, BQU} | {error, nil}.
reduce(Iterator, F) ->
    case (erlang:element(2, Iterator))() of
        stop ->
            {error, nil};

        {continue, E, Next} ->
            _pipe = do_fold(Next, F, E),
            {ok, _pipe}
    end.

-spec last(iterator(BQY)) -> {ok, BQY} | {error, nil}.
last(Iterator) ->
    _pipe = Iterator,
    reduce(_pipe, fun(_, Elem) -> Elem end).

-spec empty() -> iterator(any()).
empty() ->
    {iterator, fun stop/0}.

-spec once(fun(() -> BRE)) -> iterator(BRE).
once(F) ->
    _pipe = fun() -> {continue, F(), fun stop/0} end,
    {iterator, _pipe}.

-spec single(BRG) -> iterator(BRG).
single(Elem) ->
    once(fun() -> Elem end).

-spec do_interleave(fun(() -> action(BRI)), fun(() -> action(BRI))) -> action(BRI).
do_interleave(Current, Next) ->
    case Current() of
        stop ->
            Next();

        {continue, E, Next_other} ->
            {continue, E, fun() -> do_interleave(Next, Next_other) end}
    end.

-spec interleave(iterator(BRM), iterator(BRM)) -> iterator(BRM).
interleave(Left, Right) ->
    _pipe = fun() ->
        do_interleave(erlang:element(2, Left), erlang:element(2, Right))
    end,
    {iterator, _pipe}.

-spec do_fold_until(
    fun(() -> action(BRQ)),
    fun((BRS, BRQ) -> gleam@list:continue_or_stop(BRS)),
    BRS
) -> BRS.
do_fold_until(Continuation, F, Accumulator) ->
    case Continuation() of
        stop ->
            Accumulator;

        {continue, Elem, Next} ->
            case F(Accumulator, Elem) of
                {continue, Accumulator@1} ->
                    do_fold_until(Next, F, Accumulator@1);

                {stop, Accumulator@2} ->
                    Accumulator@2
            end
    end.

-spec fold_until(
    iterator(BRU),
    BRW,
    fun((BRW, BRU) -> gleam@list:continue_or_stop(BRW))
) -> BRW.
fold_until(Iterator, Initial, F) ->
    _pipe = erlang:element(2, Iterator),
    do_fold_until(_pipe, F, Initial).

-spec do_try_fold(
    fun(() -> action(BRY)),
    fun((BSA, BRY) -> {ok, BSA} | {error, BSB}),
    BSA
) -> {ok, BSA} | {error, BSB}.
do_try_fold(Continuation, F, Accumulator) ->
    case Continuation() of
        stop ->
            {ok, Accumulator};

        {continue, Elem, Next} ->
            case F(Accumulator, Elem) of
                {error, _try} -> {error, _try};
                {ok, Accumulator@1} ->
                    do_try_fold(Next, F, Accumulator@1)
            end
    end.

-spec try_fold(iterator(BSG), BSI, fun((BSI, BSG) -> {ok, BSI} | {error, BSJ})) -> {ok,
                                                                                    BSI} |
    {error, BSJ}.
try_fold(Iterator, Initial, F) ->
    _pipe = erlang:element(2, Iterator),
    do_try_fold(_pipe, F, Initial).

-spec first(iterator(BSO)) -> {ok, BSO} | {error, nil}.
first(Iterator) ->
    case (erlang:element(2, Iterator))() of
        stop ->
            {error, nil};

        {continue, E, _@1} ->
            {ok, E}
    end.

-spec at(iterator(BSS), integer()) -> {ok, BSS} | {error, nil}.
at(Iterator, Index) ->
    _pipe = Iterator,
    _pipe@1 = drop(_pipe, Index),
    first(_pipe@1).