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

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

-type step(CKC, CKD) :: {next, CKC, CKD} | done.

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

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

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

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

            done ->
                stop
        end end.

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

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

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

-spec from_list(list(CKZ)) -> iterator(CKZ).
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(CLC)), fun((CLE, CLC) -> CLE), CLE) -> CLE.
do_fold(Continuation, F, Accumulator) ->
    case Continuation() of
        {continue, Elem, Next} ->
            do_fold(Next, F, F(Accumulator, Elem));

        stop ->
            Accumulator
    end.

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

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

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

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

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

-spec do_map(fun(() -> action(CME)), fun((CME) -> CMG)) -> fun(() -> action(CMG)).
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(CMI), fun((CMI) -> CMK)) -> iterator(CMK).
map(Iterator, F) ->
    _pipe = erlang:element(2, Iterator),
    _pipe@1 = do_map(_pipe, F),
    {iterator, _pipe@1}.

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

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

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

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

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

-spec range(integer(), integer()) -> iterator(integer()).
range(Start, Stop) ->
    Increment = case Start < Stop of
        true ->
            1;

        false ->
            -1
    end,
    Next_step = fun(Current) -> case Current =:= Stop of
            true ->
                done;

            false ->
                {next, Current, Current + Increment}
        end end,
    unfold(Start, Next_step).

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

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

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

-spec do_take_while(fun(() -> action(COH)), fun((COH) -> boolean())) -> fun(() -> action(COH)).
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(COK), fun((COK) -> boolean())) -> iterator(COK).
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(CON)), fun((CON) -> boolean())) -> action(CON).
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(COQ), fun((COQ) -> boolean())) -> iterator(COQ).
drop_while(Iterator, Predicate) ->
    _pipe = fun() -> do_drop_while(erlang:element(2, Iterator), Predicate) end,
    {iterator, _pipe}.

-spec do_scan(fun(() -> action(COT)), fun((COV, COT) -> COV), COV) -> fun(() -> action(COV)).
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(COX), COZ, fun((COZ, COX) -> COZ)) -> iterator(COZ).
scan(Iterator, Initial, F) ->
    _pipe = erlang:element(2, Iterator),
    _pipe@1 = do_scan(_pipe, F, Initial),
    {iterator, _pipe@1}.

-spec do_zip(fun(() -> action(CPB)), fun(() -> action(CPD))) -> fun(() -> action({CPB,
                                                                                  CPD})).
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(CPG), iterator(CPI)) -> iterator({CPG, CPI}).
zip(Left, Right) ->
    _pipe = do_zip(erlang:element(2, Left), erlang:element(2, Right)),
    {iterator, _pipe}.

-spec next_chunk(fun(() -> action(CPO)), fun((CPO) -> CPQ), CPQ, list(CPO)) -> chunk(CPO, CPQ).
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(CPU)), fun((CPU) -> CPW), CPW, CPU) -> action(list(CPU)).
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(CPZ), fun((CPZ) -> any())) -> iterator(list(CPZ)).
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(CQH)), integer(), list(CQH)) -> sized_chunk(CQH).
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(CQL)), integer()) -> fun(() -> action(list(CQL))).
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(CQP), integer()) -> iterator(list(CQP)).
sized_chunk(Iterator, Count) ->
    _pipe = erlang:element(2, Iterator),
    _pipe@1 = do_sized_chunk(_pipe, Count),
    {iterator, _pipe@1}.

-spec do_intersperse(fun(() -> action(CQT)), CQT) -> action(CQT).
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(CQW), CQW) -> iterator(CQW).
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(CQZ)), fun((CQZ) -> 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(CRB), fun((CRB) -> boolean())) -> boolean().
any(Iterator, Predicate) ->
    _pipe = erlang:element(2, Iterator),
    do_any(_pipe, Predicate).

-spec do_all(fun(() -> action(CRD)), fun((CRD) -> 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(CRF), fun((CRF) -> boolean())) -> boolean().
all(Iterator, Predicate) ->
    _pipe = erlang:element(2, Iterator),
    do_all(_pipe, Predicate).

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

            none ->
                [El]
        end end.

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

-spec group(iterator(CRT), fun((CRT) -> CRV)) -> gleam@map:map_(CRV, list(CRT)).
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(CRZ), fun((CRZ, CRZ) -> CRZ)) -> {ok, CRZ} | {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(CSD)) -> {ok, CSD} | {error, nil}.
last(Iterator) ->
    _pipe = Iterator,
    reduce(_pipe, fun(_, Elem) -> Elem end).

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

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

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

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

-spec do_fold_until(
    fun(() -> action(CSV)),
    fun((CSX, CSV) -> gleam@list:continue_or_stop(CSX)),
    CSX
) -> CSX.
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(CSZ),
    CTB,
    fun((CTB, CSZ) -> gleam@list:continue_or_stop(CTB))
) -> CTB.
fold_until(Iterator, Initial, F) ->
    _pipe = erlang:element(2, Iterator),
    do_fold_until(_pipe, F, Initial).

-spec do_try_fold(
    fun(() -> action(CTD)),
    fun((CTF, CTD) -> {ok, CTF} | {error, CTG}),
    CTF
) -> {ok, CTF} | {error, CTG}.
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(CTL), CTN, fun((CTN, CTL) -> {ok, CTN} | {error, CTO})) -> {ok,
                                                                                    CTN} |
    {error, CTO}.
try_fold(Iterator, Initial, F) ->
    _pipe = erlang:element(2, Iterator),
    do_try_fold(_pipe, F, Initial).

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

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

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