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

-export([all/1, is_some/1, is_none/1, to_result/2, from_result/1, unwrap/2, map/2, flatten/1, then/2, 'or'/2, values/1]).
-export_type([option/1]).

-type option(DHR) :: {some, DHR} | none.

-spec all(list(option(DHS))) -> option(list(DHS)).
all(List) ->
    gleam@list:fold_right(
        List,
        {some, []},
        fun(Item, Acc) -> case {Acc, Item} of
                {{some, Values}, {some, Value}} ->
                    {some, [Value | Values]};

                {_, _} ->
                    none
            end end
    ).

-spec is_some(option(any())) -> boolean().
is_some(Option) ->
    Option /= none.

-spec is_none(option(any())) -> boolean().
is_none(Option) ->
    Option =:= none.

-spec to_result(option(DIB), DIE) -> {ok, DIB} | {error, DIE}.
to_result(Option, E) ->
    case Option of
        {some, A} ->
            {ok, A};

        _ ->
            {error, E}
    end.

-spec from_result({ok, DIH} | {error, any()}) -> option(DIH).
from_result(Result) ->
    case Result of
        {ok, A} ->
            {some, A};

        _ ->
            none
    end.

-spec unwrap(option(DIM), DIM) -> DIM.
unwrap(Option, Default) ->
    case Option of
        {some, X} ->
            X;

        none ->
            Default
    end.

-spec map(option(DIO), fun((DIO) -> DIQ)) -> option(DIQ).
map(Option, Fun) ->
    case Option of
        {some, X} ->
            {some, Fun(X)};

        none ->
            none
    end.

-spec flatten(option(option(DIS))) -> option(DIS).
flatten(Option) ->
    case Option of
        {some, X} ->
            X;

        none ->
            none
    end.

-spec then(option(DIW), fun((DIW) -> option(DIY))) -> option(DIY).
then(Option, Fun) ->
    case Option of
        {some, X} ->
            Fun(X);

        none ->
            none
    end.

-spec 'or'(option(DJB), option(DJB)) -> option(DJB).
'or'(First, Second) ->
    case First of
        {some, _} ->
            First;

        none ->
            Second
    end.

-spec values(list(option(DJF))) -> list(DJF).
values(Options) ->
    gleam@list:filter_map(Options, fun(Op) -> to_result(Op, <<""/utf8>>) end).