gens

-module(gens@stream).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).
-define(FILEPATH, "src/gens/stream.gleam").
-export([take/2, map/2, drop/2, zip/2, list_zip/2, while/2, scan/3, merge/3, fold/2, from_lazy_list/1, flatten/1, filter/2]).
-export_type([stream/1]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC("================== Stream ==================\n").

-type stream(HSO) :: {stream, fun(() -> HSO), fun(() -> stream(HSO))}.

-file("src/gens/stream.gleam", 12).
?DOC(" `Tail recursive` function for **take**\n").
-spec take_acc(stream(HSP), integer(), list(HSP)) -> list(HSP).
take_acc(Stream, N, Acc) ->
    case N > 0 of
        false ->
            lists:reverse(Acc);

        true ->
            take_acc(
                (erlang:element(3, Stream))(),
                N - 1,
                [(erlang:element(2, Stream))() | Acc]
            )
    end.

-file("src/gens/stream.gleam", 30).
?DOC(
    " **Takes** a `finite` number of elements from the Stream\n"
    " ```gleam\n"
    " pub fn ones() -> Stream(Int) {\n"
    "   Stream(head: fn() { 1 }, tail: ones)\n"
    " }\n"
    " ```\n"
    " ```gleam\n"
    " ones()\n"
    " |> take(5)\n"
    " // -> [1, 1, 1, 1, 1]\n"
    " ```\n"
).
-spec take(stream(HST), integer()) -> list(HST).
take(Stream, N) ->
    take_acc(Stream, N, []).

-file("src/gens/stream.gleam", 55).
?DOC(
    " **Maps** each element of the Stream\n"
    " ```gleam\n"
    " pub fn alt(positive: Bool) -> Stream(Int) {\n"
    "   Stream(\n"
    "     head: fn() {\n"
    "       case positive {\n"
    "         True -> 1\n"
    "         False -> -1\n"
    "       }\n"
    "     },\n"
    "     tail: fn() { alt(!positive) },\n"
    "   )\n"
    " }\n"
    " ```\n"
    " ```gleam\n"
    " alt(True)\n"
    " |> map(fn(x) { x * 2 })\n"
    " |> map(fn(x) { int.to_string(x) <> \" oranges\" })\n"
    " |> take(5)\n"
    " // -> [\"2 oranges\", \"-2 oranges\", \"2 oranges\", \"-2 oranges\", \"2 oranges\"]\n"
    " ```\n"
).
-spec map(stream(HSW), fun((HSW) -> HSY)) -> stream(HSY).
map(Stream, F) ->
    {stream,
        fun() -> F((erlang:element(2, Stream))()) end,
        fun() -> map((erlang:element(3, Stream))(), F) end}.

-file("src/gens/stream.gleam", 60).
?DOC(" Lazy function for getting the filtered stream's head\n").
-spec loop_head(stream(HTA), fun((HTA) -> boolean())) -> HTA.
loop_head(Stream, Pred) ->
    Current = (erlang:element(2, Stream))(),
    case Pred(Current) of
        true ->
            Current;

        false ->
            loop_head((erlang:element(3, Stream))(), Pred)
    end.

-file("src/gens/stream.gleam", 106).
?DOC(
    " **Drops** the first n elements from the Stream\n"
    " ```gleam\n"
    " pub fn powers() -> Stream(Int) {\n"
    "   Stream(head: fn() { 1 }, tail: fn() { map(powers(), fn(x) { x * 2 }) })\n"
    " }\n"
    " ```\n"
    " ```gleam\n"
    " powers() // 1, 2, 4, 8, 16..\n"
    " |> drop(3)\n"
    " |> take(5)\n"
    " // -> [8, 16, 32, 64, 128]\n"
    " ```\n"
).
-spec drop(stream(HTI), integer()) -> stream(HTI).
drop(Stream, N) ->
    case N > 0 of
        true ->
            drop((erlang:element(3, Stream))(), N - 1);

        false ->
            Stream
    end.

-file("src/gens/stream.gleam", 119).
?DOC(
    " **Zips** two Streams togheter\n"
    " ```gleam\n"
    " zip(naturals(), drop(naturals(), 5))\n"
    " |> take(3)\n"
    " |> [#(0, 5), #(1, 6), #(2, 7)]\n"
    " ```\n"
).
-spec zip(stream(HTL), stream(HTN)) -> stream({HTL, HTN}).
zip(A_stream, B_stream) ->
    {stream,
        fun() ->
            {(erlang:element(2, A_stream))(), (erlang:element(2, B_stream))()}
        end,
        fun() ->
            zip(
                (erlang:element(3, A_stream))(),
                (erlang:element(3, B_stream))()
            )
        end}.

-file("src/gens/stream.gleam", 130).
?DOC(
    " **Zips** a list with a Stream\n"
    " ```gleam\n"
    " list_zip([\"a\", \"b\", \"c\"], naturals())\n"
    " // -> [#(\"a\", 0), #(\"b\", 1), #(\"c\", 2)]\n"
    " ```\n"
).
-spec list_zip(list(HTQ), stream(HTS)) -> list({HTQ, HTS}).
list_zip(List, Stream) ->
    case List of
        [] ->
            [];

        [X | Xs] ->
            [{X, (erlang:element(2, Stream))()} |
                list_zip(Xs, (erlang:element(3, Stream))())]
    end.

-file("src/gens/stream.gleam", 143).
?DOC(
    " **Takes** elements from the Stream until the condition is false\n"
    " ```gleam\n"
    "   naturals()\n"
    " |> while(fn(x) { x < 5 })\n"
    " // -> [0, 1, 2, 3, 4]\n"
    " ```\n"
).
-spec while(stream(HTV), fun((HTV) -> boolean())) -> list(HTV).
while(Stream, Condition) ->
    case Condition((erlang:element(2, Stream))()) of
        false ->
            [];

        true ->
            [(erlang:element(2, Stream))() |
                while((erlang:element(3, Stream))(), Condition)]
    end.

-file("src/gens/stream.gleam", 162).
?DOC(
    " **Scans** the Stream and reconstructs it using an accumulator\n"
    " ```gleam\n"
    " pub fn dummy() -> Stream(Nil) {\n"
    "   Stream(head: fn() { Nil }, tail: dummy)\n"
    " }\n"
    " ```\n"
    " ```gleam\n"
    " let evens: Stream(Int) = scan(dummy(), 0, fn(_, acc) { acc + 2 })\n"
    " evens\n"
    " |> take(5)\n"
    " // -> [0, 2, 4, 6, 8]\n"
    " ```\n"
).
-spec scan(stream(HTY), HUA, fun((HTY, HUA) -> HUA)) -> stream(HUA).
scan(Stream, Acc, F) ->
    {stream,
        fun() -> Acc end,
        fun() ->
            scan(
                (erlang:element(3, Stream))(),
                F((erlang:element(2, Stream))(), Acc),
                F
            )
        end}.

-file("src/gens/stream.gleam", 174).
?DOC(
    " **Merges** two sorted Streams\n"
    " ```gleam\n"
    " merge(naturals(), naturals() |> map(fn(x) { x * 2 }), int.compare)\n"
    " |> take(8)\n"
    " // -> [0, 0, 1, 2, 2, 3, 4, 4]\n"
    " ```\n"
).
-spec merge(stream(HUC), stream(HUC), fun((HUC, HUC) -> gleam@order:order())) -> stream(HUC).
merge(Stream1, Stream2, Compare) ->
    {stream,
        fun() ->
            case Compare(
                (erlang:element(2, Stream1))(),
                (erlang:element(2, Stream2))()
            ) of
                gt ->
                    (erlang:element(2, Stream2))();

                _ ->
                    (erlang:element(2, Stream1))()
            end
        end,
        fun() ->
            case Compare(
                (erlang:element(2, Stream1))(),
                (erlang:element(2, Stream2))()
            ) of
                gt ->
                    merge(Stream1, (erlang:element(3, Stream2))(), Compare);

                _ ->
                    merge((erlang:element(3, Stream1))(), Stream2, Compare)
            end
        end}.

-file("src/gens/stream.gleam", 205).
?DOC(
    " **Folds** the Stream into a single value using an accumulator\n"
    " ```gleam\n"
    " let stream_or = fn(s: Stream(Bool)) -> Bool {\n"
    "   fold(s, fn(x, next) { x || next() })\n"
    " }\n"
    " // If at least one element is True, then the fold ends\n"
    " // If all elements in the Stream are False, the fold runs infinitely\n"
    " stream_or(naturals() |> map(fn(x) { x == 10 }))\n"
    " // -> True\n"
    " ```\n"
).
-spec fold(stream(HUG), fun((HUG, fun(() -> HUI)) -> HUI)) -> HUI.
fold(Stream, F) ->
    F(
        (erlang:element(2, Stream))(),
        fun() -> fold((erlang:element(3, Stream))(), F) end
    ).

-file("src/gens/stream.gleam", 210).
?DOC(" Lazy function for getting the flattened stream's head\n").
-spec loop_flatten_head(stream(list(HUJ))) -> HUJ.
loop_flatten_head(Stream) ->
    case (erlang:element(2, Stream))() of
        [X | _] ->
            X;

        [] ->
            loop_flatten_head((erlang:element(3, Stream))())
    end.

-file("src/gens/stream.gleam", 256).
?DOC(
    " Conversion from **LazyList** to **Stream**\n"
    " ```gleam\n"
    " let lazy_odds =\n"
    "   lazy.new()\n"
    "   |> lazy.filter(int.is_odd)\n"
    "   |> lazy.map(int.to_string)\n"
    " let stream_odds = from_lazy_list(lazy_odds)\n"
    " stream_odds\n"
    " |> take(5)\n"
    " // -> [\"1\", \"3\", \"5\", \"7\", \"9\"]\n"
    " ```\n"
).
-spec from_lazy_list(gens@lazy:lazy_list(HUU)) -> stream(HUU).
from_lazy_list(Lz) ->
    {stream, fun() -> case gens@lazy:take(Lz, 1) of
                [] ->
                    erlang:error(#{gleam_error => panic,
                            message => <<"`panic` expression evaluated."/utf8>>,
                            file => <<?FILEPATH/utf8>>,
                            module => <<"gens/stream"/utf8>>,
                            function => <<"from_lazy_list"/utf8>>,
                            line => 260});

                [X | _] ->
                    X
            end end, fun() -> from_lazy_list(gens@lazy:drop(Lz, 1)) end}.

-file("src/gens/stream.gleam", 239).
?DOC(
    " **Flatten** a Stream of Lists\n"
    " ```gleam\n"
    " let repeat_stream = naturals() |> map(fn(x) { list.repeat(x, x) })\n"
    " repeat_stream\n"
    " |> take(5)\n"
    " // -> [[], [1], [2, 2], [3, 3, 3], [4, 4, 4, 4]]\n"
    " repeat_stream\n"
    " |> flatten()\n"
    " |> take(10)\n"
    " // -> [1, 2, 2, 3, 3, 3, 4, 4, 4, 4]\n"
    " ```\n"
).
-spec flatten(stream(list(HUQ))) -> stream(HUQ).
flatten(Stream) ->
    {stream,
        fun() -> loop_flatten_head(Stream) end,
        fun() -> loop_flatten_tail(Stream) end}.

-file("src/gens/stream.gleam", 218).
?DOC(" Lazy function for getting the flattened stream's tail\n").
-spec loop_flatten_tail(stream(list(HUM))) -> stream(HUM).
loop_flatten_tail(Stream) ->
    case (erlang:element(2, Stream))() of
        [_ | Xs] ->
            New_stream = {stream, fun() -> Xs end, erlang:element(3, Stream)},
            flatten(New_stream);

        [] ->
            loop_flatten_tail((erlang:element(3, Stream))())
    end.

-file("src/gens/stream.gleam", 88).
?DOC(
    " **Filters** elements from the Stream\n"
    " ```gleam\n"
    " pub fn naturals() -> Stream(Int) {\n"
    "   Stream(head: fn() { 0 }, tail: fn() { map(naturals(), fn(x) { x + 1 }) })\n"
    " }\n"
    " ```\n"
    " ```gleam\n"
    " filter(naturals(), fn(x) { x % 3 == 0 })\n"
    " |> take(5)\n"
    " // -> [0, 3, 6, 9, 12]\n"
    " ```\n"
).
-spec filter(stream(HTF), fun((HTF) -> boolean())) -> stream(HTF).
filter(Stream, Pred) ->
    {stream,
        fun() -> loop_head(Stream, Pred) end,
        fun() -> loop_tail(Stream, Pred) end}.

-file("src/gens/stream.gleam", 69).
?DOC(" Lazy function for getting the filtered stream's tail\n").
-spec loop_tail(stream(HTC), fun((HTC) -> boolean())) -> stream(HTC).
loop_tail(Stream, Pred) ->
    Current = (erlang:element(2, Stream))(),
    case Pred(Current) of
        true ->
            filter((erlang:element(3, Stream))(), Pred);

        false ->
            loop_tail((erlang:element(3, Stream))(), Pred)
    end.