-module(distribute@codec@variant).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/distribute/codec/variant.gleam").
-export([new/0, add/6, unit/5, build/1]).
-export_type([variant_encode_outcome/0, variant_strategy/1, variant_builder/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.

-type variant_encode_outcome() :: {encoded, bitstring()} |
    not_this_variant |
    {variant_encode_failed, distribute@codec:encode_error()}.

-type variant_strategy(JCK) :: {variant_strategy,
        integer(),
        binary(),
        fun((JCK) -> variant_encode_outcome()),
        fun((bitstring()) -> {ok, {JCK, bitstring()}} |
            {error, distribute@codec:decode_error()})}.

-opaque variant_builder(JCL) :: {variant_builder, list(variant_strategy(JCL))}.

-file("src/distribute/codec/variant.gleam", 40).
?DOC(" Create a new builder for an ADT codec.\n").
-spec new() -> variant_builder(any()).
new() ->
    {variant_builder, []}.

-file("src/distribute/codec/variant.gleam", 48).
?DOC(
    " Add a variant with a payload to the codec.\n"
    " id: unique identifier (0-255). name: for error messages.\n"
    " inner: codec for the payload. wrap: ADT constructor.\n"
    " unwrap: extract payload or return Error(Nil) if wrong variant.\n"
).
-spec add(
    variant_builder(JCO),
    integer(),
    binary(),
    distribute@codec:codec(JCQ),
    fun((JCQ) -> JCO),
    fun((JCO) -> {ok, JCQ} | {error, nil})
) -> variant_builder(JCO).
add(Builder, Id, Name, Inner, Wrap, Unwrap) ->
    Strategy = {variant_strategy, Id, Name, fun(Value) -> case Unwrap(Value) of
                {ok, Payload} ->
                    case (erlang:element(2, Inner))(Payload) of
                        {ok, Bits} ->
                            {encoded, gleam@bit_array:append(<<Id:8>>, Bits)};

                        {error, E} ->
                            {variant_encode_failed, E}
                    end;

                {error, _} ->
                    not_this_variant
            end end, fun(Data) -> case Data of
                <<Tag:8, Rest/bitstring>> when Tag =:= Id ->
                    case (erlang:element(4, Inner))(Rest) of
                        {ok, {Val, Remaining}} ->
                            {ok, {Wrap(Val), Remaining}};

                        {error, E@1} ->
                            {error, E@1}
                    end;

                _ ->
                    {error, {tag_mismatch, Name, <<"unknown"/utf8>>}}
            end end},
    {variant_builder, [Strategy | erlang:element(2, Builder)]}.

-file("src/distribute/codec/variant.gleam", 87).
?DOC(" Add a variant without a payload (unit/constant).\n").
-spec unit(
    variant_builder(JCV),
    integer(),
    binary(),
    JCV,
    fun((JCV) -> boolean())
) -> variant_builder(JCV).
unit(Builder, Id, Name, Value, Match) ->
    Strategy = {variant_strategy, Id, Name, fun(Val) -> case Match(Val) of
                true ->
                    {encoded, <<Id:8>>};

                false ->
                    not_this_variant
            end end, fun(Data) -> case Data of
                <<Tag:8, Rest/bitstring>> when Tag =:= Id ->
                    {ok, {Value, Rest}};

                _ ->
                    {error, {tag_mismatch, Name, <<"unknown"/utf8>>}}
            end end},
    {variant_builder, [Strategy | erlang:element(2, Builder)]}.

-file("src/distribute/codec/variant.gleam", 172).
-spec find_encoder(list(variant_strategy(JDB)), JDB) -> variant_encode_outcome().
find_encoder(Strategies, Value) ->
    case Strategies of
        [] ->
            not_this_variant;

        [S | Rest] ->
            case (erlang:element(4, S))(Value) of
                not_this_variant ->
                    find_encoder(Rest, Value);

                Outcome ->
                    Outcome
            end
    end.

-file("src/distribute/codec/variant.gleam", 186).
-spec validate_strategies(list(variant_strategy(any()))) -> nil.
validate_strategies(Strategies) ->
    Ids = gleam@list:map(Strategies, fun(S) -> erlang:element(2, S) end),
    case gleam@list:all(Ids, fun(Id) -> (Id >= 0) andalso (Id =< 255) end) of
        true ->
            nil;

        false ->
            erlang:error(#{gleam_error => panic,
                    message => <<"Variant codec: variant id out of range, must be 0-255 (the tag is a single wire byte)"/utf8>>,
                    file => <<?FILEPATH/utf8>>,
                    module => <<"distribute/codec/variant"/utf8>>,
                    function => <<"validate_strategies"/utf8>>,
                    line => 191})
    end,
    case begin
        _pipe = gleam@list:unique(Ids),
        erlang:length(_pipe)
    end
    =:= erlang:length(Ids) of
        true ->
            nil;

        false ->
            erlang:error(#{gleam_error => panic,
                    message => <<"Variant codec: Duplicate IDs detected in builder"/utf8>>,
                    file => <<?FILEPATH/utf8>>,
                    module => <<"distribute/codec/variant"/utf8>>,
                    function => <<"validate_strategies"/utf8>>,
                    line => 195})
    end.

-file("src/distribute/codec/variant.gleam", 121).
?DOC(
    " Finalize the builder and return a Codec(a).\n"
    " Panics if duplicate IDs are found.\n"
).
-spec build(variant_builder(JCY)) -> distribute@codec:codec(JCY).
build(Builder) ->
    Strategies = lists:reverse(erlang:element(2, Builder)),
    validate_strategies(Strategies),
    Encoder = fun(Value) -> case find_encoder(Strategies, Value) of
            {encoded, Bits} ->
                {ok, Bits};

            {variant_encode_failed, E} ->
                {error, E};

            not_this_variant ->
                {error,
                    {encode_failed,
                        <<"No variant matched for encoding ADT value"/utf8>>}}
        end end,
    Decoder_dict = gleam@list:fold(
        Strategies,
        maps:new(),
        fun(Acc, S) -> gleam@dict:insert(Acc, erlang:element(2, S), S) end
    ),
    Sized_decoder = fun(Data) -> case Data of
            <<Tag:8, _/bitstring>> ->
                case gleam_stdlib:map_get(Decoder_dict, Tag) of
                    {ok, Strategy} ->
                        (erlang:element(5, Strategy))(Data);

                    {error, _} ->
                        {error,
                            {tag_mismatch,
                                <<"one of "/utf8,
                                    (begin
                                        _pipe = gleam@list:map(
                                            Strategies,
                                            fun(S@1) ->
                                                erlang:element(3, S@1)
                                            end
                                        ),
                                        _pipe@1 = gleam@list:unique(_pipe),
                                        gleam@list:fold(
                                            _pipe@1,
                                            <<""/utf8>>,
                                            fun(Acc@1, N) -> case Acc@1 of
                                                    <<""/utf8>> ->
                                                        N;

                                                    _ ->
                                                        <<<<Acc@1/binary,
                                                                ", "/utf8>>/binary,
                                                            N/binary>>
                                                end end
                                        )
                                    end)/binary>>,
                                erlang:integer_to_binary(Tag)}}
                end;

            _ ->
                {error, {insufficient_data, <<"missing variant tag"/utf8>>}}
        end end,
    {codec, Encoder, distribute@codec:to_decoder(Sized_decoder), Sized_decoder}.