%%%-------------------------------------------------------------------
%%% @copyright (C) 2018, Aeternity Anstalt
%%% @doc
%%% Functions for serializing generic objects to/from binary format.
%%% @end
%%%-------------------------------------------------------------------

-module(aeserialization).

-export([ decode_fields/2
        , deserialize/5
        , deserialize_tag_and_vsn/1
        , encode_fields/2
        , serialize/4 ]).

%%%===================================================================
%%% Types
%%%===================================================================

-export_type([ template/0
             , fields/0
             ]).

-type template() :: [{field_name(), type()}].
-type field_name() :: atom().
-type type() :: 'int'
              | 'bool'
              | 'binary'
              | 'id'     %% As defined in aec_id.erl
              | [type()] %% Length one in the type. This means a list of any length.
              | #{items := [{field_name(), type()}]} %% Record with named fields represented as a map. Encoded as a list in the given order.
              | tuple(). %% Any arity, containing type(). This means a static size array.

-type encodable_term() :: non_neg_integer()
                        | binary()
                        | boolean()
                        | [encodable_term()] %% Of any length
			| #{atom() => encodable_term()}
                        | tuple()  %% Any arity, containing encodable_term().
                        | aeser_id:id().

-type fields() :: [{field_name(), encodable_term()}].

%%%===================================================================
%%% API
%%%===================================================================

-spec serialize(non_neg_integer(), non_neg_integer(), template(), fields()) -> binary().
serialize(Tag, Vsn, Template, Fields) ->
    List = encode_fields([{tag, int}, {vsn, int}|Template],
                         [{tag, Tag}, {vsn, Vsn}|Fields]),
    aeser_rlp:encode(List).

%% Type isn't strictly necessary, but will give a better error reason
-spec deserialize(atom(), non_neg_integer(), non_neg_integer(),
                  template(), binary()) -> fields().
deserialize(Type, Tag, Vsn, Template0, Binary) ->
    Decoded = aeser_rlp:decode(Binary),
    Template = [{tag, int}, {vsn, int}|Template0],
    case decode_fields(Template, Decoded) of
        [{tag, Tag}, {vsn, Vsn}|Left] ->
            Left;
        Other ->
            error({illegal_serialization, Type, Vsn,
                   Other, Binary, Decoded, Template})
    end.

-spec deserialize_tag_and_vsn(binary()) ->
               {non_neg_integer(), non_neg_integer(), fields()}.
deserialize_tag_and_vsn(Binary) ->
    [TagBin, VsnBin|Fields] = aeser_rlp:decode(Binary),
    Template = [{tag, int}, {vsn, int}],
    [{tag, Tag}, {vsn, Vsn}] = decode_fields(Template, [TagBin, VsnBin]),
    {Tag, Vsn, Fields}.

encode_fields([{Field, Type}|TypesLeft],
               [{Field, Val}|FieldsLeft]) ->
    try encode_field(Type, Val) of
        Encoded -> [Encoded | encode_fields(TypesLeft, FieldsLeft)]
    catch error:{illegal, T, V} ->
        error({illegal_field, Field, Type, Val, T, V})
    end;
encode_fields([], []) ->
    [];
encode_fields(Template, Values) ->
    error({illegal_template_or_values, Template, Values}).

decode_fields([{Field, Type}|TypesLeft],
              [Bin          |FieldsLeft]) ->
    try decode_field(Type, Bin) of
        Decoded -> [{Field, Decoded} | decode_fields(TypesLeft, FieldsLeft)]
    catch error:{illegal, T, V} ->
        error({illegal_field, Field, Type, Bin, T, V})
    end;
decode_fields([], []) ->
    [];
decode_fields(Template, Values) ->
    error({illegal_template_or_values, Template, Values}).

%%%===================================================================
%%% Internal functions
%%%===================================================================

encode_field([Type], L) when is_list(L) ->
    [encode_field(Type, X) || X <- L];
encode_field(#{items := Items}, Map) ->
    lists:map(
      fun({K, Type}) ->
              V = maps:get(K, Map),
              encode_field(Type, V)
      end, Items);
encode_field(Type, T) when tuple_size(Type) =:= tuple_size(T) ->
    Zipped = lists:zip(tuple_to_list(Type), tuple_to_list(T)),
    [encode_field(X, Y) || {X, Y} <- Zipped];
encode_field(int, X) when is_integer(X), X >= 0 ->
    binary:encode_unsigned(X);
encode_field(binary, X) when is_binary(X) -> X;
encode_field(bool, true) -> <<1:8>>;
encode_field(bool, false) -> <<0:8>>;
encode_field(id, Val) ->
    try aeser_id:encode(Val)
    catch _:_ -> error({illegal, id, Val})
    end;
encode_field(Type, Val) -> error({illegal, Type, Val}).

decode_field([Type], List) when is_list(List) ->
    [decode_field(Type, X) || X <- List];
decode_field(#{items := Items}, List) when length(List) =:= length(Items) ->
    Zipped = lists:zip(Items, List),
    lists:foldl(
      fun({{K, Type}, V}, Map) ->
              maps:is_key(K, Map) andalso error(badarg, duplicate_field),
              Map#{ K => decode_field(Type, V) }
      end, #{}, Zipped);
decode_field(Type, List) when length(List) =:= tuple_size(Type) ->
    Zipped = lists:zip(tuple_to_list(Type), List),
    list_to_tuple([decode_field(X, Y) || {X, Y} <- Zipped]);
decode_field(int, <<0:8, X/binary>> = B) when X =/= <<>> ->
    error({illegal, int, B});
decode_field(int, X) when is_binary(X) -> binary:decode_unsigned(X);
decode_field(binary, X) when is_binary(X) -> X;
decode_field(bool, <<1:8>>) -> true;
decode_field(bool, <<0:8>>) -> false;
decode_field(id, Val) ->
    try aeser_id:decode(Val)
    catch _:_ -> error({illegal, id, Val})
    end;
decode_field(Type, X) -> error({illegal, Type, X}).