%%% Copyright (C) 2009 - Will Glozer.  All rights reserved.
%%% Copyright (C) 2011 - Anton Lebedevich.  All rights reserved.

-module(epgsql_wire).

-export([decode_message/1,
         decode_error/1,
         decode_strings/1,
         decode_columns/3,
         decode_parameters/2,
         encode/1,
         encode/2,
         build_decoder/2,
         decode_data/2,
         decode_complete/1,
         encode_types/2,
         encode_formats/1,
         format/2,
         encode_parameters/2,
         encode_standby_status_update/3]).

-include("epgsql.hrl").
-include("epgsql_binary.hrl").


decode_message(<<Type:8, Len:?int32, Rest/binary>> = Bin) ->
    Len2 = Len - 4,
    case Rest of
        <<Data:Len2/binary, Tail/binary>> ->
            {Type, Data, Tail};
        _Other ->
            Bin
    end;

decode_message(Bin) ->
    Bin.

%% decode a single null-terminated string
decode_string(Bin) ->
    binary:split(Bin, <<0>>).

%% decode multiple null-terminated string
decode_strings(Bin) ->
    [<<>> | T] = lists:reverse(binary:split(Bin, <<0>>, [global])),
    lists:reverse(T).

%% decode field
decode_fields(Bin) ->
    decode_fields(Bin, []).

decode_fields(<<0>>, Acc) ->
    Acc;
decode_fields(<<Type:8, Rest/binary>>, Acc) ->
    [Str, Rest2] = decode_string(Rest),
    decode_fields(Rest2, [{Type, Str} | Acc]).

%% decode ErrorResponse
%% See http://www.postgresql.org/docs/current/interactive/protocol-error-fields.html
decode_error(Bin) ->
    Fields = decode_fields(Bin),
    ErrCode = proplists:get_value($C, Fields),
    ErrName = epgsql_errcodes:to_name(ErrCode),
    {ErrSeverity, Extra} = case proplists:get_value($V, Fields) of
        undefined ->
            {proplists:get_value($S, Fields), []};
        Severity ->
            {Severity, [{severity, proplists:get_value($S, Fields)}]}
    end,
    Error = #error{
      severity = lower_atom(ErrSeverity),
      code     = ErrCode,
      codename = ErrName,
      message  = proplists:get_value($M, Fields),
      extra    = lists:sort(Extra ++ lists:foldl(fun decode_error_extra/2, [], Fields))},
    Error.

%% consider updating #error.extra typespec when changing/adding extras
decode_error_extra({$D, Val}, Acc) ->
    [{detail, Val} | Acc];
decode_error_extra({$H, Val}, Acc) ->
    [{hint, Val} | Acc];
decode_error_extra({$P, Val}, Acc) ->
    [{position, Val} | Acc];
decode_error_extra({$p, Val}, Acc) ->
    [{internal_position, Val} | Acc];
decode_error_extra({$q, Val}, Acc) ->
    [{internal_query, Val} | Acc];
decode_error_extra({$W, Val}, Acc) ->
    [{where, Val} | Acc];
decode_error_extra({$s, Val}, Acc) ->
    [{schema_name, Val} | Acc];
decode_error_extra({$t, Val}, Acc) ->
    [{table_name, Val} | Acc];
decode_error_extra({$c, Val}, Acc) ->
    [{column_name, Val} | Acc];
decode_error_extra({$d, Val}, Acc) ->
    [{data_type_name, Val} | Acc];
decode_error_extra({$n, Val}, Acc) ->
    [{constraint_name, Val} | Acc];
decode_error_extra({$F, Val}, Acc) ->
    [{file, Val} | Acc];
decode_error_extra({$L, Val}, Acc) ->
    [{line, Val} | Acc];
decode_error_extra({$R, Val}, Acc) ->
    [{routine, Val} | Acc];
decode_error_extra({_, _}, Acc) ->
    Acc.

lower_atom(Str) when is_binary(Str) ->
    lower_atom(binary_to_list(Str));
lower_atom(Str) when is_list(Str) ->
    list_to_atom(string:to_lower(Str)).

%% FIXME: return iolist
encode(Data) ->
    Bin = iolist_to_binary(Data),
    <<(byte_size(Bin) + 4):?int32, Bin/binary>>.

encode(Type, Data) ->
    Bin = iolist_to_binary(Data),
    <<Type:8, (byte_size(Bin) + 4):?int32, Bin/binary>>.

%% Build decoder for DataRow
build_decoder(Columns, Codec) ->
    {Columns, Codec}.

%% decode row data
%% FIXME: use body recursion
decode_data(Bin, {Columns, Codec}) ->
    decode_data(Columns, Bin, [], Codec).

decode_data([], _Bin, Acc, _Codec) ->
    list_to_tuple(lists:reverse(Acc));
decode_data([_C | T], <<-1:?int32, Rest/binary>>, Acc, Codec) ->
    decode_data(T, Rest, [null | Acc], Codec);
decode_data([C | T], <<Len:?int32, Value:Len/binary, Rest/binary>>, Acc, Codec) ->
    Value2 = case C of
        #column{type = Type, format = 1} ->
            epgsql_binary:decode(Type, Value, Codec);
        #column{} ->
            Value
    end,
    decode_data(T, Rest, [Value2 | Acc], Codec).

%% decode column information
%% TODO: use body-recursion
decode_columns(Count, Bin, Codec) ->
    decode_columns(Count, Bin, [], Codec).

decode_columns(0, _Bin, Acc, _Codec) ->
    lists:reverse(Acc);
decode_columns(N, Bin, Acc, Codec) ->
    [Name, Rest] = decode_string(Bin),
    <<_Table_Oid:?int32, _Attrib_Num:?int16, Type_Oid:?int32,
     Size:?int16, Modifier:?int32, Format:?int16, Rest2/binary>> = Rest,
    Desc = #column{
      name     = Name,
      type     = epgsql_binary:oid2type(Type_Oid, Codec),
      size     = Size,
      modifier = Modifier,
      format   = Format},
    decode_columns(N - 1, Rest2, [Desc | Acc], Codec).

%% decode ParameterDescription
decode_parameters(<<_Count:?int16, Bin/binary>>, Codec) ->
    [epgsql_binary:oid2type(Oid, Codec) || <<Oid:?int32>> <= Bin].

%% decode command complete msg
decode_complete(<<"SELECT", 0>>)        -> select;
decode_complete(<<"SELECT", _/binary>>) -> select;
decode_complete(<<"BEGIN", 0>>)         -> 'begin';
decode_complete(<<"ROLLBACK", 0>>)      -> rollback;
decode_complete(Bin) ->
    [Str, _] = decode_string(Bin),
    case string:tokens(binary_to_list(Str), " ") of
        ["INSERT", _Oid, Rows] -> {insert, list_to_integer(Rows)};
        ["UPDATE", Rows]       -> {update, list_to_integer(Rows)};
        ["DELETE", Rows]       -> {delete, list_to_integer(Rows)};
        ["MOVE", Rows]         -> {move, list_to_integer(Rows)};
        ["FETCH", Rows]        -> {fetch, list_to_integer(Rows)};
        [Type | _Rest]         -> lower_atom(Type)
    end.

%% encode types
encode_types(Types, Codec) ->
    encode_types(Types, 0, <<>>, Codec).

encode_types([], Count, Acc, _Codec) ->
    <<Count:?int16, Acc/binary>>;

encode_types([Type | T], Count, Acc, Codec) ->
    Oid = case Type of
        undefined -> 0;
        _Any      -> epgsql_binary:type2oid(Type, Codec)
    end,
    encode_types(T, Count + 1, <<Acc/binary, Oid:?int32>>, Codec).

%% encode column formats
encode_formats(Columns) ->
    encode_formats(Columns, 0, <<>>).

encode_formats([], Count, Acc) ->
    <<Count:?int16, Acc/binary>>;

encode_formats([#column{format = Format} | T], Count, Acc) ->
    encode_formats(T, Count + 1, <<Acc/binary, Format:?int16>>).

format(Type, _Codec) ->
    case epgsql_binary:supports(Type) of
        true  -> 1;
        false -> 0
    end.

%% encode parameters
encode_parameters(Parameters, Codec) ->
    encode_parameters(Parameters, 0, <<>>, <<>>, Codec).

encode_parameters([], Count, Formats, Values, _Codec) ->
    <<Count:?int16, Formats/binary, Count:?int16, Values/binary>>;

encode_parameters([P | T], Count, Formats, Values, Codec) ->
    {Format, Value} = encode_parameter(P, Codec),
    Formats2 = <<Formats/binary, Format:?int16>>,
    Values2 = <<Values/binary, Value/binary>>,
    encode_parameters(T, Count + 1, Formats2, Values2, Codec).

%% encode parameter

encode_parameter({Type, Value}, Codec) ->
    case epgsql_binary:encode(Type, Value, Codec) of
        Bin when is_binary(Bin) -> {1, Bin};
        {error, unsupported}    -> encode_parameter(Value)
    end;
encode_parameter(Value, _Codec) -> encode_parameter(Value).

encode_parameter(A) when is_atom(A)    -> {0, encode_list(atom_to_list(A))};
encode_parameter(B) when is_binary(B)  -> {0, <<(byte_size(B)):?int32, B/binary>>};
encode_parameter(I) when is_integer(I) -> {0, encode_list(integer_to_list(I))};
encode_parameter(F) when is_float(F)   -> {0, encode_list(float_to_list(F))};
encode_parameter(L) when is_list(L)    -> {0, encode_list(L)}.

encode_list(L) ->
    Bin = list_to_binary(L),
    <<(byte_size(Bin)):?int32, Bin/binary>>.

encode_standby_status_update(ReceivedLSN, FlushedLSN, AppliedLSN) ->
    {MegaSecs, Secs, MicroSecs} = os:timestamp(),
    Timestamp = ((MegaSecs * 1000000 + Secs) * 1000000 + MicroSecs) - 946684800*1000000, %% microseconds since midnight on 2000-01-01
    <<$r:8, ReceivedLSN:?int64, FlushedLSN:?int64, AppliedLSN:?int64, Timestamp:?int64, 0:8>>.