%%
%% Licensed to the Apache Software Foundation (ASF) under one
%% or more contributor license agreements. See the NOTICE file
%% distributed with this work for additional information
%% regarding copyright ownership. The ASF licenses this file
%% to you under the Apache License, Version 2.0 (the
%% "License"); you may not use this file except in compliance
%% with the License. You may obtain a copy of the License at
%%
%%   http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing,
%% software distributed under the License is distributed on an
%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
%% KIND, either express or implied. See the License for the
%% specific language governing permissions and limitations
%% under the License.
%%

-module(thrift_framed_transport).

-behaviour(thrift_transport).

%% API
-export([new/1]).

%% thrift_transport callbacks
-export([write/2, read/2, flush/1, close/1]).

-record(framed_transport, {wrapped, % a thrift_transport
                           read_buffer, % iolist()
                           write_buffer % iolist()
                          }).
-type state() :: #framed_transport{}.
-include("thrift_transport_behaviour.hrl").

new(WrappedTransport) ->
    State = #framed_transport{wrapped = WrappedTransport,
                              read_buffer = [],
                              write_buffer = []},
    thrift_transport:new(?MODULE, State).

%% Writes data into the buffer
write(State = #framed_transport{write_buffer = WBuf}, Data) ->
    {State#framed_transport{write_buffer = [WBuf, Data]}, ok}.

%% Flushes the buffer through to the wrapped transport
flush(State0 = #framed_transport{write_buffer = Buffer,
                                   wrapped = Wrapped0}) ->
    FrameLen = iolist_size(Buffer),
    Data     = [<<FrameLen:32/integer-signed-big>>, Buffer],

    {Wrapped1, Response} = thrift_transport:write(Wrapped0, Data),

    {Wrapped2, _} = thrift_transport:flush(Wrapped1),

    State1 = State0#framed_transport{wrapped = Wrapped2, write_buffer = []},
    {State1, Response}.

%% Closes the transport and the wrapped transport
close(State = #framed_transport{wrapped = Wrapped0}) ->
    {Wrapped1, Result} = thrift_transport:close(Wrapped0),
    NewState = State#framed_transport{wrapped = Wrapped1},
    {NewState, Result}.

%% Reads data through from the wrapped transport
read(State0 = #framed_transport{wrapped = Wrapped0, read_buffer = RBuf},
     Len) when is_integer(Len) ->
    {Wrapped1, {RBuf1, RBuf1Size}} =
        %% if the read buffer is empty, read another frame
        %% otherwise, just read from what's left in the buffer
        case iolist_size(RBuf) of
            0 ->
                %% read the frame length
                case thrift_transport:read(Wrapped0, 4) of
                  {WrappedS1,
                    {ok, <<FrameLen:32/integer-signed-big, _/binary>>}} ->
                    %% then read the data
                    case thrift_transport:read(WrappedS1, FrameLen) of
                      {WrappedS2, {ok, Bin}} ->
                        {WrappedS2, {Bin, erlang:byte_size(Bin)}};
                      {WrappedS2, {error, Reason1}} ->
                        {WrappedS2, {error, Reason1}}
                    end;
                  {WrappedS1, {error, Reason2}} ->
                    {WrappedS1, {error, Reason2}}
                end;
            Sz ->
                {Wrapped0, {RBuf, Sz}}
        end,

    %% pull off Give bytes, return them to the user, leave the rest in the buffer
    case RBuf1 of
      error ->
        { State0#framed_transport {wrapped = Wrapped1, read_buffer = [] },
          {RBuf1, RBuf1Size} };
      _ ->
        Give = min(RBuf1Size, Len),
        <<Data:Give/binary, RBuf2/binary>> = iolist_to_binary(RBuf1),

        { State0#framed_transport{wrapped = Wrapped1, read_buffer=RBuf2},
          {ok, Data} }
    end.

%%--------------------------------------------------------------------
%% Internal functions
%%--------------------------------------------------------------------

min(A,B) when A<B -> A;
min(_,B)          -> B.