-module(midibin).
-export([
    decode/1,
    encode/1
]).

-include_lib("midilib/include/errors.hrl").

-define(MLSB_MASK, 127).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% DECODE: Channel Voice Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

decode(<<1:1, 0:3, Channel:4, 0:1, Pitch:7, 0:1, Velocity:7>>) ->
    {midi, {note_off, [{channel, Channel + 1},
                       {pitch, Pitch}, 
                       {velocity, Velocity}]}};

decode(<<1:1, 1:3, Channel:4, 0:1, Pitch:7, 0:1, Velocity:7>>) ->
    {midi, {note_on, [{channel, Channel + 1},
                      {pitch, Pitch},
                      {velocity, Velocity}]}};

decode(<<1:1, 2:3, Channel:4, 0:1, Pitch:7, 0:1, Pressure:7>>) ->
    {midi, {poly_aftertouch, [{channel, Channel + 1},
                              {pitch, Pitch},
                              {pressure, Pressure}]}};

decode(<<1:1, 4:3, Channel:4, 0:1, Program:7>>) ->
    {midi, {program_change, [{channel, Channel + 1},
                             {program, Program}]}};

decode(<<1:1, 5:3, Channel:4, 0:1, Pressure:7>>) ->
    {midi, {aftertouch, [{channel, Channel + 1},
                         {pressure, Pressure}]}};

decode(<<1:1, 6:3, Channel:4, 0:1, Lsb:7, 0:1, Msb:7>>) ->
    {midi, {pitch_bend, [{channel, Channel + 1},
                         {value, (Msb bsl 7) + Lsb}]}};

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% DECODE: Channel Mode Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

decode(<<1:1, 3:3, Channel:4, 0:1, 120:7, 0:1, 0:7>>) ->
    {midi, {mode, [{channel, Channel + 1},
                   {control, all_sound_off}]}};

decode(<<1:1, 3:3, Channel:4, 0:1, 121:7, 0:1, 0:7>>) ->
    {midi, {mode, [{channel, Channel + 1},
                   {control, reset_all}]}};

decode(<<1:1, 3:3, Channel:4, 0:1, 122:7, 0:1, 0:7>>) ->
    {midi, {mode, [{channel, Channel + 1},
                   {control, local_control_off}]}};

decode(<<1:1, 3:3, Channel:4, 0:1, 122:7, 0:1, 127:7>>) ->
    {midi, {mode, [{channel, Channel + 1},
                   {control, local_control_on}]}};

decode(<<1:1, 3:3, Channel:4, 0:1, 123:7, 0:1, 0:7>>) ->
    {midi, {mode, [{channel, Channel + 1},
                   {control, all_notes_off}]}};

decode(<<1:1, 3:3, Channel:4, 0:1, 124:7, 0:1, 0:7>>) ->
    {midi, {mode, [{channel, Channel + 1},
                   {control, omni_mode_off}]}};

decode(<<1:1, 3:3, Channel:4, 0:1, 125:7, 0:1, 0:7>>) ->
    {midi, {mode, [{channel, Channel + 1},
                   {control, omni_mode_on}]}};

%%decode(<<1:1, 3:3, Channel:4, 0:1, 126:7, 0:1, 0:7>>) ->
%%    {midi, mono_mode_on};
decode(<<1:1, 3:3, _:4, 0:1, 126:7, 0:1, _:7>>) ->
    ?ERR_NOT_IMPL;

decode(<<1:1, 3:3, Channel:4, 0:1, 127:7, 0:1, 0:7>>) ->
    {midi, {mode, [{channel, Channel + 1},
                   {control, poly_mode_on}]}};

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% DECODE: Control Change Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

decode(<<1:1, 3:3, Channel:4, 0:1, Control:7, 0:1, Value:7>>) ->
    {midi, {cc, [{channel, Channel + 1},
                 {control, Control},
                 {value, Value}]}};

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% DECODE: System Common Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

decode(<<1:1, 7:3, 1:4, 0:1, MessageType:3, Value:4>>) ->
    {midi, {time_code_quarter_frame, MessageType, Value}};

decode(<<1:1, 7:3, 2:4, 0:1, Lsb:7, 0:1, Msb:7>>) ->
    {midi, {song_position_pointer, (Msb bsl 7) + Lsb}};

decode(<<1:1, 7:3, 3:4, 0:1, Value:7>>) ->
    {midi, {song_select, Value}};

decode(<<1:1, 7:3, 6:4>>) ->
    {midi, tune_request};

decode(<<1:1, 7:3, 7:4>>) ->
    {midi, end_of_sys_ex};

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% DECODE: Real-Time Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

decode(<<248:8>>) ->
    {midi, {realtime, clock}};

decode(<<250:8>>) ->
    {midi, {realtime, start}};

decode(<<251:8>>) ->
    {midi, {realtime, continue}};

decode(<<252:8>>) ->
    {midi, {realtime, stop}};

decode(<<254:8>>) ->
    {midi, {realtime, active_sensing}};

decode(<<255:8>>) ->
    {midi, {realtime, reset}};

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% DECODE: System Exclusive Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

decode(<<1:1, 7:3, 0:4, 0:1, Data:7>>) ->
    {midi, {sys_ex, Data}};

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% DECODE: midilib Custom Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% batch

decode(Batch) when is_list(Batch) ->
    decode_batch(Batch, []);

%% bank_select

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% DECODE: Unexpected Messages & Errors %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

decode({error, _}=Error) ->
    Error;

decode(Bin) ->
    {unknown, Bin}.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% ENCODE: Channel Voice Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Aftertouch

encode({midi, {aftertouch, [{channel, Channel},
                            {pressure, Pressure}]}}) ->
    <<1:1, 5:3, (Channel - 1):4, 0:1, Pressure:7>>;
encode({midi, {aftertouch, Pressure}}) ->
    encode({midi, {aftertouch, [{channel, 1},
                                {pressure, Pressure}]}});

%% Note off

encode({midi, {note_off, [{channel, Channel},
                          {pitch, Pitch},
                          {velocity, Velocity}]}}) ->
    <<1:1, 0:3, (Channel - 1):4, 0:1, Pitch:7, 0:1, Velocity:7>>;
encode({midi, {note_off, [{pitch, Pitch},
                          {velocity, Velocity}]}}) ->
    encode({midi, {note_off, [{channel, 1},
                              {pitch, Pitch},
                              {velocity, Velocity}]}});
encode({midi, {note_off, Pitch}}) ->
    encode({midi, {note_off, [{pitch, Pitch},
                              {velocity, 64}]}});

%% Note on

encode({midi, {note_on, [{channel, Channel},
                         {pitch, Pitch},
                         {velocity, Velocity}]}}) ->
    <<1:1, 1:3, (Channel - 1):4, 0:1, Pitch:7, 0:1, Velocity:7>>;
encode({midi, {note_on, [{pitch, Pitch},
                         {velocity, Velocity}]}}) ->
    encode({midi, {note_on, [{channel, 1},
                             {pitch, Pitch},
                             {velocity, Velocity}]}});

%% Pitchbend

encode({midi, {pitchbend, Data}}) ->
    encode({midi, {pitch_bend, Data}});
encode({midi, {pitch_bend, [{channel, Channel},
                            {msb, Msb},
                            {lsb, Lsb}]}}) ->
    <<1:1, 6:3, (Channel - 1):4, 0:1, Lsb:7, 0:1, Msb:7>>;
encode({midi, {pitch_bend, [{channel, Channel},
                            {value, Value}]}}) ->
    Msb = (Value band (?MLSB_MASK bsl 7)) bsr 7,
    Lsb = Value band ?MLSB_MASK,
    encode({midi, {pitch_bend, [{channel, Channel},
                                {msb, Msb},
                                {lsb, Lsb}]}});
encode({midi, {pitch_bend, Value}}) ->
    encode({midi, {pitch_bend, [{channel, 1},
                                {value, Value}]}});

%% Poly-aftertouch

encode({midi, {poly_aftertouch, [{channel, Channel},
                                 {pitch, Pitch},
                                 {pressure, Pressure}]}}) ->
    <<1:1, 2:3, (Channel - 1):4, 0:1, Pitch:7, 0:1, Pressure:7>>;
encode({midi, {poly_aftertouch, [{pitch, Pitch},
                                 {pressure, Pressure}]}}) ->
    encode({midi, {poly_aftertouch, [{channel, 1},
                                     {pitch, Pitch},
                                     {pressure, Pressure}]}});

%% Program change

encode({midi, {program_change, [{channel, Channel},
                                {program, Program}]}}) ->
    <<1:1, 4:3, (Channel - 1):4, 0:1, Program:7>>;
encode({midi, {program_change, [{program, Program}]}}) ->
    encode({midi, {program_change, [{channel, 1},
                                    {program, Program}]}});

encode({midi, {program_change, Program}}) ->
    encode({midi, {program_change, [{program, Program}]}});


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% ENCODE: Channel Mode Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% all_sound_off

encode({midi, {mode, [{channel, Channel},
                      {control, all_sound_off}]}}) ->
    <<1:1, 3:3, (Channel - 1):4, 0:1, 120:7, 0:1, 0:7>>;

encode({midi, all_sound_off}) ->
    encode({midi, {mode, [{channel, 1},
                          {control, all_sound_off}]}});

%% reset_all

encode({midi, {mode, [{channel, Channel},
                      {control, reset_all}]}}) ->
    <<1:1, 3:3, (Channel - 1):4, 0:1, 121:7, 0:1, 0:7>>;

encode({midi, reset_all}) ->
    encode({midi, {mode, [{channel, 1},
                          {control, reset_all}]}});

%% local_control_off

encode({midi, {mode, [{channel, Channel},
                      {control, local_control_off}]}}) ->
    <<1:1, 3:3, (Channel - 1):4, 0:1, 122:7, 0:1, 0:7>>;

encode({midi, local_control_off}) ->
    encode({midi, {mode, [{channel, 1},
                          {control, local_control_off}]}});

%% local_control_on

encode({midi, {mode, [{channel, Channel},
                      {control, local_control_on}]}}) ->
    <<1:1, 3:3, (Channel - 1):4, 0:1, 122:7, 0:1, 127:7>>;

encode({midi, local_control_on}) ->
    encode({midi, {mode, [{channel, 1},
                          {control, local_control_on}]}});

%% all_notes_off

encode({midi, {mode, [{channel, Channel},
                      {control, all_notes_off}]}}) ->
    <<1:1, 3:3, (Channel - 1):4, 0:1, 123:7, 0:1, 0:7>>;

encode({midi, all_notes_off}) ->
    encode({midi, {mode, [{channel, 1},
                          {control, all_notes_off}]}});

%% omni_mode_off

encode({midi, {mode, [{channel, Channel},
                      {control, omni_mode_off}]}}) ->
    <<1:1, 3:3, (Channel - 1):4, 0:1, 124:7, 0:1, 0:7>>;

encode({midi, omni_mode_off}) ->
    encode({midi, {mode, [{channel, 1},
                          {control, omni_mode_off}]}});

%% all_notes_on

encode({midi, {mode, [{channel, Channel},
                      {control, omni_mode_on}]}}) ->
    <<1:1, 3:3, (Channel - 1):4, 0:1, 125:7, 0:1, 0:7>>;

encode({midi, omni_mode_on}) ->
    encode({midi, {mode, [{channel, 1},
                          {control, omni_mode_on}]}});

%% mono_mode_on

encode({midi, {mode, [{channel, _},
                      {control, mono_mode_on}]}}) ->
    %%<<1:1, 3:3, Channel:4, 0:1, 126:7, 0:1, 0:7>>;
    ?ERR_NOT_IMPL;

encode({midi, mono_mode_on}) ->
    encode({midi, {mode, [{channel, 1},
                          {control, mono_mode_on}]}});

%% poly_mode_on

encode({midi, {mode, [{channel, Channel},
                      {control, poly_mode_on}]}}) ->
    <<1:1, 3:3, (Channel - 1):4, 0:1, 127:7, 0:1, 0:7>>;

encode({midi, poly_mode_on}) ->
    encode({midi, {mode, [{channel, 1},
                          {control, poly_mode_on}]}});

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% ENCODE: Control Change Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

encode({midi, {cc, [{channel, Channel},
                    {control, Control},
                    {value, Value}]}}) ->
    <<1:1, 3:3, (Channel - 1):4, 0:1, Control:7, 0:1, Value:7>>;

encode({midi, {cc, [{control, Control},
                    {value, Value}]}}) ->
    encode({midi, {cc, [{channel, 1},
                        {control, Control},
                        {value, Value}]}});

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% ENCODE: System Common Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% time_code_quarter_frame

encode({midi, {time_code_quarter_frame, MessageType, Value}}) ->
    <<1:1, 7:3, 1:4, 0:1, MessageType:3, Value:4>>;

%% song_position_pointer

encode({midi, {song_position_pointer, [{msb, Msb},
                                       {lsb, Lsb}]}}) ->
    <<1:1, 7:3, 2:4, 0:1, Lsb:7, 0:1, Msb:7>>;
encode({midi, {song_position_pointer, Value}}) ->
    Msb = (Value band (?MLSB_MASK bsl 7)) bsr 7,
    Lsb = Value band ?MLSB_MASK,
    encode({midi, {song_position_pointer, [{msb, Msb}, {lsb, Lsb}]}});

%% song_select

encode({midi, {song_select, Value}}) ->
    <<1:1, 7:3, 3:4, 0:1, Value:7>>;

%% tune_request

encode({midi, tune_request}) ->
    <<1:1, 7:3, 6:4>>;

%% end_of_sys_ex

encode({midi, end_of_sys_ex}) ->
    <<1:1, 7:3, 7:4>>;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% ENCODE: Real-Time Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

encode({midi, {realtime, active_sensing}}) ->
    <<254:8>>;
encode({midi, {realtime, clock}}) ->
    <<248:8>>;
encode({midi, {realtime, continue}}) ->
    <<251:8>>;
encode({midi, {realtime, reset}}) ->
    <<255:8>>;
encode({midi, {realtime, start}}) ->
    <<250:8>>;
encode({midi, {realtime, stop}}) ->
    <<252:8>>;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% ENCODE: System Exclusive Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

encode({midi, {sys_ex, Data}}) ->
    <<1:1, 7:3, 0:4, 0:1, Data:7>>;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% ENCODE: midilib Custom Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% batch

encode({midi, {batch, Batch}}) ->
    encode_batch(Batch, []);

%% bank_select

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% ENCODE: Unexpected Messages %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

encode({midi, _}) ->
    ?ERR_MIDI_UNSUP;
encode(_) ->
    ?ERR_NON_MIDI.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% Support Functions %%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

decode_batch([], Acc) ->
    {midi, {batch, Acc}};
decode_batch([Head|Tail], Acc) ->
    decode_batch(Tail, Acc ++ [decode(Head)]).

encode_batch([], Acc) ->
    Acc;
encode_batch([Head|Tail], Acc) ->
    Encoded = encode(Head),
    case Encoded of
        {error, _} ->
            Acc ++ [Encoded]; % stop immediately in case of error
        _ ->
            encode_batch(Tail, Acc ++ [Encoded])
    end.