// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/

#include "Gym_Emu.h"

#include "blargg_endian.h"
#include <string.h>

/* Copyright (C) 2003-2006 Shay Green. This module is free software; you
can redistribute it and/or modify it under the terms of the GNU Lesser
General Public License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version. This
module is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
details. You should have received a copy of the GNU Lesser General Public
License along with this module; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */

#include "blargg_source.h"

static double const min_tempo = 0.25;
static double const oversample_factor = 5 / 3.0;
static double const fm_gain = 3.0;

static const long base_clock = 53700300;
static const long clock_rate = base_clock / 15;

Gym_Emu::Gym_Emu()
{
	data = 0;
	pos  = 0;
	set_type( gme_gym_type );

	static const char* const names [] = {
		"FM 1", "FM 2", "FM 3", "FM 4", "FM 5", "FM 6", "PCM", "PSG"
	};
	set_voice_names( names );
	set_silence_lookahead( 1 ); // tracks should already be trimmed
}

Gym_Emu::~Gym_Emu() { }

// Track info

static void get_gym_info( Gym_Emu::header_t const& h, long length, track_info_t* out )
{
	if ( !memcmp( h.tag, "GYMX", 4 ) )
	{
		length = length * 50 / 3; // 1000 / 60
		long loop = get_le32( h.loop_start );
		if ( loop )
		{
			out->intro_length = loop * 50 / 3;
			out->loop_length  = length - out->intro_length;
		}
		else
		{
			out->length = length;
			out->intro_length = length; // make it clear that track is no longer than length
			out->loop_length = 0;
		}

		// more stupidity where the field should have been left
		if ( strcmp( h.song, "Unknown Song" ) )
			GME_COPY_FIELD( h, out, song );

		if ( strcmp( h.game, "Unknown Game" ) )
			GME_COPY_FIELD( h, out, game );

		if ( strcmp( h.copyright, "Unknown Publisher" ) )
			GME_COPY_FIELD( h, out, copyright );

		if ( strcmp( h.dumper, "Unknown Person" ) )
			GME_COPY_FIELD( h, out, dumper );

		if ( strcmp( h.comment, "Header added by YMAMP" ) )
			GME_COPY_FIELD( h, out, comment );
	}
}

blargg_err_t Gym_Emu::track_info_( track_info_t* out, int ) const
{
	get_gym_info( header_, track_length(), out );
	return 0;
}

static long gym_track_length( byte const* p, byte const* end )
{
	long time = 0;
	while ( p < end )
	{
		switch ( *p++ )
		{
			case 0:
				time++;
				break;

			case 1:
			case 2:
				p += 2;
				break;

			case 3:
				p += 1;
				break;
		}
	}
	return time;
}

long Gym_Emu::track_length() const { return gym_track_length( data, data_end ); }

static blargg_err_t check_header( byte const* in, long size, int* data_offset = 0 )
{
	if ( size < 4 )
		return gme_wrong_file_type;

	if ( memcmp( in, "GYMX", 4 ) == 0 )
	{
		if ( size < Gym_Emu::header_size + 1 )
			return gme_wrong_file_type;

		if ( memcmp( ((Gym_Emu::header_t const*) in)->packed, "\0\0\0\0", 4 ) != 0 )
			return "Packed GYM file not supported";

		if ( data_offset )
			*data_offset = Gym_Emu::header_size;
	}
	else if ( *in > 3 )
	{
		return gme_wrong_file_type;
	}

	return 0;
}

struct Gym_File : Gme_Info_
{
	byte const* file_begin;
	byte const* file_end;
	int data_offset;

	Gym_File() { set_type( gme_gym_type ); }

	blargg_err_t load_mem_( byte const* in, long size )
	{
		file_begin = in;
		file_end   = in + size;
		data_offset = 0;
		return check_header( in, size, &data_offset );
	}

	blargg_err_t track_info_( track_info_t* out, int ) const
	{
		long length = gym_track_length( &file_begin [data_offset], file_end );
		get_gym_info( *(Gym_Emu::header_t const*) file_begin, length, out );
		return 0;
	}
};

static Music_Emu* new_gym_emu () { return BLARGG_NEW Gym_Emu ; }
static Music_Emu* new_gym_file() { return BLARGG_NEW Gym_File; }

static gme_type_t_ const gme_gym_type_ = { "Sega Genesis", 1, &new_gym_emu, &new_gym_file, "GYM", 0 };
extern gme_type_t const gme_gym_type = &gme_gym_type_;

// Setup

blargg_err_t Gym_Emu::set_sample_rate_( long sample_rate )
{
	blip_eq_t eq( -32, 8000, sample_rate );
	apu.treble_eq( eq );
	dac_synth.treble_eq( eq );
	apu.volume( 0.135 * fm_gain * gain() );
	dac_synth.volume( 0.125 / 256 * fm_gain * gain() );
	double factor = Dual_Resampler::setup( oversample_factor, 0.990, fm_gain * gain() );
	fm_sample_rate = sample_rate * factor;

	RETURN_ERR( blip_buf.set_sample_rate( sample_rate, int (1000 / 60.0 / min_tempo) ) );
	blip_buf.clock_rate( clock_rate );

	RETURN_ERR( fm.set_rate( fm_sample_rate, base_clock / 7.0 ) );
	RETURN_ERR( Dual_Resampler::reset( long (1.0 / 60 / min_tempo * sample_rate) ) );

	return 0;
}

void Gym_Emu::set_tempo_( double t )
{
	if ( t < min_tempo )
	{
		set_tempo( min_tempo );
		return;
	}

	if ( blip_buf.sample_rate() )
	{
		clocks_per_frame = long (clock_rate / 60 / tempo());
		Dual_Resampler::resize( long (sample_rate() / (60.0 * tempo())) );
	}
}

void Gym_Emu::mute_voices_( int mask )
{
	Music_Emu::mute_voices_( mask );
	fm.mute_voices( mask );
	dac_muted = (mask & 0x40) != 0;
	apu.output( (mask & 0x80) ? 0 : &blip_buf );
}

blargg_err_t Gym_Emu::load_mem_( byte const* in, long size )
{
	blaarg_static_assert( offsetof (header_t,packed [4]) == header_size, "GYM Header layout incorrect!" );
	int offset = 0;
	RETURN_ERR( check_header( in, size, &offset ) );
	set_voice_count( 8 );

	data     = in + offset;
	data_end = in + size;
	loop_begin = 0;

	if ( offset )
		header_ = *(header_t const*) in;
	else
		memset( &header_, 0, sizeof header_ );

	return 0;
}

// Emulation

blargg_err_t Gym_Emu::start_track_( int track )
{
	RETURN_ERR( Music_Emu::start_track_( track ) );

	pos         = data;
	loop_remain = get_le32( header_.loop_start );

	prev_dac_count = 0;
	dac_enabled    = false;
	dac_amp        = -1;

	fm.reset();
	apu.reset();
	blip_buf.clear();
	Dual_Resampler::clear();
	return 0;
}

void Gym_Emu::run_dac( int dac_count )
{
	// Guess beginning and end of sample and adjust rate and buffer position accordingly.

	// count dac samples in next frame
	int next_dac_count = 0;
	const byte* p = this->pos;
	int cmd;
	while ( (cmd = *p++) != 0 )
	{
		int data = *p++;
		if ( cmd <= 2 )
			++p;
		if ( cmd == 1 && data == 0x2A )
			next_dac_count++;
	}

	// detect beginning and end of sample
	int rate_count = dac_count;
	int start = 0;
	if ( !prev_dac_count && next_dac_count && dac_count < next_dac_count )
	{
		rate_count = next_dac_count;
		start = next_dac_count - dac_count;
	}
	else if ( prev_dac_count && !next_dac_count && dac_count < prev_dac_count )
	{
		rate_count = prev_dac_count;
	}

	// Evenly space samples within buffer section being used
	blip_resampled_time_t period = blip_buf.resampled_duration( clocks_per_frame ) / rate_count;

	blip_resampled_time_t time = blip_buf.resampled_time( 0 ) +
			period * start + (period >> 1);

	int dac_amp = this->dac_amp;
	if ( dac_amp < 0 )
		dac_amp = dac_buf [0];

	for ( int i = 0; i < dac_count; i++ )
	{
		int delta = dac_buf [i] - dac_amp;
		dac_amp += delta;
		dac_synth.offset_resampled( time, delta, &blip_buf );
		time += period;
	}
	this->dac_amp = dac_amp;
}

void Gym_Emu::parse_frame()
{
	int dac_count = 0;
	const byte* pos = this->pos;

	if ( loop_remain && !--loop_remain )
		loop_begin = pos; // find loop on first time through sequence

	int cmd;
	while ( (cmd = *pos++) != 0 )
	{
		int data = *pos++;
		if ( cmd == 1 )
		{
			int data2 = *pos++;
			if ( data != 0x2A )
			{
				if ( data == 0x2B )
					dac_enabled = (data2 & 0x80) != 0;

				fm.write0( data, data2 );
			}
			else if ( dac_count < (int) sizeof dac_buf )
			{
				dac_buf [dac_count] = data2;
				dac_count += dac_enabled;
			}
		}
		else if ( cmd == 2 )
		{
			fm.write1( data, *pos++ );
		}
		else if ( cmd == 3 )
		{
			apu.write_data( 0, data );
		}
		else
		{
			// to do: many GYM streams are full of errors, and error count should
			// reflect cases where music is really having problems
			//log_error();
			--pos; // put data back
		}
	}

	// loop
	if ( pos >= data_end )
	{
		check( pos == data_end );

		if ( loop_begin )
			pos = loop_begin;
		else
			set_track_ended();
	}
	this->pos = pos;

	// dac
	if ( dac_count && !dac_muted )
		run_dac( dac_count );
	prev_dac_count = dac_count;
}

int Gym_Emu::play_frame( blip_time_t blip_time, int sample_count, sample_t* buf )
{
	if ( !track_ended() )
		parse_frame();

	apu.end_frame( blip_time );

	memset( buf, 0, sample_count * sizeof *buf );
	fm.run( sample_count >> 1, buf );

	return sample_count;
}

blargg_err_t Gym_Emu::play_( long count, sample_t* out )
{
	Dual_Resampler::dual_play( count, out, blip_buf );
	return 0;
}
