#include <fcntl.h> 
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <linux/soundcard.h>
#include <pthread.h>
#include <sys/ioctl.h>
#include <unistd.h>


#define COMMAND_STOP        0
#define COMMAND_PLAY_FIRST  1
#define COMMAND_PLAY_SECOND 2
#define COMMAND_PLAY_BOTH   3
#define COMMAND_EXIT        4

#define BUFSIZE 4096


/* WAVE ファイルの情報を格納する構造体 */
typedef struct {
	FILE* fp;        /* ファイル構造体 */
	short is_pcm;    /* PCM フォーマットの場合は 1、それ以外は 0 */
	short channel;   /* モノラルの場合は 1、ステレオの場合は 2 */
	int   rate;      /* サンプリング周波数 */
	short bits;      /* 量子化ビット数 */
	long  offset;    /* ファイル先頭から PCM データまでのオフセット */
	int   len;       /* PCM データ部の長さ */
	int   current;   /* 現在の再生位置 */
}
WAVE;


/* 再生に必要なデータをまとめた構造体 */
typedef struct {
	pthread_t thread_id;
	int command;
	int  dsp;
	WAVE wave[2];
	short buffer[ BUFSIZE / sizeof( short ) ];
}
Context;

static Context context;


static int   read_file( char** fnames, WAVE* wave );
static int   setup_dsp( int* fd, WAVE* wave );
static void  show_menu( void );
static void* play_thread( void* param );
static void  fill_buffer( short* dst, WAVE* wave );
static void  mix( short* dst, WAVE* wave );
static void  shutdown();


int 
main( int argc, char** argv )
{
	pthread_attr_t attr;
	int ret;

	if ( argc != 3 ) {
		fprintf( stderr, "usage : ./wave filename1 filename2\n" );
		return 1;
	}

	if ( read_file( &( argv[1] ), &( context.wave[0] ) ) != 0 ) {
		fprintf( stderr, "Failed to read wave files.\n" );
		return 1;
	}

	if ( setup_dsp( &( context.dsp ), &( context.wave[0] ) ) != 0 ) {
		fprintf( stderr, "Failed to setup /dev/dsp.\n" );
		return 1;
	}

	pthread_attr_init( &attr );
	pthread_attr_setdetachstate( &attr, PTHREAD_CREATE_JOINABLE );

	ret = pthread_create( &( context.thread_id ), &attr, 
			      play_thread, ( void* )( &context ) );

	pthread_attr_destroy( &attr );

	if ( ret ) {
		fprintf( stderr, "Failed to create thread.\n" );
		shutdown();
		return 1;
	}

	show_menu();
	pthread_join( context.thread_id, NULL );
	shutdown();

	return 0;
}


static int 
read_file( char** fnames, WAVE* wave )
{
	char buf[32];
	int  len;
	int  i;

	for ( i = 0; i < 2; i ++ ) {
		if ( ( wave[i].fp = fopen( fnames[i], "r" ) ) == NULL ) {
			fprintf( stderr, "Failed to open %s\n", fnames[i] );
			goto err;
		}

		/* 
		 * 先頭 4 バイトが "RIFF" であることを確認 
		 * 更に 4 バイトスキップしておく
		 */
		fread( buf, 8, 1, wave[i].fp );

		if ( strncmp( buf, "RIFF", 4 ) != 0 ) {
			fprintf( stderr, "Specified file is not RIFF file.\n" );
			goto err;
		}


		/* 次の 4 バイトが "WAVE" であることを確認 */
		fread( buf, 4, 1, wave[i].fp );

		if ( strncmp( buf, "WAVE", 4 ) != 0 ) {
			fprintf( stderr, "Specified file is not WAVE file.\n" );
			goto err;
		}

		/* fmt チャンクを探す */
		while ( 1 ) {
			fread( buf, 8, 1, wave[i].fp );
			len = *( int* )( &buf[4] );

			if ( strncmp( buf, "fmt ", 4 ) != 0 ) {
				if ( fseek( wave[i].fp, len, SEEK_CUR ) == -1 ) {
					fprintf( stderr, "Failed to find fmt.\n" );
					goto err;
				}
			}
			else {
				break;
			}
		}

		fread( buf, len, 1, wave[i].fp );

		wave[i].is_pcm  = *( ( short* )( &buf[0]  ) );
		wave[i].channel = *( ( short* )( &buf[2]  ) );
		wave[i].rate    = *( ( int*   )( &buf[4]  ) );
		wave[i].bits    = *( ( short* )( &buf[14] ) );

		/*
		 * PCM / 16 bits / Monoral 以外の WAVE データについては
		 * 本プログラムでは対象外
		 */
		if ( wave[i].is_pcm != 1 ) {
			fprintf( stderr, "WAVE file must be PCM format.\n" );
			goto err;
		}

		if ( wave[i].bits != 16 ) {
			fprintf( stderr, "WAVE file must be 16 bits .\n" );
			goto err;
		}

		if ( wave[i].channel != 1 ) {
			fprintf( stderr, "WAVE file must be monoral.\n" );
			goto err;
		}

		/* data チャンクを探す */
		while ( 1 ) {
			fread( buf, 8, 1, wave[i].fp );
			len = *( int* )( &buf[4] );

			if ( strncmp( buf, "data", 4 ) != 0 ) {
				if ( fseek( wave[i].fp, len, SEEK_CUR ) == -1 ) {
					fprintf( stderr, "Failed to find data.\n" );
					goto err;
				}
			}
			else {
				break;
			}
		}

		wave[i].len = len;

		if ( ( wave[i].offset = ftell( wave[i].fp ) ) == -1 ) {
			fprintf( stderr, "Failed to find offset of PCM data.\n" );
			goto err;
		}

		printf( "\n" );
		printf( "WAVE file format of %s:\n", fnames[i] );
		printf( " rate    = %d\n",  wave[i].rate );
		printf( " channel = %d\n",  wave[i].channel );
		printf( " bits    = %d\n",  wave[i].bits );
		printf( " offsets = %ld\n", wave[i].offset );
		printf( " length  = %d\n",  wave[i].len );
		printf( "\n" );
	}
	
	if ( wave[0].rate != wave[1].rate ) {
		fprintf( stderr, "Specified 2 WAVE files "
			 "must have the same sampling rate.\n" );
		goto err;
	}

	return 0;

err:
	if ( wave[0].fp != NULL ) {
		fclose( wave[0].fp );
	}

	if ( wave[1].fp != NULL ) {
		fclose( wave[1].fp );
	}

	return 1;
}


static int 
setup_dsp( int* dsp, WAVE* wave )
{
	int fragment = 0x0004000c; /* size = 4096 bytes, num of fragments = 4. */
	int format = AFMT_S16_LE;
	int rate;
	int channel;

	rate    = ( int )wave[0].rate;
	channel = ( int )wave[0].channel;

	if ( ( *dsp = open( "/dev/dsp", O_WRONLY ) ) == -1 ) {
		perror( "open()" );
		return 1;
	}

	if ( ioctl( *dsp, SNDCTL_DSP_SETFRAGMENT, &fragment ) == -1 ) {
		perror( "ioctl( SNDCTL_DSP_SETFRAGMENT )" );
		close( *dsp );
		return 1;
	}

	if ( ioctl( *dsp, SNDCTL_DSP_SETFMT, &format ) == -1 ) {
		perror( "ioctl( SNDCTL_DSP_SETFMT )" );
		close( *dsp );
		return 1;
	}

	if ( ioctl( *dsp, SNDCTL_DSP_SPEED, &rate ) == -1 ) {
		perror( "ioctl( SNDCTL_DSP_SPEED )" );
		close( *dsp );
		return 1;
	}

	if ( ioctl( *dsp, SNDCTL_DSP_CHANNELS, &channel ) == -1 ) {
		perror( "ioctl( SNDCTL_DSP_CHANNELS )" );
		close( *dsp );
		return 1;
	}

	return 0;
}


static void 
show_menu( void )
{
	char line[4];
	int  command;

	while ( 1 ) {
		printf( "Select menu ...\n" );
		printf( "  1. Play first  specified wave file only.\n" );
		printf( "  2. Play second specified wave file only.\n" );
		printf( "  3. Play both wave files simultaneously.\n" );
		printf( "  4. Stop playing.\n" );
		printf( " 99. Exit.\n" );
		printf( "\n" );
		printf( "Command ? " );

		fgets( line, sizeof( line ), stdin );
		sscanf( line, "%d\n", &command );

		switch ( command ) {
			case 1:
				context.command = COMMAND_PLAY_FIRST;
				break;
			case 2:
				context.command = COMMAND_PLAY_SECOND;
				break;
			case 3:
				context.command = COMMAND_PLAY_BOTH;
				break;
			case 4:
				context.command = COMMAND_STOP;
				break;
			case 99:
				context.command = COMMAND_EXIT;
				return;
		}
	}
}


static void*
play_thread( void* param )
{
	Context* context = ( Context* )param;

	while ( context->command != COMMAND_EXIT ) {
		memset( ( void* )( context->buffer ), 0, BUFSIZE );

		switch ( context->command ) {
			case COMMAND_PLAY_FIRST:
				fill_buffer( ( void* )( context->buffer ), 
					     &( context->wave[0] ) );
				break;

			case COMMAND_PLAY_SECOND:
				fill_buffer( ( void* )( context->buffer ), 
					     &( context->wave[1] ) );
				break;

			case COMMAND_PLAY_BOTH:
				mix( ( void* )( context->buffer ), 
				     &( context->wave[0] ) );
				break;

			case COMMAND_STOP:
			default:
				break;
		}

		write( context->dsp, ( void* )( context->buffer ), BUFSIZE );
	}

	pthread_exit( NULL );
}


static void
fill_buffer( short* dst, WAVE* wave )
{
	int copied = 0;

	while ( 1 ) {
		int src_left = wave->len - wave->current;
		int dst_left = BUFSIZE - copied;
		int copy_len = src_left > dst_left ? dst_left : src_left;

		if ( src_left == 0 ) {
			fseek( wave->fp, wave->offset, SEEK_SET );
			wave->current = 0;
			continue;
		}

		if ( dst_left == 0 ) {
			break;
		}

		fread( ( void* )( dst + copied / sizeof( short ) ), 
		       copy_len, 1, wave->fp );
		wave->current += copy_len;
		copied += copy_len;
	}
}


#define MIN( a, b ) ( ( (a) < (b) ) ? (a) : (b) )
#define MAX( a, b ) ( ( (a) > (b) ) ? (a) : (b) )


static void
mix( short* dst, WAVE* wave )
{
	short src[ BUFSIZE ];
	int copied;
	int dst_index;
	int i;
	int j;

	for ( i = 0; i < 2; i ++ ) {
		memset( src, 0, BUFSIZE );
		copied = 0;

		while ( 1 ) {
			int src_left = wave[i].len - wave[i].current;
			int dst_left = BUFSIZE - copied;
			int copy_len = src_left > dst_left ? dst_left : src_left;

			if ( src_left == 0 ) {
				fseek( wave[i].fp, wave[i].offset, SEEK_SET );
				wave[i].current = 0;
				continue;
			}

			if ( dst_left == 0 ) {
				break;
			}

			fread( ( void* )src, copy_len, 1, wave[i].fp );
			
			for ( j = 0; j < copy_len / sizeof( short ); j ++ ) {
				dst_index = copied / sizeof( short ) + j;

				if ( src[j] < 0 ) {
					dst[ dst_index ] = ( short )MAX( 
						(int)dst[ dst_index ] + (int)src[j], 
						(int)SHRT_MIN );
				}
				else {
					dst[ dst_index ] = ( short )MIN( 
						(int)dst[ dst_index ] + (int)src[j], 
						(int)SHRT_MAX );
				}
			}

			wave[i].current += copy_len;
			copied += copy_len;
		}
	}
}


static void
shutdown( void )
{
	fclose( context.wave[0].fp );
	fclose( context.wave[1].fp );
	close( context.dsp );
}


/* End of mix.c */