package ibxm;
import java.io.*;
public class FastTracker2 {
        public static boolean is_xm( byte[] header_60_bytes ) {
                String xm_identifier;
                xm_identifier = ascii_text( header_60_bytes, 0, 17 );
                return xm_identifier.equals( "Extended Module: " );
        }
        public static Module load_xm( byte[] header_60_bytes, DataInput data_input ) throws IOException {
                int xm_version, song_header_length, sequence_length;
                int num_channels, num_patterns, num_instruments, xm_flags, idx;
                byte[] structure_header, song_header;
                Module module;
                if( !is_xm( header_60_bytes ) ) {
                        throw new IllegalArgumentException( "Not an XM file!" );
                }
                xm_version = unsigned_short_le( header_60_bytes, 58 );
                if( xm_version != 0x0104 ) {
                        throw new IllegalArgumentException( "Sorry, XM version " + xm_version + " is not supported!" );
                }
                module = new Module();
                module.song_title = ascii_text( header_60_bytes, 17, 20 );
                structure_header = new byte[ 4 ];
                data_input.readFully( structure_header );
                song_header_length = int_le( structure_header, 0 );
                song_header = new byte[ song_header_length ];
                data_input.readFully( song_header, 4, song_header_length - 4 );
                sequence_length = unsigned_short_le( song_header, 4 );
                module.restart_sequence_index = unsigned_short_le( song_header, 6 );
                num_channels = unsigned_short_le( song_header, 8 );
                num_patterns = unsigned_short_le( song_header, 10 );
                num_instruments = unsigned_short_le( song_header, 12 );
                xm_flags = unsigned_short_le( song_header, 14 );
                module.linear_periods = ( xm_flags & 0x1 ) == 0x1;
                module.global_volume = 64;
                module.channel_gain = IBXM.FP_ONE * 3 / 8;
                module.default_speed = unsigned_short_le( song_header, 16 );
                module.default_tempo = unsigned_short_le( song_header, 18 );
                module.set_num_channels( num_channels );
                for( idx = 0; idx < num_channels; idx++ ) {
                        module.set_initial_panning( idx, 128 );
                }
                module.set_sequence_length( sequence_length );         
                for( idx = 0; idx < sequence_length; idx++ ) {
                        module.set_sequence( idx, song_header[ 20 + idx ] & 0xFF );
                }
                module.set_num_patterns( num_patterns );
                for( idx = 0; idx < num_patterns; idx++ ) {
                        module.set_pattern( idx, read_xm_pattern( data_input, num_channels ) );
                }
                module.set_num_instruments( num_instruments );
                for( idx = 1; idx <= num_instruments; idx++ ) {
                        module.set_instrument( idx, read_xm_instrument( data_input ) );
                }
                return module;
        }
        private static Pattern read_xm_pattern( DataInput data_input, int num_channels ) throws IOException {
                int pattern_header_length, packing_type, num_rows, pattern_data_length;
                byte[] structure_header, pattern_header, pattern_data;
                Pattern pattern;
                structure_header = new byte[ 4 ];
                data_input.readFully( structure_header );
                pattern_header_length = int_le( structure_header, 0 );
                pattern_header = new byte[ pattern_header_length ];
                data_input.readFully( pattern_header, 4, pattern_header_length - 4 );
                packing_type = pattern_header[ 4 ];
                if( packing_type != 0 ) {
                        throw new IllegalArgumentException( "Pattern packing type " + packing_type + " is not supported!" );
                }
                pattern = new Pattern();
                pattern.num_rows = unsigned_short_le( pattern_header, 5 );
                pattern_data_length = unsigned_short_le( pattern_header, 7 );
                pattern_data = new byte[ pattern_data_length ];
                data_input.readFully( pattern_data );           
                pattern.set_pattern_data( pattern_data );
                return pattern;
        }
       
        private static Instrument read_xm_instrument( DataInput data_input ) throws IOException {
                int instrument_header_length, num_samples, idx;
                int env_tick, env_ampl, env_num_points, flags;
                byte[] structure_header, instrument_header, sample_headers;
                Instrument instrument;
                Envelope envelope;
                structure_header = new byte[ 4 ];
                data_input.readFully( structure_header );
                instrument_header_length = int_le( structure_header, 0 );
                instrument_header = new byte[ instrument_header_length ];
                data_input.readFully( instrument_header, 4, instrument_header_length - 4 );
                instrument = new Instrument();
                instrument.name = ascii_text( instrument_header, 4, 22 );
                num_samples = unsigned_short_le( instrument_header, 27 );
                if( num_samples > 0 ) {
                        instrument.set_num_samples( num_samples );
                        for( idx = 0; idx < 96; idx++ ) {
                                instrument.set_key_to_sample( idx + 1, instrument_header[ 33 + idx ] & 0xFF );
                        }
                        envelope = new Envelope();
                        env_num_points = instrument_header[ 225 ] & 0xFF;
                        envelope.set_num_points( env_num_points );
                        for( idx = 0; idx < env_num_points; idx++ ) {
                                env_tick = unsigned_short_le( instrument_header, 129 + idx * 4 );
                                env_ampl = unsigned_short_le( instrument_header, 131 + idx * 4 );
                                envelope.set_point( idx, env_tick, env_ampl );
                        }
                        envelope.set_sustain_point( instrument_header[ 227 ] & 0xFF );
                        envelope.set_loop_points( instrument_header[ 228 ] & 0xFF, instrument_header[ 229 ] & 0xFF );
                        flags = instrument_header[ 233 ] & 0xFF;
                        instrument.volume_envelope_active = ( flags & 0x1 ) == 0x1;
                        envelope.sustain = ( flags & 0x2 ) == 0x2;
                        envelope.looped = ( flags & 0x4 ) == 0x4;
                        instrument.set_volume_envelope( envelope );
                        envelope = new Envelope();
                        env_num_points = instrument_header[ 226 ] & 0xFF;
                        envelope.set_num_points( env_num_points );
                        for( idx = 0; idx < env_num_points; idx++ ) {
                                env_tick = unsigned_short_le( instrument_header, 177 + idx * 4 );
                                env_ampl = unsigned_short_le( instrument_header, 179 + idx * 4 );
                                envelope.set_point( idx, env_tick, env_ampl );
                        }
                        envelope.set_sustain_point( instrument_header[ 230 ] & 0xFF );
                        envelope.set_loop_points( instrument_header[ 231 ] & 0xFF, instrument_header[ 232 ] & 0xFF );
                        flags = instrument_header[ 234 ] & 0xFF;
                        instrument.panning_envelope_active = ( flags & 0x1 ) == 0x1;
                        envelope.sustain = ( flags & 0x2 ) == 0x2;
                        envelope.looped = ( flags & 0x4 ) == 0x4;
                        instrument.set_panning_envelope( envelope );
                        instrument.vibrato_type = instrument_header[ 235 ] & 0xFF;
                        instrument.vibrato_sweep = instrument_header[ 236 ] & 0xFF;
                        instrument.vibrato_depth = instrument_header[ 237 ] & 0xFF;
                        instrument.vibrato_rate = instrument_header[ 238 ] & 0xFF;
                        instrument.volume_fade_out = unsigned_short_le( instrument_header, 239 );
                        sample_headers = new byte[ num_samples * 40 ];
                        data_input.readFully( sample_headers );
                        for( idx = 0; idx < num_samples; idx++ ) {
                                instrument.set_sample( idx, read_xm_sample( sample_headers, idx, data_input ) );
                        }
                }
                return instrument;
        }
        private static Sample read_xm_sample( byte[] sample_headers, int sample_idx, DataInput data_input ) throws IOException {
                int header_offset, sample_length, loop_start, loop_length;
                int flags, in_idx, out_idx, sam, last_sam;
                boolean sixteen_bit, ping_pong;
                byte[] raw_sample_data;
                short[] decoded_sample_data;
                Sample sample;
                header_offset = sample_idx * 40;
                sample = new Sample();
                sample_length = int_le( sample_headers, header_offset );               
                loop_start = int_le( sample_headers, header_offset + 4 );
                loop_length = int_le( sample_headers, header_offset + 8 );
                sample.volume = sample_headers[ header_offset + 12 ] & 0xFF;
                sample.fine_tune = sample_headers[ header_offset + 13 ];
                sample.set_panning = true;
                flags = sample_headers[ header_offset + 14 ] & 0xFF;
                if( ( flags & 0x03 ) == 0 ) {
                        loop_length = 0;
                }
                ping_pong = ( flags & 0x02 ) == 0x02;
                sixteen_bit = ( flags & 0x10 ) == 0x10;
                sample.panning = sample_headers[ header_offset + 15 ] & 0xFF;
                sample.relative_note = sample_headers[ header_offset + 16 ];
                sample.name = ascii_text( sample_headers, header_offset + 18, 22 );
                raw_sample_data = new byte[ sample_length ];
                data_input.readFully( raw_sample_data );
                in_idx = 0;
                out_idx = 0;
                sam = 0;
                last_sam = 0;
                if( sixteen_bit ) {
                        decoded_sample_data = new short[ sample_length >> 1 ];
                        while( in_idx < raw_sample_data.length ) {
                                sam = raw_sample_data[ in_idx ] & 0xFF;
                                sam = sam | ( ( raw_sample_data[ in_idx + 1 ] & 0xFF ) << 8 );
                                last_sam = last_sam + sam;
                                decoded_sample_data[ out_idx ] = ( short ) last_sam;
                                in_idx += 2;
                                out_idx += 1;
                        }
                        sample.set_sample_data( decoded_sample_data, loop_start >> 1, loop_length >> 1, ping_pong );
                } else {
                        decoded_sample_data = new short[ sample_length ];
                        while( in_idx < raw_sample_data.length ) {
                                sam = raw_sample_data[ in_idx ] & 0xFF;
                                last_sam = last_sam + sam;
                                decoded_sample_data[ out_idx ] = ( short ) ( last_sam << 8 );
                                in_idx += 1;
                                out_idx += 1;
                        }
                        sample.set_sample_data( decoded_sample_data, loop_start, loop_length, ping_pong );
                }
                return sample;
        }
        private static int unsigned_short_le( byte[] buffer, int offset ) {
                int value;
                value = buffer[ offset ] & 0xFF;
                value = value | ( ( buffer[ offset + 1 ] & 0xFF ) << 8 );
                return value;
        }
        private static int int_le( byte[] buffer, int offset ) {
                int value;
                value = buffer[ offset ] & 0xFF;
                value = value | ( ( buffer[ offset + 1 ] & 0xFF ) << 8 );
                value = value | ( ( buffer[ offset + 2 ] & 0xFF ) << 16 );
                value = value | ( ( buffer[ offset + 3 ] & 0x7F ) << 24 );
                return value;
        }
       
        private static String ascii_text( byte[] buffer, int offset, int length ) {
                int idx, chr;
                byte[] string_buffer;
                String string;
                string_buffer = new byte[ length ];
                for( idx = 0; idx < length; idx++ ) {
                        chr = buffer[ offset + idx ];
                        if( chr < 32 ) {
                                chr = 32;
                        }
                        string_buffer[ idx ] = ( byte ) chr;
                }
                try {
                        string = new String( string_buffer, 0, length, "ISO-8859-1" );
                } catch( UnsupportedEncodingException e ) {
                        string = "";
                }
                return string;
        }
}