c64.music.h

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef FREESCAPE_DARK_C64_MUSIC_H
#define FREESCAPE_DARK_C64_MUSIC_H

#include "audio/sid.h"
#include "freescape/music.h"

namespace Freescape {

// 3-channel SID music player for Dark Side C64.
// Implements the Wally Beben byte-stream sequencer from darkside.prg ($0901).
class DarkSideC64MusicPlayer : public MusicPlayer {
public:
    DarkSideC64MusicPlayer();
    ~DarkSideC64MusicPlayer();

    void startMusic() override;
    void stopMusic() override;
    bool isPlaying() const override;

private:
    SID::SID *_sid;

    void sidWrite(int reg, uint8 data);
    void onTimer();

    // Song setup
    void setupSong();
    void silenceAll();
    void loadNextPattern(int ch);
    void buildEffectArpeggio(int ch);
    void loadCurrentFrequency(int ch);
    void finalizeChannel(int ch);

    // Per-tick processing
    void processChannel(int ch, bool newBeat);
    void parseCommands(int ch);
    void applyNote(int ch, uint8 note);
    void applyFrameEffects(int ch);
    bool applySpecialAttack(int ch);
    bool applyEnvelopeSequence(int ch);
    bool applyInstrumentVibrato(int ch);
    void applyEffectArpeggio(int ch);
    void applyTimedSlide(int ch);
    void applyPWModulation(int ch);

    uint8 readPatByte(int ch);

    void initSID();
    void destroySID();

    // Global state
    bool _musicActive;
    uint8 _speedDiv;       // $15A1: speed divider
    uint8 _speedCounter;   // $15A2: frames until next beat

    // Per-channel state
    struct ChannelState {
        const uint8 *orderData;
        uint8 orderPos;        // $15A3

        const uint8 *patData;
        int patOffset;

        uint8 instIdx;         // $15F6: instrument# * 8
        uint8 curNote;         // $159C: note index (with transpose)
        uint8 transpose;       // $15C4

        uint8 freqLo;          // $15A6
        uint8 freqHi;          // $15A9
        uint8 pwLo;            // $15AC
        uint8 pwHi;            // $15AF

        uint8 durReload;       // $15B8
        uint8 durCounter;      // $15BB

        uint8 effectMode;      // $15BE: mode 2 keeps effectParam alive across note loads
        uint8 effectParam;     // $15C1

        uint8 arpPattern;      // $15C7
        uint8 arpParam2;       // $15CA
        uint8 arpSeqPos;       // $15D9
        uint8 arpSeqData[20];  // $160C
        uint8 arpSeqLen;

        uint8 noteStepCommand; // $15D0: self-modified INC/DEC opcode for beat step
        uint8 stepDownCounter; // $15D3: short downward slide counter

        uint8 vibPhase;        // $15DE
        uint8 vibCounter;      // $15E1

        uint8 pwDirection;     // $15D6: 0=up, 1=down

        uint8 delayValue;      // $15E4
        uint8 delayCounter;    // $15E7

        uint8 envCounter;      // $15FC
        bool gateOffDisabled;  // $1606: set when SR release nibble is $F
        bool gateModeControl;  // $1600: flags bit 7
        bool specialAttack;    // flags bit 3
        bool attackDone;       // $1603
        uint8 waveform;        // current instrument ctrl byte
        uint8 instFlags;       // current instrument flags byte

        void reset();
    };

    ChannelState _ch[3];
};

} // namespace Freescape

#endif // FREESCAPE_DARK_C64_MUSIC_H