apu.rs

use crate::warnln;

pub struct Apu {
    ch1_sweep_slope: u8,
    ch1_sweep_increase: bool,
    ch1_sweep_pace: u8,
    ch1_length_timer: u8,
    ch1_wave_duty: u8,
    ch1_pace: u8,
    ch1_direction: u8,
    ch1_volume: u8,
    ch1_wave_length: u16,
    ch1_sound_length: bool,
    ch1_enabled: bool,

    ch2_length_timer: u8,
    ch2_wave_duty: u8,
    ch2_pace: u8,
    ch2_direction: u8,
    ch2_volume: u8,
    ch2_wave_length: u16,
    ch2_sound_length: bool,
    ch2_enabled: bool,
}

impl Apu {
    pub fn new() -> Self {
        Self {
            ch1_sweep_slope: 0x0,
            ch1_sweep_increase: false,
            ch1_sweep_pace: 0x0,
            ch1_length_timer: 0x0,
            ch1_wave_duty: 0x0,
            ch1_pace: 0x0,
            ch1_direction: 0x0,
            ch1_volume: 0x0,
            ch1_wave_length: 0x0,
            ch1_sound_length: false,
            ch1_enabled: false,

            ch2_length_timer: 0x0,
            ch2_wave_duty: 0x0,
            ch2_pace: 0x0,
            ch2_direction: 0x0,
            ch2_volume: 0x0,
            ch2_wave_length: 0x0,
            ch2_sound_length: false,
            ch2_enabled: false,
        }
    }

    pub fn clock(&mut self, cycles: u8) {
        // @todo implement the clock and allow for the proper
        // writing of the output buffer at a fixed frequency
    }

    pub fn read(&mut self, addr: u16) -> u8 {
        match addr {
            0xff26 => 1 as u8, // @todo implement this
            _ => {
                warnln!("Reading from unknown APU location 0x{:04x}", addr);
                0xff
            }
        }
    }

    pub fn write(&mut self, addr: u16, value: u8) {
        match addr {
            // 0xFF10 — NR10: Channel 1 length timer & duty cycle
            0xff10 => {
                self.ch1_sweep_slope = value & 0x03;
                self.ch1_sweep_increase = value & 0x04 == 0x04;
                self.ch1_sweep_pace = (value & 0x70) >> 4;
            }
            // 0xFF11 — NR11: Channel 1 length timer & duty cycle
            0xff11 => {
                self.ch1_length_timer = value & 0x3f;
                self.ch1_wave_duty = (value & 0xc0) >> 6;
            }
            // 0xFF12 — NR12: Channel 1 volume & envelope
            0xff12 => {
                self.ch1_pace = value & 0x07;
                self.ch1_direction = (value & 0x08) >> 3;
                self.ch1_volume = (value & 0xf0) >> 4;
            }
            // 0xFF13 — NR13: Channel 1 wavelength low
            0xff13 => {
                self.ch1_wave_length = (self.ch1_wave_length & 0xff00) | value as u16;
            }
            // 0xFF14 — NR14: Channel 1 wavelength high & control
            0xff14 => {
                self.ch1_wave_length =
                    (self.ch1_wave_length & 0x00ff) | (((value & 0x07) as u16) << 8);
                self.ch1_sound_length |= value & 0x40 == 0x40;
                self.ch1_enabled |= value & 0x80 == 0x80;
                println!("CH1 Enabled {}", self.ch1_enabled);
            }

            // 0xFF16 — NR21: Channel 2 length timer & duty cycle
            0xff16 => {
                self.ch2_length_timer = value & 0x3f;
                self.ch2_wave_duty = (value & 0xc0) >> 6;
            }
            // 0xFF17 — NR22: Channel 2 volume & envelope
            0xff17 => {
                self.ch2_pace = value & 0x07;
                self.ch2_direction = (value & 0x08) >> 3;
                self.ch2_volume = (value & 0xf0) >> 4;
            }
            // 0xFF18 — NR23: Channel 2 wavelength low
            0xff18 => {
                self.ch2_wave_length = (self.ch2_wave_length & 0xff00) | value as u16;
            }
            // 0xFF19 — NR24: Channel 1 wavelength high & control
            0xff19 => {
                self.ch2_wave_length =
                    (self.ch2_wave_length & 0x00ff) | (((value & 0x07) as u16) << 8);
                self.ch2_sound_length |= value & 0x40 == 0x40;
                self.ch2_enabled |= value & 0x80 == 0x80;
                println!("CH2 Enabled {}", self.ch2_enabled);
            }

            _ => warnln!("Writing in unknown APU location 0x{:04x}", addr),
        }
    }
}