gb-emu/src/processor/memory.rs

use self::rom::ROM;
use crate::{
    processor::{clear_bit, get_bit},
    verbose_println,
};
use minifb::Key;
use std::io::{stdout, Write};

pub(crate) mod rom;

pub(crate) type Address = u16;

enum JoypadBank {
    Action,
    Direction,
}

struct Joypad {
    bank_sel: JoypadBank,
    down: bool,
    up: bool,
    left: bool,
    right: bool,
    start: bool,
    select: bool,
    b: bool,
    a: bool,
}

impl Joypad {
    fn as_register(&self) -> u8 {
        let mut reg = 0xFF;
        match self.bank_sel {
            JoypadBank::Action => {
                if self.start {
                    reg = clear_bit(reg, 3);
                }
                if self.select {
                    reg = clear_bit(reg, 2);
                }
                if self.b {
                    reg = clear_bit(reg, 1);
                }
                if self.a {
                    reg = clear_bit(reg, 0);
                }
            }
            JoypadBank::Direction => {
                if self.down {
                    reg = clear_bit(reg, 3);
                }
                if self.up {
                    reg = clear_bit(reg, 2);
                }
                if self.left {
                    reg = clear_bit(reg, 1);
                }
                if self.right {
                    reg = clear_bit(reg, 0);
                }
            }
        }
        reg
    }
}

impl Default for Joypad {
    fn default() -> Self {
        Self {
            bank_sel: JoypadBank::Action,
            down: false,
            up: false,
            left: false,
            right: false,
            start: false,
            select: false,
            b: false,
            a: false,
        }
    }
}

#[allow(dead_code)]
pub struct Memory {
    bootrom: Vec<u8>,
    bootrom_enabled: bool,
    rom: ROM,
    vram: [u8; 8192],
    ram: [u8; 8192],
    switchable_ram: [u8; 8192],
    cpu_ram: [u8; 128],
    oam: [u8; 160],
    interrupts: u8,
    pub(super) ime: bool,
    pub(super) ime_scheduled: u8,
    io: [u8; 76],
    pub(super) user_mode: bool,
    joypad: Joypad,
}

impl Memory {
    pub fn init(bootrom: Vec<u8>, bootrom_enabled: bool, rom: ROM) -> Self {
        Self {
            bootrom,
            bootrom_enabled,
            rom,
            vram: [0x0; 8192],
            ram: [0x0; 8192],
            switchable_ram: [0x0; 8192],
            cpu_ram: [0x0; 128],
            oam: [0x0; 160],
            interrupts: 0x0,
            ime: false,
            ime_scheduled: 0x0,
            io: [0xFF; 76],
            user_mode: false,
            joypad: Joypad::default(),
        }
    }

    pub fn get(&self, address: Address) -> u8 {
        match address {
            0x0..0x8000 => {
                // rom access
                // todo - switchable rom banks
                if self.bootrom_enabled && ((address as usize) < self.bootrom.len()) {
                    return self.bootrom[address as usize];
                } else {
                    return self.rom.get(address);
                }
            }
            0x8000..0xA000 => {
                return self.vram[(address - 0x8000) as usize];
            }
            0xA000..0xC000 => {
                // cart ram
                0xFF
            }
            0xC000..0xE000 => {
                return self.ram[(address - 0xC000) as usize];
            }
            0xE000..0xFE00 => {
                return self.ram[(address - 0xE000) as usize];
            }
            0xFE00..0xFEA0 => {
                return self.oam[(address - 0xFE00) as usize];
            }
            0xFEA0..0xFF00 => {
                return 0xFF;
            }
            0xFF00..0xFF4C => self.get_io(address),
            0xFF4C..0xFF80 => {
                // println!("empty space 2 read");
                return 0xFF;
            }
            0xFF80..0xFFFF => {
                return self.cpu_ram[(address - 0xFF80) as usize];
            }
            0xFFFF => {
                return self.interrupts;
            }
        }
    }

    pub fn set(&mut self, address: Address, data: u8) {
        // verbose_println!("write addr: {:#X}, data: {:#X}", address, data);

        match address {
            0x0..0x8000 => {
                // change this with MBC code...
                // println!("tried to write {:#5X} at {:#X}", data, address);
            }
            0x8000..0xA000 => {
                self.vram[(address - 0x8000) as usize] = data;
            }
            0xA000..0xC000 => {
                // panic!("switchable write");
                // self.switchable_ram[(address - 0xA000) as usize] = data;
            }
            0xC000..0xE000 => {
                self.ram[(address - 0xC000) as usize] = data;
            }
            0xE000..0xFE00 => {
                self.ram[(address - 0xE000) as usize] = data;
            }
            0xFE00..0xFEA0 => {
                self.oam[(address - 0xFE00) as usize] = data;
            }
            0xFEA0..0xFF00 => {
                // println!("empty space write: {:#X} to addr {:#X}", data, address);
            }
            0xFF00..0xFF4C => {
                self.set_io(address, data);
                // verbose_print!("writing to addr {:#X}\r", address);
                stdout().flush().unwrap();
            }
            0xFF50 => {
                self.bootrom_enabled = false;
            }
            0xFF4C..0xFF50 | 0xFF51..0xFF80 => {
                // println!("empty space 2 write: {:#X} to addr {:#X}", data, address);
            }
            0xFF80..0xFFFF => {
                self.cpu_ram[(address - 0xFF80) as usize] = data;
            }
            0xFFFF => {
                verbose_println!("interrupts set to {:#b}", data);
                verbose_println!("                / {:#X}", data);
                self.interrupts = data;
            }
        }
    }

    fn get_io(&self, address: Address) -> u8 {
        if address == 0xFF00 {
            return self.joypad.as_register();
        }
        return self.io[(address - 0xFF00) as usize];
    }

    fn set_io(&mut self, address: Address, data: u8) {
        let addr_l = (address - 0xFF00) as usize;
        if !self.user_mode {
            self.io[addr_l] = data;
        } else {
            match address {
                0xFF02 => {
                    if data == 0x81 {
                        print!("{}", self.get(0xFF01) as char);
                        stdout().flush().unwrap();
                    }
                }
                0xFF04 => self.io[addr_l] = 0,
                0xFF00 => {
                    // joypad
                    if !get_bit(data, 5) {
                        self.joypad.bank_sel = JoypadBank::Action
                    }
                    if !get_bit(data, 4) {
                        self.joypad.bank_sel = JoypadBank::Direction
                    }
                }
                0xFF11 | 0xFF14 | 0xFF16 | 0xFF19 | 0xFF1E | 0xFF23 | 0xFF26 => {
                    // sound
                }
                0xFF41 => {
                    // mixed read/write addresses...
                    // need to fill these out more...
                    // just seeing what breaks...
                }
                0xFF4D | 0xFF56 => {
                    // cgb only
                }
                0xFF44 | 0xFF76 | 0xFF77 => {
                    // read-only addresses
                    println!("BANNED write: {:#X} to {:#X}", data, address);
                }
                _ => {
                    self.io[addr_l] = data;
                    // panic!("passed non-io address to io handler!");
                }
            }
        }
    }

    pub fn update_pressed_keys(&mut self, keys: Vec<Key>) {
        self.joypad.down = keys.contains(&Key::Down) || keys.contains(&Key::S);
        self.joypad.up = keys.contains(&Key::Up) || keys.contains(&Key::W);
        self.joypad.left = keys.contains(&Key::Left) || keys.contains(&Key::A);
        self.joypad.right = keys.contains(&Key::Right) || keys.contains(&Key::D);
        self.joypad.start = keys.contains(&Key::Equal);
        self.joypad.select = keys.contains(&Key::Minus);
        self.joypad.a = keys.contains(&Key::Apostrophe);
        self.joypad.b = keys.contains(&Key::Semicolon);
    }
}