use super::Mapper;
use crate::cartridge::Mirroring;
use crate::cartridge::mappers::{decode_mirroring, encode_mirroring};
use crate::savestate::{SaveStateError, StateReader, StateWriter};
const PRG_BANK_16K: usize = 0x4000;
fn prg_bank_count_16k(prg_rom: &[u8]) -> usize {
prg_rom.len() / PRG_BANK_16K
}
pub(super) struct IremTamS1 {
prg_rom: Vec<u8>,
chr: Vec<u8>,
prg_bank: usize,
mirroring: Mirroring,
}
impl IremTamS1 {
pub(super) fn new(prg_rom: Vec<u8>, chr_rom: Vec<u8>, mirroring: Mirroring) -> Self {
Self {
prg_rom,
chr: if chr_rom.is_empty() {
vec![0; 0x2000]
} else {
chr_rom
},
prg_bank: 0,
mirroring,
}
}
}
impl Mapper for IremTamS1 {
fn cpu_read(&mut self, addr: u16) -> Option<u8> {
let max_bank = prg_bank_count_16k(&self.prg_rom).max(1);
match addr {
0x8000..=0xBFFF => {
let last = max_bank.saturating_sub(1);
let offset = last * PRG_BANK_16K + (addr as usize - 0x8000);
Some(self.prg_rom[offset % self.prg_rom.len()])
}
0xC000..=0xFFFF => {
let bank = self.prg_bank % max_bank;
let offset = bank * PRG_BANK_16K + (addr as usize - 0xC000);
Some(self.prg_rom[offset % self.prg_rom.len()])
}
_ => None,
}
}
fn cpu_write(&mut self, addr: u16, data: u8) -> bool {
match addr {
0x8000..=0xFFFF => {
self.prg_bank = (data & 0x0F) as usize;
self.mirroring = match (data >> 6) & 0x03 {
0 => Mirroring::SPAGE0,
1 => Mirroring::Horizontal,
2 => Mirroring::Vertical,
3 => Mirroring::SPAGE1,
_ => unreachable!(),
};
true
}
_ => false,
}
}
fn ppu_read(&mut self, addr: u16) -> Option<u8> {
if !matches!(addr, 0x0000..=0x1FFF) {
return None;
}
Some(self.chr[addr as usize % self.chr.len()])
}
fn ppu_write(&mut self, addr: u16, data: u8) -> bool {
if !matches!(addr, 0x0000..=0x1FFF) {
return false;
}
let len = self.chr.len();
self.chr[addr as usize % len] = data;
true
}
fn mirroring(&self) -> Mirroring {
self.mirroring
}
fn save_state(&self, writer: &mut StateWriter) {
writer.write_u8(self.prg_bank as u8);
writer.write_u8(encode_mirroring(self.mirroring));
}
fn load_state(&mut self, reader: &mut StateReader<'_>) -> Result<(), SaveStateError> {
self.prg_bank = reader.read_u8()? as usize;
self.mirroring = decode_mirroring(reader.read_u8()?)?;
Ok(())
}
}