state.rs

use std::{
    convert::TryInto,
    fmt::{self, Display, Formatter},
    fs::File,
    io::{Cursor, Read, Seek, SeekFrom, Write},
    mem::size_of,
};

use crate::{
    gb::GameBoy,
    info::{name, version},
};

pub trait Serialize {
    fn save(&self, buffer: &mut Vec<u8>);
    fn load(&mut self, data: &mut Cursor<Vec<u8>>);
}

pub trait State {
    fn from_gb(gb: &GameBoy) -> Self;
    fn to_gb(&self, gb: &mut GameBoy);
}

#[derive(Default)]
pub struct BeesState {
    footer: BeesFooter,
    name: BeesName,
    info: BeesInfo,
    core: BeesCore,
}

impl BeesState {
    pub fn description(&self, column_length: usize) -> String {
        let emulator_l = format!("{:width$}", "Emulator", width = column_length);
        let title_l: String = format!("{:width$}", "Title", width = column_length);
        let version_l: String = format!("{:width$}", "Version", width = column_length);
        let model_l: String = format!("{:width$}", "Model", width = column_length);
        format!(
            "{}  {}\n{}  {}\n{}  {}.{}\n{}  {}\n",
            emulator_l,
            self.name.name,
            title_l,
            self.info.title(),
            version_l,
            self.core.major,
            self.core.minor,
            model_l,
            self.core.model,
        )
    }

    pub fn verify(&self) -> Result<(), String> {
        self.footer.verify()?;
        self.core.verify()?;
        Ok(())
    }
}

impl Serialize for BeesState {
    fn save(&self, buffer: &mut Vec<u8>) {
        self.name.save(buffer);
        self.info.save(buffer);
        self.core.save(buffer);
        self.footer.save(buffer);
    }

    fn load(&mut self, data: &mut Cursor<Vec<u8>>) {
        // moves the cursor to the end of the file
        // to read the footer, and then places the
        // the cursor in the start of the BEES data
        // according to the footer information
        data.seek(SeekFrom::End(-8)).unwrap();
        self.footer.load(data);
        data.seek(SeekFrom::Start(self.footer.start_offset as u64))
            .unwrap();

        self.name.load(data);
        self.info.load(data);
        self.core.load(data);
    }
}

impl State for BeesState {
    fn from_gb(gb: &GameBoy) -> Self {
        Self {
            footer: BeesFooter::default(), // @TODO: check if this makes sense
            name: BeesName::from_gb(gb),
            info: BeesInfo::from_gb(gb),
            core: BeesCore::from_gb(gb),
        }
    }

    fn to_gb(&self, gb: &mut GameBoy) {
        self.verify().unwrap();
        self.name.to_gb(gb);
        self.info.to_gb(gb);
        self.core.to_gb(gb);
    }
}

impl Display for BeesState {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.description(9))
    }
}

pub struct BeesBlockHeader {
    magic: String,
    size: u32,
}

impl BeesBlockHeader {
    pub fn new(magic: String, size: u32) -> Self {
        Self { magic, size }
    }
}

impl Serialize for BeesBlockHeader {
    fn save(&self, buffer: &mut Vec<u8>) {
        buffer.write_all(self.magic.as_bytes()).unwrap();
        buffer.write_all(&self.size.to_le_bytes()).unwrap();
    }

    fn load(&mut self, data: &mut Cursor<Vec<u8>>) {
        let mut buffer = [0x00; 4];
        data.read_exact(&mut buffer).unwrap();
        self.magic = String::from_utf8(Vec::from(buffer)).unwrap();
        let mut buffer = [0x00; 4];
        data.read_exact(&mut buffer).unwrap();
        self.size = u32::from_le_bytes(buffer);
    }
}

pub struct BeesBuffer {
    size: u32,
    offset: u32,
    buffer: Vec<u8>,
}

impl BeesBuffer {
    pub fn new(size: u32, offset: u32, buffer: Vec<u8>) -> Self {
        Self {
            size,
            offset,
            buffer,
        }
    }

    fn load_buffer(&self, data: &mut Cursor<Vec<u8>>) -> Vec<u8> {
        let mut buffer = vec![0x00; self.size as usize];
        let position = data.position();
        data.seek(SeekFrom::Start(self.offset as u64)).unwrap();
        data.read_exact(&mut buffer).unwrap();
        data.set_position(position);
        buffer
    }
}

impl Serialize for BeesBuffer {
    fn save(&self, buffer: &mut Vec<u8>) {
        buffer.write_all(&self.size.to_le_bytes()).unwrap();
        buffer.write_all(&self.offset.to_le_bytes()).unwrap();
    }

    fn load(&mut self, data: &mut Cursor<Vec<u8>>) {
        let mut buffer = [0x00; 4];
        data.read_exact(&mut buffer).unwrap();
        self.size = u32::from_le_bytes(buffer);
        let mut buffer = [0x00; 4];
        data.read_exact(&mut buffer).unwrap();
        self.offset = u32::from_le_bytes(buffer);
        self.buffer = self.load_buffer(data);
    }
}

impl Default for BeesBuffer {
    fn default() -> Self {
        Self::new(0, 0, vec![])
    }
}

pub struct BeesFooter {
    start_offset: u32,
    magic: u32,
}

impl BeesFooter {
    pub fn new(start_offset: u32, magic: u32) -> Self {
        Self {
            start_offset,
            magic,
        }
    }

    pub fn verify(&self) -> Result<(), String> {
        if self.magic != 0x53534542 {
            return Err(String::from("Invalid magic"));
        }
        Ok(())
    }
}

impl Serialize for BeesFooter {
    fn save(&self, buffer: &mut Vec<u8>) {
        buffer.write_all(&self.start_offset.to_le_bytes()).unwrap();
        buffer.write_all(&self.magic.to_le_bytes()).unwrap();
    }

    fn load(&mut self, data: &mut Cursor<Vec<u8>>) {
        let mut buffer = [0x00; 4];
        data.read_exact(&mut buffer).unwrap();
        self.start_offset = u32::from_le_bytes(buffer);
        let mut buffer = [0x00; 4];
        data.read_exact(&mut buffer).unwrap();
        self.magic = u32::from_le_bytes(buffer);
    }
}

impl Default for BeesFooter {
    fn default() -> Self {
        Self::new(0x00, 0x53534542)
    }
}

pub struct BeesName {
    header: BeesBlockHeader,
    name: String,
}

impl BeesName {
    pub fn new(name: String) -> Self {
        Self {
            header: BeesBlockHeader::new(String::from("NAME"), name.len() as u32),
            name,
        }
    }
}

impl Serialize for BeesName {
    fn save(&self, buffer: &mut Vec<u8>) {
        self.header.save(buffer);
        buffer.write_all(self.name.as_bytes()).unwrap();
    }

    fn load(&mut self, data: &mut Cursor<Vec<u8>>) {
        self.header.load(data);
        let mut buffer = vec![0x00; self.header.size as usize];
        data.read_exact(&mut buffer).unwrap();
        self.name = String::from_utf8(buffer).unwrap();
    }
}

impl State for BeesName {
    fn from_gb(_gb: &GameBoy) -> Self {
        Self::new(format!("{} v{}", name(), version()))
    }

    fn to_gb(&self, _gb: &mut GameBoy) {}
}

impl Default for BeesName {
    fn default() -> Self {
        Self::new(String::from(""))
    }
}

pub struct BeesInfo {
    header: BeesBlockHeader,
    title: [u8; 16],
    checksum: [u8; 2],
}

impl BeesInfo {
    pub fn new(title: &[u8], checksum: &[u8]) -> Self {
        Self {
            header: BeesBlockHeader::new(
                String::from("INFO"),
                title.len() as u32 + checksum.len() as u32,
            ),
            title: title.try_into().unwrap(),
            checksum: checksum.try_into().unwrap(),
        }
    }

    pub fn title(&self) -> String {
        String::from_utf8(Vec::from(&self.title[..])).unwrap()
    }
}

impl Serialize for BeesInfo {
    fn save(&self, buffer: &mut Vec<u8>) {
        self.header.save(buffer);
        buffer.write_all(&self.title).unwrap();
        buffer.write_all(&self.checksum).unwrap();
    }

    fn load(&mut self, data: &mut Cursor<Vec<u8>>) {
        self.header.load(data);
        data.read_exact(&mut self.title).unwrap();
        data.read_exact(&mut self.checksum).unwrap();
    }
}

impl State for BeesInfo {
    fn from_gb(gb: &GameBoy) -> Self {
        Self::new(
            &gb.cartridge_i().rom_data()[0x134..=0x143],
            &gb.cartridge_i().rom_data()[0x14e..=0x14f],
        )
    }

    fn to_gb(&self, _gb: &mut GameBoy) {}
}

impl Default for BeesInfo {
    fn default() -> Self {
        Self::new(&[0_u8; 16], &[0_u8; 2])
    }
}

pub struct BeesCore {
    header: BeesBlockHeader,

    major: u16,
    minor: u16,

    model: String,

    pc: u16,
    af: u16,
    bc: u16,
    de: u16,
    hl: u16,
    sp: u16,

    ime: bool,
    ie: u8,
    // 0 = running; 1 = halted; 2 = stopped
    execution_mode: u8,
    _padding: u8,

    io_registers: [u8; 128],

    ram: BeesBuffer,
    vram: BeesBuffer,
    mbc_ram: BeesBuffer,
    oam: BeesBuffer,
    hram: BeesBuffer,
    background_palettes: BeesBuffer,
    object_palettes: BeesBuffer,
}

impl BeesCore {
    pub fn new(model: String, pc: u16, af: u16, bc: u16, de: u16, hl: u16, sp: u16) -> Self {
        Self {
            header: BeesBlockHeader::new(
                String::from("CORE"),
                ((size_of::<u16>() * 2)
                    + size_of::<u32>()
                    + (size_of::<u16>() * 6)
                    + (size_of::<u8>() * 4)
                    + (size_of::<u8>() * 128)
                    + ((size_of::<u32>() + size_of::<u32>()) * 7)) as u32,
            ),
            major: 1,
            minor: 1,
            model,
            pc,
            af,
            bc,
            de,
            hl,
            sp,
            ime: false,
            ie: 0,
            execution_mode: 0,
            _padding: 0,
            io_registers: [0x00; 128],
            ram: BeesBuffer::default(),
            vram: BeesBuffer::default(),
            mbc_ram: BeesBuffer::default(),
            oam: BeesBuffer::default(),
            hram: BeesBuffer::default(),
            background_palettes: BeesBuffer::default(),
            object_palettes: BeesBuffer::default(),
        }
    }

    pub fn verify(&self) -> Result<(), String> {
        if self.header.magic != "CORE" {
            return Err(String::from("Invalid magic"));
        }
        if self.oam.size != 0xa0 {
            return Err(String::from("Invalid OAM size"));
        }
        if self.hram.size != 0x7f {
            return Err(String::from("Invalid HRAM size"));
        }
        Ok(())
    }
}

impl Serialize for BeesCore {
    fn save(&self, buffer: &mut Vec<u8>) {
        self.header.save(buffer);
    }

    fn load(&mut self, data: &mut Cursor<Vec<u8>>) {
        self.header.load(data);

        let mut buffer = [0x00; 2];
        data.read_exact(&mut buffer).unwrap();
        self.major = u16::from_le_bytes(buffer);
        let mut buffer = [0x00; 2];
        data.read_exact(&mut buffer).unwrap();
        self.minor = u16::from_le_bytes(buffer);

        let mut buffer = [0x00; 4];
        data.read_exact(&mut buffer).unwrap();
        self.model = String::from_utf8(Vec::from(buffer)).unwrap();

        let mut buffer = [0x00; 2];
        data.read_exact(&mut buffer).unwrap();
        self.pc = u16::from_le_bytes(buffer);
        let mut buffer = [0x00; 2];
        data.read_exact(&mut buffer).unwrap();
        self.af = u16::from_le_bytes(buffer);
        let mut buffer = [0x00; 2];
        data.read_exact(&mut buffer).unwrap();
        self.bc = u16::from_le_bytes(buffer);
        let mut buffer = [0x00; 2];
        data.read_exact(&mut buffer).unwrap();
        self.de = u16::from_le_bytes(buffer);
        let mut buffer = [0x00; 2];
        data.read_exact(&mut buffer).unwrap();
        self.hl = u16::from_le_bytes(buffer);
        let mut buffer = [0x00; 2];
        data.read_exact(&mut buffer).unwrap();
        self.sp = u16::from_le_bytes(buffer);

        let mut buffer = [0x00; 1];
        data.read_exact(&mut buffer).unwrap();
        self.ime = buffer[0] != 0;
        let mut buffer = [0x00; 1];
        data.read_exact(&mut buffer).unwrap();
        self.ie = u8::from_le_bytes(buffer);
        let mut buffer = [0x00; 1];
        data.read_exact(&mut buffer).unwrap();
        self.execution_mode = u8::from_le_bytes(buffer);
        let mut buffer = [0x00; 1];
        data.read_exact(&mut buffer).unwrap();
        self._padding = u8::from_le_bytes(buffer);

        data.read_exact(&mut self.io_registers).unwrap();

        self.ram.load(data);
        self.vram.load(data);
        self.mbc_ram.load(data);
        self.oam.load(data);
        self.hram.load(data);
        self.background_palettes.load(data);
        self.object_palettes.load(data);
    }
}

impl State for BeesCore {
    fn from_gb(gb: &GameBoy) -> Self {
        Self::new(
            String::from("GD  "),
            gb.cpu_i().pc(),
            gb.cpu_i().af(),
            gb.cpu_i().bc(),
            gb.cpu_i().de(),
            gb.cpu_i().hl(),
            gb.cpu_i().sp(),
        )
    }

    fn to_gb(&self, gb: &mut GameBoy) {
        gb.cpu().set_pc(self.pc);
        gb.cpu().set_af(self.af);
        gb.cpu().set_bc(self.bc);
        gb.cpu().set_de(self.de);
        gb.cpu().set_hl(self.hl);
        gb.cpu().set_sp(self.sp);

        gb.cpu().set_ime(self.ime);
        gb.mmu().ie = self.ie;

        gb.mmu().write_many(0xff00, &self.io_registers);

        gb.mmu().set_ram(self.ram.buffer.clone());
        gb.mmu().write_many(0x8000, &self.vram.buffer);
        //@TODO the MBC is missing
        gb.mmu().write_many(0xfe00, &self.oam.buffer);
        gb.mmu().write_many(0xff80, &self.hram.buffer);
        //@TODO the background palettes are missing
        //@TODO the object palettes are missing
    }
}

impl Default for BeesCore {
    fn default() -> Self {
        Self::new(
            String::from("GD  "),
            0x0000_u16,
            0x0000_u16,
            0x0000_u16,
            0x0000_u16,
            0x0000_u16,
            0x0000_u16,
        )
    }
}

pub fn save_state_file(file_path: &str, gb: &GameBoy) {
    let mut file = File::create(file_path).unwrap();
    let data = save_state(gb);
    file.write_all(&data).unwrap();
}

pub fn save_state(gb: &GameBoy) -> Vec<u8> {
    let mut data: Vec<u8> = vec![];
    BeesState::from_gb(gb).save(&mut data);
    data
}

pub fn load_state_file(file_path: &str, gb: &mut GameBoy) {
    let mut file = File::open(file_path).unwrap();
    let mut data = vec![];
    file.read_to_end(&mut data).unwrap();
    load_state(&data, gb);
}

pub fn load_state(data: &[u8], gb: &mut GameBoy) {
    let mut state = BeesState::default();
    state.load(&mut Cursor::new(data.to_vec()));
    state.to_gb(gb);
    print!("{}", state);
}