tgba 0.3.0

use log::error;

use crate::backup::Backup;

#[derive(Default, Clone)]
pub struct Rom {
    pub data: Vec<u8>,
    pub title: Vec<u8>,
    pub game_code: [u8; 4],
    pub maker_code: [u8; 2],
    pub main_unit_code: u8,
    pub device_type: u8,
    pub rom_version: u8,
}

#[derive(thiserror::Error, Debug)]
pub enum RomError {
    #[error("Invalid magic number: 0x{0:02X}, expected: 0x96")]
    InvalidMagic(u8),
}

impl Rom {
    pub fn from_bytes(data: &[u8]) -> Result<Self, RomError> {
        let header = &data[0xA0..0xC0];

        let title = header[..0xC].to_vec();
        let game_code = header[0xC..0x10].try_into().unwrap();
        let maker_code = header[0x10..0x12].try_into().unwrap();

        let magic = header[0x12];
        if magic != 0x96 {
            Err(RomError::InvalidMagic(magic))?
        }

        let main_unit_code = header[0x13];
        let device_type = header[0x14];

        let rom_version = header[0x1C];
        let complement_check = header[0x1D];

        for i in (0x15..=0x1B).chain(0x1E..=0x1F) {
            if header[i] != 0 {
                error!("Non-zero value in reserved area: {:02X}", header[i]);
            }
        }

        let sum = header[..=0x1C]
            .iter()
            .fold(0_u8, |a, b| a.wrapping_add(*b))
            .wrapping_add(0x19);

        if sum.wrapping_add(complement_check) != 0 {
            error!("Invalid complement check: {sum:02X} + {complement_check:02X} != 0");
        }

        let ret = Rom {
            data: data.to_vec(),
            title,
            game_code,
            maker_code,
            main_unit_code,
            device_type,
            rom_version,
        };

        Ok(ret)
    }

    pub fn backup_type(&self) -> &'static str {
        Backup::detect_backup(&self.data, None).backup_type()
    }
}