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use super::cartridge::Cartridge;
use super::mbc::Mbc;

pub struct Mbc1 {
    cartridge: Cartridge,
    selected_rom_bank: usize,
    selected_eram_bank: usize,
    in_ram_banking_mode: bool,
    external_ram_enabled: bool,
    higher_rom_bank_bits: usize,
    ram_change_callback: Box<dyn FnMut(usize, u8)>,
}

impl Mbc for Mbc1 {
    fn read_byte(&self, index: u16) -> u8 {
        match index {
            0x0000..=0x3FFF => {
                let rom = self.cartridge.get_rom();
                rom[index as usize]
            }
            0x4000..=0x7FFF => {
                let rom = self.cartridge.get_rom();
                let offset = self.selected_rom_bank * 0x4000;
                rom[index as usize - 0x4000 + offset]
            }
            0xA000..=0xBFFF => {
                if self.external_ram_enabled {
                    let selected_bank = if self.in_ram_banking_mode {
                        self.selected_eram_bank
                    } else {
                        0
                    };
                    let offset = selected_bank * 0x2000;
                    let address = index as usize - 0xA000 + offset;
                    let ram = self.cartridge.get_ram();
                    ram[address]
                } else {
                    0xFF
                }
            }
            _ => panic!("index out of range: {:04X}", index),
        }
    }

    fn write_byte(&mut self, index: u16, value: u8) {
        match index {
            0x0000..=0x1FFF => {
                if self.cartridge.get_ram_size() > 0 {
                    self.external_ram_enabled = (value & 0x0F) == 0x0A
                }
            }
            0x2000..=0x3FFF => {
                if self.in_ram_banking_mode {
                    self.selected_rom_bank = usize::from(value & 0x1F);
                } else {
                    self.selected_rom_bank =
                        usize::from(value & 0x1F) | (self.higher_rom_bank_bits << 5);
                }

                if self.selected_rom_bank == 0x00
                    || self.selected_rom_bank == 0x20
                    || self.selected_rom_bank == 0x40
                    || self.selected_rom_bank == 0x60
                {
                    self.selected_rom_bank += 1;
                }

                self.selected_rom_bank &= self.cartridge.get_rom_banks() - 1;
            }
            0x4000..=0x5FFF => {
                if self.in_ram_banking_mode {
                    self.selected_eram_bank = usize::from(value & 0x03);
                    self.selected_eram_bank &= self.cartridge.get_ram_banks() - 1;
                } else {
                    self.higher_rom_bank_bits = usize::from(value & 0x03);
                    self.selected_rom_bank =
                        (self.selected_rom_bank & 0x1F) | (self.higher_rom_bank_bits << 5);

                    if self.selected_rom_bank == 0x00
                        || self.selected_rom_bank == 0x20
                        || self.selected_rom_bank == 0x40
                        || self.selected_rom_bank == 0x60
                    {
                        self.selected_rom_bank += 1;
                    }
                    self.selected_rom_bank &= self.cartridge.get_rom_banks() - 1;
                }
            }
            0x6000..=0x7FFF => {
                if !(self.cartridge.get_ram_size() != 3 && (value & 0x01 != 0)) {
                    self.in_ram_banking_mode = (value & 1) == 1;
                }
            }
            0xA000..=0xBFFF => {
                if self.external_ram_enabled {
                    let selected_bank = if self.in_ram_banking_mode {
                        self.selected_eram_bank
                    } else {
                        0
                    };
                    let offset = selected_bank * 0x2000;
                    let address = index as usize - 0xA000 + offset;
                    let ram = self.cartridge.get_ram_mut();
                    ram[address] = value;

                    (self.ram_change_callback)(address, value);
                }
            }
            _ => panic!("index out of range: {:04X}", index),
        }
    }

    fn get_cartridge(&self) -> &Cartridge {
        &self.cartridge
    }

    fn get_cartridge_mut(&mut self) -> &mut Cartridge {
        &mut self.cartridge
    }

    fn set_ram_change_callback(&mut self, f: Box<dyn FnMut(usize, u8)>) {
        self.ram_change_callback = f;
    }
}

impl Mbc1 {
    pub fn new(cartridge: Cartridge) -> Mbc1 {
        Mbc1 {
            cartridge,
            selected_rom_bank: 1,
            selected_eram_bank: 0,
            in_ram_banking_mode: false,
            external_ram_enabled: false,
            higher_rom_bank_bits: 0,
            ram_change_callback: Box::new(|_, _| {}),
        }
    }
}