gb-emu/src/processor/instructions/instructions.rs

use crate::{
    processor::{Cpu, Direction, Flags, Reg8, SplitRegister},
    util::{clear_bit, get_bit, set_bit},
};

impl Cpu {
    pub(crate) fn and(&mut self, first: u8, second: u8) -> u8 {
        let result = first & second;
        self.set_or_clear_flag(Flags::Zero, result == 0x0);
        self.clear_flag(Flags::NSubtract);
        self.clear_flag(Flags::Carry);
        self.set_flag(Flags::HalfCarry);
        result
    }

    pub(crate) fn xor(&mut self, first: u8, second: u8) -> u8 {
        let result = first ^ second;
        self.set_or_clear_flag(Flags::Zero, result == 0x0);
        self.clear_flag(Flags::NSubtract);
        self.clear_flag(Flags::Carry);
        self.clear_flag(Flags::HalfCarry);
        result
    }

    pub(crate) fn or(&mut self, first: u8, second: u8) -> u8 {
        let result = first | second;
        self.set_or_clear_flag(Flags::Zero, result == 0x0);
        self.clear_flag(Flags::NSubtract);
        self.clear_flag(Flags::Carry);
        self.clear_flag(Flags::HalfCarry);
        result
    }

    pub(crate) fn cp(&mut self, first: u8, second: u8) {
        self.sub_u8s(first, second);
    }

    pub(crate) fn add(&mut self, first: u8, second: u8) -> u8 {
        self.add_u8s(first, second)
    }

    pub(crate) fn adc(&mut self, first: u8, second: u8) -> u8 {
        let val = second.wrapping_add(self.get_flag(Flags::Carry));
        self.add_u8s(first, val)
    }

    pub(crate) fn sub(&mut self, first: u8, second: u8) -> u8 {
        self.sub_u8s(first, second)
    }

    pub(crate) fn sbc(&mut self, first: u8, second: u8) -> u8 {
        let val = second.wrapping_add(self.get_flag(Flags::Carry));
        self.sub_u8s(first, val)
    }

    pub(crate) fn inc(&mut self, reg: Reg8) {
        let result = self.reg.get_8(reg);
        let val = self.inc_raw(result);
        self.reg.set_8(reg, val);
    }

    pub(crate) fn dec(&mut self, reg: Reg8) {
        let result = self.reg.get_8(reg);
        let val = self.dec_raw(result);
        self.reg.set_8(reg, val);
    }

    pub(crate) fn inc_pair(&mut self, val: u16) -> u16 {
        val.wrapping_add(0x1)
    }

    pub(crate) fn dec_pair(&mut self, val: u16) -> u16 {
        val.wrapping_sub(0x1)
    }

    pub(crate) fn rlc(&mut self, byte: u8) -> u8 {
        self.rotate_with_carry(byte, Direction::Left)
    }

    pub(crate) fn rrc(&mut self, byte: u8) -> u8 {
        self.rotate_with_carry(byte, Direction::Right)
    }

    pub(crate) fn rl(&mut self, byte: u8) -> u8 {
        self.rotate(byte, Direction::Left)
    }

    pub(crate) fn rr(&mut self, byte: u8) -> u8 {
        self.rotate(byte, Direction::Right)
    }

    pub(crate) fn sla(&mut self, byte: u8) -> u8 {
        self.shift(byte, Direction::Left)
    }

    pub(crate) fn sra(&mut self, byte: u8) -> u8 {
        let b = get_bit(byte, 7);
        let val = self.shift(byte, Direction::Right);
        if b {
            val + 0b10000000
        } else {
            val
        }
    }

    pub(crate) fn srl(&mut self, byte: u8) -> u8 {
        self.shift(byte, Direction::Right)
    }

    pub(crate) fn swap(&mut self, byte: u8) -> u8 {
        let swapped = (byte & 0x0F) << 4 | (byte & 0xF0) >> 4;
        self.set_or_clear_flag(Flags::Zero, swapped == 0x0);
        self.clear_flag(Flags::Carry);
        self.clear_flag(Flags::HalfCarry);
        self.clear_flag(Flags::NSubtract);
        swapped
    }

    pub(crate) fn bit(&mut self, byte: u8, bit: u8) {
        self.set_or_clear_flag(Flags::Zero, !get_bit(byte, bit));
        self.clear_flag(Flags::NSubtract);
        self.set_flag(Flags::HalfCarry);
    }

    pub(crate) fn rst(&mut self, address: u8) {
        self.push(self.reg.pc);
        self.reg.pc.set_high(0x0);
        self.reg.pc.set_low(address);
    }

    pub(crate) fn ret(&mut self) {
        self.reg.pc = self.pop_word();
    }

    pub(crate) fn jr(&mut self, jump: i8) {
        self.reg.pc = self.reg.pc.wrapping_add_signed(jump.into());
    }
}

pub(crate) fn res(byte: u8, bit: u8) -> u8 {
    clear_bit(byte, bit)
}

pub(crate) fn set(byte: u8, bit: u8) -> u8 {
    set_bit(byte, bit)
}