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use m68000::{MemoryAccess, M68000};

const START_ADDRESS: u32 = 0x10000;

const PROGRAM: [u16; 4] = [
    0x51c8, // dbf d0,nnnn
    0xfffe, // negative offset
    0x4e72, // stop
    0x2700,
];

struct Memory;

#[allow(unused_variables)]
impl MemoryAccess for Memory {
    fn get_byte(&mut self, addr: u32) -> Option<u8> {
        unimplemented!();
    }
    fn get_word(&mut self, addr: u32) -> Option<u16> {
        PROGRAM
            .get(addr.checked_sub(START_ADDRESS)? as usize / 2)
            .copied()
    }
    fn set_byte(&mut self, addr: u32, value: u8) -> Option<()> {
        unimplemented!()
    }
    fn set_word(&mut self, addr: u32, value: u16) -> Option<()> {
        unimplemented!()
    }
    fn reset_instruction(&mut self) {
        unimplemented!()
    }
}

fn main() {
    let mut memory = Memory;
    let mut cpu = M68000::new_no_reset();
    cpu.regs.pc = START_ADDRESS;
    cpu.regs.sr = 0x2700.into();
    cpu.regs.d[0] = 1;  // ensure dbf tries to branch
    let cycles = cpu.interpreter(&mut memory);  // panics
    println!("Done in {cycles} cycles");
}