unsafe extern "C" {
    unsafe fn parse_gpr(src: *mut Source, prefix: u8) -> (u64, u64);
    unsafe fn parse_reg(src: *mut Source) -> (u64, u64);
}

struct Source<'a> {
    iter: core::iter::Peekable<core::slice::Iter<'a, u8>>,
}

impl<'a> From<&'a [u8]> for Source<'a> {
    fn from(value: &'a [u8]) -> Self {
        Self {
            iter: value.iter().peekable(),
        }
    }
}

#[unsafe(no_mangle)]
extern "C" fn peekc(src: *mut Source) -> u8 {
    unsafe { (*src).iter.peek().cloned().unwrap_or(&0).clone() }
}

#[unsafe(no_mangle)]
extern "C" fn getc(src: *mut Source) -> u8 {
    unsafe { (*src).iter.next().unwrap_or(&0).clone() }
}

#[test]
fn test_parse_reg() {
    let cases = [
        (&b"rax"[..], (0, 8)),
        (&b"rbx"[..], (1, 8)),
        (&b"rcx"[..], (2, 8)),
        (&b"rdx"[..], (3, 8)),
        (&b"rsp"[..], (4, 8)),
        (&b"rbp"[..], (5, 8)),
        (&b"rsi"[..], (6, 8)),
        (&b"rdi"[..], (7, 8)),
        (&b"eax"[..], (0, 4)),
        (&b"ebx"[..], (1, 4)),
        (&b"ecx"[..], (2, 4)),
        (&b"edx"[..], (3, 4)),
        (&b"esp"[..], (4, 4)),
        (&b"ebp"[..], (5, 4)),
        (&b"esi"[..], (6, 4)),
        (&b"edi"[..], (7, 4)),
        (&b"r8"[..], (8, 8)),
        (&b"r9"[..], (9, 8)),
        (&b"r10"[..], (10, 8)),
        (&b"r11"[..], (11, 8)),
        (&b"r12"[..], (12, 8)),
        (&b"r13"[..], (13, 8)),
        (&b"r14"[..], (14, 8)),
        (&b"r15"[..], (15, 8)),
        (&b"r8d"[..], (8, 4)),
        (&b"r9d"[..], (9, 4)),
        (&b"r10d"[..], (10, 4)),
        (&b"r11d"[..], (11, 4)),
        (&b"r12d"[..], (12, 4)),
        (&b"r13d"[..], (13, 4)),
        (&b"r14d"[..], (14, 4)),
        (&b"r15d"[..], (15, 4)),
        (&b"r8w"[..], (8, 2)),
        (&b"r9w"[..], (9, 2)),
        (&b"r10w"[..], (10, 2)),
        (&b"r11w"[..], (11, 2)),
        (&b"r12w"[..], (12, 2)),
        (&b"r13w"[..], (13, 2)),
        (&b"r14w"[..], (14, 2)),
        (&b"r15w"[..], (15, 2)),
        (&b"r8b"[..], (8, 1)),
        (&b"r9b"[..], (9, 1)),
        (&b"r10b"[..], (10, 1)),
        (&b"r11b"[..], (11, 1)),
        (&b"r12b"[..], (12, 1)),
        (&b"r13b"[..], (13, 1)),
        (&b"r14b"[..], (14, 1)),
        (&b"r15b"[..], (15, 1)),
        (&b"ax"[..], (0, 2)),
        (&b"bx"[..], (1, 2)),
        (&b"cx"[..], (2, 2)),
        (&b"dx"[..], (3, 2)),
        (&b"sp"[..], (4, 2)),
        (&b"bp"[..], (5, 2)),
        (&b"si"[..], (6, 2)),
        (&b"di"[..], (7, 2)),
        (&b"al"[..], (0, 1)),
        (&b"bl"[..], (1, 1)),
        (&b"cl"[..], (2, 1)),
        (&b"dl"[..], (3, 1)),
        (&b"ah"[..], (0, 3)),
        (&b"bh"[..], (1, 3)),
        (&b"ch"[..], (2, 3)),
        (&b"dh"[..], (3, 3)),
        (&b"sil"[..], (6, 1)),
        (&b"dil"[..], (7, 1)),
        (&b"asd"[..], (0, 0)),
    ];

    for (text, result) in cases {
        let mut src = Source::from(text);
        unsafe {
            assert_eq!(
                parse_reg(&mut src),
                result,
                "Failed to parse '{}'",
                std::str::from_utf8(text).unwrap()
            );
        }
    }
}

#[test]
fn test_parse_gpr() {
    let cases = [
        (&b"ax"[..], (0, 2)),
        (&b"bx"[..], (1, 2)),
        (&b"cx"[..], (2, 2)),
        (&b"dx"[..], (3, 2)),
        (&b"sp"[..], (4, 2)),
        (&b"bp"[..], (5, 2)),
        (&b"si"[..], (6, 2)),
        (&b"di"[..], (7, 2)),
        (&b"al"[..], (0, 1)),
        (&b"bl"[..], (1, 1)),
        (&b"cl"[..], (2, 1)),
        (&b"dl"[..], (3, 1)),
        (&b"ah"[..], (0, 3)),
        (&b"bh"[..], (1, 3)),
        (&b"ch"[..], (2, 3)),
        (&b"dh"[..], (3, 3)),
        (&b"sil"[..], (6, 1)),
        (&b"dil"[..], (7, 1)),
        (&b"asd"[..], (0, 0)),
    ];

    for (text, result) in cases {
        let mut src = Source::from(text);
        unsafe {
            assert_eq!(
                parse_gpr(&mut src, b'r'),
                result,
                "Failed to parse '{}'",
                std::str::from_utf8(text).unwrap()
            );
        }
    }
}