#[derive(Clone, Copy, PartialEq)]
pub struct Reg {
    val: u8,
    high: bool,
    width: Width,
}

#[derive(Debug, Clone, Copy, PartialEq, PartialOrd)]
#[repr(u8)]
pub enum Width {
    B8 = 0,
    B16 = 1,
    B32 = 2,
    B64 = 3,
}

def_regs! {
    0b0000 : rax eax ax al,
    0b0001 : rcx ecx cx cl !_,
    0b0010 : rdx edx dx dl,
    0b0011 : rbx ebx bx bl,

    0b0100 : rsp esp sp spl norex=ah !_,
    0b0101 : rbp ebp bp bpl norex=ch,
    0b0110 : rsi esi si sil norex=dh !_,
    0b0111 : rdi edi di dil norex=bh,

    0b1000 : r8  r8d  r8w  r8b,
    0b1001 : r9  r9d  r9w  r9b !_,
    0b1010 : r10 r10d r10w r10b,
    0b1011 : r11 r11d r11w r11b,
    0b1100 : r12 r12d r12w r12b !_,
    0b1101 : r13 r13d r13w r13b,
    0b1110 : r14 r14d r14w r14b,
    0b1111 : r15 r15d r15w r15b,
}

impl Reg {
    pub fn base(&self) -> u8 {
        self.val & 0b111
    }
    /// checks if register is not one of the first 8 (0-7)
    pub fn gt8(&self) -> bool {
        self.val >= 0b1000
    }
    pub fn gt4(&self) -> bool {
        self.val >= 0b0100
    }

    pub fn width(&self) -> Width {
        self.width
    }

    pub fn not8(&self) -> u8 {
        self.width.not8()
    }

    pub fn high(&self) -> bool {
        self.high
    }

    /// if self has 64 bit width, changes width to 32 bit
    pub fn lower64(&self) -> Self {
        let mut new = *self;
        new.width = new.width.min(Width::B32);
        new
    }

    pub fn requires_rex(&self) -> bool {
        self.gt8()
            || self.width == Width::B64
            || (self.gt4() && self.width == Width::B8 && !self.high)
    }

    pub fn incompatible(&self, other: &Reg) -> bool {
        (self.requires_rex() && other.high) || (self.high && other.requires_rex())
    }

    const fn new(val: u8, width: Width, high: bool) -> Self {
        Self { val, high, width }
    }
}

impl Width {
    pub const fn max_val(&self) -> u64 {
        match self {
            Self::B64 => u64::MAX,
            Self::B32 => u32::MAX as u64,
            Self::B16 => u16::MAX as u64,
            Self::B8 { .. } => u8::MAX as u64,
        }
    }

    pub fn min(self, other: Self) -> Self {
        if self <= other { self } else { other }
    }

    pub const fn bytes(&self) -> usize {
        match self {
            Self::B64 => 8,
            Self::B32 => 4,
            Self::B16 => 2,
            Self::B8 { .. } => 1,
        }
    }

    /// greater than 8 bits
    pub const fn not8(&self) -> u8 {
        !matches!(self, Self::B8) as u8
    }
}

macro_rules! filter {
    ($($filtered:ident)*; ! $_:tt $($item:ident)*; $($rest:tt)*) => {
        filter!($($filtered)* $($item)*; $($rest)*)
    };
    ($($filtered:ident)*; $($item:ident)*; $($rest:tt)*) => {
        filter!($($filtered)*; $($rest)*)
    };
    ($($filtered:ident)*;) => {
        [$($filtered, )*]
    };
}
use filter;

macro_rules! def_regs {
    ($($val:literal : $B64:ident $B32:ident $B16:ident $B8:ident $(norex=$B8H:ident)? $(!$imp:tt)?,)*) => {
        $(
        #[allow(non_upper_case_globals)]
        pub const $B64: Reg = Reg::new($val, Width::B64, false);
        #[allow(non_upper_case_globals)]
        pub const $B32: Reg = Reg::new($val, Width::B32, false);
        #[allow(non_upper_case_globals)]
        pub const $B16: Reg = Reg::new($val, Width::B16, false);
        #[allow(non_upper_case_globals)]
        pub const $B8 : Reg = Reg::new($val, Width::B8 , false);
        $(
        #[allow(non_upper_case_globals)]
        pub const $B8H: Reg = Reg::new($val, Width::B8, true);
        )?
        )*

        impl Reg {
            // #[cfg(test)]
            // pub const ALL: &[Reg] = &[
            //     $( $B64, $B32, $B16, $B8, $($B8H,)? )*
            // ];

            #[cfg(test)]
            pub const IMPORTANT: &[Reg] = &
                filter!(; $($(!$imp)? $B64 $B32 $B16 $B8 $($B8H)?; )* )
            ;

            pub fn parse(s: &str) -> Option<Self> {
                Some(match s.to_lowercase().as_str() {
                    $(
                    stringify!($B64) => $B64,
                    stringify!($B32) => $B32,
                    stringify!($B16) => $B16,
                    stringify!($B8 ) => $B8,
                    $(
                    stringify!($B8H) => $B8H,
                    )?
                    )*
                    _ => return None,
                })
            }
        }
        impl std::fmt::Display for Reg {
            #[allow(non_upper_case_globals)]
            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                write!(f, "{}", match *self {
                    $(
                    $B64 => stringify!($B64),
                    $B32 => stringify!($B32),
                    $B16 => stringify!($B16),
                    $B8  => stringify!($B8),
                    $(
                    $B8H => stringify!($B8H),
                    )?
                    )*
                    _ => "UNKNOWN",
                })
            }
        }
    };
}

use def_regs;

use crate::arch::x86_64::Imm;

impl From<Reg> for Width {
    fn from(value: Reg) -> Self {
        value.width
    }
}