use core::convert::TryInto;
use core::fmt::Debug;
use core::hash::Hash;
use core::ops::*;

/// A trait marking valid underlying bitset storage types and providing the
/// operations `EnumSet` and related types use.
pub trait EnumSetTypeRepr :
    // Basic traits used to derive traits
    Copy +
    Ord +
    Eq +
    Debug +
    Hash +
    // Operations used by enumset
    BitAnd<Output = Self> +
    BitOr<Output = Self> +
    BitXor<Output = Self> +
    Not<Output = Self> +
{
    const WIDTH: u32;

    fn is_empty(&self) -> bool;
    fn empty() -> Self;

    fn add_bit(&mut self, bit: u32);
    fn remove_bit(&mut self, bit: u32);
    fn has_bit(&self, bit: u32) -> bool;

    fn count_ones(&self) -> u32;
    fn count_remaining_ones(&self, cursor: u32) -> usize;
    fn leading_zeros(&self) -> u32;
    fn trailing_zeros(&self) -> u32;

    fn and_not(&self, other: Self) -> Self;

    fn from_u8(v: u8) -> Self;
    fn from_u16(v: u16) -> Self;
    fn from_u32(v: u32) -> Self;
    fn from_u64(v: u64) -> Self;
    fn from_u128(v: u128) -> Self;
    fn from_usize(v: usize) -> Self;

    fn to_u8(&self) -> u8;
    fn to_u16(&self) -> u16;
    fn to_u32(&self) -> u32;
    fn to_u64(&self) -> u64;
    fn to_u128(&self) -> u128;
    fn to_usize(&self) -> usize;

    fn from_u8_opt(v: u8) -> Option<Self>;
    fn from_u16_opt(v: u16) -> Option<Self>;
    fn from_u32_opt(v: u32) -> Option<Self>;
    fn from_u64_opt(v: u64) -> Option<Self>;
    fn from_u128_opt(v: u128) -> Option<Self>;
    fn from_usize_opt(v: usize) -> Option<Self>;

    fn to_u8_opt(&self) -> Option<u8>;
    fn to_u16_opt(&self) -> Option<u16>;
    fn to_u32_opt(&self) -> Option<u32>;
    fn to_u64_opt(&self) -> Option<u64>;
    fn to_u128_opt(&self) -> Option<u128>;
    fn to_usize_opt(&self) -> Option<usize>;
}
macro_rules! prim {
    ($name:ty, $width:expr) => {
        impl EnumSetTypeRepr for $name {
            const WIDTH: u32 = $width;

            #[inline(always)]
            fn is_empty(&self) -> bool {
                *self == 0
            }
            #[inline(always)]
            fn empty() -> Self {
                0
            }

            #[inline(always)]
            fn add_bit(&mut self, bit: u32) {
                *self |= 1 << bit as $name;
            }
            #[inline(always)]
            fn remove_bit(&mut self, bit: u32) {
                *self &= !(1 << bit as $name);
            }
            #[inline(always)]
            fn has_bit(&self, bit: u32) -> bool {
                (self & (1 << bit as $name)) != 0
            }

            #[inline(always)]
            fn count_ones(&self) -> u32 {
                (*self).count_ones()
            }
            #[inline(always)]
            fn leading_zeros(&self) -> u32 {
                (*self).leading_zeros()
            }
            #[inline(always)]
            fn trailing_zeros(&self) -> u32 {
                (*self).trailing_zeros()
            }

            #[inline(always)]
            fn and_not(&self, other: Self) -> Self {
                (*self) & !other
            }

            #[inline(always)]
            fn count_remaining_ones(&self, cursor: u32) -> usize {
                let left_mask = !((1 as $name)
                    .checked_shl(cursor)
                    .unwrap_or(0)
                    .wrapping_sub(1));
                (*self & left_mask).count_ones() as usize
            }

            #[inline(always)]
            fn from_u8(v: u8) -> Self {
                v as $name
            }
            #[inline(always)]
            fn from_u16(v: u16) -> Self {
                v as $name
            }
            #[inline(always)]
            fn from_u32(v: u32) -> Self {
                v as $name
            }
            #[inline(always)]
            fn from_u64(v: u64) -> Self {
                v as $name
            }
            #[inline(always)]
            fn from_u128(v: u128) -> Self {
                v as $name
            }
            #[inline(always)]
            fn from_usize(v: usize) -> Self {
                v as $name
            }

            #[inline(always)]
            fn to_u8(&self) -> u8 {
                (*self) as u8
            }
            #[inline(always)]
            fn to_u16(&self) -> u16 {
                (*self) as u16
            }
            #[inline(always)]
            fn to_u32(&self) -> u32 {
                (*self) as u32
            }
            #[inline(always)]
            fn to_u64(&self) -> u64 {
                (*self) as u64
            }
            #[inline(always)]
            fn to_u128(&self) -> u128 {
                (*self) as u128
            }
            #[inline(always)]
            fn to_usize(&self) -> usize {
                (*self) as usize
            }

            #[inline(always)]
            fn from_u8_opt(v: u8) -> Option<Self> {
                v.try_into().ok()
            }
            #[inline(always)]
            fn from_u16_opt(v: u16) -> Option<Self> {
                v.try_into().ok()
            }
            #[inline(always)]
            fn from_u32_opt(v: u32) -> Option<Self> {
                v.try_into().ok()
            }
            #[inline(always)]
            fn from_u64_opt(v: u64) -> Option<Self> {
                v.try_into().ok()
            }
            #[inline(always)]
            fn from_u128_opt(v: u128) -> Option<Self> {
                v.try_into().ok()
            }
            #[inline(always)]
            fn from_usize_opt(v: usize) -> Option<Self> {
                v.try_into().ok()
            }

            #[inline(always)]
            fn to_u8_opt(&self) -> Option<u8> {
                (*self).try_into().ok()
            }
            #[inline(always)]
            fn to_u16_opt(&self) -> Option<u16> {
                (*self).try_into().ok()
            }
            #[inline(always)]
            fn to_u32_opt(&self) -> Option<u32> {
                (*self).try_into().ok()
            }
            #[inline(always)]
            fn to_u64_opt(&self) -> Option<u64> {
                (*self).try_into().ok()
            }
            #[inline(always)]
            fn to_u128_opt(&self) -> Option<u128> {
                (*self).try_into().ok()
            }
            #[inline(always)]
            fn to_usize_opt(&self) -> Option<usize> {
                (*self).try_into().ok()
            }
        }
    };
}
prim!(u8, 8);
prim!(u16, 16);
prim!(u32, 32);
prim!(u64, 64);
prim!(u128, 128);