//! Bitwise XOR via the [`BitXor`] trait.
use super::U320;
use core::ops::BitXor;

/// Computes the bitwise XOR of two 320-bit integers, producing a
/// result where each bit is set if exactly one of the corresponding
/// input bits is set.
///
/// Applied independently to each of the five `u64` limbs.
///
/// # Examples
///
/// ```
/// use cnfy_uint::u320::U320;
///
/// let a = U320::from_be_limbs([0xFF, 0, 0, 0, 0]);
/// let b = U320::from_be_limbs([0x0F, 0, 0, 0, 0]);
/// assert_eq!(a ^ b, U320::from_be_limbs([0xF0, 0, 0, 0, 0]));
/// ```
impl BitXor for U320 {
    type Output = U320;

    #[inline]
    fn bitxor(self, rhs: U320) -> U320 {
        U320([
            self.0[0] ^ rhs.0[0],
            self.0[1] ^ rhs.0[1],
            self.0[2] ^ rhs.0[2],
            self.0[3] ^ rhs.0[3],
            self.0[4] ^ rhs.0[4],
        ])
    }
}

#[cfg(test)]
mod ai_tests {
    use super::*;

    /// XOR with self is zero.
    #[test]
    fn self_cancellation() {
        let a = U320::from_be_limbs([0x1234, 0x5678, 0x9ABC, 0xDEF0, 0x1111]);
        assert_eq!(a ^ a, U320::ZERO);
    }

    /// XOR with zero is identity.
    #[test]
    fn xor_zero() {
        let a = U320::from_be_limbs([0x1234, 0x5678, 0x9ABC, 0xDEF0, 0x1111]);
        assert_eq!(a ^ U320::ZERO, a);
    }

    /// XOR with MAX flips all bits.
    #[test]
    fn xor_max() {
        let a = U320::ZERO;
        assert_eq!(a ^ U320::MAX, U320::MAX);
    }

    /// XOR flips specific bits.
    #[test]
    fn flips_bits() {
        let a = U320::from_be_limbs([0xFF, 0, 0, 0, 0]);
        let b = U320::from_be_limbs([0x0F, 0, 0, 0, 0]);
        assert_eq!(a ^ b, U320::from_be_limbs([0xF0, 0, 0, 0, 0]));
    }

    /// XOR is commutative.
    #[test]
    fn commutative() {
        let a = U320::from_be_limbs([1, 2, 3, 4, 5]);
        let b = U320::from_be_limbs([5, 6, 7, 8, 9]);
        assert_eq!(a ^ b, b ^ a);
    }
}
