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use std::ops::ShrAssign;

use alloy_primitives::U256;

use super::error::UniswapV3MathError;

pub fn most_significant_bit(mut x: U256) -> Result<u8, UniswapV3MathError> {
    let mut r = 0;

    if x.is_zero() {
        return Err(UniswapV3MathError::ZeroValue);
    }

    if x >= U256::from_str_radix("100000000000000000000000000000000", 16).unwrap() {
        x.shr_assign(128);
        r += 128;
    }

    if x >= U256::from(0x10000000000000000_u128) {
        x.shr_assign(64);
        r += 64;
    }

    if x >= U256::from(0x100000000_usize) {
        x.shr_assign(32);
        r += 32;
    }

    if x >= U256::from(0x10000_usize) {
        x.shr_assign(16);
        r += 16;
    }

    if x >= U256::from(0x100_usize) {
        x.shr_assign(8);
        r += 8;
    }

    if x >= U256::from(0x10) {
        x.shr_assign(4);
        r += 4;
    }
    if x >= U256::from(0x4) {
        x.shr_assign(2);
        r += 2;
    }

    if x >= U256::from(0x2) {
        r += 1;
    }

    Ok(r)
}

pub fn least_significant_bit(mut x: U256) -> Result<u8, UniswapV3MathError> {
    if x.is_zero() {
        return Err(UniswapV3MathError::ZeroValue);
    }

    let mut r = 255;

    //TODO: update this to use constants for each U256 comparison

    if x & U256::from(u128::MAX) > U256::ZERO {
        r -= 128;
    } else {
        x >>= 128;
    }

    if x & U256::from(u64::MAX) > U256::ZERO {
        r -= 64;
    } else {
        x >>= 64;
    }

    if x & U256::from(u32::MAX) > U256::ZERO {
        r -= 32;
    } else {
        x >>= 32;
    }

    if x & U256::from(u16::MAX) > U256::ZERO {
        r -= 16;
    } else {
        x >>= 16;
    }

    if x & U256::from(u8::MAX) > U256::ZERO {
        r -= 8;
    } else {
        x >>= 8;
    }

    if x & U256::from(0xf) > U256::ZERO {
        r -= 4;
    } else {
        x >>= 4;
    }

    if x & U256::from(0x3) > U256::ZERO {
        r -= 2;
    } else {
        x >>= 2;
    }

    if x & U256::from(0x1) > U256::ZERO {
        r -= 1;
    }

    Ok(r)
}

// #[cfg(test)]
// mod test {
//
//     use ethers::types::U256;
//
//     use super::most_significant_bit;
//     use crate::bit_math::least_significant_bit;
//
//     #[test]
//     fn test_most_significant_bit() {
//         //0
//         let result = most_significant_bit(U256::ZERO);
//         assert_eq!(
//             result.unwrap_err().to_string(),
//             "Can not get most significant bit or least significant bit on
// zero value"         );
//
//         //1
//         let result = most_significant_bit(U256::from(1));
//         assert_eq!(result.unwrap(), 0);
//
//         //2
//         let result = most_significant_bit(U256::from(2));
//         assert_eq!(result.unwrap(), 1);
//
//         //all powers of 2
//         for i in 0..=255 {
//             let result =
// most_significant_bit(U256::from(2).pow(U256::from(i)));
// assert_eq!(result.unwrap(), i as u8);         }
//
//         //uint256(-1)
//         let result = most_significant_bit(
//             U256::from_dec_str(
//
// "115792089237316195423570985008687907853269984665640564039457584007913129639935"
// ,             )
//             .unwrap(),
//         );
//         assert_eq!(result.unwrap(), 255);
//     }
//
//     #[test]
//     fn test_least_significant_bit() {
//         //0
//         let result = least_significant_bit(U256::ZERO);
//         assert_eq!(
//             result.unwrap_err().to_string(),
//             "Can not get most significant bit or least significant bit on
// zero value"         );
//
//         //1
//         let result = least_significant_bit(U256::from(1));
//         assert_eq!(result.unwrap(), 0);
//
//         //2
//         let result = least_significant_bit(U256::from(2));
//         assert_eq!(result.unwrap(), 1);
//
//         //all powers of 2
//         for i in 0..=255 {
//             let result =
// least_significant_bit(U256::from(2).pow(U256::from(i)));
// assert_eq!(result.unwrap(), i as u8);         }
//
//         //uint256(-1)
//         let result = least_significant_bit(
//             U256::from_dec_str(
//
// "115792089237316195423570985008687907853269984665640564039457584007913129639935"
// ,             )
//             .unwrap(),
//         );
//         assert_eq!(result.unwrap(), 0);
//     }
// }