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use crate::error::*;
use crate::{Decoder, Encoder};

pub struct Hex;

impl Encoder for Hex {
    #[inline]
    fn encoded_len(bin_len: usize) -> Result<usize, Error> {
        bin_len.checked_mul(2).ok_or(Error::Overflow)
    }

    fn encode<IN: AsRef<[u8]>>(hex: &mut [u8], bin: IN) -> Result<&[u8], Error> {
        let bin = bin.as_ref();
        let bin_len = bin.len();
        let hex_maxlen = hex.len();
        if hex_maxlen < bin_len.checked_shl(1).ok_or(Error::Overflow)? {
            return Err(Error::Overflow);
        }
        for (i, v) in bin.iter().enumerate() {
            let (b, c) = ((v >> 4) as u16, (v & 0xf) as u16);
            let x = (((87 + c + (((c.wrapping_sub(10)) >> 8) & !38)) as u8) as u16) << 8
                | ((87 + b + (((b.wrapping_sub(10)) >> 8) & !38)) as u8) as u16;
            hex[i * 2] = x as u8;
            hex[i * 2 + 1] = (x >> 8) as u8;
        }
        Ok(&hex[..bin_len * 2])
    }
}

impl Decoder for Hex {
    fn decode<'t, IN: AsRef<[u8]>>(
        bin: &'t mut [u8],
        hex: IN,
        ignore: Option<&[u8]>,
    ) -> Result<&'t [u8], Error> {
        let hex = hex.as_ref();
        let bin_maxlen = bin.len();
        let mut bin_pos = 0;
        let mut state = false;
        let mut c_acc = 0;
        for &c in hex {
            let c_num = c ^ 48;
            let c_num0 = ((c_num as u16).wrapping_sub(10) >> 8) as u8;
            let c_alpha = (c & !32).wrapping_sub(55);
            let c_alpha0 = (((c_alpha as u16).wrapping_sub(10)
                ^ ((c_alpha as u16).wrapping_sub(16)))
                >> 8) as u8;
            if (c_num0 | c_alpha0) == 0 {
                match ignore {
                    Some(ignore) if ignore.contains(&c) => continue,
                    _ => return Err(Error::InvalidInput),
                };
            }
            let c_val = (c_num0 & c_num) | (c_alpha0 & c_alpha);
            if bin_pos >= bin_maxlen {
                return Err(Error::Overflow);
            }
            if !state {
                c_acc = c_val << 4;
            } else {
                bin[bin_pos] = c_acc | c_val;
                bin_pos += 1;
            }
            state = !state;
        }
        if state {
            return Err(Error::InvalidInput);
        }
        Ok(&bin[..bin_pos])
    }
}

#[cfg(feature = "std")]
#[test]
fn test_hex() {
    let bin = [1u8, 5, 11, 15, 19, 131];
    let hex = Hex::encode_to_string(&bin).unwrap();
    let expected = "01050b0f1383";
    assert_eq!(hex, expected);
    let bin2 = Hex::decode_to_vec(&hex, None).unwrap();
    assert_eq!(bin, &bin2[..]);
}

#[test]
fn test_hex_no_std() {
    let bin = [1u8, 5, 11, 15, 19, 131];
    let expected = "01050b0f1383";
    let mut hex = [0u8; 12];
    let hex = Hex::encode_to_str(&mut hex, &bin).unwrap();
    assert_eq!(&hex, &expected);
    let mut bin2 = [0u8; 6];
    let bin2 = Hex::decode(&mut bin2, &hex, None).unwrap();
    assert_eq!(bin, bin2);
}