use crate::{decode_inner, Error};

#[cfg(feature = "alloc")]

use crate::{decoded_len, Vec};

/// Decode a mixed Base16 (hex) string into the provided destination buffer.

pub fn decode(src: impl AsRef<[u8]>, dst: &mut [u8]) -> Result<&[u8], Error> {

    decode_inner(src.as_ref(), dst, decode_nibble)

}

/// Decode a mixed Base16 (hex) string into a byte vector.

#[cfg(feature = "alloc")]

pub fn decode_vec(input: impl AsRef<[u8]>) -> Result<Vec<u8>, Error> {

    let mut output = vec![0u8; decoded_len(input.as_ref())?];

    decode(input, &mut output)?;

    Ok(output)

}

/// Decode a single nibble of lower hex

#[inline(always)]

fn decode_nibble(src: u8) -> u16 {

    // 0-9  0x30-0x39

    // A-F  0x41-0x46 or a-f  0x61-0x66

    let byte = src as i16;

    let mut ret: i16 = -1;

    // 0-9  0x30-0x39

    // if (byte > 0x2f && byte < 0x3a) ret += byte - 0x30 + 1; // -47

    ret += (((0x2fi16 - byte) & (byte - 0x3a)) >> 8) & (byte - 47);

    // A-F  0x41-0x46

    // if (byte > 0x40 && byte < 0x47) ret += byte - 0x41 + 10 + 1; // -54

    ret += (((0x40i16 - byte) & (byte - 0x47)) >> 8) & (byte - 54);

    // a-f  0x61-0x66

    // if (byte > 0x60 && byte < 0x67) ret += byte - 0x61 + 10 + 1; // -86

    ret += (((0x60i16 - byte) & (byte - 0x67)) >> 8) & (byte - 86);

    ret as u16

}