//! ASN.1 `INTEGER` support.

pub(super) mod int;

pub(super) mod uint;

use core::{cmp::Ordering, mem};

use crate::{EncodeValue, Result, SliceWriter};

/// Is the highest bit of the first byte in the slice set to `1`? (if present)

#[inline]

fn is_highest_bit_set(bytes: &[u8]) -> bool {

    bytes

        .first()

        .map(|byte| byte & 0b10000000 != 0)

        .unwrap_or(false)

}

/// Compare two integer values

fn value_cmp<T>(a: T, b: T) -> Result<Ordering>

where

    T: Copy + EncodeValue + Sized,

{

    const MAX_INT_SIZE: usize = 16;

    debug_assert!(mem::size_of::<T>() <= MAX_INT_SIZE);

    let mut buf1 = [0u8; MAX_INT_SIZE];

    let mut encoder1 = SliceWriter::new(&mut buf1);

    a.encode_value(&mut encoder1)?;

    let mut buf2 = [0u8; MAX_INT_SIZE];

    let mut encoder2 = SliceWriter::new(&mut buf2);

    b.encode_value(&mut encoder2)?;

    Ok(encoder1.finish()?.cmp(encoder2.finish()?))

}

Unexecuted instantiation: der::asn1::integer::value_cmp::<i8>

Unexecuted instantiation: der::asn1::integer::value_cmp::<u8>

Unexecuted instantiation: der::asn1::integer::value_cmp::<i32>

Unexecuted instantiation: der::asn1::integer::value_cmp::<u32>

Unexecuted instantiation: der::asn1::integer::value_cmp::<i128>

Unexecuted instantiation: der::asn1::integer::value_cmp::<u128>

Unexecuted instantiation: der::asn1::integer::value_cmp::<i16>

Unexecuted instantiation: der::asn1::integer::value_cmp::<u16>

Unexecuted instantiation: der::asn1::integer::value_cmp::<i64>

Unexecuted instantiation: der::asn1::integer::value_cmp::<u64>

#[cfg(test)]

pub(crate) mod tests {

    use crate::{Decode, Encode};

    // Vectors from Section 5.7 of:

    // https://luca.ntop.org/Teaching/Appunti/asn1.html

    pub(crate) const I0_BYTES: &[u8] = &[0x02, 0x01, 0x00];

    pub(crate) const I127_BYTES: &[u8] = &[0x02, 0x01, 0x7F];

    pub(crate) const I128_BYTES: &[u8] = &[0x02, 0x02, 0x00, 0x80];

    pub(crate) const I256_BYTES: &[u8] = &[0x02, 0x02, 0x01, 0x00];

    pub(crate) const INEG128_BYTES: &[u8] = &[0x02, 0x01, 0x80];

    pub(crate) const INEG129_BYTES: &[u8] = &[0x02, 0x02, 0xFF, 0x7F];

    // Additional vectors

    pub(crate) const I255_BYTES: &[u8] = &[0x02, 0x02, 0x00, 0xFF];

    pub(crate) const I32767_BYTES: &[u8] = &[0x02, 0x02, 0x7F, 0xFF];

    pub(crate) const I65535_BYTES: &[u8] = &[0x02, 0x03, 0x00, 0xFF, 0xFF];

    pub(crate) const INEG32768_BYTES: &[u8] = &[0x02, 0x02, 0x80, 0x00];

    #[test]

    fn decode_i8() {

        assert_eq!(0, i8::from_der(I0_BYTES).unwrap());

        assert_eq!(127, i8::from_der(I127_BYTES).unwrap());

        assert_eq!(-128, i8::from_der(INEG128_BYTES).unwrap());

    }

    #[test]

    fn decode_i16() {

        assert_eq!(0, i16::from_der(I0_BYTES).unwrap());

        assert_eq!(127, i16::from_der(I127_BYTES).unwrap());

        assert_eq!(128, i16::from_der(I128_BYTES).unwrap());

        assert_eq!(255, i16::from_der(I255_BYTES).unwrap());

        assert_eq!(256, i16::from_der(I256_BYTES).unwrap());

        assert_eq!(32767, i16::from_der(I32767_BYTES).unwrap());

        assert_eq!(-128, i16::from_der(INEG128_BYTES).unwrap());

        assert_eq!(-129, i16::from_der(INEG129_BYTES).unwrap());

        assert_eq!(-32768, i16::from_der(INEG32768_BYTES).unwrap());

    }

    #[test]

    fn decode_u8() {

        assert_eq!(0, u8::from_der(I0_BYTES).unwrap());

        assert_eq!(127, u8::from_der(I127_BYTES).unwrap());

        assert_eq!(255, u8::from_der(I255_BYTES).unwrap());

    }

    #[test]

    fn decode_u16() {

        assert_eq!(0, u16::from_der(I0_BYTES).unwrap());

        assert_eq!(127, u16::from_der(I127_BYTES).unwrap());

        assert_eq!(255, u16::from_der(I255_BYTES).unwrap());

        assert_eq!(256, u16::from_der(I256_BYTES).unwrap());

        assert_eq!(32767, u16::from_der(I32767_BYTES).unwrap());

        assert_eq!(65535, u16::from_der(I65535_BYTES).unwrap());

    }

    #[test]

    fn encode_i8() {

        let mut buffer = [0u8; 3];

        assert_eq!(I0_BYTES, 0i8.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I127_BYTES, 127i8.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(

            INEG128_BYTES,

            (-128i8).encode_to_slice(&mut buffer).unwrap()

        );

    }

    #[test]

    fn encode_i16() {

        let mut buffer = [0u8; 4];

        assert_eq!(I0_BYTES, 0i16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I127_BYTES, 127i16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I128_BYTES, 128i16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I255_BYTES, 255i16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I256_BYTES, 256i16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I32767_BYTES, 32767i16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(

            INEG128_BYTES,

            (-128i16).encode_to_slice(&mut buffer).unwrap()

        );

        assert_eq!(

            INEG129_BYTES,

            (-129i16).encode_to_slice(&mut buffer).unwrap()

        );

        assert_eq!(

            INEG32768_BYTES,

            (-32768i16).encode_to_slice(&mut buffer).unwrap()

        );

    }

    #[test]

    fn encode_u8() {

        let mut buffer = [0u8; 4];

        assert_eq!(I0_BYTES, 0u8.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I127_BYTES, 127u8.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I255_BYTES, 255u8.encode_to_slice(&mut buffer).unwrap());

    }

    #[test]

    fn encode_u16() {

        let mut buffer = [0u8; 5];

        assert_eq!(I0_BYTES, 0u16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I127_BYTES, 127u16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I128_BYTES, 128u16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I255_BYTES, 255u16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I256_BYTES, 256u16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I32767_BYTES, 32767u16.encode_to_slice(&mut buffer).unwrap());

        assert_eq!(I65535_BYTES, 65535u16.encode_to_slice(&mut buffer).unwrap());

    }

    /// Integers must be encoded with a minimum number of octets

    #[test]

    fn reject_non_canonical() {

        assert!(i8::from_der(&[0x02, 0x02, 0x00, 0x00]).is_err());

        assert!(i16::from_der(&[0x02, 0x02, 0x00, 0x00]).is_err());

        assert!(u8::from_der(&[0x02, 0x02, 0x00, 0x00]).is_err());

        assert!(u16::from_der(&[0x02, 0x02, 0x00, 0x00]).is_err());

    }

}