use crate::PrefixLenError;

#[cfg(not(feature = "std"))]

use core::net::{IpAddr, Ipv4Addr, Ipv6Addr};

#[cfg(feature = "std")]

use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};

/// Converts a `IpAddr` network mask into a prefix.

///

/// # Errors

/// If the mask is invalid this will return an `PrefixLenError`.

pub fn ip_mask_to_prefix(mask: IpAddr) -> Result<u8, PrefixLenError> {

    match mask {

        IpAddr::V4(mask) => ipv4_mask_to_prefix(mask),

        IpAddr::V6(mask) => ipv6_mask_to_prefix(mask),

    }

}

/// Converts a `Ipv4Addr` network mask into a prefix.

///

/// # Errors

/// If the mask is invalid this will return an `PrefixLenError`.

pub fn ipv4_mask_to_prefix(mask: Ipv4Addr) -> Result<u8, PrefixLenError> {

    let mask = u32::from(mask);

    let prefix = mask.leading_ones();

    if mask.checked_shl(prefix).unwrap_or(0) == 0 {

        Ok(prefix as u8)

    } else {

        Err(PrefixLenError)

    }

}

/// Converts a `Ipv6Addr` network mask into a prefix.

///

/// # Errors

/// If the mask is invalid this will return an `PrefixLenError`.

pub fn ipv6_mask_to_prefix(mask: Ipv6Addr) -> Result<u8, PrefixLenError> {

    let mask = u128::from(mask);

    let prefix = mask.leading_ones();

    if mask.checked_shl(prefix).unwrap_or(0) == 0 {

        Ok(prefix as u8)

    } else {

        Err(PrefixLenError)

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    use crate::{Ipv4Net, Ipv6Net};

    #[test]

    fn v4_mask_to_prefix() {

        let mask = Ipv4Addr::new(255, 255, 255, 128);

        let prefix = ipv4_mask_to_prefix(mask);

        assert_eq!(prefix, Ok(25));

    }

    #[test]

    fn v4_mask_to_prefix_max() {

        let mask = Ipv4Addr::from(u32::MAX);

        let prefix = ipv4_mask_to_prefix(mask);

        assert_eq!(prefix, Ok(32));

    }

    #[test]

    fn invalid_v4_mask_to_prefix() {

        let mask = Ipv4Addr::new(255, 0, 255, 0);

        let prefix = ipv4_mask_to_prefix(mask);

        assert!(prefix.is_err());

    }

    #[test]

    fn ipv4net_with_netmask() {

        {

            // Positive test-case.

            let addr = Ipv4Addr::new(127, 0, 0, 1);

            let mask = Ipv4Addr::new(255, 0, 0, 0);

            let net = Ipv4Net::with_netmask(addr, mask).unwrap();

            let expected = Ipv4Net::new(Ipv4Addr::new(127, 0, 0, 1), 8).unwrap();

            assert_eq!(net, expected);

        }

        {

            // Negative test-case.

            let addr = Ipv4Addr::new(127, 0, 0, 1);

            let mask = Ipv4Addr::new(255, 0, 255, 0);

            Ipv4Net::with_netmask(addr, mask).unwrap_err();

        }

    }

    #[test]

    fn v6_mask_to_prefix() {

        let mask = Ipv6Addr::new(0xffff, 0xffff, 0xffff, 0, 0, 0, 0, 0);

        let prefix = ipv6_mask_to_prefix(mask);

        assert_eq!(prefix, Ok(48));

    }

    #[test]

    fn v6_mask_to_prefix_max() {

        let mask = Ipv6Addr::from(u128::MAX);

        let prefix = ipv6_mask_to_prefix(mask);

        assert_eq!(prefix, Ok(128));

    }

    #[test]

    fn invalid_v6_mask_to_prefix() {

        let mask = Ipv6Addr::new(0, 0, 0xffff, 0xffff, 0, 0, 0, 0);

        let prefix = ipv6_mask_to_prefix(mask);

        assert!(prefix.is_err());

    }

    #[test]

    fn ipv6net_with_netmask() {

        {

            // Positive test-case.

            let addr = Ipv6Addr::new(0xff01, 0, 0, 0x17, 0, 0, 0, 0x2);

            let mask = Ipv6Addr::new(0xffff, 0xffff, 0xffff, 0, 0, 0, 0, 0);

            let net = Ipv6Net::with_netmask(addr, mask).unwrap();

            let expected =

                Ipv6Net::new(Ipv6Addr::new(0xff01, 0, 0, 0x17, 0, 0, 0, 0x2), 48).unwrap();

            assert_eq!(net, expected);

        }

        {

            // Negative test-case.

            let addr = Ipv6Addr::new(0xff01, 0, 0, 0x17, 0, 0, 0, 0x2);

            let mask = Ipv6Addr::new(0, 0, 0xffff, 0xffff, 0, 0, 0, 0);

            Ipv6Net::with_netmask(addr, mask).unwrap_err();

        }

    }

}