use core::fmt;

/// A four-octet IPv4 address.
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Default)]
pub struct Address(pub [u8; 4]);

impl Address {
    pub const BROADCAST: Address = Address([255; 4]);

    /// Construct an IPv4 address from a sequence of octets, in big-endian.
    ///
    /// # Panics
    /// The function panics if `data` is not four octets long.
    pub fn from_bytes(data: &[u8]) -> Address {
        let mut bytes = [0; 4];
        bytes.copy_from_slice(data);
        Address(bytes)
    }

    /// Return an IPv4 address as a sequence of octets, in big-endian.
    pub fn as_bytes(&self) -> &[u8] {
        &self.0
    }

    /// Query whether the address is an unicast address.
    pub fn is_unicast(&self) -> bool {
        !(self.is_broadcast() ||
          self.is_multicast() ||
          self.is_unspecified())
    }

    /// Query whether the address is the broadcast address.
    pub fn is_broadcast(&self) -> bool {
        self.0[0..4] == [255; 4]
    }

    /// Query whether the address is a multicast address.
    pub fn is_multicast(&self) -> bool {
        self.0[0] & 0xf0 == 224
    }

    /// Query whether the address falls into the "unspecified" range.
    pub fn is_unspecified(&self) -> bool {
        self.0[0] == 0
    }

    /// Query whether the address falls into the "link-local" range.
    pub fn is_link_local(&self) -> bool {
        self.0[0..2] == [169, 254]
    }

    /// Query whether the address falls into the "loopback" range.
    pub fn is_loopback(&self) -> bool {
        self.0[0] == 127
    }
}

impl fmt::Display for Address {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let bytes = self.0;
        write!(f, "{}.{}.{}.{}", bytes[0], bytes[1], bytes[2], bytes[3])
    }
}