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use heapless::{consts, String};

use crate::addr::HostAddr;
use no_std_net::IpAddr;

use core::fmt::Debug;

/// DNS errors
#[derive(Debug)]
pub enum DnsError {
    UnsupportedAddressType,
    NoSuchHost,
}

/// This is the host address type to be returned by `gethostbyname`.
///
/// An IPv4 address type always looks for `A` records, while IPv6 address type
/// will look for `AAAA` records
#[derive(Clone, Debug, PartialEq)]
pub enum AddrType {
    /// Result is `A` record
    IPv4,
    /// Result is `AAAA` record
    IPv6,
    /// Result is either a `A` record, or a `AAAA` record
    Either,
}

/// This trait is an extension trait for [`TcpStack`] and [`UdpStack`] for dns
/// resolutions. It does not handle every DNS record type, but is meant as an
/// embedded alternative to [`ToSocketAddrs`], and is as such meant to resolve
/// an ip address from a hostname, or a hostname from an ip address. This means
/// that it only deals in host address records `A` (IPv4) and `AAAA` (IPv6).
///
/// [`TcpStack`]: trait.TcpStack.html
/// [`UdpStack`]: trait.UdpStack.html
/// [`ToSocketAddrs`]:
/// https://doc.rust-lang.org/std/net/trait.ToSocketAddrs.html
pub trait Dns {
    /// The type returned when we have an error
    type Error: Into<DnsError> + Debug;

    /// Resolve the first ip address of a host, given its hostname and a desired
    /// address record type to look for
    fn gethostbyname(&self, hostname: &str, addr_type: AddrType) -> Result<HostAddr, Self::Error>;

    /// Resolve the hostname of a host, given its ip address
    ///
    /// **Note**: A fully qualified domain name (FQDN), has a maximum length of
    /// 255 bytes [`rfc1035`]
    ///
    /// [`rfc1035`]: https://tools.ietf.org/html/rfc1035
    fn gethostbyaddr(&self, addr: IpAddr) -> Result<String<consts::U256>, Self::Error>;
}