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use std::fmt;
use std::mem;
use std::net::Ipv4Addr;
use std::os::raw::{c_int, c_uchar, c_void};
use std::ptr;
use std::slice;

use itertools::Itertools;

use crate::error::{Error, Result};
use crate::panic;
use crate::types::MAX_ADDRTTLS;
use crate::utils::ipv4_from_in_addr;

/// The result of a successful A lookup.
#[derive(Clone, Copy)]
pub struct AResults {
    naddrttls: usize,
    addrttls: [c_ares_sys::ares_addrttl; MAX_ADDRTTLS],
}

/// The contents of a single A record.
#[derive(Clone, Copy)]
pub struct AResult<'a> {
    addrttl: &'a c_ares_sys::ares_addrttl,
}

impl AResults {
    /// Obtain an `AResults` from the response to an A lookup.
    pub fn parse_from(data: &[u8]) -> Result<AResults> {
        let mut results: AResults = AResults {
            naddrttls: MAX_ADDRTTLS,
            addrttls: unsafe { mem::MaybeUninit::zeroed().assume_init() },
        };
        let parse_status = unsafe {
            c_ares_sys::ares_parse_a_reply(
                data.as_ptr(),
                data.len() as c_int,
                ptr::null_mut(),
                results.addrttls.as_mut_ptr(),
                (&mut results.naddrttls as *mut usize).cast(),
            )
        };
        if parse_status == c_ares_sys::ares_status_t::ARES_SUCCESS as i32 {
            Ok(results)
        } else {
            Err(Error::from(parse_status))
        }
    }

    /// Returns an iterator over the `AResult` values in this `AResults`.
    pub fn iter(&self) -> AResultsIter {
        AResultsIter {
            addrttls: self.addrttls[0..self.naddrttls].iter(),
        }
    }
}

impl fmt::Display for AResults {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        let results = self.iter().format("}, {");
        write!(fmt, "[{{{results}}}]")
    }
}

/// Iterator of `AResult`s.
#[derive(Clone)]
pub struct AResultsIter<'a> {
    addrttls: slice::Iter<'a, c_ares_sys::ares_addrttl>,
}

impl<'a> Iterator for AResultsIter<'a> {
    type Item = AResult<'a>;
    fn next(&mut self) -> Option<Self::Item> {
        self.addrttls.next().map(|addrttl| AResult { addrttl })
    }
}

impl<'a> IntoIterator for &'a AResults {
    type Item = AResult<'a>;
    type IntoIter = AResultsIter<'a>;

    fn into_iter(self) -> Self::IntoIter {
        self.iter()
    }
}

impl<'a> AResult<'a> {
    /// Returns the IPv4 address in this `AResult`.
    pub fn ipv4(self) -> Ipv4Addr {
        ipv4_from_in_addr(self.addrttl.ipaddr)
    }

    /// Returns the time-to-live in this `AResult`.
    pub fn ttl(self) -> i32 {
        #[allow(clippy::unnecessary_cast)]
        let ttl = self.addrttl.ttl as i32;
        ttl
    }
}

impl<'a> fmt::Display for AResult<'a> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "IPv4: {}, ", self.ipv4())?;
        write!(fmt, "TTL: {}", self.ttl())
    }
}

pub(crate) unsafe extern "C" fn query_a_callback<F>(
    arg: *mut c_void,
    status: c_int,
    _timeouts: c_int,
    abuf: *mut c_uchar,
    alen: c_int,
) where
    F: FnOnce(Result<AResults>) + Send + 'static,
{
    ares_callback!(arg.cast::<F>(), status, abuf, alen, AResults::parse_from);
}