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

use c_ares_sys;
use c_types;
use itertools::Itertools;

use error::{Error, Result};
use hostent::{HasHostent, HostAliasResultsIter, HostentOwned};
use panic;

/// The result of a successful PTR lookup.
#[derive(Debug)]
pub struct PTRResults {
    hostent: HostentOwned,
}

impl PTRResults {
    /// Obtain a `PTRResults` from the response to a PTR lookup.
    pub fn parse_from(data: &[u8]) -> Result<PTRResults> {
        let mut hostent: *mut c_types::hostent = ptr::null_mut();
        let dummy_ip = [0, 0, 0, 0];
        let parse_status = unsafe {
            c_ares_sys::ares_parse_ptr_reply(
                data.as_ptr(),
                data.len() as c_int,
                dummy_ip.as_ptr() as *const c_void,
                dummy_ip.len() as c_int,
                c_types::AF_INET,
                &mut hostent,
            )
        };
        if parse_status == c_ares_sys::ARES_SUCCESS {
            let result = PTRResults::new(hostent);
            Ok(result)
        } else {
            Err(Error::from(parse_status))
        }
    }

    fn new(hostent: *mut c_types::hostent) -> PTRResults {
        PTRResults {
            hostent: HostentOwned::new(hostent),
        }
    }

    /// Returns the hostname from this `PTRResults`.
    pub fn hostname(&self) -> &str {
        self.hostent.hostname()
    }

    /// Returns an iterator over the host aliases in this `PTRResults`.
    pub fn aliases(&self) -> HostAliasResultsIter {
        self.hostent.aliases()
    }
}

impl fmt::Display for PTRResults {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "Hostname: {}, ", self.hostname())?;
        let aliases = self.aliases().format(", ");
        write!(fmt, "Aliases: [{}]", aliases)
    }
}

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