use std::ffi::CStr;
use std::net::IpAddr;
use std::{net, ptr};

use ::std::io::{Error, ErrorKind};

use crate::ifaces::{Interface, Kind, NextHop};

// https://github.com/Exa-Networks/exaproxy/blob/master/lib/exaproxy/util/interfaces.py

pub const AF_INET: i32 = nix::sys::socket::AddressFamily::Inet as i32;
pub const AF_INET6: i32 = nix::sys::socket::AddressFamily::Inet6 as i32;

#[cfg(any(
    target_os = "macos",
    target_os = "ios",
    target_os = "freebsd",
    target_os = "openbsd",
    target_os = "netbsd"
))]
pub const AF_LINK: i32 = nix::libc::AF_LINK;
#[cfg(any(
    target_os = "macos",
    target_os = "ios",
    target_os = "freebsd",
    target_os = "openbsd",
    target_os = "netbsd"
))]
pub const AF_PACKET: i32 = -1;

#[cfg(any(target_os = "linux", target_os = "android"))]
pub const AF_LINK: i32 = -1;
#[cfg(any(target_os = "linux", target_os = "android"))]
pub const AF_PACKET: i32 = nix::libc::AF_PACKET;

#[allow(dead_code, non_camel_case_types)]
#[repr(C)]
pub enum SiocgifFlags {
    Up = 0x1,           /* Interface is up.  */
    Broadcast = 0x2,    /* Broadcast address valid.  */
    Debug = 0x4,        /* Turn on debugging.  */
    Loopback = 0x8,     /* Is a loopback net.  */
    Pointopoint = 0x10, /* Interface is point-to-point link.  */
    Notrailers = 0x20,  /* Avoid use of trailers.  */
    Running = 0x40,     /* Resources allocated.  */
    Noarp = 0x80,       /* No address resolution protocol.  */
    Promisc = 0x100,    /* Receive all packets.  */

    /* Not supported */
    Allmulti = 0x200, /* Receive all multicast packets.  */

    Master = 0x400, /* Master of a load balancer.  */
    Slave = 0x800,  /* Slave of a load balancer.  */

    Multicast = 0x1000, /* Supports multicast.  */

    Portsel = 0x2000,   /* Can set media type.  */
    Automedia = 0x4000, /* Auto media select active.  */
    Dynamic = 0x8000,   /* Dialup device with changing addresses.  */
}

#[repr(C)]
pub struct union_ifa_ifu {
    pub data: *mut ::std::os::raw::c_void,
}
impl union_ifa_ifu {
    pub fn ifu_broadaddr(&mut self) -> *mut nix::sys::socket::sockaddr {
        self.data as *mut nix::sys::socket::sockaddr
    }
    pub fn ifu_dstaddr(&mut self) -> *mut nix::sys::socket::sockaddr {
        self.data as *mut nix::sys::socket::sockaddr
    }
}

#[repr(C)]
pub struct ifaddrs {
    pub ifa_next: *mut ifaddrs,
    pub ifa_name: *mut ::std::os::raw::c_char,
    pub ifa_flags: ::std::os::raw::c_uint,
    pub ifa_addr: *mut nix::sys::socket::sockaddr,
    pub ifa_netmask: *mut nix::sys::socket::sockaddr,
    pub ifa_ifu: union_ifa_ifu,
    pub ifa_data: *mut ::std::os::raw::c_void,
}

extern "C" {
    pub fn getifaddrs(ifap: *mut *mut ifaddrs) -> ::std::os::raw::c_int;
    pub fn freeifaddrs(ifa: *mut ifaddrs) -> ::std::os::raw::c_void;
    #[allow(dead_code)]
    pub fn if_nametoindex(ifname: *const ::std::os::raw::c_char) -> ::std::os::raw::c_uint;
}

pub fn nix_socketaddr_to_sockaddr(sa: *mut nix::sys::socket::sockaddr) -> Option<net::SocketAddr> {
    if sa.is_null() {
        return None;
    }

    let (addr, port) = match unsafe { *sa }.sa_family as i32 {
        AF_INET => {
            let sa: *const nix::sys::socket::sockaddr_in = sa as *const nix::libc::sockaddr_in;
            let sa = &unsafe { *sa };
            let (addr, port) = (sa.sin_addr.s_addr, sa.sin_port);
            (IpAddr::V4(Into::into(u32::from_be(addr))), port)
        }
        AF_INET6 => {
            let sa: *const nix::sys::socket::sockaddr_in6 = sa as *const nix::libc::sockaddr_in6;
            let sa = &unsafe { *sa };
            let (addr, port) = (sa.sin6_addr.s6_addr, sa.sin6_port);
            (Into::into(addr), port)
        }
        _ => return None,
    };
    Some(net::SocketAddr::new(addr, port))
}

/// Query the local system for all interface addresses.
pub fn ifaces() -> Result<Vec<Interface>, Error> {
    let mut ifaddrs_ptr: *mut ifaddrs = ptr::null_mut();
    match unsafe { getifaddrs(&mut ifaddrs_ptr as *mut _) } {
        0 => {
            let mut ret = Vec::new();
            let mut item: *mut ifaddrs = ifaddrs_ptr;
            loop {
                if item.is_null() {
                    break;
                }
                let name = String::from_utf8(
                    unsafe { CStr::from_ptr((*item).ifa_name) }
                        .to_bytes()
                        .to_vec(),
                );
                unsafe {
                    if name.is_err() || (*item).ifa_addr.is_null() {
                        item = (*item).ifa_next;
                        continue;
                    }
                }
                let kind = match unsafe { (*(*item).ifa_addr).sa_family as i32 } {
                    AF_INET => Some(Kind::Ipv4),
                    AF_INET6 => Some(Kind::Ipv6),
                    AF_PACKET => Some(Kind::Packet),
                    AF_LINK => Some(Kind::Link),
                    code => Some(Kind::Unknow(code)),
                };
                if kind.is_none() {
                    item = unsafe { (*item).ifa_next };
                    continue;
                }

                let addr = nix_socketaddr_to_sockaddr(unsafe { (*item).ifa_addr });
                let mask = nix_socketaddr_to_sockaddr(unsafe { (*item).ifa_netmask });
                let hop = unsafe {
                    if (*item).ifa_flags & SiocgifFlags::Broadcast as ::std::os::raw::c_uint
                        == SiocgifFlags::Broadcast as ::std::os::raw::c_uint
                    {
                        nix_socketaddr_to_sockaddr((*item).ifa_ifu.ifu_broadaddr())
                            .map(NextHop::Broadcast)
                    } else {
                        nix_socketaddr_to_sockaddr((*item).ifa_ifu.ifu_dstaddr())
                            .map(NextHop::Destination)
                    }
                };

                if let Some(kind) = kind {
                    match kind {
                        Kind::Unknow(_) => {}
                        _ => {
                            ret.push(Interface {
                                name: name.unwrap(),
                                kind,
                                addr,
                                mask,
                                hop,
                            });
                        }
                    };
                };

                item = unsafe { (*item).ifa_next };
            }
            unsafe { freeifaddrs(ifaddrs_ptr) };
            Ok(ret)
        }
        _ => Err(Error::new(ErrorKind::Other, "Oh, no ...")), // Err(nix::errno::Errno::last());
    }
}