use windows::Win32::Foundation::{ERROR_BUFFER_OVERFLOW, NO_ERROR};
use windows::Win32::Networking::WinSock::{SOCKADDR_IN, SOCKADDR_IN6};
use windows::Win32::NetworkManagement::IpHelper::{GetAdaptersAddresses, AF_UNSPEC, AF_INET, AF_INET6, GAA_FLAG_INCLUDE_GATEWAYS, IP_ADAPTER_ADDRESSES_LH, SendARP};
use std::convert::TryInto;
use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
use std::convert::TryFrom;
use core::ffi::c_void;
use libc::{c_char, strlen, wchar_t, wcslen};
use memalloc::{allocate, deallocate};

use crate::ip::{Ipv4Net, Ipv6Net};
use crate::interface::{Interface, MacAddr,InterfaceType};
use crate::gateway::Gateway;

#[cfg(target_endian = "little")]
fn htonl(val : u32) -> u32 {
    let o3 = (val >> 24) as u8;
    let o2 = (val >> 16) as u8;
    let o1 = (val >> 8)  as u8;
    let o0 =  val        as u8;
    (o0 as u32) << 24 | (o1 as u32) << 16 | (o2 as u32) << 8 | (o3 as u32)
}

#[cfg(target_endian = "big")]
fn htonl(val : u32) -> u32 {
    val
}

fn get_mac_through_arp(src_ip: Ipv4Addr, dst_ip: Ipv4Addr) -> MacAddr {
    let src_ip_int: u32 = htonl(u32::from(src_ip));
    let dst_ip_int: u32 = htonl(u32::from(dst_ip));
    let mut out_buf_len : u32 = 6;
    let mut target_mac_addr: [u8; 6] =  [0; 6];
    let res = unsafe { SendARP(dst_ip_int, src_ip_int, target_mac_addr.as_mut_ptr() as *mut c_void, &mut out_buf_len) };
    if res == NO_ERROR {
        MacAddr::new(target_mac_addr)
    }else{
        MacAddr::zero()
    }
}

// Get network interfaces using the IP Helper API
// Reference: https://docs.microsoft.com/en-us/windows/win32/api/iphlpapi/nf-iphlpapi-getadaptersaddresses
pub fn interfaces() -> Vec<Interface> {
    let mut interfaces: Vec<Interface> = vec![];
    let mut dwsize: u32 = 2000;
    let mut mem = unsafe { allocate(dwsize as usize) } as *mut IP_ADAPTER_ADDRESSES_LH;
    let mut retries = 3;
    let mut ret_val;
    let family: u32 = AF_UNSPEC;
    let flags: u32 = GAA_FLAG_INCLUDE_GATEWAYS;
    loop {
        let old_size = dwsize as usize;
        ret_val = unsafe { GetAdaptersAddresses(family, flags, std::ptr::null_mut::<std::ffi::c_void>(), mem, &mut dwsize) };
        if ret_val != ERROR_BUFFER_OVERFLOW || retries <= 0 {
            break;
        }
        unsafe { deallocate(mem as *mut u8, old_size as usize) };
        mem = unsafe { allocate(dwsize as usize) as *mut IP_ADAPTER_ADDRESSES_LH };
        retries -= 1;
    }
    if ret_val == NO_ERROR {
        // Enumerate all adapters
        let mut cur = mem;
        while !cur.is_null() {
            let if_type: u32 = unsafe{ (*cur).IfType };
            match InterfaceType::try_from(if_type) {
                Ok(_) => {},
                Err(_) => {
                    cur = unsafe { (*cur).Next };
                    continue;
                },
            }
            // Index
            let anon1 = unsafe { (*cur).Anonymous1 };
            let anon = unsafe { anon1.Anonymous};
            let index = anon.IfIndex;
            // Flags
            let anon2 = unsafe { (*cur).Anonymous2 };
            let flags = unsafe { anon2.Flags };
            // Name
            let p_aname = unsafe { (*cur).AdapterName.0 };
            let aname_len = unsafe { strlen(p_aname as *const c_char) };
            let aname_slice = unsafe { std::slice::from_raw_parts(p_aname, aname_len) };
            let adapter_name = String::from_utf8(aname_slice.to_vec()).unwrap();
            // Friendly Name
            let p_fname = unsafe { (*cur).FriendlyName.0 };
            let fname_len = unsafe { wcslen(p_fname as *const wchar_t) };
            let fname_slice = unsafe { std::slice::from_raw_parts(p_fname, fname_len) };
            let friendly_name = String::from_utf16(fname_slice).unwrap();
            // Description
            let p_desc = unsafe { (*cur).Description.0};
            let desc_len = unsafe { wcslen(p_desc as *const wchar_t) };
            let desc_slice = unsafe { std::slice::from_raw_parts(p_desc, desc_len) };
            let description = String::from_utf16(desc_slice).unwrap();
            // MAC address
            let mac_addr_arr: [u8; 6] = unsafe { (*cur).PhysicalAddress }[..6].try_into().unwrap_or([0, 0, 0, 0, 0, 0]);
            let mac_addr: MacAddr = MacAddr::new(mac_addr_arr);
            // TransmitLinkSpeed (bits per second)
            let transmit_speed = unsafe { (*cur).TransmitLinkSpeed};
            // ReceiveLinkSpeed (bits per second)
            let receive_speed = unsafe { (*cur).ReceiveLinkSpeed};
            let mut ipv4_vec: Vec<Ipv4Net> = vec![];
            let mut ipv6_vec: Vec<Ipv6Net> = vec![];
            // Enumerate all IPs
            let mut cur_a = unsafe { (*cur).FirstUnicastAddress };
            while !cur_a.is_null() {
                let addr = unsafe { (*cur_a).Address };
                let prefix_len = unsafe{ (*cur_a).OnLinkPrefixLength }; 
                let sockaddr = unsafe { *addr.lpSockaddr };
                if sockaddr.sa_family == AF_INET as u16 {
                    let sockaddr: *mut SOCKADDR_IN = addr.lpSockaddr as *mut SOCKADDR_IN;
                    let a = unsafe { (*sockaddr).sin_addr.S_un.S_addr };
                    let ipv4 = if cfg!(target_endian = "little") {
                        Ipv4Addr::from(a.swap_bytes())
                    } else {
                        Ipv4Addr::from(a)
                    };
                    let ipv4_net: Ipv4Net = Ipv4Net::new(ipv4, prefix_len);
                    ipv4_vec.push(ipv4_net);
                } else if sockaddr.sa_family == AF_INET6 as u16 {
                    let sockaddr: *mut SOCKADDR_IN6 = addr.lpSockaddr as *mut SOCKADDR_IN6;
                    let a = unsafe { (*sockaddr).sin6_addr.u.Byte };
                    let ipv6 = Ipv6Addr::from(a);
                    let ipv6_net: Ipv6Net = Ipv6Net::new(ipv6, prefix_len);
                    ipv6_vec.push(ipv6_net);
                }
                cur_a = unsafe { (*cur_a).Next };
            }
            // Gateway
            // TODO: IPv6 support
            let mut gateway_ips: Vec<Ipv4Addr> = vec![];
            let mut cur_g = unsafe { (*cur).FirstGatewayAddress };
            while !cur_g.is_null() {
                let addr = unsafe { (*cur_g).Address };
                let sockaddr = unsafe { *addr.lpSockaddr };
                if sockaddr.sa_family == AF_INET as u16 {
                    let sockaddr: *mut SOCKADDR_IN = addr.lpSockaddr as *mut SOCKADDR_IN;
                    let a = unsafe { (*sockaddr).sin_addr.S_un.S_addr };
                    let ipv4 = if cfg!(target_endian = "little") {
                        Ipv4Addr::from(a.swap_bytes())
                    } else {
                        Ipv4Addr::from(a)
                    };
                    gateway_ips.push(ipv4);
                }
                cur_g = unsafe { (*cur_g).Next };
            }
            let default_gateway: Option<Gateway> = match gateway_ips.get(0) {
                Some(gateway_ip) => {
                    if let Some(ip_net) = ipv4_vec.get(0) {
                        let mac_addr = get_mac_through_arp(ip_net.addr, *gateway_ip);
                        let gateway = Gateway {
                            mac_addr: mac_addr,
                            ip_addr: IpAddr::V4(*gateway_ip),
                        };
                        Some(gateway)
                    }else{
                        None
                    }
                },
                None => None,
            };
            let interface: Interface = Interface{
                index: index,
                name: adapter_name,
                friendly_name: Some(friendly_name),
                description: Some(description),
                if_type: InterfaceType::try_from(if_type).unwrap_or(InterfaceType::Unknown),
                mac_addr: Some(mac_addr),
                ipv4: ipv4_vec,
                ipv6: ipv6_vec,
                flags: flags,
                transmit_speed: Some(transmit_speed),
                receive_speed: Some(receive_speed),
                gateway: default_gateway,
            };
            interfaces.push(interface);
            cur = unsafe { (*cur).Next };
        }
    } else {
        unsafe {
            deallocate(mem as *mut u8, dwsize as usize);
        }
    }
    unsafe {
        deallocate(mem as *mut u8, dwsize as usize);
    }
    return interfaces;
}