use windows::Win32::Foundation::{ERROR_BUFFER_OVERFLOW, NO_ERROR};
use windows::Win32::NetworkManagement::IpHelper::{GetAdaptersInfo, IP_ADAPTER_INFO, IP_ADDR_STRING, SendARP};
use std::convert::TryInto;
use std::mem;
use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
use std::ffi::CStr;
use std::convert::TryFrom;
use core::ffi::c_void;

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

// Convert C string to Rust string without trailing null bytes
fn bytes_to_string(bytes: &[u8]) -> String {
    let result: String = match CStr::from_bytes_with_nul(bytes) {
        Ok(cstr) => {
            match cstr.to_str() {
                Ok(rstr) => rstr.to_string(),
                Err(_) => cstr.to_string_lossy().replace("\u{0}", "").to_string(),
            }  
        },
        Err(_) => {
            String::from_utf8_lossy(bytes).replace("\u{0}", "").to_string()
        }
    };
    result
}

#[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
// TODO: Make more rusty ...
// Reference: https://docs.microsoft.com/en-us/windows/win32/api/iphlpapi/nf-iphlpapi-getadaptersinfo
pub fn interfaces() -> Vec<Interface> {
    let mut interfaces: Vec<Interface> = vec![];
    let mut out_buf_len : u32 = mem::size_of::<IP_ADAPTER_INFO>().try_into().unwrap();
    let mut raw_adaptor_mem: Vec<u8> = Vec::with_capacity(out_buf_len  as usize);
    let mut p_adaptor: *mut IP_ADAPTER_INFO;
    let mut res = unsafe { GetAdaptersInfo(raw_adaptor_mem.as_mut_ptr() as *mut IP_ADAPTER_INFO, &mut out_buf_len ) };
    // Make an initial call to GetAdaptersInfo to get the necessary size into the out_buf_len variable
    if res == ERROR_BUFFER_OVERFLOW {
		raw_adaptor_mem = Vec::with_capacity(out_buf_len as usize);
		unsafe {
			res = GetAdaptersInfo(raw_adaptor_mem.as_mut_ptr() as *mut IP_ADAPTER_INFO, &mut out_buf_len);
		}
	}
    if res != NO_ERROR {
        return interfaces;
	}
    //Enumerate all adapters
	p_adaptor = unsafe { mem::transmute(&raw_adaptor_mem) };
    while p_adaptor as u64 != 0 {
        let adapter: IP_ADAPTER_INFO = unsafe { *p_adaptor };
        match InterfaceType::try_from(adapter.Type) {
            Ok(_) => {},
            Err(_) => {
                unsafe { p_adaptor = (*p_adaptor).Next; }
                continue;
            },
        }
        let adapter_name: String = bytes_to_string(&adapter.AdapterName);
        let adapter_desc: String = bytes_to_string(&adapter.Description);
        let mac_addr:[u8; 6] = adapter.Address[..6].try_into().unwrap_or([0, 0, 0, 0, 0, 0]);
        //Enumerate all IPs
        let mut ipv4_vec: Vec<Ipv4Net> = vec![];
        let mut ipv6_vec: Vec<Ipv6Net> = vec![];
        let mut p_ip_addr: *mut IP_ADDR_STRING;
        p_ip_addr = unsafe { mem::transmute(&(*p_adaptor).IpAddressList) };
        while p_ip_addr as u64 != 0 {
            let ip_addr_string: IP_ADDR_STRING = unsafe{ *p_ip_addr };
            let ip_addr: String = bytes_to_string(&ip_addr_string.IpAddress.String);
            let netmask: String = bytes_to_string(&ip_addr_string.IpMask.String);
            match ip_addr.parse::<IpAddr>() {
                Ok(ip_addr) => {
                    match ip_addr {
                        IpAddr::V4(ipv4_addr) => {
                            let netmask: Ipv4Addr = match netmask.parse::<IpAddr>() {
                                Ok(netmask) => {
                                    match netmask {
                                        IpAddr::V4(netmask) => netmask,
                                        IpAddr::V6(_) => Ipv4Addr::UNSPECIFIED,
                                    }
                                },
                                Err(_) => Ipv4Addr::UNSPECIFIED,
                            };
                            let ipv4_net: Ipv4Net = Ipv4Net::new_with_netmask(ipv4_addr, netmask);
                            ipv4_vec.push(ipv4_net);
                        },
                        IpAddr::V6(ipv6_addr) => {
                            let netmask: Ipv6Addr = match netmask.parse::<IpAddr>() {
                                Ok(netmask) => {
                                    match netmask {
                                        IpAddr::V4(_) => Ipv6Addr::UNSPECIFIED,
                                        IpAddr::V6(netmask) => netmask,
                                    }
                                },
                                Err(_) => Ipv6Addr::UNSPECIFIED,
                            };
                            let ipv6_net: Ipv6Net = Ipv6Net::new_with_netmask(ipv6_addr, netmask);
                            ipv6_vec.push(ipv6_net);
                        }
                    }
                },
                Err(_) => {},
            }
            unsafe { p_ip_addr = (*p_ip_addr).Next; }
        }
        //Enumerate all gateways
        let mut gateway_ips: Vec<IpAddr> = vec![];
        let mut p_gateway_addr: *mut IP_ADDR_STRING;
        p_gateway_addr = unsafe { mem::transmute(&(*p_adaptor).GatewayList) };
        while p_gateway_addr as u64 != 0 {
            let gateway_addr_string: IP_ADDR_STRING = unsafe { *p_gateway_addr };
            let gateway_addr: String = bytes_to_string(&gateway_addr_string.IpAddress.String);
            match gateway_addr.parse::<IpAddr>() {
                Ok(ip_addr) => {
                    gateway_ips.push(ip_addr);
                },
                Err(_) => {},
            }
            unsafe { p_gateway_addr = (*p_gateway_addr).Next; }
        }
        let default_gateway: Option<Gateway> = match gateway_ips.get(0) {
            Some(gateway_ip) => {
                let gateway_ip: IpAddr = *gateway_ip;
                let default_gateway: Option<Gateway> = if gateway_ip != IpAddr::V4(Ipv4Addr::UNSPECIFIED) {
                    match gateway_ip {
                        IpAddr::V4(dst_ip) => {
                            if let Some(ip_net) = ipv4_vec.get(0) {
                                let mac_addr = get_mac_through_arp(ip_net.addr, dst_ip);
                                let gateway = Gateway {
                                    mac_addr: mac_addr,
                                    ip_addr: IpAddr::V4(dst_ip),
                                };
                                Some(gateway)
                            }else{
                                None
                            }
                        },
                        IpAddr::V6(_dst_ip) => {
                            None
                        },
                    }
                }else{
                    None
                };
                default_gateway
            },
            None => None,
        };
        let interface: Interface = Interface{
            index: adapter.Index,
            name: adapter_name,
            description: Some(adapter_desc),
            if_type: InterfaceType::try_from(adapter.Type).unwrap_or(InterfaceType::Unknown),
            mac_addr: Some(MacAddr::new(mac_addr)),
            ipv4: ipv4_vec,
            ipv6: ipv6_vec,
            flags: adapter.Type,
            gateway: default_gateway,
        };
        interfaces.push(interface);
        unsafe { p_adaptor = (*p_adaptor).Next; }
    }
    return interfaces;
}