use std::fmt;
use tun::Error;

// Here we will recieve bytes and try to get their destanation & apply Rules for them.
use crate::config::Config;

#[derive(Debug, PartialEq)]
pub enum Protocol {
    TCP,
    UDP,
    Unsupported(u8),
}
type SourceV4Ip = Ipv4;
type SourceV6Ip = Ipv6;
#[derive(PartialEq, Debug)]
pub enum IpVersion {
    V4,
    V6,
}
type Ipv4 = [u8; 4];
type Ipv6 = [u16; 8];
type Port = u16;
#[derive(Debug, PartialEq)]
pub enum PacketInfo {
    // <https://www.geeksforgeeks.org/computer-networks/what-is-ipv4/>
    V4 {
        src_ip: Ipv4,
        src_port: Port,
        dst_ip: Ipv4,
        dst_port: Port,
        protocol: Protocol,
        dns: bool,
    },
    // <https://www.geeksforgeeks.org/computer-networks/internet-protocol-version-6-ipv6-header/>
    V6 {
        src_ip: Ipv6,
        src_port: Port,
        dst_ip: Ipv6,
        dst_port: Port,
        protocol: Protocol,
        dns: bool,
    },
}

impl fmt::Display for PacketInfo {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if self.version() == &IpVersion::V4 {
            let src_ip = self.src_ipv4_ip().unwrap();
            let dst_ip = self.dst_ipv4_ip().unwrap();
            write!(
                f,
                "{}.{}.{}.{}:{} -> {}.{}.{}.{}:{} {:?} is dns? {:?}",
                src_ip[0],
                src_ip[1],
                src_ip[2],
                src_ip[3],
                self.src_port(),
                dst_ip[0],
                dst_ip[1],
                dst_ip[2],
                dst_ip[3],
                self.dst_port(),
                self.protocol(),
                self.dns()
            )
        } else {
            let src_ip = self.src_ipv6_ip().unwrap();
            let dst_ip = self.dst_ipv6_ip().unwrap();
            // y:y:y:y:y:y:y:y = 8 hexademical; y = segment, pair of 2 u8 big endian
            write!(
                f,
            // FIXME: fe80:0:0:0:93a:245e:daac:7a75 -> ff12:0:0:0:0:0:0:8384
            //        we should drop zeroes in display: fe80::93a:245e:daac:7a75 -> ff12::8384
            // NOTE:  fe80:0:0:93a:0:245e and fe80:0:93a:0:0:245e can NOT both be compressed to fe80::93a::245e by obvious reasons
                "{:x}:{:x}:{:x}:{:x}:{:x}:{:x}:{:x}:{:x} port:{} -> {:x}:{:x}:{:x}:{:x}:{:x}:{:x}:{:x}:{:x} port:{} {:?} is dns? {:?}",
                src_ip[0],
                src_ip[1],
                src_ip[2],
                src_ip[3],
                src_ip[4],
                src_ip[5],
                src_ip[6],
                src_ip[7],
                self.src_port(),
                dst_ip[0],
                dst_ip[1],
                dst_ip[2],
                dst_ip[3],
                dst_ip[4],
                dst_ip[5],
                dst_ip[6],
                dst_ip[7],
                self.dst_port(),
                self.protocol(),
                self.dns()
            )
        }
    }
}

impl PacketInfo {
    pub fn dns(&self) -> &bool {
        match self {
            PacketInfo::V4 { dns, .. } => dns,
            PacketInfo::V6 { dns, .. } => dns,
        }
    }
    pub fn src_ipv6_ip(&self) -> Option<&SourceV6Ip> {
        match self {
            PacketInfo::V6 { src_ip, .. } => Some(src_ip),
            _ => None,
        }
    }
    pub fn dst_ipv6_ip(&self) -> Option<&SourceV6Ip> {
        match self {
            PacketInfo::V6 { dst_ip, .. } => Some(dst_ip),
            _ => None,
        }
    }
    pub fn src_ipv4_ip(&self) -> Option<&SourceV4Ip> {
        match self {
            PacketInfo::V4 { src_ip, .. } => Some(src_ip),
            _ => None,
        }
    }
    pub fn dst_ipv4_ip(&self) -> Option<&SourceV4Ip> {
        match self {
            PacketInfo::V4 { dst_ip, .. } => Some(dst_ip),
            _ => None,
        }
    }
    pub fn src_port(&self) -> &Port {
        match self {
            PacketInfo::V4 { src_port, .. } => src_port,
            PacketInfo::V6 { src_port, .. } => src_port,
        }
    }
    pub fn dst_port(&self) -> &Port {
        match self {
            PacketInfo::V4 { dst_port, .. } => dst_port,
            PacketInfo::V6 { dst_port, .. } => dst_port,
        }
    }
    pub fn version(&self) -> &IpVersion {
        match self {
            PacketInfo::V4 { .. } => &IpVersion::V4,
            PacketInfo::V6 { .. } => &IpVersion::V6,
        }
    }
    pub fn protocol(&self) -> &Protocol {
        match self {
            PacketInfo::V4 { protocol, .. } => protocol,
            PacketInfo::V6 { protocol, .. } => protocol,
        }
    }
}

// TODO: move these to some appropriate file for code readability.
type GenericError = Box<dyn std::error::Error + Send + Sync + 'static>;
type SniffedPacket = Result<PacketInfo, Box<dyn std::error::Error + Send + Sync + 'static>>;
type Packet = [u8];

pub fn sniff_raw_packets(packet: &Packet) -> SniffedPacket {
    let ver = packet[0] >> 4;
    match ver {
        4 => {
            // Internet Header Length (IHL).
            let ihl = (packet[0] & 0x0F) as usize * 4;
            let dst_port = Port::from_be_bytes([packet[ihl + 2], packet[ihl + 3]]);
            let dns;
            if dst_port == 53 {
                dns = true;
            } else {
                dns = false;
            };
            let v4 = PacketInfo::V4 {
                src_ip: <Ipv4>::try_from(&packet[12..16])?,
                src_port: Port::from_be_bytes([packet[ihl], packet[ihl + 1]]),
                dst_ip: <Ipv4>::try_from(&packet[16..20])?,
                dst_port,
                protocol: match packet[9] {
                    6 => Protocol::TCP,
                    17 => Protocol::UDP,
                    p => Protocol::Unsupported(p),
                },
                dns,
            };
            if !matches!(v4.protocol(), Protocol::Unsupported(_)) {
                println!("{v4}");
            } else {
                // TODO: make --debug option which will include this diagnostic, for general use this
                // should be off
                // println!("oppsie unsupported protocol: {:?}", v4.protocol());
            }
            Ok(v4)
        }
        6 => {
            // y:y:y:y:y:y:y:y hexademical; y = segment, pair of 2 u8 in big endian
            let src_ip = std::array::from_fn(|i| {
                u16::from_be_bytes([packet[8 + i * 2], packet[8 + i * 2 + 1]])
            });
            let dst_ip = std::array::from_fn(|i| {
                u16::from_be_bytes([packet[24 + i * 2], packet[24 + i * 2 + 1]])
            });

            let dst_port = Port::from_be_bytes([packet[42], packet[43]]);
            let dns;
            if dst_port == 53 {
                dns = true;
            } else {
                dns = false;
            };
            let v6 = PacketInfo::V6 {
                src_ip,
                src_port: Port::from_be_bytes([packet[40], packet[41]]),
                dst_ip,
                dst_port,
                protocol: match packet[6] {
                    6 => Protocol::TCP,
                    17 => Protocol::UDP,
                    p => Protocol::Unsupported(p),
                },
                dns,
            };
            if !matches!(v6.protocol(), Protocol::Unsupported(_)) {
                println!("{v6}");
            } else {
                // TODO: make --debug option which will include this diagnostic, for general use this
                // should be off
                // println!("oppsie unsupported protocol: {:?}", v6.protocol());
            }
            Ok(v6)
        }
        ver => Err(format!("unsuppiorted ver: {ver}").into()),
    }
}

pub fn apply_rules(config: Config, pinfo: PacketInfo) {
    todo!()
}