use std::net::Ipv4Addr;
use std::{fmt, io};

/*
   0                                            15                                              31
   0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5  6  7  8  9  0  1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | p|unused|  版本(4)   |      协议(8)          |      上层协议(8)        | 初始ttl(4) | 生存时间(4) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                                          源ip地址(32)                                         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                                          目的ip地址(32)                                       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                                           数据体                                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/

pub mod control_packet;
pub mod error_packet;
pub mod service_packet;
pub mod ip_turn_packet;
pub mod other_turn_packet;

#[derive(Eq, PartialEq, Copy, Clone, Debug)]
pub enum Version {
    V1,
    UnKnow(u8),
}

impl From<u8> for Version {
    fn from(value: u8) -> Self {
        match value {
            1 => Version::V1,
            val => Version::UnKnow(val),
        }
    }
}

impl Into<u8> for Version {
    fn into(self) -> u8 {
        match self {
            Version::V1 => 1,
            Version::UnKnow(val) => val,
        }
    }
}

#[derive(Eq, PartialEq, Copy, Clone, Debug)]
pub enum Protocol {
    /// 服务包 用于和服务端交互
    Service,
    /// 响应异常
    Error,
    /// 控制协议
    Control,
    /// 转发ip数据
    IpTurn,
    /// 转发其他数据
    OtherTurn,
    UnKnow(u8),
}

impl From<u8> for Protocol {
    fn from(value: u8) -> Self {
        match value {
            1 => Protocol::Service,
            2 => Protocol::Error,
            3 => Protocol::Control,
            4 => Protocol::IpTurn,
            5 => Protocol::OtherTurn,
            val => Protocol::UnKnow(val),
        }
    }
}

impl Into<u8> for Protocol {
    fn into(self) -> u8 {
        match self {
            Protocol::Service => 1,
            Protocol::Error => 2,
            Protocol::Control => 3,
            Protocol::IpTurn => 4,
            Protocol::OtherTurn => 5,
            Protocol::UnKnow(val) => val,
        }
    }
}

pub const MAX_TTL: u8 = 0b1111;
pub const MAX_SOURCE: u8 = 0b11110000;

#[derive(Copy, Clone)]
pub struct NetPacket<B> {
    buffer: B,
}

impl<B: AsRef<[u8]>> NetPacket<B> {
    pub fn new(buffer: B) -> io::Result<NetPacket<B>> {
        let len = buffer.as_ref().len();
        // 不能大于udp最大载荷长度
        if len < 12 || len > 65535 - 20 - 8 {
            return Err(io::Error::new(
                io::ErrorKind::InvalidData,
                "length overflow",
            ));
        }
        Ok(NetPacket { buffer })
    }
    pub fn buffer(&self) -> &[u8] {
        self.buffer.as_ref()
    }
    pub fn into_buffer(self) -> B {
        self.buffer
    }
}

impl<B: AsRef<[u8]>> NetPacket<B> {
    pub fn is_encrypt(&self) -> bool {
        self.buffer.as_ref()[0] & 0x80 == 0x80
    }
    pub fn version(&self) -> Version {
        Version::from(self.buffer.as_ref()[0] & 0x0F)
    }
    pub fn protocol(&self) -> Protocol {
        Protocol::from(self.buffer.as_ref()[1])
    }
    pub fn transport_protocol(&self) -> u8 {
        self.buffer.as_ref()[2]
    }
    pub fn ttl(&self) -> u8 {
        self.buffer.as_ref()[3] & MAX_TTL
    }
    pub fn source_ttl(&self) -> u8 {
        self.buffer.as_ref()[3] >> 4
    }
    pub fn source(&self) -> Ipv4Addr {
        let tmp: [u8; 4] = self.buffer.as_ref()[4..8].try_into().unwrap();
        Ipv4Addr::from(tmp)
    }
    pub fn destination(&self) -> Ipv4Addr {
        let tmp: [u8; 4] = self.buffer.as_ref()[8..12].try_into().unwrap();
        Ipv4Addr::from(tmp)
    }
    pub fn payload(&self) -> &[u8] {
        &self.buffer.as_ref()[12..]
    }
}

impl<B: AsRef<[u8]> + AsMut<[u8]>> NetPacket<B> {
    pub fn buffer_mut(&mut self) -> &mut [u8] {
        self.buffer.as_mut()
    }
    pub fn set_encrypt_flag(&mut self, is_encrypt: bool) {
        if is_encrypt {
            self.buffer.as_mut()[0] = self.buffer.as_ref()[0] | 0x80
        } else {
            self.buffer.as_mut()[0] = self.buffer.as_ref()[0] & 0x7F
        };
    }
    pub fn set_version(&mut self, version: Version) {
        let v: u8 = version.into();
        self.buffer.as_mut()[0] = (self.buffer.as_ref()[0] & 0xF0) | (0x0F & v);
    }
    pub fn set_protocol(&mut self, protocol: Protocol) {
        self.buffer.as_mut()[1] = protocol.into();
    }
    pub fn set_transport_protocol(&mut self, transport_protocol: u8) {
        self.buffer.as_mut()[2] = transport_protocol;
    }
    pub fn first_set_ttl(&mut self, ttl: u8) {
        self.buffer.as_mut()[3] = ttl << 4 | ttl;
    }
    pub fn set_ttl(&mut self, ttl: u8) {
        self.buffer.as_mut()[3] = (self.buffer.as_mut()[3] & MAX_SOURCE) | (MAX_TTL & ttl);
    }
    pub fn set_source_ttl(&mut self, source_ttl: u8) {
        self.buffer.as_mut()[3] = (source_ttl << 4) | (MAX_TTL & self.buffer.as_ref()[3]);
    }
    pub fn set_source(&mut self, source: Ipv4Addr) {
        self.buffer.as_mut()[4..8].copy_from_slice(&source.octets());
    }
    pub fn set_destination(&mut self, destination: Ipv4Addr) {
        self.buffer.as_mut()[8..12].copy_from_slice(&destination.octets());
    }
    pub fn set_payload(&mut self, payload: &[u8]) {
        self.buffer.as_mut()[12..payload.len() + 12].copy_from_slice(payload);
    }
    pub fn payload_mut(&mut self) -> &mut [u8] {
        &mut self.buffer.as_mut()[12..]
    }
}

impl<B: AsRef<[u8]>> fmt::Debug for NetPacket<B> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("NetPacket")
            .field("version", &self.version())
            .field("protocol", &self.protocol())
            .field("transport_protocol", &self.transport_protocol())
            .field("ttl", &self.ttl())
            .field("source_ttl", &self.source_ttl())
            .field("source", &self.source())
            .field("destination", &self.destination())
            .field("payload", &self.payload())
            .finish()
    }
}