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//            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
//                    Version 2, December 2004
//
// Copyleft (ↄ) meh. <meh@schizofreni.co> | http://meh.schizofreni.co
//
// Everyone is permitted to copy and distribute verbatim or modified
// copies of this license document, and changing it is allowed as long
// as the name is changed.
//
//            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
//   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
//
//  0. You just DO WHAT THE FUCK YOU WANT TO.

use std::fmt;
use std::net::Ipv4Addr;

use crate::error::*;
use crate::packet::{Packet as P, PacketMut as PM, AsPacket, AsPacketMut};
use crate::size;
use crate::ip;
use crate::icmp::Kind;

/// Redirect Message packet parser.
pub struct Packet<B> {
	buffer: B,
}

sized!(Packet,
	header {
		min:  8,
		max:  8,
		size: 8,
	}

	payload {
		min:  <ip::v4::Packet<()> as size::header::Min>::min(),
		max:  <ip::v4::Packet<()> as size::header::Max>::max(),
		size: p => {
			if let Ok(ip) = p.packet() {
				size::header::Size::size(&ip)
			}
			else {
				p.buffer.as_ref().len() - 8
			}
		},
	});

impl<B: AsRef<[u8]>> fmt::Debug for Packet<B> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		f.debug_struct("icmp::redirect_message::Packet")
			.field("gateway", &self.gateway())
			.field("packet", &self.packet())
			.finish()
	}
}

impl<B: AsRef<[u8]>> Packet<B> {
	/// Create a Redirect Message packet without checking the buffer contents.
	pub fn unchecked(buffer: B) -> Packet<B> {
		Packet { buffer }
	}

	/// Parse a Redirect Message packet, checking the buffer contents are correct.
	pub fn new(buffer: B) -> Result<Packet<B>> {
		use crate::size::header::Min;

		let packet = Packet::unchecked(buffer);

		if packet.buffer.as_ref().len() < Self::min() {
			Err(Error::SmallBuffer)?
		}

		match Kind::from(packet.buffer.as_ref()[0]) {
			Kind::RedirectMessage =>
				(),

			_ =>
				Err(Error::InvalidPacket)?
		}

		Ok(packet)
	}
}

impl<B: AsRef<[u8]>> Packet<B> {
	/// Convert the packet to its owned version.
	///
	/// # Notes
	///
	/// It would be nice if `ToOwned` could be implemented, but `Packet` already
	/// implements `Clone` and the impl would conflict.
	pub fn to_owned(&self) -> Packet<Vec<u8>> {
		Packet::unchecked(self.buffer.as_ref().to_vec())
	}
}

impl<B: AsRef<[u8]>> AsRef<[u8]> for Packet<B> {
	fn as_ref(&self) -> &[u8] {
		use crate::size::Size;

		&self.buffer.as_ref()[.. self.size()]
	}
}

impl<B: AsRef<[u8]> + AsMut<[u8]>> AsMut<[u8]> for Packet<B> {
	fn as_mut(&mut self) -> &mut [u8] {
		use crate::size::Size;

		let size = self.size();
		&mut self.buffer.as_mut()[.. size]
	}
}

impl<'a, B: AsRef<[u8]>> AsPacket<'a, Packet<&'a [u8]>> for B {
	fn as_packet(&self) -> Result<Packet<&[u8]>> {
		Packet::new(self.as_ref())
	}
}

impl<'a, B: AsRef<[u8]> + AsMut<[u8]>> AsPacketMut<'a, Packet<&'a mut [u8]>> for B {
	fn as_packet_mut(&mut self) -> Result<Packet<&mut [u8]>> {
		Packet::new(self.as_mut())
	}
}

impl<B: AsRef<[u8]>> P for Packet<B> {
	fn split(&self) -> (&[u8], &[u8]) {
		self.buffer.as_ref().split_at(8)
	}
}

impl<B: AsRef<[u8]> + AsMut<[u8]>> PM for Packet<B> {
	fn split_mut(&mut self) -> (&mut [u8], &mut [u8]) {
		self.buffer.as_mut().split_at_mut(8)
	}
}

impl<B: AsRef<[u8]>> Packet<B> {
	/// Gateway to redirect the packet to.
	pub fn gateway(&self) -> Ipv4Addr {
		Ipv4Addr::new(
			self.buffer.as_ref()[4],
			self.buffer.as_ref()[5],
			self.buffer.as_ref()[6],
			self.buffer.as_ref()[7])
	}

	/// Packet to redirect.
	pub fn packet(&self) -> Result<ip::v4::Packet<&[u8]>> {
		ip::v4::Packet::new(&self.buffer.as_ref()[8 ..])
	}
}