//            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::io::Cursor;
use byteorder::{WriteBytesExt, BigEndian};
use hwaddr::HwAddr;

use crate::error::*;
use crate::buffer::{self, Buffer};
use crate::builder::{Builder as Build, Finalization};
use crate::packet::{AsPacket, AsPacketMut};
use crate::ether::Packet;
use crate::ether::Protocol;

/// Ethernet frame builder.
#[derive(Debug)]
pub struct Builder<B: Buffer = buffer::Dynamic> {
	buffer:    B,
	finalizer: Finalization,

	payload: bool,
}

impl<B: Buffer> Build<B> for Builder<B> {
	fn with(mut buffer: B) -> Result<Self> {
		use crate::size::header::Min;
		buffer.next(Packet::<()>::min())?;

		Ok(Builder {
			buffer:    buffer,
			finalizer: Default::default(),

			payload: false,
		})
	}

	fn finalizer(&mut self) -> &mut Finalization {
		&mut self.finalizer
	}

	fn build(self) -> Result<B::Inner> {
		let mut buffer = self.buffer.into_inner();
		self.finalizer.finalize(buffer.as_mut())?;
		Ok(buffer)
	}
}

impl Default for Builder<buffer::Dynamic> {
	fn default() -> Self {
		Builder::with(buffer::Dynamic::default()).unwrap()
	}
}

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

impl<'a, B: Buffer> AsPacketMut<'a, Packet<&'a mut [u8]>> for Builder<B> {
	fn as_packet_mut(&mut self) -> Result<Packet<&mut [u8]>> {
		Packet::new(self.buffer.data_mut())
	}
}

impl<B: Buffer> Builder<B> {
	/// MAC address for the destination.
	pub fn destination(mut self, value: HwAddr) -> Result<Self> {
		Packet::unchecked(self.buffer.data_mut()).set_destination(value)?;

		Ok(self)
	}

	/// MAC address for the source.
	pub fn source(mut self, value: HwAddr) -> Result<Self> {
		Packet::unchecked(self.buffer.data_mut()).set_source(value)?;

		Ok(self)
	}

	/// Protocol of the inner packet.
	pub fn protocol(mut self, value: Protocol) -> Result<Self> {
		Packet::unchecked(self.buffer.data_mut()).set_protocol(value)?;

		Ok(self)
	}

	/// Payload for the frame.
	pub fn payload<'a, T: IntoIterator<Item = &'a u8>>(mut self, value: T) -> Result<Self> {
		if self.payload {
			Err(Error::AlreadyDefined)?
		}

		self.payload = true;

		for byte in value {
			self.buffer.more(1)?;
			*self.buffer.data_mut().last_mut().unwrap() = *byte;
		}

		Ok(self)
	}

	/// Build an IP packet inside the Ethernet frame.
	pub fn ip(mut self) -> Result<crate::ip::Builder<B>> {
		if self.payload {
			Err(Error::AlreadyDefined)?
		}

		let offset = self.buffer.offset();
		let length = self.buffer.length();

		self.finalizer.add(move |out| {
			match out[offset + length] >> 4 {
				4 =>
					Cursor::new(&mut out[offset + 12 ..])
						.write_u16::<BigEndian>(Protocol::Ipv4.into())?,

				6 =>
					Cursor::new(&mut out[offset + 12 ..])
						.write_u16::<BigEndian>(Protocol::Ipv6.into())?,

				_ =>
					unreachable!()
			}

			Ok(())
		});

		let mut ip = crate::ip::Builder::with(self.buffer)?;
		ip.finalizer().extend(self.finalizer);

		Ok(ip)
	}
}

#[cfg(test)]
mod test {
	use std::net::Ipv4Addr;
	use crate::builder::Builder;
	use crate::packet::Packet;
	use crate::ether;
	use crate::ip;
	use crate::udp;

	#[test]
	fn simple() {
		let packet = ether::Builder::default()
			.destination("00:23:69:63:59:be".parse().unwrap()).unwrap()
			.source("e4:b3:18:26:63:a3".parse().unwrap()).unwrap()
			.ip().unwrap().v4().unwrap()
				.id(0x2d87).unwrap()
				.ttl(64).unwrap()
				.source("66.102.1.108".parse().unwrap()).unwrap()
				.destination("192.168.0.79".parse().unwrap()).unwrap()
				.udp().unwrap()
					.source(1337).unwrap()
					.destination(9001).unwrap()
					.build().unwrap();

		let ether = ether::Packet::new(packet).unwrap();
		assert_eq!(ether.destination(), "00:23:69:63:59:be".parse().unwrap());
		assert_eq!(ether.source(), "e4:b3:18:26:63:a3".parse().unwrap());
		assert_eq!(ether.protocol(), ether::Protocol::Ipv4);

		let ip = ip::v4::Packet::new(ether.payload()).unwrap();
		assert_eq!(ip.id(), 0x2d87);
		assert!(ip.flags().is_empty());
		assert_eq!(ip.length(), 28);
		assert_eq!(ip.ttl(), 64);
		assert_eq!(ip.protocol(), ip::Protocol::Udp);
		assert_eq!(ip.source(), "66.102.1.108".parse::<Ipv4Addr>().unwrap());
		assert_eq!(ip.destination(), "192.168.0.79".parse::<Ipv4Addr>().unwrap());
		assert!(ip.is_valid());

		let udp = udp::Packet::new(ip.payload()).unwrap();
		assert_eq!(udp.source(), 1337);
		assert_eq!(udp.destination(), 9001);
		assert!(udp.is_valid(&ip::Packet::from(&ip)));
	}
}