// Copyright 2016 The Grin Developers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Message types that transit over the network and related serialization code.

use std::net::*;

use num::FromPrimitive;

use core::ser::{self, Writeable, Readable, Writer, Reader, Error};

use types::*;

/// Current latest version of the protocol
pub const PROTOCOL_VERSION: u32 = 1;
/// Grin's user agent with current version (TODO externalize)
pub const USER_AGENT: &'static str = "MW/Grin 0.1";

/// Magic number expected in the header of every message
const MAGIC: [u8; 2] = [0x1e, 0xc5];

/// Codes for each error that can be produced reading a message.
pub enum ErrCodes {
	UnsupportedVersion = 100,
}

/// Types of messages
enum_from_primitive! {
#[derive(Clone, Copy)]
pub enum Type {
	Error,
	Hand,
	Shake,
	Ping,
	Pong,
	GetPeerAddrs,
	PeerAddrs,
}
}

/// Header of any protocol message, used to identify incoming messages.
pub struct MsgHeader {
	magic: [u8; 2],
	pub msg_type: Type,
}

impl MsgHeader {
	pub fn new(msg_type: Type) -> MsgHeader {
		MsgHeader {
			magic: MAGIC,
			msg_type: msg_type,
		}
	}

	pub fn acceptable(&self) -> bool {
		Type::from_u8(self.msg_type as u8).is_some()
	}

  /// Serialized length of the header in bytes
  pub fn serialized_len(&self) -> u64 { 3 }
}

impl Writeable for MsgHeader {
	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
		ser_multiwrite!(writer,
		                [write_u8, self.magic[0]],
		                [write_u8, self.magic[1]],
		                [write_u8, self.msg_type as u8]);
		None
	}
}

impl Readable<MsgHeader> for MsgHeader {
	fn read(reader: &mut Reader) -> Result<MsgHeader, ser::Error> {
		try!(reader.expect_u8(MAGIC[0]));
		try!(reader.expect_u8(MAGIC[1]));
		let t = try!(reader.read_u8());
		match Type::from_u8(t)  {
			Some(ty) => Ok(MsgHeader {magic: MAGIC, msg_type: ty}),
			None => Err(ser::Error::CorruptedData)
		}
	}
}

/// First part of a handshake, sender advertises its version and
/// characteristics.
pub struct Hand {
	/// protocol version of the sender
	pub version: u32,
	/// capabilities of the sender
	pub capabilities: Capabilities,
	/// randomly generated for each handshake, helps detect self
	pub nonce: u64,
	/// network address of the sender
	pub sender_addr: SockAddr,
	/// network address of the receiver
	pub receiver_addr: SockAddr,
	/// name of version of the software
	pub user_agent: String,
}

impl Writeable for Hand {
	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
		ser_multiwrite!(writer,
		                [write_u32, self.version],
		                [write_u32, self.capabilities.bits()],
		                [write_u64, self.nonce]);
		self.sender_addr.write(writer);
		self.receiver_addr.write(writer);
		writer.write_vec(&mut self.user_agent.clone().into_bytes())
	}
}

impl Readable<Hand> for Hand {
	fn read(reader: &mut Reader) -> Result<Hand, ser::Error> {
		let (version, capab, nonce) = ser_multiread!(reader, read_u32, read_u32, read_u64);
		let sender_addr = try!(SockAddr::read(reader));
		let receiver_addr = try!(SockAddr::read(reader));
		let ua = try!(reader.read_vec());
		let user_agent = try!(String::from_utf8(ua).map_err(|_| ser::Error::CorruptedData));
		let capabilities = try!(Capabilities::from_bits(capab).ok_or(ser::Error::CorruptedData));
		Ok(Hand {
			version: version,
			capabilities: capabilities,
			nonce: nonce,
			sender_addr: sender_addr,
			receiver_addr: receiver_addr,
			user_agent: user_agent,
		})
	}
}

/// Second part of a handshake, receiver of the first part replies with its own
/// version and characteristics.
pub struct Shake {
	/// sender version
	pub version: u32,
	/// sender capabilities
	pub capabilities: Capabilities,
	/// name of version of the software
	pub user_agent: String,
}

impl Writeable for Shake {
	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
		ser_multiwrite!(writer,
		                [write_u32, self.version],
		                [write_u32, self.capabilities.bits()],
		                [write_vec, &mut self.user_agent.as_bytes().to_vec()]);
		None
	}
}

impl Readable<Shake> for Shake {
	fn read(reader: &mut Reader) -> Result<Shake, ser::Error> {
		let (version, capab, ua) = ser_multiread!(reader, read_u32, read_u32, read_vec);
		let user_agent = try!(String::from_utf8(ua).map_err(|_| ser::Error::CorruptedData));
		let capabilities = try!(Capabilities::from_bits(capab).ok_or(ser::Error::CorruptedData));
		Ok(Shake {
			version: version,
			capabilities: capabilities,
			user_agent: user_agent,
		})
	}
}

/// Ask for other peers addresses, required for network discovery.
pub struct GetPeerAddrs {
	/// Filters on the capabilities we'd like the peers to have
	pub capabilities: Capabilities,
}

impl Writeable for GetPeerAddrs {
	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
		writer.write_u32(self.capabilities.bits())
	}
}

impl Readable<GetPeerAddrs> for GetPeerAddrs {
	fn read(reader: &mut Reader) -> Result<GetPeerAddrs, ser::Error> {
		let capab = try!(reader.read_u32());
		let capabilities = try!(Capabilities::from_bits(capab).ok_or(ser::Error::CorruptedData));
		Ok(GetPeerAddrs { capabilities: capabilities })
	}
}

/// Peer addresses we know of that are fresh enough, in response to
/// GetPeerAddrs.
pub struct PeerAddrs {
	pub peers: Vec<SockAddr>,
}

impl Writeable for PeerAddrs {
	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
		try_o!(writer.write_u32(self.peers.len() as u32));
		for p in &self.peers {
			p.write(writer);
		}
		None
	}
}

impl Readable<PeerAddrs> for PeerAddrs {
	fn read(reader: &mut Reader) -> Result<PeerAddrs, ser::Error> {
		let peer_count = try!(reader.read_u32());
		if peer_count > 1000 {
			return Err(ser::Error::TooLargeReadErr(format!("Too many peers provided: {}",
			                                               peer_count)));
		}
		let peers = try_map_vec!([0..peer_count], |_| SockAddr::read(reader));
		Ok(PeerAddrs { peers: peers })
	}
}

/// We found some issue in the communication, sending an error back, usually
/// followed by closing the connection.
pub struct PeerError {
	/// error code
	pub code: u32,
	/// slightly more user friendly message
	pub message: String,
}

impl Writeable for PeerError {
	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
		ser_multiwrite!(writer,
		                [write_u32, self.code],
		                [write_vec, &mut self.message.clone().into_bytes()]);
		None
	}
}

impl Readable<PeerError> for PeerError {
	fn read(reader: &mut Reader) -> Result<PeerError, ser::Error> {
		let (code, msg) = ser_multiread!(reader, read_u32, read_vec);
		let message = try!(String::from_utf8(msg).map_err(|_| ser::Error::CorruptedData));
		Ok(PeerError {
			code: code,
			message: message,
		})
	}
}

/// Only necessary so we can implement Readable and Writeable. Rust disallows
/// implementing traits when both types are outside of this crate (which is the
/// case for SocketAddr and Readable/Writeable).
pub struct SockAddr(pub SocketAddr);

impl Writeable for SockAddr {
	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
		match self.0 {
			SocketAddr::V4(sav4) => {
				ser_multiwrite!(writer,
				                [write_u8, 0],
				                [write_fixed_bytes, &sav4.ip().octets().to_vec()],
				                [write_u16, sav4.port()]);
			}
			SocketAddr::V6(sav6) => {
				try_o!(writer.write_u8(1));
				for seg in &sav6.ip().segments() {
					try_o!(writer.write_u16(*seg));
				}
				try_o!(writer.write_u16(sav6.port()));
			}
		}
		None
	}
}

impl Readable<SockAddr> for SockAddr {
	fn read(reader: &mut Reader) -> Result<SockAddr, ser::Error> {
		let v4_or_v6 = try!(reader.read_u8());
		if v4_or_v6 == 0 {
			let ip = try!(reader.read_fixed_bytes(4));
			let port = try!(reader.read_u16());
			Ok(SockAddr(SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(ip[0],
			                                                           ip[1],
			                                                           ip[2],
			                                                           ip[3]),
			                                             port))))
		} else {
			let ip = try_map_vec!([0..8], |_| reader.read_u16());
			let port = try!(reader.read_u16());
			Ok(SockAddr(SocketAddr::V6(SocketAddrV6::new(Ipv6Addr::new(ip[0],
			                                                           ip[1],
			                                                           ip[2],
			                                                           ip[3],
			                                                           ip[4],
			                                                           ip[5],
			                                                           ip[6],
			                                                           ip[7]),
			                                             port,
			                                             0,
			                                             0))))
		}
	}
}