//! A very simple serialization framework which is used to serialize/deserialize messages as well
//! as ChannelsManagers and ChannelMonitors.

use std::result::Result;
use std::io::{Read, Write};
use std::collections::HashMap;
use std::hash::Hash;

use secp256k1::{Secp256k1, Signature};
use secp256k1::key::{PublicKey, SecretKey};
use bitcoin::util::hash::Sha256dHash;
use bitcoin::blockdata::script::Script;
use std::marker::Sized;
use ln::msgs::DecodeError;
use util::byte_utils;

use util::byte_utils::{be64_to_array, be48_to_array, be32_to_array, be16_to_array, slice_to_be16, slice_to_be32, slice_to_be48, slice_to_be64};

const MAX_BUF_SIZE: usize = 64 * 1024;

/// A trait that is similar to std::io::Write but has one extra function which can be used to size
/// buffers being written into.
/// An impl is provided for any type that also impls std::io::Write which simply ignores size
/// hints.
pub trait Writer {
	/// Writes the given buf out. See std::io::Write::write_all for more
	fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error>;
	/// Hints that data of the given size is about the be written. This may not always be called
	/// prior to data being written and may be safely ignored.
	fn size_hint(&mut self, size: usize);
}

impl<W: Write> Writer for W {
	#[inline]
	fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error> {
		<Self as ::std::io::Write>::write_all(self, buf)
	}
	#[inline]
	fn size_hint(&mut self, _size: usize) { }
}

pub(crate) struct WriterWriteAdaptor<'a, W: Writer + 'a>(pub &'a mut W);
impl<'a, W: Writer + 'a> Write for WriterWriteAdaptor<'a, W> {
	fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error> {
		self.0.write_all(buf)
	}
	fn write(&mut self, buf: &[u8]) -> Result<usize, ::std::io::Error> {
		self.0.write_all(buf)?;
		Ok(buf.len())
	}
	fn flush(&mut self) -> Result<(), ::std::io::Error> {
		Ok(())
	}
}

struct VecWriter(Vec<u8>);
impl Writer for VecWriter {
	fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error> {
		self.0.extend_from_slice(buf);
		Ok(())
	}
	fn size_hint(&mut self, size: usize) {
		self.0.reserve_exact(size);
	}
}

/// A trait that various rust-lightning types implement allowing them to be written out to a Writer
pub trait Writeable {
	/// Writes self out to the given Writer
	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error>;

	/// Writes self out to a Vec<u8>
	fn encode(&self) -> Vec<u8> {
		let mut msg = VecWriter(Vec::new());
		self.write(&mut msg).unwrap();
		msg.0
	}

	/// Writes self out to a Vec<u8>
	fn encode_with_len(&self) -> Vec<u8> {
		let mut msg = VecWriter(Vec::new());
		0u16.write(&mut msg).unwrap();
		self.write(&mut msg).unwrap();
		let len = msg.0.len();
		msg.0[..2].copy_from_slice(&byte_utils::be16_to_array(len as u16 - 2));
		msg.0
	}
}

/// A trait that various rust-lightning types implement allowing them to be read in from a Read
pub trait Readable<R>
	where Self: Sized,
	      R: Read
{
	/// Reads a Self in from the given Read
	fn read(reader: &mut R) -> Result<Self, DecodeError>;
}

/// A trait that various higher-level rust-lightning types implement allowing them to be read in
/// from a Read given some additional set of arguments which is required to deserialize.
pub trait ReadableArgs<R, P>
	where Self: Sized,
	      R: Read
{
	/// Reads a Self in from the given Read
	fn read(reader: &mut R, params: P) -> Result<Self, DecodeError>;
}

pub(crate) struct U48(pub u64);
impl Writeable for U48 {
	#[inline]
	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
		writer.write_all(&be48_to_array(self.0))
	}
}
impl<R: Read> Readable<R> for U48 {
	#[inline]
	fn read(reader: &mut R) -> Result<U48, DecodeError> {
		let mut buf = [0; 6];
		reader.read_exact(&mut buf)?;
		Ok(U48(slice_to_be48(&buf)))
	}
}

macro_rules! impl_writeable_primitive {
	($val_type:ty, $meth_write:ident, $len: expr, $meth_read:ident) => {
		impl Writeable for $val_type {
			#[inline]
			fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
				writer.write_all(&$meth_write(*self))
			}
		}
		impl<R: Read> Readable<R> for $val_type {
			#[inline]
			fn read(reader: &mut R) -> Result<$val_type, DecodeError> {
				let mut buf = [0; $len];
				reader.read_exact(&mut buf)?;
				Ok($meth_read(&buf))
			}
		}
	}
}

impl_writeable_primitive!(u64, be64_to_array, 8, slice_to_be64);
impl_writeable_primitive!(u32, be32_to_array, 4, slice_to_be32);
impl_writeable_primitive!(u16, be16_to_array, 2, slice_to_be16);

impl Writeable for u8 {
	#[inline]
	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
		writer.write_all(&[*self])
	}
}
impl<R: Read> Readable<R> for u8 {
	#[inline]
	fn read(reader: &mut R) -> Result<u8, DecodeError> {
		let mut buf = [0; 1];
		reader.read_exact(&mut buf)?;
		Ok(buf[0])
	}
}

impl Writeable for bool {
	#[inline]
	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
		writer.write_all(&[if *self {1} else {0}])
	}
}
impl<R: Read> Readable<R> for bool {
	#[inline]
	fn read(reader: &mut R) -> Result<bool, DecodeError> {
		let mut buf = [0; 1];
		reader.read_exact(&mut buf)?;
		if buf[0] != 0 && buf[0] != 1 {
			return Err(DecodeError::InvalidValue);
		}
		Ok(buf[0] == 1)
	}
}

// u8 arrays
macro_rules! impl_array {
	( $size:expr ) => (
		impl Writeable for [u8; $size]
		{
			#[inline]
			fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
				w.write_all(self)
			}
		}

		impl<R: Read> Readable<R> for [u8; $size]
		{
			#[inline]
			fn read(r: &mut R) -> Result<Self, DecodeError> {
				let mut buf = [0u8; $size];
				r.read_exact(&mut buf)?;
				Ok(buf)
			}
		}
	);
}

//TODO: performance issue with [u8; size] with impl_array!()
impl_array!(32); // for channel id & hmac
impl_array!(33); // for PublicKey
impl_array!(64); // for Signature
impl_array!(1300); // for OnionPacket.hop_data

// HashMap
impl<K, V> Writeable for HashMap<K, V>
	where K: Writeable + Eq + Hash,
	      V: Writeable
{
	#[inline]
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
	(self.len() as u16).write(w)?;
		for (key, value) in self.iter() {
			key.write(w)?;
			value.write(w)?;
		}
		Ok(())
	}
}

impl<R, K, V> Readable<R> for HashMap<K, V>
	where R: Read,
	      K: Readable<R> + Eq + Hash,
	      V: Readable<R>
{
	#[inline]
	fn read(r: &mut R) -> Result<Self, DecodeError> {
		let len: u16 = Readable::read(r)?;
		let mut ret = HashMap::with_capacity(len as usize);
		for _ in 0..len {
			ret.insert(K::read(r)?, V::read(r)?);
		}
		Ok(ret)
	}
}

// Vectors
impl Writeable for Vec<u8> {
	#[inline]
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
		(self.len() as u16).write(w)?;
		w.write_all(&self)
	}
}

impl<R: Read> Readable<R> for Vec<u8> {
	#[inline]
	fn read(r: &mut R) -> Result<Self, DecodeError> {
		let len: u16 = Readable::read(r)?;
		let mut ret = Vec::with_capacity(len as usize);
		ret.resize(len as usize, 0);
		r.read_exact(&mut ret)?;
		Ok(ret)
	}
}
impl Writeable for Vec<Signature> {
	#[inline]
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
		(self.len() as u16).write(w)?;
		for e in self.iter() {
			e.write(w)?;
		}
		Ok(())
	}
}

impl<R: Read> Readable<R> for Vec<Signature> {
	#[inline]
	fn read(r: &mut R) -> Result<Self, DecodeError> {
		let len: u16 = Readable::read(r)?;
		let byte_size = (len as usize)
		                .checked_mul(33)
		                .ok_or(DecodeError::BadLengthDescriptor)?;
		if byte_size > MAX_BUF_SIZE {
			return Err(DecodeError::BadLengthDescriptor);
		}
		let mut ret = Vec::with_capacity(len as usize);
		for _ in 0..len { ret.push(Signature::read(r)?); }
		Ok(ret)
	}
}

impl Writeable for Script {
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
		(self.len() as u16).write(w)?;
		w.write_all(self.as_bytes())
	}
}

impl<R: Read> Readable<R> for Script {
	fn read(r: &mut R) -> Result<Self, DecodeError> {
		let len = <u16 as Readable<R>>::read(r)? as usize;
		let mut buf = vec![0; len];
		r.read_exact(&mut buf)?;
		Ok(Script::from(buf))
	}
}

impl Writeable for Option<Script> {
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
		if let &Some(ref script) = self {
			script.write(w)?;
		}
		Ok(())
	}
}

impl<R: Read> Readable<R> for Option<Script> {
	fn read(r: &mut R) -> Result<Self, DecodeError> {
		match <u16 as Readable<R>>::read(r) {
			Ok(len) => {
				let mut buf = vec![0; len as usize];
				r.read_exact(&mut buf)?;
				Ok(Some(Script::from(buf)))
			},
			Err(DecodeError::ShortRead) => Ok(None),
			Err(e) => Err(e)
		}
	}
}

impl Writeable for PublicKey {
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
		self.serialize().write(w)
	}
}

impl<R: Read> Readable<R> for PublicKey {
	fn read(r: &mut R) -> Result<Self, DecodeError> {
		let buf: [u8; 33] = Readable::read(r)?;
		match PublicKey::from_slice(&Secp256k1::without_caps(), &buf) {
			Ok(key) => Ok(key),
			Err(_) => return Err(DecodeError::InvalidValue),
		}
	}
}

impl Writeable for SecretKey {
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
		let mut ser = [0; 32];
		ser.copy_from_slice(&self[..]);
		ser.write(w)
	}
}

impl<R: Read> Readable<R> for SecretKey {
	fn read(r: &mut R) -> Result<Self, DecodeError> {
		let buf: [u8; 32] = Readable::read(r)?;
		match SecretKey::from_slice(&Secp256k1::without_caps(), &buf) {
			Ok(key) => Ok(key),
			Err(_) => return Err(DecodeError::InvalidValue),
		}
	}
}

impl Writeable for Sha256dHash {
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
		self.as_bytes().write(w)
	}
}

impl<R: Read> Readable<R> for Sha256dHash {
	fn read(r: &mut R) -> Result<Self, DecodeError> {
		let buf: [u8; 32] = Readable::read(r)?;
		Ok(From::from(&buf[..]))
	}
}

impl Writeable for Signature {
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
		self.serialize_compact(&Secp256k1::without_caps()).write(w)
	}
}

impl<R: Read> Readable<R> for Signature {
	fn read(r: &mut R) -> Result<Self, DecodeError> {
		let buf: [u8; 64] = Readable::read(r)?;
		match Signature::from_compact(&Secp256k1::without_caps(), &buf) {
			Ok(sig) => Ok(sig),
			Err(_) => return Err(DecodeError::InvalidValue),
		}
	}
}