use bytes::Bytes;
use futures::{Async, Future, Poll};
use io::{read_header, ReadHeader};
use std::io;
use tokio_io::io::{read_exact, ReadExact};
use tokio_io::AsyncRead;
use zebra_crypto::checksum;
use zebra_message::{Command, Error, MessageHeader, MessageResult};
use zebra_network::Magic;

pub fn read_any_message<A>(a: A, magic: Magic) -> ReadAnyMessage<A>
where
    A: AsyncRead,
{
    ReadAnyMessage {
        state: ReadAnyMessageState::ReadHeader(read_header(a, magic)),
    }
}

pub enum ReadAnyMessageState<A> {
    ReadHeader(ReadHeader<A>),
    ReadPayload {
        header: MessageHeader,
        future: ReadExact<A, Bytes>,
    },
}

pub struct ReadAnyMessage<A> {
    state: ReadAnyMessageState<A>,
}

impl<A> Future for ReadAnyMessage<A>
where
    A: AsyncRead,
{
    type Item = MessageResult<(Command, Bytes)>;
    type Error = io::Error;

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        loop {
            let next_state = match self.state {
                ReadAnyMessageState::ReadHeader(ref mut header) => {
                    let (stream, header) = try_ready!(header.poll());
                    let header = match header {
                        Ok(header) => header,
                        Err(err) => return Ok(Err(err).into()),
                    };
                    ReadAnyMessageState::ReadPayload {
                        future: read_exact(stream, Bytes::new_with_len(header.len as usize)),
                        header: header,
                    }
                }
                ReadAnyMessageState::ReadPayload {
                    ref mut header,
                    ref mut future,
                } => {
                    let (_stream, bytes) = try_ready!(future.poll());
                    if checksum(&bytes) != header.checksum {
                        return Ok(Err(Error::InvalidChecksum).into());
                    }

                    return Ok(Async::Ready(Ok((header.command.clone(), bytes))));
                }
            };

            self.state = next_state;
        }
    }
}

#[cfg(test)]
mod tests {
    use super::read_any_message;
    use bytes::Bytes;
    use futures::Future;
    use zebra_message::Error;
    use zebra_network::Network;

    #[test]
    fn test_read_any_message() {
        let raw: Bytes = "24e9276470696e6700000000000000000800000083c00c765845303b6da97786".into();
        let name = "ping".into();
        let nonce = "5845303b6da97786".into();
        let expected = (name, nonce);

        assert_eq!(
            read_any_message(raw.as_ref(), Network::Mainnet.magic())
                .wait()
                .unwrap(),
            Ok(expected)
        );
        assert_eq!(
            read_any_message(raw.as_ref(), Network::Testnet.magic())
                .wait()
                .unwrap(),
            Err(Error::InvalidMagic)
        );
    }

    #[test]
    fn test_read_too_short_any_message() {
        let raw: Bytes = "24e9276470696e6700000000000000000800000083c00c765845303b6da977".into();
        assert!(read_any_message(raw.as_ref(), Network::Mainnet.magic())
            .wait()
            .is_err());
    }

    #[test]
    fn test_read_any_message_with_invalid_checksum() {
        let raw: Bytes = "24e9276470696e6700000000000000000800000083c01c765845303b6da97786".into();
        assert_eq!(
            read_any_message(raw.as_ref(), Network::Mainnet.magic())
                .wait()
                .unwrap(),
            Err(Error::InvalidChecksum)
        );
    }
}