//! Client-to-Server IRC protocol.
pub mod client;
pub mod server;

use std::io::Result;

use nom::{
    branch::alt,
    bytes::complete::{tag, take, take_while},
    IResult,
};
use tokio::io::{AsyncWrite, AsyncWriteExt};

type ByteVec = Vec<u8>;

/// Single message tag value.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Tag {
    key: ByteVec,
    value: Option<u8>,
}

fn receiver(input: &[u8]) -> IResult<&[u8], &[u8]> {
    take_while(|i| i != b'\n' && i != b'\r' && i != b' ')(input)
}

fn token(input: &[u8]) -> IResult<&[u8], &[u8]> {
    take_while(|i| i != b'\n' && i != b'\r')(input)
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum Chan {
    /// #<name> — network-global channel, available from any server in the network.
    Global(ByteVec),
    /// &<name> — server-local channel, available only to connections to the same server. Rarely used in practice.
    Local(ByteVec),
}
impl Chan {
    pub async fn write_async(&self, writer: &mut (impl AsyncWrite + Unpin)) -> Result<()> {
        match self {
            Chan::Global(name) => {
                writer.write_all(b"#").await?;
                writer.write_all(&name).await?;
            }
            Chan::Local(name) => {
                writer.write_all(b"&").await?;
                writer.write_all(&name).await?;
            }
        }
        Ok(())
    }
}

fn chan(input: &[u8]) -> IResult<&[u8], Chan> {
    fn chan_global(input: &[u8]) -> IResult<&[u8], Chan> {
        let (input, _) = tag("#")(input)?;
        let (input, name) = receiver(input)?;
        Ok((input, Chan::Global(name.to_vec())))
    }

    fn chan_local(input: &[u8]) -> IResult<&[u8], Chan> {
        let (input, _) = tag("&")(input)?;
        let (input, name) = receiver(input)?;
        Ok((input, Chan::Local(name.to_vec())))
    }

    alt((chan_global, chan_local))(input)
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum Recipient {
    Nick(ByteVec),
    Chan(Chan),
}
impl Recipient {
    pub async fn write_async(&self, writer: &mut (impl AsyncWrite + Unpin)) -> Result<()> {
        match self {
            Recipient::Nick(nick) => writer.write_all(&nick).await?,
            Recipient::Chan(chan) => chan.write_async(writer).await?,
        }
        Ok(())
    }
}

fn recipient(input: &[u8]) -> IResult<&[u8], Recipient> {
    fn recipient_chan(input: &[u8]) -> IResult<&[u8], Recipient> {
        let (input, chan) = chan(input)?;
        Ok((input, Recipient::Chan(chan)))
    }

    fn recipient_nick(input: &[u8]) -> IResult<&[u8], Recipient> {
        let (input, nick) = receiver(input)?;
        Ok((input, Recipient::Nick(nick.to_vec())))
    }

    alt((recipient_chan, recipient_nick))(input)
}

#[cfg(test)]
mod test {
    use assert_matches::*;

    use super::*;
    use crate::util::testkit::*;

    #[test]
    fn test_chan_global() {
        let input = b"#testchan";
        let expected = Chan::Global(b"testchan".to_vec());

        let result = chan(input);
        assert_matches!(result, Ok((_, result)) => assert_eq!(expected, result));

        let mut bytes = vec![];
        sync_future(expected.write_async(&mut bytes))
            .unwrap()
            .unwrap();

        assert_eq!(bytes.as_slice(), input);
    }

    #[test]
    fn test_chan_local() {
        let input = b"&localchan";
        let expected = Chan::Local(b"localchan".to_vec());

        let result = chan(input);
        assert_matches!(result, Ok((_, result)) => assert_eq!(expected, result));

        let mut bytes = vec![];
        sync_future(expected.write_async(&mut bytes))
            .unwrap()
            .unwrap();

        assert_eq!(bytes.as_slice(), input);
    }

    #[test]
    fn test_recipient_user() {
        let input = b"User";
        let expected = Recipient::Nick(b"User".to_vec());

        let result = recipient(input);
        assert_matches!(result, Ok((_, result)) => assert_eq!(expected, result));

        let mut bytes = vec![];
        sync_future(expected.write_async(&mut bytes))
            .unwrap()
            .unwrap();

        assert_eq!(bytes.as_slice(), input);
    }
}