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//! Use log server through Channel.
use crate::log::*;
use futures::{future, prelude::*, sync::mpsc};
use std::sync::Arc;

/// Channel is a instance as interface for Library User.
pub trait Channel {
    /// LogSender send log to this Channel
    type LogSender: LogSender;

    /// get LogSender
    fn get_sender(&self) -> &Self::LogSender;

    /// run channel
    fn run(self) -> Box<dyn Future<Item = (), Error = ()>>;
}

/// LogSender send log to a Channel
pub trait LogSender {
    /// send Log
    fn send<L>(&self, log: L) -> Box<dyn Future<Item = Arc<L>, Error = Error>>
    where
        L: Log + 'static;
}

/// Error type about Channel
pub enum Error {
    /// Failed to send
    FailedToSend,
}

impl From<mpsc::SendError<Arc<dyn Log>>> for Error {
    fn from(error: mpsc::SendError<Arc<dyn Log>>) -> Self {
        panic!("LogSendError: {:#?}", error)
    }
}

impl From<()> for Error {
    fn from(_: ()) -> Self {
        unreachable!()
    }
}

/// This Channel output to stdout
pub struct StdoutChannel {
    log_sender: mpsc::Sender<Arc<dyn Log>>,
    log_receiver: mpsc::Receiver<Arc<dyn Log>>,
}

impl StdoutChannel {
    /// constructor
    pub fn new() -> Self {
        let (sender, receiver) = mpsc::channel(5);
        Self {
            log_sender: sender,
            log_receiver: receiver,
        }
    }
}

impl Channel for StdoutChannel {
    type LogSender = mpsc::Sender<Arc<dyn Log>>;

    fn run(self) -> Box<dyn Future<Item = (), Error = ()>> {
        Box::new(self.log_receiver.for_each(|l| {
            if let Some(s) = l.log_message() {
                println!("{}", s)
            }
            future::ok(())
        }))
    }

    fn get_sender(&self) -> &Self::LogSender {
        &self.log_sender
    }
}

impl LogSender for mpsc::Sender<Arc<dyn Log>> {
    fn send<L>(&self, log: L) -> Box<dyn Future<Item = Arc<L>, Error = Error>>
    where
        L: Log + 'static,
    {
        let log = Arc::new(log);
        let sender = self.clone();
        Box::new(
            sender
                .send(log.clone())
                .map_err(Into::into)
                .and_then(|_| future::ok(log)),
        )
    }
}