// Copyright (c) 2013-2015 Sandstorm Development Group, Inc. and contributors
// Licensed under the MIT License:
//
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// of this software and associated documentation files (the "Software"), to deal
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// furnished to do so, subject to the following conditions:
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//! Tasks scheduled on a GJ event loop are not preemptive. For an event loop to make progress,
//! event callbacks must yield control by returning.
//!
//! GJ event loops are thread-local. To take advantage of multiprocessor hardware or to deal with
//! tasks that cannot easily yield, you can send tasks to separate threads where they will execute
//! on separate event loops. The example program illustrates how that might work, using
//! `std::thread::sleep_ms()` as a stand-in for a blocking computation.

extern crate gj;
extern crate gjio;

pub fn main() {
    main::main()
}

#[cfg(not(unix))]
mod main {
    pub fn main() {}
}

#[cfg(unix)]
mod main {
    use gj::Promise;
    use gjio::{AsyncRead, AsyncWrite, SocketStream};
    use std::time::Duration;

    fn child_loop(delay: Duration,
                  mut stream: SocketStream,
                  buf: Vec<u8>) -> Promise<(), ::std::io::Error> {

        // This blocks the entire thread. This is okay because we are on a child thread
        // where nothing else needs to happen.
        ::std::thread::sleep(delay);

        stream.write(buf).then(move |buf| {
            child_loop(delay, stream, buf)
        })
    }

    fn child(network: ::gjio::Network, delay: Duration) -> Result<SocketStream, Box<::std::error::Error>> {
        let (_, stream) = try!(network.socket_spawn(move |parent_stream, wait_scope, mut event_port| {
            try!(child_loop(delay, parent_stream, vec![0u8]).lift::<Box<::std::error::Error>>().wait(wait_scope, &mut event_port));
            Ok(())
        }));
        Ok(stream)
    }

    fn listen_to_child(id: &'static str,
                       mut stream: SocketStream,
                       buf: Vec<u8>) -> Promise<(), ::std::io::Error> {
        stream.read(buf, 1).then(move |(buf, _n)| {
            println!("heard back from {}", id);
            listen_to_child(id, stream, buf)
        })
    }

    fn parent_wait_loop(timer: ::gjio::Timer) -> Promise<(), ::std::io::Error> {
        println!("parent wait loop...");

        // If we used ::std::thread::sleep() here, we would block the main event loop.
        timer.after_delay(Duration::from_millis(3000)).then(|()| {
            parent_wait_loop(timer)
        })
    }

    pub fn main() {
        ::gj::EventLoop::top_level(|wait_scope| -> Result<(), Box<::std::error::Error>> {
            let mut event_port = try!(::gjio::EventPort::new());
            let network = event_port.get_network();
            let timer = event_port.get_timer();
            let children = vec![
                parent_wait_loop(timer),
                listen_to_child("CHILD 1", try!(child(network.clone(), Duration::from_millis(700))), vec![0]),
                listen_to_child("CHILD 2", try!(child(network.clone(), Duration::from_millis(1900))), vec![0]),
                listen_to_child("CHILD 3", try!(child(network.clone(), Duration::from_millis(2600))), vec![0])];

            try!(Promise::all(children.into_iter()).wait(wait_scope, &mut event_port));

            Ok(())
        }).unwrap();
    }
}