Added a basic event-loop driver.

[jagi.git] / src / jagi / event / Driver.java

package jagi.event;

import java.util.*;
import java.util.logging.*;
import java.util.concurrent.*;
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.channels.spi.*;

public class Driver {
    private static final Logger log = Logger.getLogger("jagi.event");
    private static final Logger hlog = Logger.getLogger("jagi.event.handler");
    private static final ThreadLocal<Driver> current = new ThreadLocal<>();
    private final Map<SelectorProvider, SelectPool> selectors = new HashMap<>();
    private final ExecutorService worker = new ThreadPoolExecutor(0, Runtime.getRuntime().availableProcessors(),
								  5, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(128),
								  this::thread);

    protected Thread thread(Runnable tgt) {
	return(new Thread(tgt));
    }

    protected void handle(Watcher w, int evs) {
	try {
	    current.set(this);
	    w.handle(evs);
	} catch(Throwable t) {
	    error(w, t);
	} finally {
	    current.remove();
	}
    }

    protected void submit(Runnable task) {
	worker.submit(task);
    }

    protected void error(Watcher w, Throwable t) {
	hlog.log(Level.WARNING, w + ": uncaught error when handling event", t);
	remove(w);
    }

    class SelectPool implements Runnable {
	final SelectorProvider provider;
	final Selector poll;
	final Map<Watcher, SelectionKey> watching = new IdentityHashMap<>();
	final Heap<Watcher, Double> timeheap = new Heap<>(Comparator.naturalOrder());
	final Map<Watcher, Object> paused = new IdentityHashMap<>();

	SelectPool(SelectorProvider provider) {
	    this.provider = provider;
	    try {
		this.poll = provider.openSelector();
	    } catch(IOException e) {
		/* I think this counts more as an assertion error. */
		throw(new RuntimeException(e));
	    }
	}

	void handle(Watcher w, int evs) {
	    try {
		pause(w);
		submit(() -> {
			try {
			    Driver.this.handle(w, evs);
			} finally {
			    resume(w);
			}
		    });
	    } catch(Throwable t) {
		try {
		    synchronized(selectors) {
			remove(w);
		    }
		} catch(Exception e) {
		    t.addSuppressed(e);
		}
		log.log(Level.SEVERE, "unexpected error when submitting event", t);
	    }
	}

	void start() {
	    thread(this).start();
	}

	public void run() {
	    boolean quit = false;
	    Throwable error = null;
	    try {
		while(true) {
		    double now = time();
		    long timeout = 0;
		    synchronized(selectors) {
			Double first = timeheap.keypeek();
			if((first == null) && watching.isEmpty()) {
			    quit = true;
			    selectors.remove(provider);
			    return;
			}
			if(first != null)
			    timeout = (long)Math.ceil((first - now) * 1000);
		    }
		    poll.selectedKeys().clear();
		    try {
			poll.select(timeout);
		    } catch(IOException e) {
			throw(new RuntimeException(e));
		    }
		    for(SelectionKey key : poll.selectedKeys())
			handle((Watcher)key.attachment(), key.readyOps());
		}
	    } catch(Throwable t) {
		error = t;
		throw(t);
	    } finally {
		if(!quit)
		    log.log(Level.SEVERE, "selector exited abnormally", error);
	    }
	}

	void pause(Watcher w) {
	    if(paused.containsKey(w))
		throw(new IllegalStateException(w + ": already paused"));
	    SelectionKey wc = watching.get(w);
	    Object tc = timeheap.remove(w);
	    if((wc == null) && (tc == null))
		throw(new IllegalStateException(w + ": not registered"));
	    if(wc != null)
		wc.interestOps(0);
	    paused.put(w, this);
	}

	void resume(Watcher w) {
	    if(paused.remove(w) == null)
		return;
	    SelectionKey wc = watching.get(w);
	    int evs = w.events();
	    double timeout = w.timeout();
	    boolean hastime = timeout < Double.POSITIVE_INFINITY;
	    if((evs == 0) && !hastime) {
		remove(w);
		return;
	    }
	    wc.interestOps(evs);
	    if(hastime)
		timeheap.add(w, timeout);
	    poll.wakeup();
	}

	void add(Watcher w, SelectableChannel ch) {
	    if(watching.containsKey(w) || paused.containsKey(w) || timeheap.contains(w))
		throw(new IllegalStateException(w + ": already registered"));
	    int evs = w.events();
	    double timeout = w.timeout();
	    boolean hastime = timeout < Double.POSITIVE_INFINITY;
	    if((evs == 0) && !hastime) {
		w.close();
		return;
	    }
	    try {
		watching.put(w, ch.register(poll, evs, w));
	    } catch(ClosedChannelException e) {
		throw(new RuntimeException("attempted to watch closed channel", e));
	    }
	    if(hastime)
		timeheap.add(w, timeout);
	    poll.wakeup();
	}

	void remove(Watcher w) {
	    SelectionKey wc = watching.remove(w);
	    Object tc = timeheap.remove(w);
	    Object pc = paused.remove(w);
	    if(wc != null)
		wc.cancel();
	    if(((wc != null) || (tc != null)) && (pc != null))
		throw(new RuntimeException(w + ": inconsistent internal state"));
	    if(wc == null)
		throw(new IllegalStateException(w + ": not registered"));
	    w.close();
	    poll.wakeup();
	}

	void update(Watcher w) {
	    SelectionKey wc = watching.get(w);
	    if(wc == null)
		throw(new IllegalStateException(w + ": not registered"));
	    int evs = w.events();
	    double timeout = w.timeout();
	    boolean hastime = timeout < Double.POSITIVE_INFINITY;
	    if((evs == 0) && !hastime) {
		remove(w);
		return;
	    }
	    wc.interestOps(evs);
	    if(hastime)
		timeheap.set(w, timeout);
	    else
		timeheap.remove(w);
	    poll.wakeup();
	}
    }

    private SelectPool pool(SelectorProvider provider) {
	SelectPool pool = selectors.get(provider);
	if(pool == null) {
	    pool = new SelectPool(provider);
	    selectors.put(provider, pool);
	    pool.start();
	}
	return(pool);
    }

    public void add(Watcher w) {
	SelectableChannel ch = w.channel();
	synchronized(selectors) {
	    pool(ch.provider()).add(w, ch);
	}
    }

    public void remove(Watcher w) {
	SelectableChannel ch = w.channel();
	synchronized(selectors) {
	    pool(ch.provider()).remove(w);
	}
    }

    public void update(Watcher w) {
	SelectableChannel ch = w.channel();
	synchronized(selectors) {
	    pool(ch.provider()).update(w);
	}
    }

    public double time() {
	return(rtime());
    }

    private static final long rtimeoff = System.nanoTime();
    public static double rtime() {
	return((System.nanoTime() - rtimeoff) / 1e9);
    }

    private static Driver global = null;
    public static Driver get() {
	if(global == null) {
	    synchronized(Driver.class) {
		if(global == null)
		    global = new Driver();
	    }
	}
	return(global);
    }

    public static Driver current() {
	Driver ret = current.get();
	if(ret == null)
	    throw(new IllegalStateException("no current driver"));
	return(ret);
    }
}