package edu.washington.cs.oneswarm;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.logging.Logger;

import edu.washington.cs.oneswarm.ui.gwt.BackendErrorLog;

/**
 * Class which periodically profiles the overall state of the F2F plugin to
 * check invariants that we expect, thread liveness, etc.
 * 
 * If an error is detected, it is logged as a reportable bug in the UI.
 */
public class HealthChecker extends Thread {

    private static Logger logger = Logger.getLogger(HealthChecker.class.getName());

    public static final List<String> EXPECTED_THREAD_NAMES = new ArrayList<String>();

    public HealthChecker() {
        setDaemon(true);
        setName("OneSwarmHealthChecker");

        for (String s : new String[] { "DelayedSearchQueue", "QueueLengthChecker",
                "CommunityServer polling", "torrent pruning and F2F startstop",
                "OS Friend Connector", }) {
            EXPECTED_THREAD_NAMES.add(s);
        }
    }

    @Override
    public void run() {

        try {
            // Wait until a minute after startup before first run to allow
            // everything to boot
            Thread.sleep(60 * 1000);
        } catch (Exception e) {
        }

        while (true) {

            try {
                // Inspect the set of running threads and timers for the
                // expected set.
                Thread[] threads = new Thread[Thread.activeCount()];
                Thread.enumerate(threads);

                Set<String> currentNames = new HashSet<String>();
                for (Thread t : threads) {
                    if (t != null) {
                        currentNames.add(t.getName());
                    }
                }

                // If a thread has died, remove it from the expected set after
                // logging
                // the error to avoid polluting the log.
                List<String> toRemove = new ArrayList<String>();
                for (String expected : EXPECTED_THREAD_NAMES) {
                    if (currentNames.contains(expected) == false) {
                        String errorStr = "*** Required thread seems to have died: " + expected;
                        logger.severe(errorStr);
                        BackendErrorLog.get().logString(errorStr);
                        toRemove.add(expected);
                    }
                }

                for (String r : toRemove) {
                    EXPECTED_THREAD_NAMES.remove(r);
                }

                Thread.sleep(30 * 1000);

            } catch (Throwable t) {
                logger.warning("Unhandled error in the health checker: " + t.toString());
                t.printStackTrace();
            }
        }
    }
}