rse/plugins/org.eclipse.dltk.rse.core/src/org/eclipse/dltk/core/internal/rse/RSEConnectionQueryManager.java

package org.eclipse.dltk.core.internal.rse;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.core.runtime.Platform;
import org.eclipse.dltk.utils.LazyExtensionManager;
import org.eclipse.dltk.utils.LazyExtensionManager.Descriptor;
import org.eclipse.rse.core.model.IHost;
import org.eclipse.rse.core.subsystems.ISubSystem;
import org.eclipse.rse.subsystems.files.core.subsystems.IRemoteFileSubSystem;

/**
 * This class is designed to synchronize connections to RSE to display only one
 * connection dialog per time.
 * 
 * @author haiodo
 * @since 2.0
 * 
 */
public class RSEConnectionQueryManager {
	/**
	 * 5 minutes for connection to be established.
	 */
	private static final long CONNECTION_TIMEOUT = 1000 * 10; // ten seconds.

	private static RSEConnectionQueryManager queryManager = null;

	public static synchronized RSEConnectionQueryManager getInstance() {
		if (queryManager == null) {
			queryManager = new RSEConnectionQueryManager();
		}
		return queryManager;
	}

	private static class ConnectionRequest {
		private IHost host;
		private boolean finished = false;

		public ConnectionRequest(IHost host, long id) {
			this.host = host;
		}

		public synchronized boolean isFinished() {
			return finished;
		}

		public synchronized void setFinished(boolean finished) {
			this.finished = finished;
		}

		@Override
		public int hashCode() {
			final int prime = 31;
			int result = 1;
			result = prime * result + ((host == null) ? 0 : host.hashCode());
			return result;
		}

		@Override
		public boolean equals(Object obj) {
			if (this == obj)
				return true;
			if (obj == null)
				return false;
			if (getClass() != obj.getClass())
				return false;
			ConnectionRequest other = (ConnectionRequest) obj;
			if (host == null) {
				if (other.host != null)
					return false;
			} else if (!host.equals(other.host))
				return false;
			return true;
		}
	}

	public interface IConnector {
		void register();

		boolean isDirectProcessingRequired();

		void runDisplayRunnables(long connectionTimeout);
	}

	public void setConnectingStatus(boolean status) {
		synchronized (requests) {
			isConnecting = status;
		}
	}

	public boolean isConnecting() {
		synchronized (requests) {
			return isConnecting;
		}
	}

	public void markHostAsFinished(IHost host) {
		synchronized (requests) {
			List<ConnectionRequest> toRemove = new ArrayList<>();
			for (ConnectionRequest request : requests) {
				if (request.host.equals(host)) {
					toRemove.add(request);
					request.setFinished(true);
				}
			}
			setConnectingStatus(false);
			if (!toRemove.isEmpty()) {
				requests.removeAll(toRemove);
				requests.notifyAll();
			}
		}
	}

	/**
	 * Get host and set state to isConnecting()
	 * 
	 * @return
	 */
	public IHost getNextHost(boolean wait) {
		synchronized (requests) {
			if (wait) {
				while (isConnecting() || requests.isEmpty()) {
					try {
						requests.wait(100);
					} catch (InterruptedException e) {
						DLTKRSEPlugin.log(e);
					}
				}
			}
			if (!requests.isEmpty()) {
				ConnectionRequest request = requests.get(0);
				setConnectingStatus(true);
				return request.host;
			}
			return null;
		}
	}

	private LazyExtensionManager<IConnector> connectors = new LazyExtensionManager<>(
			DLTKRSEPlugin.PLUGIN_ID + ".rseConnector");

	private List<ConnectionRequest> requests = new ArrayList<>();
	private boolean isConnecting = false;
	private long currentId;

	public RSEConnectionQueryManager() {
		Descriptor<IConnector>[] descriptors = connectors.getDescriptors();
		for (Descriptor<IConnector> descriptor : descriptors) {
			IConnector connector = descriptor.get();
			connector.register();
		}
	}

	public boolean connectTo(IHost host) {
		if (isConnected(host)) {
			return true;
		}
		ConnectionRequest request = new ConnectionRequest(host, currentId++);
		synchronized (requests) {
			requests.add(request);
			requests.notifyAll(); // Notify all connectors
		}
		// are in display thread.
		Descriptor<IConnector>[] descriptors = connectors.getDescriptors();
		for (Descriptor<IConnector> descriptor : descriptors) {
			IConnector connector = descriptor.get();
			if (connector.isDirectProcessingRequired()) {
				connector.runDisplayRunnables(CONNECTION_TIMEOUT);
			}
		}
		long endTime = System.currentTimeMillis() + CONNECTION_TIMEOUT;
		synchronized (requests) {
			while (!request.isFinished() && Platform.isRunning()) {
				try {
					requests.wait(100);
					long currentTime = System.currentTimeMillis();
					if (currentTime > endTime) {
						// Just break
						// markHostAsFinished(host);
						break;
					}
				} catch (InterruptedException e) {
					DLTKRSEPlugin.log(e);
				}
			}
		}

		return isConnected(host);
	}

	private boolean isConnected(IHost host) {
		ISubSystem[] subSystems = host.getSubSystems();
		for (ISubSystem subsystem : subSystems) {
			if (subsystem instanceof IRemoteFileSubSystem) {
				return subsystem.isConnected();
			}
		}
		return false;
	}

	public boolean hasHosts() {
		synchronized (requests) {
			return !requests.isEmpty();
		}
	}
}