/*******************************************************************************
 * Copyright (c) 2011, 2013 Wind River Systems, Inc. and others. All rights reserved.
 * This program and the accompanying materials are made available under the terms
 * of the Eclipse Public License v1.0 which accompanies this distribution, and is
 * available at http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * Wind River Systems - initial API and implementation
 *******************************************************************************/
package org.eclipse.tcf.te.tcf.locator;

import java.net.ConnectException;
import java.net.InetAddress;
import java.net.SocketTimeoutException;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.tcf.core.Command;
import org.eclipse.tcf.protocol.IChannel;
import org.eclipse.tcf.protocol.IPeer;
import org.eclipse.tcf.protocol.IToken;
import org.eclipse.tcf.protocol.Protocol;
import org.eclipse.tcf.services.ILocator;
import org.eclipse.tcf.te.runtime.callback.Callback;
import org.eclipse.tcf.te.runtime.interfaces.callback.ICallback;
import org.eclipse.tcf.te.runtime.utils.net.IPAddressUtil;
import org.eclipse.tcf.te.tcf.core.Tcf;
import org.eclipse.tcf.te.tcf.core.peers.Peer;
import org.eclipse.tcf.te.tcf.locator.activator.CoreBundleActivator;
import org.eclipse.tcf.te.tcf.locator.interfaces.IScanner;
import org.eclipse.tcf.te.tcf.locator.interfaces.ITracing;
import org.eclipse.tcf.te.tcf.locator.interfaces.nodes.ILocatorModel;
import org.eclipse.tcf.te.tcf.locator.interfaces.nodes.IPeerModel;
import org.eclipse.tcf.te.tcf.locator.interfaces.nodes.IPeerModelProperties;
import org.eclipse.tcf.te.tcf.locator.interfaces.services.ILocatorModelLookupService;
import org.eclipse.tcf.te.tcf.locator.interfaces.services.ILocatorModelUpdateService;
import org.eclipse.tcf.te.tcf.locator.nodes.PeerModel;
import org.eclipse.tcf.te.tcf.locator.nodes.PeerRedirector;


/**
 * Scanner runnable to be executed for each peer to probe within the
 * TCF event dispatch thread.
 */
public class ScannerRunnable implements Runnable, IChannel.IChannelListener {

	// Reference to the parent model scanner
	private final IScanner parentScanner;
	// Reference to the peer model node to update
	/* default */ final IPeerModel peerNode;
	// Reference to the channel
	/* default */ IChannel channel = null;
	// Mark if the used channel is a shared channel instance
	/* default */ boolean sharedChannel = false;

	// Optional callback to invoke once the scan has been completed
	private final ICallback callback;

	/**
	 * Constructor.
	 *
	 * @param scanner The parent model scanner or <code>null</code> if the runnable is constructed from outside a scanner.
	 * @param peerNode The peer model instance. Must not be <code>null</code>.
	 */
	public ScannerRunnable(IScanner scanner, IPeerModel peerNode) {
		this(scanner, peerNode, null);
	}

	/**
	 * Constructor.
	 *
	 * @param scanner The parent model scanner or <code>null</code> if the runnable is constructed from outside a scanner.
	 * @param peerNode The peer model instance. Must not be <code>null</code>.
	 * @param callback The callback to invoke once the scan has been completed or <code>null</code>.
	 */
	public ScannerRunnable(IScanner scanner, IPeerModel peerNode, ICallback callback) {
		super();

		parentScanner = scanner;

		Assert.isNotNull(peerNode);
		this.peerNode = peerNode;

		this.callback = callback;
	}

	/**
	 * Returns the parent scanner instance.
	 *
	 * @return The parent scanner instance or <code>null</code>.
	 */
	protected final IScanner getParentScanner() {
		return parentScanner;
	}

	/* (non-Javadoc)
	 * @see java.lang.Runnable#run()
	 */
	@Override
	public void run() {
		Assert.isTrue(Protocol.isDispatchThread(), "Illegal Thread Access"); //$NON-NLS-1$

		// If the parent scanner is terminated, don't do anything
		IScanner scanner = getParentScanner();
		if (scanner != null && scanner.isTerminated()) {
			if (callback != null) callback.done(this, Status.OK_STATUS);
			return;
		}

		// If a scanner runnable already active for this peer node, there
		// is no need to run another scan.
		if (peerNode.getProperty("scanner.transient") != null) { //$NON-NLS-1$
			if (callback != null) callback.done(this, Status.OK_STATUS);
			return;
		}
		peerNode.setProperty("scanner.transient", this); //$NON-NLS-1$

		// Determine the peer
		IPeer peer = peerNode.getPeer();
		if (peer == null) {
			if (callback != null) callback.done(this, Status.OK_STATUS);
			return;
		}

		// Don't scan value-adds
		String value = peer.getAttributes().get("ValueAdd"); //$NON-NLS-1$
		boolean isValueAdd = value != null && ("1".equals(value.trim()) || Boolean.parseBoolean(value.trim())); //$NON-NLS-1$

		if (isValueAdd) {
			if (callback != null) callback.done(this, Status.OK_STATUS);
			return;
		}

		// Don't scan command server peers
		boolean isCommandServer = peer.getName() != null
						&& peer.getName().endsWith("Command Server"); //$NON-NLS-1$
		if (isCommandServer) {
			if (callback != null) callback.done(this, Status.OK_STATUS);
			return;
		}

		// Do not open a channel to incomplete peer nodes
		if (peerNode.isComplete()) {
			if (CoreBundleActivator.getTraceHandler().isSlotEnabled(ITracing.ID_TRACE_SCANNER)) {
				CoreBundleActivator.getTraceHandler().trace("Scanner runnable invoked for peer '" + peerNode.getName() + "' (" + peerNode.getPeerId() + "). Attempting to open channel ...", //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
															ITracing.ID_TRACE_SCANNER, ScannerRunnable.this);
			}

			// Check if there is a shared channel available which is still in open state
			channel = Tcf.getChannelManager().getChannel(peer);
			if (channel == null || channel.getState() != IChannel.STATE_OPEN) {
				sharedChannel = false;
				// Open the channel
				channel = peer.openChannel();
				// Add ourself as channel listener
				channel.addChannelListener(this);
			} else {
				sharedChannel = true;
				// Shared channel is in open state -> use it
				onChannelOpened();
			}
		}
	}

	/* (non-Javadoc)
	 * @see org.eclipse.tcf.protocol.IChannel.IChannelListener#onChannelOpened()
	 */
    @Override
	public void onChannelOpened() {
		// Peer is reachable
		if (channel != null && !sharedChannel) {
			// Remove ourself as channel listener
			channel.removeChannelListener(this);
		}

		if (CoreBundleActivator.getTraceHandler().isSlotEnabled(ITracing.ID_TRACE_SCANNER)) {
			CoreBundleActivator.getTraceHandler().trace("Scanner runnable onChannelOpened invoked for peer '" + peerNode.getName() + "' (" + peerNode.getPeerId() + ").", //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
														ITracing.ID_TRACE_SCANNER, ScannerRunnable.this);
		}

		// Turn off change notifications temporarily
		final boolean changed = peerNode.setChangeEventsEnabled(false);

		// Set the peer state property
		int counter = peerNode.getIntProperty(IPeerModelProperties.PROP_CHANNEL_REF_COUNTER);
		if (!peerNode.isProperty(IPeerModelProperties.PROP_STATE, IPeerModelProperties.STATE_WAITING_FOR_READY)) {
			peerNode.setProperty(IPeerModelProperties.PROP_STATE, counter > 0 ? IPeerModelProperties.STATE_CONNECTED : IPeerModelProperties.STATE_REACHABLE);
			peerNode.setProperty(IPeerModelProperties.PROP_LAST_SCANNER_ERROR, null);
		}

		// Get the parent model from the model mode
		final ILocatorModel model = (ILocatorModel)peerNode.getAdapter(ILocatorModel.class);

		if (channel != null && channel.getState() == IChannel.STATE_OPEN) {

			// Update the services lists
			ILocatorModelUpdateService updateService = model != null ? model.getService(ILocatorModelUpdateService.class) : null;
			if (updateService != null) {
				Collection<String> localServices = channel.getLocalServices();
				Collection<String> remoteServices = channel.getRemoteServices();

				updateService.updatePeerServices(peerNode, localServices, remoteServices);

				if (CoreBundleActivator.getTraceHandler().isSlotEnabled(ITracing.ID_TRACE_SCANNER)) {
					CoreBundleActivator.getTraceHandler().trace("Services: local = " + localServices + ", remote = " + remoteServices, //$NON-NLS-1$ //$NON-NLS-2$
																ITracing.ID_TRACE_SCANNER, ScannerRunnable.this);
				}
			}

			// If we don't queried the DNS name of the peer, or the peer IP changed,
			// trigger a query (can run in any thread, outside TCF dispatch and UI
			// thread). This make sense only if there is an IP address to query at all.
			final String ip = channel.getRemotePeer().getAttributes().get(IPeer.ATTR_IP_HOST);
			if (ip != null && !"".equals(ip)) { //$NON-NLS-1$
				if (peerNode.getStringProperty("dns.name.transient") == null || !ip.equals(peerNode.getStringProperty("dns.lastIP.transient"))) { //$NON-NLS-1$ //$NON-NLS-2$
					// If the IP address changed, reset the "do not query again" marker
					if (!ip.equals(peerNode.getStringProperty("dns.lastIP.transient"))) { //$NON-NLS-1$
						peerNode.setProperty("dns.lastIP.transient", ip); //$NON-NLS-1$
						peerNode.setProperty("dns.skip.transient", false); //$NON-NLS-1$
					}

					if (!peerNode.getBooleanProperty("dns.skip.transient")) { //$NON-NLS-1$
						Runnable runnable = new Runnable() {
							@Override
							public void run() {
								try {
									InetAddress address = InetAddress.getByName(ip);
									final AtomicReference<String> nameRef = new AtomicReference<String>();
									nameRef.set(address.getCanonicalHostName());

									if (ip.equals(nameRef.get()) && IPAddressUtil.getInstance().isLocalHost(ip)) {
										String[] candidates = IPAddressUtil.getInstance().getCanonicalHostNames();
										for (String candidate : candidates) {
											if (!ip.equals(candidate)) {
												nameRef.set(candidate);
												break;
											}
										}
									}

									Protocol.invokeLater(new Runnable() {
										@Override
										public void run() {
											String name = nameRef.get();
											if (name != null && !"".equals(name) && !ip.equals(name)) { //$NON-NLS-1$
												String dnsName = name.indexOf('.') != -1 ? name.substring(0, name.indexOf('.')) : name;
												if (!ip.equalsIgnoreCase(dnsName)) {
													peerNode.setProperty("dns.name.transient", dnsName.toLowerCase()); //$NON-NLS-1$
												}
											}
										}
									});
								}
								catch (UnknownHostException e) {
									Protocol.invokeLater(new Runnable() {
										@Override
                                        public void run() {
											peerNode.setProperty("dns.skip.transient", true); //$NON-NLS-1$
										}
									});
								}
							}
						};

						Thread thread = new Thread(runnable, "DNS Query Thread for " + ip); //$NON-NLS-1$
						thread.start();
					}
				}
			}

			// Check if the agent ID is already set
			String agentID = channel.getRemotePeer().getAgentID();
			if (agentID == null && channel.getRemotePeer() instanceof Peer) {
				// Determine the agent ID of the remote agent
				ILocator locator = channel.getRemoteService(ILocator.class);
				if (locator != null) {
					locator.getAgentID(new ILocator.DoneGetAgentID() {
						@Override
						public void doneGetAgentID(IToken token, Exception error, String agentID) {
							// Ignore errors. If the agent does not implement this command, we
							// do not fail.
							if (agentID != null) {
								// Update the peer attributes
								Map<String, String> attrs = new HashMap<String, String>(channel.getRemotePeer().getAttributes());
								attrs.put(IPeer.ATTR_AGENT_ID, agentID);
								peerNode.setProperty(IPeerModelProperties.PROP_INSTANCE, new Peer(attrs));
							}

							if (isGetPeersAllowed(channel)) {
								// Get the peers from the remote locator
								getPeers(channel, model, ip, new Callback() {
									@Override
									protected void internalDone(Object caller, IStatus status) {
										// Complete
										onDone(peerNode, changed);
									}
								});
							} else {
								onDone(peerNode, changed);
							}
						}
					});
				} else {
					// Complete
					onDone(peerNode, changed);
				}
			} else {
				if (isGetPeersAllowed(channel)) {
					// Get the peers from the remote locator
					getPeers(channel, model, ip, new Callback() {
						@Override
						protected void internalDone(Object caller, IStatus status) {
							// Complete
							onDone(peerNode, changed);
						}
					});
				} else {
					onDone(peerNode, changed);
				}
			}
		} else {
			// Complete
			onDone(peerNode, changed);
		}
	}

    /**
     * Returns if or if not "getPeers" is allowed for the given channel.
     *
     * @param channel The channel. Must not be <code>null</code>.
     * @return <code>True</code> if "getPeers" is allowed, <code>false</code> otherwise.
     */
    /* default */ boolean isGetPeersAllowed(IChannel channel) {
		String remoteIP = channel.getRemotePeer().getAttributes().get(IPeer.ATTR_IP_HOST);
		boolean isLocal = remoteIP != null && IPAddressUtil.getInstance().isLocalHost(remoteIP);

		boolean isCommandServer = channel.getRemotePeer().getName() != null
						&& channel.getRemotePeer().getName().endsWith("Command Server"); //$NON-NLS-1$

		isCommandServer |= channel.getLocalPeer().getName() != null
					&& channel.getLocalPeer().getName().endsWith("Command Server"); //$NON-NLS-1$

		return !isLocal && !isCommandServer;
    }

    /**
     * Query the peers from the remote locator.
     *
     * @param channel The channel. Must not be <code>null</code>.
     * @param model The locator model. Must not be <code>null</code>.
     * @param ip The IP address or <code>null</code>.
     * @param callback The callback. Must not be <code>null</code>.
     */
	@SuppressWarnings("unused")
    protected void getPeers(final IChannel channel, final ILocatorModel model, final String ip, final ICallback callback) {
		Assert.isNotNull(channel);
		Assert.isNotNull(model);
		Assert.isNotNull(callback);

		// Keep the channel open as long as the query for the remote peers is running.
		boolean keepOpen = false;

		// Get the agent ID of the remote agent we are connected too.
		// Have to use the peer model node here.
		final String agentID = peerNode.getPeer().getAgentID();

		// Ask for discovered peers from the remote agents POV.
		//
		// Note: For simulators connected via NAT, we have to do this for localhost address
		//       as well. Otherwise we miss the discoverable agents only known to the simulator.
		//       The same applies to agent being discovered. If you don't ask for discovered peers
		//       here too, we may miss some routes.
		if (ip != null && !"".equals(ip)) { //$NON-NLS-1$
			// Use the open channel to ask the remote peer what other peers it knows
			ILocator locator = channel.getRemoteService(ILocator.class);
			if (locator != null) {
				// Channel must be kept open as long as the command runs
				keepOpen = true;
				// Issue the command
				new Command(channel, locator, "getPeers", null) { //$NON-NLS-1$
					@Override
					public void done(Exception error, Object[] args) {
						if (error == null) {
							Assert.isTrue(args.length == 2);
							error = toError(args[0]);
						}
						// If the error is still null here, process the returned peers
						if (error == null && args[1] != null) {
							// Get the parent peer
							IPeer parentPeer = channel.getRemotePeer();
							// Get the old child list
							List<IPeerModel> oldChildren = new ArrayList<IPeerModel>(model.getChildren(parentPeer.getID()));

							// "getPeers" returns a collection of peer attribute maps
							@SuppressWarnings("unchecked")
							Collection<Map<String,String>> peerAttributesList = (Collection<Map<String,String>>)args[1];
							for (Map<String,String> attributes : peerAttributesList) {
								// Don't process value-add's
								String value = attributes.get("ValueAdd"); //$NON-NLS-1$
								boolean isValueAdd = value != null && ("1".equals(value.trim()) || Boolean.parseBoolean(value.trim())); //$NON-NLS-1$

								// Don't process command server service server or clients
								String name = attributes.get(IPeer.ATTR_NAME);
								boolean isCommandServer = name != null && name.endsWith("Command Server"); //$NON-NLS-1$

								if (isValueAdd || isCommandServer) continue;

								// Get the peer id
								String peerId = attributes.get(IPeer.ATTR_ID);
								// Create a peer instance
								IPeer peer = new PeerRedirector(parentPeer, attributes);
								// Try to find an existing peer node first
								IPeerModel peerNode = model.getService(ILocatorModelLookupService.class).lkupPeerModelById(parentPeer.getID(), peerId);
								if (peerNode == null) {
									// Not yet known -> add it
									peerNode = new PeerModel(model, peer);
									peerNode.setParent(ScannerRunnable.this.peerNode);
									peerNode.setProperty(IPeerModelProperties.PROP_SCANNER_EXCLUDE, true);
									// Validate the peer node before adding
									peerNode = model.validateChildPeerNodeForAdd(peerNode);
									if (peerNode != null) {
										// Add the child peer node to model
										model.getService(ILocatorModelUpdateService.class).addChild(peerNode);
									}
								} else {
									// The parent node should be set and match
									Assert.isTrue(peerNode.getParent(IPeerModel.class) != null && peerNode.getParent(IPeerModel.class).equals(ScannerRunnable.this.peerNode));
									// Peer node found, update the peer instance
									peerNode.setProperty(IPeerModelProperties.PROP_INSTANCE, peer);
									// And remove it from the old child list
									oldChildren.remove(peerNode);
								}
							}

							// Everything left in the old child list is not longer known to the remote peer
							// However, the child list may include manual redirected static peers. Do not
							// remove them here.
							for (IPeerModel child : oldChildren) {
								if (!child.isStatic()) {
									// Remove the child peer node from the model
									model.getService(ILocatorModelUpdateService.class).removeChild(child);
								}
							}
						}

						// Once everything is processed, close the channel
						if (!sharedChannel) channel.close();
						// Invoke the callback
						callback.done(ScannerRunnable.this, Status.OK_STATUS);
					}
				};
			}
		}

		// And close the channel
		if (!sharedChannel && !keepOpen) channel.close();

		// Invoke the callback
		if (!keepOpen) callback.done(ScannerRunnable.this, Status.OK_STATUS);
	}

	/* (non-Javadoc)
	 * @see org.eclipse.tcf.protocol.IChannel.IChannelListener#onChannelClosed(java.lang.Throwable)
	 */
	@Override
	public void onChannelClosed(Throwable error) {
		// Peer is not reachable

		if (channel != null) {
			// Remove ourself as channel listener
			channel.removeChannelListener(this);
		}

		if (CoreBundleActivator.getTraceHandler().isSlotEnabled(ITracing.ID_TRACE_SCANNER)) {
			CoreBundleActivator.getTraceHandler().trace("Scanner runnable onChannelClosed invoked for peer '" + peerNode.getName() + "' (" + peerNode.getPeerId() + "). Error was: " + (error != null ? error.getLocalizedMessage() : null), //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
														ITracing.ID_TRACE_SCANNER, ScannerRunnable.this);
		}

		// Set the peer state property, if the scanner the runnable
		// has been scheduled from is still active.
		if (parentScanner == null || !parentScanner.isTerminated()) {
			// Turn off change notifications temporarily
			boolean changed = peerNode.setChangeEventsEnabled(false);

			peerNode.setProperty(IPeerModelProperties.PROP_CHANNEL_REF_COUNTER, null);
			if (!peerNode.isProperty(IPeerModelProperties.PROP_STATE, IPeerModelProperties.STATE_WAITING_FOR_READY)) {
				boolean timeout = error instanceof SocketTimeoutException || (error instanceof ConnectException && error.getMessage() != null && error.getMessage().startsWith("Connection timed out:")); //$NON-NLS-1$
				peerNode.setProperty(IPeerModelProperties.PROP_STATE, timeout ? IPeerModelProperties.STATE_NOT_REACHABLE : IPeerModelProperties.STATE_ERROR);
				peerNode.setProperty(IPeerModelProperties.PROP_LAST_SCANNER_ERROR, error instanceof SocketTimeoutException ? null : error);
			}

			// Clear out previously determined services
			ILocatorModel model = (ILocatorModel)peerNode.getAdapter(ILocatorModel.class);
			if (model != null) {
				ILocatorModelUpdateService updateService = model.getService(ILocatorModelUpdateService.class);
				updateService.updatePeerServices(peerNode, null, null);

				// Clean out possible child nodes
				model.setChildren(peerNode.getPeerId(), null);
			}

			// Clean out DNS name detection
			peerNode.setProperty("dns.name.transient", null); //$NON-NLS-1$
			peerNode.setProperty("dns.lastIP.transient", null); //$NON-NLS-1$
			peerNode.setProperty("dns.skip.transient", null); //$NON-NLS-1$

			// Complete
			onDone(peerNode, changed);
		}
	}

	/**
	 * Called from {@link #onChannelOpened()} and {@link #onChannelClosed(Throwable)} once
	 * all operations of the scanner are completed.
	 *
	 * @param node The peer model node. Must not be <code>null</code>.
	 * @param changed <code>True</code> if the change events shall be enabled, <code>false</code> otherwise.
	 */
	protected void onDone(IPeerModel node, boolean changed) {
		Assert.isNotNull(node);

		// Reset the scanner runnable marker
		node.setProperty("scanner.transient", null); //$NON-NLS-1$

		// Re-enable the change events and fire a "properties" change event
		if (changed) {
			node.setChangeEventsEnabled(true);
			node.fireChangeEvent("properties", null, peerNode.getProperties()); //$NON-NLS-1$
		}

		if (callback != null) callback.done(this, Status.OK_STATUS);
	}

	/* (non-Javadoc)
	 * @see org.eclipse.tcf.protocol.IChannel.IChannelListener#congestionLevel(int)
	 */
	@Override
	public void congestionLevel(int level) {
	}

}