package de.bwlehrpool.bwlp_guac;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.Iterator;
import java.util.LinkedHashMap;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

import org.codehaus.jackson.map.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Broker for all clients available.
 * Keeps track of which clients are online, offline, assigned to a user etc.
 */
public class ConnectionManager {

	private static final Logger LOGGER = LoggerFactory.getLogger(ConnectionManager.class);

	// TODO: Config
	private static final String SOURCE_URL = SlxConfig.clientListUrl();

	private static final LinkedHashMap<String, AvailableClient> clientPool = new LinkedHashMap<String, AvailableClient>();

	/**
	 * Pass plain user name, get existing connection (if any), or a fresh one
	 * @param user (LDAP) user name
	 */
	public static WrappedConnection getForUser(String user) {
		if (SOURCE_URL == null) {
			LOGGER.warn("Don't have a source URL for client machines!");
			return null;
		}
		try {
			updateList();
			// Find existing/free client
			AvailableClient freeClient;
			for (;;) {
				freeClient = null;
				synchronized (clientPool) {
					for (AvailableClient ac : clientPool.values()) {
						if (ac.isInUseBy(user)) {
							freeClient = ac;
							break;
						}
					}
					if (freeClient == null) {
						for (AvailableClient ac : clientPool.values()) {
							if (ac.claim(user)) {
								freeClient = ac;
								break;
							}
						}
					}
				}
				if (freeClient == null)
					return null; // TODO: No more clients available -- how to handle?
				// Found free or existing client, check if connection is (still) possible
				if (freeClient.checkConnection(0)) {
					LOGGER.info("Establishing mapping for user " + user + " to " + freeClient);
					return freeClient.getConnection(user);
				}
				// Connection check failed - release and loop again
				freeClient.releaseConnection(user);
			}
		} catch (Exception e) {
			LOGGER.warn("KACKE AM DAMPFEN", e);
			return null;
		}
	}

	private static long lastUpdate = 0;

	/**
	 * Fetch fresh client list from satellite server.
	 * Cache for 15 seconds.
	 */
	private static synchronized void updateList() {
		long now = System.currentTimeMillis();
		if (now < lastUpdate) {
			lastUpdate = now;
		}
		if (now - lastUpdate < 15000)
			return;
		// OK GO
		lastUpdate = now;
		ByteArrayOutputStream baos = new ByteArrayOutputStream(3000);
		HttpURLConnection con;
		try {
			con = (HttpURLConnection) new URL(SOURCE_URL).openConnection();
		} catch (MalformedURLException e1) {
			LOGGER.warn("Bad Connection Pool URL", e1);
			return;
		} catch (IOException e1) {
			LOGGER.warn("Cannot connect to Connection Pool URL", e1);
			return;
		}
		if (con instanceof HttpsURLConnection) {
			((HttpsURLConnection) con).setHostnameVerifier(ignorer);
			((HttpsURLConnection) con).setSSLSocketFactory(sockFac);
		}
		try (BufferedInputStream in = new BufferedInputStream(con.getInputStream())) {
			byte dataBuffer[] = new byte[2048];
			int bytesRead;
			while ((bytesRead = in.read(dataBuffer, 0, dataBuffer.length)) != -1) {
				baos.write(dataBuffer, 0, bytesRead);
			}
		} catch (IOException e) {
			LOGGER.warn("Error while reading reply of Connection Pool", e);
			return;
		}
		populateList(baos.toByteArray());
	}

	private static void populateList(byte[] data) {
		ObjectMapper mapper = new ObjectMapper();
		JsonClient[] list;
		JsonRoot root;
		try {
			root = mapper.readValue(data, JsonRoot.class);
		} catch (Exception e) {
			LOGGER.warn("Could not deserialize JSON from Connection Pool", e);
			LOGGER.warn("Not updating local list");
			return;
		}
		list = root.clients;
		if (list == null) {
			LOGGER.info("Client list null");
		}
		if (root.locations != null) {
			for (JsonLocation l : root.locations) {
				LOGGER.info("Location " + l.name + " with pw " + l.password);
			}
		}
		synchronized (clientPool) {
			for (JsonClient cnew : list) {
				if (cnew.password == null || cnew.clientip == null)
					continue; // Invalid
				AvailableClient existing = clientPool.get(cnew.clientip);
				if (existing == null) {
					// New client
					clientPool.put(cnew.clientip, new AvailableClient(cnew));
					LOGGER.info("New client " + cnew.clientip);
				} else {
					existing.update(cnew);
				}
			}
			final long NOW = System.currentTimeMillis();
			for (Iterator<AvailableClient> it = clientPool.values().iterator(); it.hasNext();) {
				AvailableClient c = it.next();
				if (c.isTimeout(NOW)) {
					LOGGER.info("Removing client " + c + " from list");
					it.remove();
				}

			}
			LOGGER.info("List updated. " + clientPool.size() + " clients.");
		}
	}

	/*
	 * Make SSL insecure
	 */

	static {
		SSLContext ctx = null;
		try {
			ctx = SSLContext.getInstance("TLSv1.2");
		} catch (NoSuchAlgorithmException e) {
			LOGGER.warn("Could not get TLSv1.2 context, SSL will be secure :-(", e);
		}
		if (ctx != null) {
			try {
				ctx.init(null, new TrustManager[] { new X509TrustManager() {
					@Override
					public void checkClientTrusted(X509Certificate[] chain, String authType)
							throws CertificateException {
					}

					@Override
					public void checkServerTrusted(X509Certificate[] chain, String authType)
							throws CertificateException {
					}

					@Override
					public X509Certificate[] getAcceptedIssuers() {
						return null;
					}

				} }, null);
			} catch (KeyManagementException e) {
				LOGGER.warn("Could not initialize TLSv1.2 SSL context", e);
				ctx = null;
			}
		}
		if (ctx == null) {
			sockFac = null;
		} else {
			sockFac = ctx.getSocketFactory();
		}
	}

	private static final SSLSocketFactory sockFac;

	private static final HostnameVerifier ignorer = new HostnameVerifier() {

		@Override
		public boolean verify(String hostname, SSLSession session) {
			return true;
		}
	};

}