/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package ch.boye.httpclientandroidlib.impl.conn;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

import ch.boye.httpclientandroidlib.annotation.GuardedBy;
import ch.boye.httpclientandroidlib.annotation.ThreadSafe;

import ch.boye.httpclientandroidlib.androidextra.HttpClientAndroidLog;
/* LogFactory removed by HttpClient for Android script. */
import ch.boye.httpclientandroidlib.conn.ClientConnectionManager;
import ch.boye.httpclientandroidlib.conn.ClientConnectionOperator;
import ch.boye.httpclientandroidlib.conn.ClientConnectionRequest;
import ch.boye.httpclientandroidlib.conn.ManagedClientConnection;
import ch.boye.httpclientandroidlib.conn.routing.HttpRoute;
import ch.boye.httpclientandroidlib.conn.routing.RouteTracker;
import ch.boye.httpclientandroidlib.conn.scheme.SchemeRegistry;
import ch.boye.httpclientandroidlib.params.HttpParams;

/**
 * A connection manager for a single connection. This connection manager
 * maintains only one active connection at a time. Even though this class
 * is thread-safe it ought to be used by one execution thread only.
 * <p>
 * SingleClientConnManager will make an effort to reuse the connection
 * for subsequent requests with the same {@link HttpRoute route}.
 * It will, however, close the existing connection and open it
 * for the given route, if the route of the persistent connection does
 * not match that of the connection request. If the connection has been
 * already been allocated {@link IllegalStateException} is thrown.
 *
 * @since 4.0
 */
@ThreadSafe
public class SingleClientConnManager implements ClientConnectionManager {

    public HttpClientAndroidLog log = new HttpClientAndroidLog(getClass());

    /** The message to be logged on multiple allocation. */
    public final static String MISUSE_MESSAGE =
    "Invalid use of SingleClientConnManager: connection still allocated.\n" +
    "Make sure to release the connection before allocating another one.";

    /** The schemes supported by this connection manager. */
    protected final SchemeRegistry schemeRegistry;

    /** The operator for opening and updating connections. */
    protected final ClientConnectionOperator connOperator;

    /** Whether the connection should be shut down  on release. */
    protected final boolean alwaysShutDown;

    /** The one and only entry in this pool. */
    @GuardedBy("this")
    protected PoolEntry uniquePoolEntry;

    /** The currently issued managed connection, if any. */
    @GuardedBy("this")
    protected ConnAdapter managedConn;

    /** The time of the last connection release, or -1. */
    @GuardedBy("this")
    protected long lastReleaseTime;

    /** The time the last released connection expires and shouldn't be reused. */
    @GuardedBy("this")
    protected long connectionExpiresTime;

    /** Indicates whether this connection manager is shut down. */
    protected volatile boolean isShutDown;

    /**
     * Creates a new simple connection manager.
     *
     * @param params    the parameters for this manager
     * @param schreg    the scheme registry
     *
     * @deprecated use {@link SingleClientConnManager#SingleClientConnManager(SchemeRegistry)}
     */
    @Deprecated
    public SingleClientConnManager(HttpParams params,
                                   SchemeRegistry schreg) {
        this(schreg);
    }
    /**
     * Creates a new simple connection manager.
     *
     * @param schreg    the scheme registry
     */
    public SingleClientConnManager(final SchemeRegistry schreg) {
        if (schreg == null) {
            throw new IllegalArgumentException
                ("Scheme registry must not be null.");
        }
        this.schemeRegistry  = schreg;
        this.connOperator    = createConnectionOperator(schreg);
        this.uniquePoolEntry = new PoolEntry();
        this.managedConn     = null;
        this.lastReleaseTime = -1L;
        this.alwaysShutDown  = false; //@@@ from params? as argument?
        this.isShutDown      = false;
    }

    /**
     * @since 4.1
     */
    public SingleClientConnManager() {
        this(SchemeRegistryFactory.createDefault());
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            shutdown();
        } finally { // Make sure we call overridden method even if shutdown barfs
            super.finalize();
        }
    }

    public SchemeRegistry getSchemeRegistry() {
        return this.schemeRegistry;
    }

    /**
     * Hook for creating the connection operator.
     * It is called by the constructor.
     * Derived classes can override this method to change the
     * instantiation of the operator.
     * The default implementation here instantiates
     * {@link DefaultClientConnectionOperator DefaultClientConnectionOperator}.
     *
     * @param schreg    the scheme registry to use, or <code>null</code>
     *
     * @return  the connection operator to use
     */
    protected ClientConnectionOperator
        createConnectionOperator(SchemeRegistry schreg) {
        return new DefaultClientConnectionOperator(schreg);
    }

    /**
     * Asserts that this manager is not shut down.
     *
     * @throws IllegalStateException    if this manager is shut down
     */
    protected final void assertStillUp() throws IllegalStateException {
        if (this.isShutDown)
            throw new IllegalStateException("Manager is shut down.");
    }

    public final ClientConnectionRequest requestConnection(
            final HttpRoute route,
            final Object state) {

        return new ClientConnectionRequest() {

            public void abortRequest() {
                // Nothing to abort, since requests are immediate.
            }

            public ManagedClientConnection getConnection(
                    long timeout, TimeUnit tunit) {
                return SingleClientConnManager.this.getConnection(
                        route, state);
            }

        };
    }

    /**
     * Obtains a connection.
     *
     * @param route     where the connection should point to
     *
     * @return  a connection that can be used to communicate
     *          along the given route
     */
    public synchronized ManagedClientConnection getConnection(HttpRoute route, Object state) {
        if (route == null) {
            throw new IllegalArgumentException("Route may not be null.");
        }
        assertStillUp();

        if (log.isDebugEnabled()) {
            log.debug("Get connection for route " + route);
        }

        if (managedConn != null)
            throw new IllegalStateException(MISUSE_MESSAGE);

        // check re-usability of the connection
        boolean recreate = false;
        boolean shutdown = false;

        // Kill the connection if it expired.
        closeExpiredConnections();

        if (uniquePoolEntry.connection.isOpen()) {
            RouteTracker tracker = uniquePoolEntry.tracker;
            shutdown = (tracker == null || // can happen if method is aborted
                        !tracker.toRoute().equals(route));
        } else {
            // If the connection is not open, create a new PoolEntry,
            // as the connection may have been marked not reusable,
            // due to aborts -- and the PoolEntry should not be reused
            // either.  There's no harm in recreating an entry if
            // the connection is closed.
            recreate = true;
        }

        if (shutdown) {
            recreate = true;
            try {
                uniquePoolEntry.shutdown();
            } catch (IOException iox) {
                log.debug("Problem shutting down connection.", iox);
            }
        }

        if (recreate)
            uniquePoolEntry = new PoolEntry();

        managedConn = new ConnAdapter(uniquePoolEntry, route);

        return managedConn;
    }

    public synchronized void releaseConnection(
            ManagedClientConnection conn,
            long validDuration, TimeUnit timeUnit) {
        assertStillUp();

        if (!(conn instanceof ConnAdapter)) {
            throw new IllegalArgumentException
                ("Connection class mismatch, " +
                 "connection not obtained from this manager.");
        }

        if (log.isDebugEnabled()) {
            log.debug("Releasing connection " + conn);
        }

        ConnAdapter sca = (ConnAdapter) conn;
        if (sca.poolEntry == null)
            return; // already released
        ClientConnectionManager manager = sca.getManager();
        if (manager != null && manager != this) {
            throw new IllegalArgumentException
                ("Connection not obtained from this manager.");
        }

        try {
            // make sure that the response has been read completely
            if (sca.isOpen() && (this.alwaysShutDown ||
                                 !sca.isMarkedReusable())
                ) {
                if (log.isDebugEnabled()) {
                    log.debug
                        ("Released connection open but not reusable.");
                }

                // make sure this connection will not be re-used
                // we might have gotten here because of a shutdown trigger
                // shutdown of the adapter also clears the tracked route
                sca.shutdown();
            }
        } catch (IOException iox) {
            if (log.isDebugEnabled())
                log.debug("Exception shutting down released connection.",
                          iox);
        } finally {
            sca.detach();
            managedConn = null;
            lastReleaseTime = System.currentTimeMillis();
            if(validDuration > 0)
                connectionExpiresTime = timeUnit.toMillis(validDuration) + lastReleaseTime;
            else
                connectionExpiresTime = Long.MAX_VALUE;
        }
    }

    public synchronized void closeExpiredConnections() {
        if(System.currentTimeMillis() >= connectionExpiresTime) {
            closeIdleConnections(0, TimeUnit.MILLISECONDS);
        }
    }

    public synchronized void closeIdleConnections(long idletime, TimeUnit tunit) {
        assertStillUp();

        // idletime can be 0 or negative, no problem there
        if (tunit == null) {
            throw new IllegalArgumentException("Time unit must not be null.");
        }

        if ((managedConn == null) && uniquePoolEntry.connection.isOpen()) {
            final long cutoff =
                System.currentTimeMillis() - tunit.toMillis(idletime);
            if (lastReleaseTime <= cutoff) {
                try {
                    uniquePoolEntry.close();
                } catch (IOException iox) {
                    // ignore
                    log.debug("Problem closing idle connection.", iox);
                }
            }
        }
    }

    public synchronized void shutdown() {

        this.isShutDown = true;

        if (managedConn != null)
            managedConn.detach();

        try {
            if (uniquePoolEntry != null) // and connection open?
                uniquePoolEntry.shutdown();
        } catch (IOException iox) {
            // ignore
            log.debug("Problem while shutting down manager.", iox);
        } finally {
            uniquePoolEntry = null;
        }
    }

    /**
     * @deprecated no longer used
     */
    @Deprecated
    protected synchronized void revokeConnection() {
        if (managedConn == null)
            return;
        managedConn.detach();
        try {
            uniquePoolEntry.shutdown();
        } catch (IOException iox) {
            // ignore
            log.debug("Problem while shutting down connection.", iox);
        }
    }

    /**
     * The pool entry for this connection manager.
     */
    protected class PoolEntry extends AbstractPoolEntry {

        /**
         * Creates a new pool entry.
         *
         */
        protected PoolEntry() {
            super(SingleClientConnManager.this.connOperator, null);
        }

        /**
         * Closes the connection in this pool entry.
         */
        protected void close() throws IOException {
            shutdownEntry();
            if (connection.isOpen())
                connection.close();
        }

        /**
         * Shuts down the connection in this pool entry.
         */
        protected void shutdown() throws IOException {
            shutdownEntry();
            if (connection.isOpen())
                connection.shutdown();
        }

    }

    /**
     * The connection adapter used by this manager.
     */
    protected class ConnAdapter extends AbstractPooledConnAdapter {

        /**
         * Creates a new connection adapter.
         *
         * @param entry   the pool entry for the connection being wrapped
         * @param route   the planned route for this connection
         */
        protected ConnAdapter(PoolEntry entry, HttpRoute route) {
            super(SingleClientConnManager.this, entry);
            markReusable();
            entry.route = route;
        }

    }

}
