/*-
 * Copyright (c) 2006, Derek Konigsberg
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/******************************************************************************
 * This class has been modified to integrate J2ME socket connection code,
 * since LogicMail has no need for a dual-use implementation.  The bulk of
 * this code is a combination of Connection.java and the J2ME ConnectionImpl.java
 * from Mail4ME, and is covered under the copyright shown below.  Any code not
 * originating from Mail4ME is covered under the copyright shown at the top of
 * this source file.
 *
 * Mail4ME - Mail for the Java 2 Micro Edition
 *
 * A lightweight, J2ME- (and also J2SE-) compatible package for sending and
 * receiving Internet mail messages using the SMTP and POP3 protocols.
 *
 * Copyright (c) 2000-2002 Jorg Pleumann <joerg@pleumann.de>
 *
 * Mail4ME is part of the EnhydraME family of projects. See the following web
 * sites for more information:
 *
 * -> http://mail4me.enhydra.org
 * -> http://me.enhydra.org
 *
 * Mail4ME is distributed under the Enhydra Public License (EPL), which is
 * discussed in great detail here:
 *
 * -> http://www.enhydra.org/software/license/index.html
 *
 * Have fun!
 ******************************************************************************/
package org.logicprobe.LogicMail.util;

import net.rim.device.api.crypto.tls.tls10.TLS10Connection;
import net.rim.device.api.i18n.ResourceBundle;
import net.rim.device.api.system.EventLogger;
import net.rim.device.api.util.DataBuffer;
import net.rim.device.cldc.io.ssl.TLSException;

import org.logicprobe.LogicMail.AppInfo;
import org.logicprobe.LogicMail.LogicMailResource;
import org.logicprobe.LogicMail.conf.ConnectionConfig;
import org.logicprobe.LogicMail.conf.GlobalConfig;
import org.logicprobe.LogicMail.conf.MailSettings;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.microedition.io.SocketConnection;
import javax.microedition.io.StreamConnection;


/**
 * Is the abstract base class for socket connections used inside the SMTP,
 * POP3 and IMAP protocols of the mail package. The rationale for using this class
 * is the difference in how networking is handled in J2ME and J2SE: While J2SE
 * has java.net.Socket, J2ME uses the Generic Connection Framework with its
 * javax.io.Connector class as a central means to open sockets or HTTP
 * connection. Unfortunately, both methods are totally incompatible with each
 * other, so a common abstraction has to be found to make the mail package
 * work in both environments.
 * <p>
 * The Connection class is such an abstraction. It provides abstract
 * versions of methods that open and close sockets, read from them and write
 * to them. It also provides a static factory method that is able to instantiate
 * one of several sub-classes of Connection that match the different run-time
 * environments. These sub-classes are all called ConnectionImpl, and they are
 * loaded "by name" from the j2me, j2se, or http packages, respectively. This
 * is the only way to get rid of compile-time dependencies on these classes.
 */
public abstract class Connection {
    protected static ResourceBundle resources = ResourceBundle.getBundle(LogicMailResource.BUNDLE_ID, LogicMailResource.BUNDLE_NAME);
    
    /** Select everything except WiFi */
    protected static final int TRANSPORT_AUTO = 0xFE;
    /** Select WiFi */
    protected static final int TRANSPORT_WIFI = 0x01;
    /** Select Direct TCP */
    protected static final int TRANSPORT_DIRECT_TCP = 0x02;
    /** Select MDS */
    protected static final int TRANSPORT_MDS = 0x04;
    /** Select WAP 2.0 */
    protected static final int TRANSPORT_WAP2 = 0x08;

    /**
     * Byte array holding carriage return and line feed
     */
    private static final byte[] CRLF = new byte[] { 13, 10 };

    private UtilFactory utilFactory;
    protected String serverName;
    protected int serverPort;
    protected boolean useSSL;
    protected int transports;
    private StreamConnection socket;
    private String localAddress;
    protected GlobalConfig globalConfig;
    protected InputStream input;
    protected OutputStream output;
    protected boolean useWiFi;
    private int fakeAvailable = -1;
    private int bytesSent = 0;
    private int bytesReceived = 0;

    /**
     * Provides a buffer used for incoming data.
     */
    private byte[] buffer = new byte[128];

    /**
     * Provides a dynamic buffer for building results
     */
    DataBuffer resultBuffer = new DataBuffer();

    /**
     * Initializes a new connection object.
     * 
     * @param connectionConfig Configuration data for the connection
     */
    protected Connection(ConnectionConfig connectionConfig) {
        this.globalConfig = MailSettings.getInstance().getGlobalConfig();
        this.utilFactory = UtilFactory.getInstance();
        
        this.serverName = connectionConfig.getServerName();
        this.serverPort = connectionConfig.getServerPort();
        this.useSSL = (connectionConfig.getServerSecurity() == ConnectionConfig.SECURITY_SSL);
        
        int transportType;
        boolean enableWiFi;
        if(connectionConfig.getTransportType() == ConnectionConfig.TRANSPORT_GLOBAL) {
            transportType = globalConfig.getTransportType();
            enableWiFi = globalConfig.getEnableWiFi();
        }
        else {
            transportType = connectionConfig.getTransportType();
            enableWiFi = connectionConfig.getEnableWiFi();
        }

        // Populate the bit-flags for the selected transport types
        // based on the configuration parameters.
        switch(transportType) {
        case ConnectionConfig.TRANSPORT_AUTO:
            transports = Connection.TRANSPORT_AUTO;
            break;
        case ConnectionConfig.TRANSPORT_DIRECT_TCP:
            transports = Connection.TRANSPORT_DIRECT_TCP;
            break;
        case ConnectionConfig.TRANSPORT_MDS:
            transports = Connection.TRANSPORT_MDS;
            break;
        case ConnectionConfig.TRANSPORT_WAP2:
            transports = Connection.TRANSPORT_WAP2;
            break;
        default:
            // Should only get here in rare cases of invalid configuration
            // data, so we select full automatic with WiFi.
            transports = Connection.TRANSPORT_AUTO;
            enableWiFi = true;
            break;
        }
        if(enableWiFi) { transports |= Connection.TRANSPORT_WIFI; }
        
        this.input = null;
        this.output = null;
        this.socket = null;
    }
    
    /**
     * Opens a connection.
     */
    public synchronized void open() throws IOException {
        if ((input != null) || (output != null) || (socket != null)) {
            close();
        }
        
        utilFactory.addOpenConnection(this);

        socket = openStreamConnection();
        if(socket == null) {
            throw new IOException(resources.getString(LogicMailResource.ERROR_UNABLE_TO_OPEN_CONNECTION));
        }
        
        input = socket.openDataInputStream();
        output = socket.openDataOutputStream();
        localAddress = ((SocketConnection) socket).getLocalAddress();
        bytesSent = 0;
        bytesReceived = 0;

        if (EventLogger.getMinimumLevel() >= EventLogger.INFORMATION) {
            String msg = "Connection established:\r\n" + "Socket: " +
            socket.getClass().toString() + "\r\n" + "Local address: " +
            localAddress + "\r\n";
            EventLogger.logEvent(AppInfo.GUID, msg.getBytes(),
                    EventLogger.INFORMATION);
        }
    }
    
    /**
     * Open a stream connection.
     * This method should encapsulate all platform-specific logic for opening
     * network connections.
     * 
     * @return the stream connection
     * 
     * @throws IOException Signals that an I/O exception has occurred.
     */
    protected abstract StreamConnection openStreamConnection() throws IOException;

    /**
     * Closes a connection.
     */
    public synchronized void close() throws IOException {
        try {
            if (input != null) {
                input.close();
                input = null;
            }
        } catch (Exception exp) {
            input = null;
        }

        try {
            if (output != null) {
                output.close();
                output = null;
            }
        } catch (Exception exp) {
            output = null;
        }

        try {
            if (socket != null) {
                socket.close();
                socket = null;
            }
        } catch (Exception exp) {
            socket = null;
        }

        utilFactory.removeOpenConnection(this);

        EventLogger.logEvent(AppInfo.GUID, "Connection closed".getBytes(),
                EventLogger.INFORMATION);
    }

    /**
     * Determine whether we are currently connected
     * @return True if connected
     */
    public boolean isConnected() {
        if (socket != null) {
            return true;
        } else {
            return false;
        }
    }

    /**
     * Get the local address to which this connection is bound
     * @return Local address
     */
    public String getLocalAddress() {
        return localAddress;
    }

    /**
     * Get the server name used when this connection was created
     * @return Server name
     */
    public String getServerName() {
        return serverName;
    }

    /**
     * Gets the number of bytes that have been sent since the
     * connection was opened.
     * <p>
     * The counter is not synchronized, so it should only be
     * called from the same thread as the send and receive
     * methods.
     * </p>
     * @return bytes sent
     */
    public int getBytesSent() {
        return bytesSent;
    }

    /**
     * Gets the number of bytes that have been received since the
     * connection was opened.
     * <p>
     * The counter is not synchronized, so it should only be
     * called from the same thread as the send and receive
     * methods.
     * </p>
     * @return bytes received
     */
    public int getBytesReceived() {
        return bytesReceived;
    }

    /**
     * Sends a string to the server. This method is used internally for
     * all outgoing communication to the server. The main thing it does
     * it terminate the line with a CR/LF. If there are occurrences of CR or
     * LF inside the string, the method ensures that proper CR/LF sequences
     * are sent for them, since this is what most Internet protocols expect.
     *
     * @see #receive
     */
    public synchronized void send(String s) throws IOException {
        byte[] bytes = s.getBytes();
        int length = bytes.length;

        /**
         * Special case for empty strings: Only CR/LF is sent.
         */
        if (s.length() == 0) {
            if (globalConfig.getConnDebug()) {
                EventLogger.logEvent(AppInfo.GUID, "[SEND]".getBytes(),
                        EventLogger.DEBUG_INFO);
            }

            output.write(CRLF, 0, 2);
            bytesSent += 2;
        }
        /**
         * The usual case goes here.
         */
        else {
            int i = 0;

            while (i < length) {
                int j = i;

                /**
                 * Find next occurrence of a line separator or the end of the
                 * string.
                 */
                while ((j < length) && (bytes[j] != 0x0A) &&
                        (bytes[j] != 0x0D)) {
                    j++;
                }

                if (globalConfig.getConnDebug()) {
                    EventLogger.logEvent(AppInfo.GUID,
                            ("[SEND] " + s.substring(i, j)).getBytes(),
                            EventLogger.DEBUG_INFO);
                }

                /**
                 * Write the string up to there and terminate it properly.
                 */
                byte[] buf = (s.substring(i, j) + "\r\n").getBytes();
                output.write(buf);
                bytesSent += buf.length;

                /**
                 * If we stopped at a CR, ignore a possibly following LF.
                 */
                if ((j < (length - 1)) && (bytes[j] == 0x0D) &&
                        (bytes[j + 1] == 0x0A)) {
                    j++;
                }

                i = j + 1;
            }
        }

        output.flush();
    }

    /**
     * Sends a string to the server, terminating it with a CRLF.
     * No cleanup is performed, as it is expected that the string
     * is a prepared protocol command.
     */
    public synchronized void sendCommand(String s) throws IOException {
        if (globalConfig.getConnDebug()) {
            EventLogger.logEvent(AppInfo.GUID, ("[SEND CMD] " + s).getBytes(),
                    EventLogger.DEBUG_INFO);
        }

        if (s == null) {
            output.write(CRLF, 0, 2);
            bytesSent += 2;
        } else {
            byte[] buf = (s + "\r\n").getBytes();
            output.write(buf);
            bytesSent += buf.length;
        }

        output.flush();
    }

    /**
     * Sends a string to the server. This method is used to bypass all
     * the processing done by the normal send method, and is most useful
     * for bulk transmissions.  It writes the provided string to the socket
     * in a single command, followed by a flush.
     *
     * @see #send
     */
    public synchronized void sendRaw(String s) throws IOException {
        byte[] buf = s.getBytes();

        if (globalConfig.getConnDebug()) {
            EventLogger.logEvent(AppInfo.GUID,
                    ("[SEND RAW]\r\n" + s).getBytes(), EventLogger.DEBUG_INFO);
        }

        output.write(buf, 0, buf.length);
        bytesSent += buf.length;

        output.flush();
    }

    /**
     * Returns the number of bytes available for reading.
     * Used to poll the connection without blocking.
     *
     * @see InputStream#available()
     */
    public int available() throws IOException {
        if (fakeAvailable == -1) {
            return input.available();
        } else {
            return fakeAvailable;
        }
    }

    /**
     * Receives a string from the server. This method is used internally for
     * incoming communication from the server. The main thing it does is
     * ensuring that only complete lines are returned to the application, that is,
     * lines that were terminated at least by a CR. LFs are ignored completely.
     * Neither CRs nor LFs are returned as part of the result.
     *
     * @see #send
     */
    public synchronized String receive() throws IOException {
        /**
         * A note on how this method works and why it is designed the
         * way it is: A previous implementation tried to read multiple
         * bytes from the InputStream, searched a possible line terminator
         * in them, and appended characters to a temporary result string.
         * That didn't work very well, because the code had to deal
         * with a large number of temporary strings that grew as more
         * characters belonging to a line were read. The result was
         * a high level of heap fragmentation, which made applications
         * unstable on MIDP devices (that don't provide compacting GC,
         * that is).
         *
         * This new implementation seems to work better: Is reads
         * characters from the InputStream one-by-one, putting them
         * in a buffer of fixed size that is large enough to hold a
         * "normal" line belonging to an e-mail. When a terminator
         * is found, a new String object is created from that buffer.
         * Since the buffer is of fixed size and used during the whole
         * lifetime of the Connection object, and the String is the
         * actual String that makes it into the final Message object,
         * there are no temporary Strings needed -- at least not in the
         * common case: If a mail server tends to send whole messages
         * without line terminators (and thus disregards for example
         * the POP3 specification that dictates a maximum response of
         * 512 characters), temporary Strings will again be necessary,
         * but there's not much one can about that.
         */
        boolean stop = false;
        resultBuffer.reset();

        int actualAvailable = input.available();
        int readBytes = 0;
        int count;

        /**
         * The "stop" flag will be set as soon as we have received
         * a complete line, that is, a line terminated by CR/LF. Until
         * this is the case, the following block is repeated.
         */
        while (!stop) {
            count = 0;

            /**
             * The inner block reads single bytes from the InputStream
             * until, again, a line terminator is read or the buffer is
             * full.
             */
            while (true) {
                int actual = input.read(buffer, count, 1);

                /**
                 * If -1 is returned, the InputStream is already closed,
                 * probably because the connection is broken, or the server
                 * didn't like is. Try to close the connection, but ignore
                 * any errors that might result from this.
                 */
                if (actual == -1) {
                    EventLogger.logEvent(AppInfo.GUID,
                            "Unable to read from socket, closing connection".getBytes(),
                            EventLogger.INFORMATION);

                    try {
                        close();
                    } catch (IOException e) {
                    }

                    throw new IOException("Connection closed");
                }
                /**
                 * If no bytes have been received, we wait a little
                 * while (by yielding processing time to other threads).
                 */
                else if (actual == 0) {
                    try {
                        Thread.yield();
                    } catch (Exception e) {
                    }
                }
                /**
                 * If a byte has been read, examine it and put it in the
                 * buffer.
                 */

                // Note: We really should look for CRLF, and not use this
                // approach which screws up on mid-line LFs. (DK)
                else {
                    bytesReceived += actual;

                    byte b = buffer[count];
                    readBytes++;

                    /**
                     * Ignore all CRs.
                     */
                    if (b == 0x0D) {
                        /* Ignore CRs */
                    }
                    /**
                     * Take LF as line separator.
                     */
                    else if (b == 0x0A) {
                        stop = true;

                        break;
                    }
                    /**
                     * Everything else makes it into the buffer.
                     */
                    else {
                        count++;

                        if (count == buffer.length) {
                            break;
                        }
                    }
                }
            }

            resultBuffer.write(buffer, 0, count);
        }

        String result = new String(resultBuffer.toArray());

        if (globalConfig.getConnDebug()) {
            EventLogger.logEvent(AppInfo.GUID,
                    ("[RECV] " + result).getBytes(),
                    EventLogger.DEBUG_INFO);
        }

        if (actualAvailable > readBytes) {
            fakeAvailable = actualAvailable - readBytes;
        } else {
            fakeAvailable = -1;
        }

        return result;
    }

    /**
     * Switches the underlying connection to SSL mode, as commonly done after
     * sending a <tt>STARTTLS</tt> command to the server.
     * 
     * @throws IOException Signals that an I/O exception has occurred.
     */
    public void startTLS() throws IOException {
        // Shortcut the method if we're already in SSL mode
        if(socket instanceof TLS10Connection) { return; }

        try {
            TLS10Connection tlsSocket = new TLS10Connection(
                    new StreamConnectionWrapper(
                            socket,
                            (DataInputStream)input,
                            (DataOutputStream)output),
                            serverName + ':' + serverPort,
                            true);

            socket = tlsSocket;
            input = socket.openDataInputStream();
            output = socket.openDataOutputStream();
        } catch (IOException e) {
            EventLogger.logEvent(AppInfo.GUID,
                    ("Unable to switch to TLS mode: " + e.getMessage()).getBytes(), EventLogger.ERROR);
            throw new IOException("Unable to switch to TLS mode");
        } catch (TLSException e) {
            EventLogger.logEvent(AppInfo.GUID,
                    ("Unable to switch to TLS mode: " + e.getMessage()).getBytes(), EventLogger.ERROR);
            throw new IOException("Unable to switch to TLS mode");
        }
    }

    /**
     * Decorator to wrap an existing stream connection so its I/O streams
     * can be reopened without throwing exceptions.
     */
    private static class StreamConnectionWrapper implements StreamConnection {
        private StreamConnection stream;
        private DataInputStream dataInputStream;
        private DataOutputStream dataOutputStream;

        public StreamConnectionWrapper(StreamConnection stream, DataInputStream dataInputStream, DataOutputStream dataOutputStream) {
            this.stream = stream;
            this.dataInputStream = dataInputStream;
            this.dataOutputStream = dataOutputStream;
        }

        public DataInputStream openDataInputStream() throws IOException {
            return dataInputStream;
        }
        public InputStream openInputStream() throws IOException {
            return dataInputStream;
        }
        public void close() throws IOException {
            stream.close();
        }
        public DataOutputStream openDataOutputStream() throws IOException {
            return dataOutputStream;
        }
        public OutputStream openOutputStream() throws IOException {
            return dataOutputStream;
        }
    }
}