/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed 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.
 */

package com.android.email.mail.store;

import android.content.Context;
import android.text.TextUtils;
import android.util.Base64DataException;

import com.android.email.DebugUtils;
import com.android.email.mail.store.ImapStore.ImapException;
import com.android.email.mail.store.ImapStore.ImapMessage;
import com.android.email.mail.store.imap.ImapConstants;
import com.android.email.mail.store.imap.ImapElement;
import com.android.email.mail.store.imap.ImapList;
import com.android.email.mail.store.imap.ImapResponse;
import com.android.email.mail.store.imap.ImapString;
import com.android.email.mail.store.imap.ImapUtility;
import com.android.email.service.ImapService;
import com.android.emailcommon.Logging;
import com.android.emailcommon.internet.BinaryTempFileBody;
import com.android.emailcommon.internet.MimeBodyPart;
import com.android.emailcommon.internet.MimeHeader;
import com.android.emailcommon.internet.MimeMultipart;
import com.android.emailcommon.internet.MimeUtility;
import com.android.emailcommon.mail.AuthenticationFailedException;
import com.android.emailcommon.mail.Body;
import com.android.emailcommon.mail.FetchProfile;
import com.android.emailcommon.mail.Flag;
import com.android.emailcommon.mail.Folder;
import com.android.emailcommon.mail.Message;
import com.android.emailcommon.mail.MessagingException;
import com.android.emailcommon.mail.Part;
import com.android.emailcommon.provider.Mailbox;
import com.android.emailcommon.service.SearchParams;
import com.android.emailcommon.utility.CountingOutputStream;
import com.android.emailcommon.utility.EOLConvertingOutputStream;
import com.android.emailcommon.utility.Utility;
import com.android.mail.utils.LogUtils;
import com.google.common.annotations.VisibleForTesting;

import static com.android.emailcommon.Logging.LOG_TAG;

import org.apache.commons.io.IOUtils;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.SocketTimeoutException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.TimeZone;

public class ImapFolder extends Folder {
    private final static Flag[] PERMANENT_FLAGS =
        { Flag.DELETED, Flag.SEEN, Flag.FLAGGED, Flag.ANSWERED };
    private static final int COPY_BUFFER_SIZE = 16*1024;

    public interface IdleCallback {
        /**
         * Invoked when the connection enters idle mode
         */
        public void onIdled();
        /**
         * Invoked when idle state is left
         */
        public void onIdlingDone();
        /**
         * Invoked when a new change is communicated by the server.
         *
         * @param needSync whether a sync is required
         * @param fetchMessages list of message UIDs to update
         */
        public void onNewServerChange(boolean needSync, List<String> fetchMessages);
        /**
         * Connection to socket timed out. The idle connection needs
         * to be considered broken when this is called.
         */
        public void onTimeout();
        /**
         * Something went wrong while waiting for push data.
         *
         * @param ex the exception detected
         */
        public void onException(MessagingException ex);
    }

    private final ImapStore mStore;
    private final String mName;
    private int mMessageCount = -1;
    private ImapConnection mConnection;
    private OpenMode mMode;
    private boolean mExists;
    /** The local mailbox associated with this remote folder */
    Mailbox mMailbox;
    /** A set of hashes that can be used to track dirtiness */
    Object mHash[];

    private final Object mIdleSync = new Object();
    private boolean mIdling;
    private boolean mIdlingCancelled;
    private boolean mDiscardIdlingConnection;
    private Thread mIdleReader;

    private static final String[] IDLE_STATUSES = {
        ImapConstants.UIDVALIDITY, ImapConstants.UIDNEXT
    };
    private Map<String, String> mIdleStatuses = new HashMap<>();

    private static class ImapIdleChanges {
        public boolean mRequiredSync = false;
        public ArrayList<String> mMessageToFetch = new ArrayList<>();
    }

    /*package*/ ImapFolder(ImapStore store, String name) {
        mStore = store;
        mName = name;
    }

    private void destroyResponses() {
        if (mConnection != null) {
            mConnection.destroyResponses();
        }
    }

    @Override
    public void open(OpenMode mode)
            throws MessagingException {
        try {
            if (isOpen()) {
                if (mMode == mode) {
                    // Make sure the connection is valid.
                    // If it's not we'll close it down and continue on to get a new one.
                    try {
                        mConnection.executeSimpleCommand(ImapConstants.NOOP);
                        return;

                    } catch (IOException ioe) {
                        ioExceptionHandler(mConnection, ioe);
                    } finally {
                        destroyResponses();
                    }
                } else {
                    // Return the connection to the pool, if exists.
                    close(false);
                }
            }
            synchronized (this) {
                mConnection = mStore.getConnection();
            }
            // * FLAGS (\Answered \Flagged \Deleted \Seen \Draft NonJunk
            // $MDNSent)
            // * OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft
            // NonJunk $MDNSent \*)] Flags permitted.
            // * 23 EXISTS
            // * 0 RECENT
            // * OK [UIDVALIDITY 1125022061] UIDs valid
            // * OK [UIDNEXT 57576] Predicted next UID
            // 2 OK [READ-WRITE] Select completed.
            try {
                mConnection.setTransportTag(mName + "-" + hashCode());
                doSelect();
            } catch (IOException ioe) {
                throw ioExceptionHandler(mConnection, ioe);
            } finally {
                destroyResponses();
            }
        } catch (AuthenticationFailedException e) {
            // Don't cache this connection, so we're forced to try connecting/login again
            mConnection = null;
            close(false);
            throw e;
        } catch (MessagingException e) {
            mExists = false;
            close(false);
            throw e;
        }
    }

    @Override
    @VisibleForTesting
    public boolean isOpen() {
        return mExists && mConnection != null;
    }

    @Override
    public OpenMode getMode() {
        return mMode;
    }

    @Override
    public void close(boolean expunge) {
        // TODO implement expunge
        mMessageCount = -1;
        synchronized (this) {
            mStore.poolConnection(mConnection);
            mConnection = null;
        }
    }

    @Override
    public String getName() {
        return mName;
    }

    public void startIdling(final IdleCallback callback) throws MessagingException {
        LogUtils.d(LOG_TAG, "startIdling on folder " + mName);
        checkOpen();
        synchronized (mIdleSync) {
            if (mIdling) {
                throw new MessagingException("Folder " + mName + " is in IDLE state already.");
            }
            mIdling = true;
            mIdlingCancelled = false;
            mDiscardIdlingConnection = false;
        }

        final ImapConnection connection;
        synchronized (this) {
            connection = mConnection;
        }

        // Run idle in background
        mIdleReader = new Thread() {
            @Override
            public void run() {
                try {
                    // Get some info before start idling
                    mIdleStatuses = getStatuses(IDLE_STATUSES);

                    // We setup the max time specified in RFC 2177 to re-issue
                    // an idle request to the server
                    connection.setReadTimeout(ImapConnection.PING_IDLE_TIMEOUT);
                    connection.destroyResponses();

                    // Enter now in idle status (we hold a connection with
                    // the server to listen for new changes)
                    synchronized (mIdleSync) {
                        if (mIdlingCancelled) {
                            mIdling = false;
                            return;
                        }
                    }

                    if (callback != null) {
                        callback.onIdled();
                    }
                    List<ImapResponse> responses = connection.executeIdleCommand();

                    // Check whether IDLE was successful (first response is an idling response)
                    if (responses.isEmpty() || (mIdling && !responses.get(0).isIdling())) {
                        if (callback != null) {
                            callback.onException(new MessagingException(
                                            MessagingException.SERVER_ERROR, "Cannot idle"));
                        }
                        synchronized (mIdleSync) {
                            mIdling = false;
                        }
                        return;
                    }

                    // Exit idle if we are still in that state
                    boolean cancelled = false;
                    boolean discardConnection = false;
                    synchronized (mIdleSync) {
                        if (!mIdlingCancelled) {
                            try {
                                connection.setReadTimeout(ImapConnection.DONE_TIMEOUT);
                                connection.executeSimpleCommand(ImapConstants.DONE);
                            } catch (MessagingException me) {
                                // Ignore this exception caused by messages in the queue
                            }
                        }

                        cancelled = mIdlingCancelled;
                        discardConnection = mDiscardIdlingConnection;
                    }

                    if (!cancelled && callback != null) {
                        // Notify that new changes exists in the server. Remove
                        // the idling status response since is only relevant for the protocol
                        // We have to enter in idle
                        ImapIdleChanges changes = extractImapChanges(
                                new ArrayList<Object>(responses.subList(1, responses.size())));
                        callback.onNewServerChange(changes.mRequiredSync, changes.mMessageToFetch);
                    }

                    if (discardConnection) {
                        // Return the connection to the pool
                        cleanupConnection(connection, false);
                    }

                    synchronized (mIdleSync) {
                        mIdling = false;
                    }

                    if (callback != null) {
                        callback.onIdlingDone();
                    }
                } catch (MessagingException me) {
                    cleanupConnection(connection, false);
                    synchronized (mIdleSync) {
                        mIdling = false;
                    }
                    if (callback != null) {
                        callback.onException(me);
                    }

                } catch (SocketTimeoutException ste) {
                    cleanupConnection(connection, false);
                    synchronized (mIdleSync) {
                        mIdling = false;
                    }
                    if (callback != null) {
                        callback.onTimeout();
                    }

                } catch (IOException ioe) {
                    synchronized (mIdleSync) {
                        mIdling = false;
                    }
                    if (callback != null) {
                        callback.onException(ioExceptionHandler(connection, ioe));
                    } else {
                        cleanupConnection(connection, false);
                    }

                }
            }
        };
        mIdleReader.setName("IdleReader " + mStore.getAccount().mId + ":" + mName);
        mIdleReader.start();
    }

    public void stopIdling(boolean discardConnection) throws MessagingException {
        LogUtils.d(LOG_TAG, "stopIdling on folder " + mName);
        if (!isOpen()) {
            throw new MessagingException("Folder " + mName + " is not open.");
        }

        final ImapConnection connection;
        synchronized (this) {
            connection = mConnection;
        }

        synchronized (mIdleSync) {
            if (!mIdling) {
                throw new MessagingException("Folder " + mName + " isn't in IDLE state.");
            }
            try {
                mIdlingCancelled = true;
                mDiscardIdlingConnection = discardConnection;
                // Send the DONE command to make the idle reader thread exit. Shorten
                // the read timeout for doing that in order to not wait indefinitely,
                // the server should respond to the DONE command quickly anyway
                connection.sendCommand(ImapConstants.DONE, false);

            } catch (MessagingException me) {
                // Treat IOERROR messaging exception as IOException
                if (me.getExceptionType() == MessagingException.IOERROR) {
                    cleanupConnection(connection, false);
                    throw me;
                }

            } catch (IOException ioe) {
                throw ioExceptionHandler(mConnection, ioe);

            }
        }

        // Try to join the thread, but make sure to not wait indefinitely. This should
        // be the normal case (server sends the response to DONE quickly)
        try {
            mIdleReader.join(1000, 0);
        } catch (InterruptedException e) {
            // ignore
        }
        // In case the server didn't respond quickly, the connection is likely broken;
        // close it (which definitely will cause the thread to return) and finally join the thread
        if (mIdleReader.isAlive()) {
            cleanupConnection(connection, true);
            try {
                mIdleReader.join();
            } catch (InterruptedException e) {
                // ignore
            }
        }
    }

    public boolean isIdling() {
        synchronized (mIdleSync) {
            return mIdling;
        }
    }

    @Override
    public boolean exists() throws MessagingException {
        if (mExists) {
            return true;
        }
        /*
         * This method needs to operate in the unselected mode as well as the selected mode
         * so we must get the connection ourselves if it's not there. We are specifically
         * not calling checkOpen() since we don't care if the folder is open.
         */
        ImapConnection connection = null;
        synchronized(this) {
            if (mConnection == null) {
                connection = mStore.getConnection();
            } else {
                connection = mConnection;
            }
        }
        try {
            connection.executeSimpleCommand(String.format(Locale.US,
                    ImapConstants.STATUS + " \"%s\" (" + ImapConstants.UIDVALIDITY + ")",
                    ImapStore.encodeFolderName(mName, mStore.mPathPrefix)));
            mExists = true;
            return true;

        } catch (MessagingException me) {
            // Treat IOERROR messaging exception as IOException
            if (me.getExceptionType() == MessagingException.IOERROR) {
                throw me;
            }
            return false;

        } catch (IOException ioe) {
            throw ioExceptionHandler(connection, ioe);

        } finally {
            connection.destroyResponses();
            if (mConnection == null) {
                mStore.poolConnection(connection);
            }
        }
    }

    // IMAP supports folder creation
    @Override
    public boolean canCreate(FolderType type) {
        return true;
    }

    @Override
    public boolean create(FolderType type) throws MessagingException {
        /*
         * This method needs to operate in the unselected mode as well as the selected mode
         * so we must get the connection ourselves if it's not there. We are specifically
         * not calling checkOpen() since we don't care if the folder is open.
         */
        ImapConnection connection = null;
        synchronized(this) {
            if (mConnection == null) {
                connection = mStore.getConnection();
            } else {
                connection = mConnection;
            }
        }
        try {
            connection.executeSimpleCommand(String.format(Locale.US,
                    ImapConstants.CREATE + " \"%s\"",
                    ImapStore.encodeFolderName(mName, mStore.mPathPrefix)));
            return true;

        } catch (MessagingException me) {
            return false;

        } catch (IOException ioe) {
            throw ioExceptionHandler(connection, ioe);

        } finally {
            connection.destroyResponses();
            if (mConnection == null) {
                mStore.poolConnection(connection);
            }
        }
    }

    @Override
    public void copyMessages(Message[] messages, Folder folder,
            MessageUpdateCallbacks callbacks) throws MessagingException {
        checkOpen();
        try {
            List<ImapResponse> responseList = mConnection.executeSimpleCommand(
                    String.format(Locale.US, ImapConstants.UID_COPY + " %s \"%s\"",
                            ImapStore.joinMessageUids(messages),
                            ImapStore.encodeFolderName(folder.getName(), mStore.mPathPrefix)));
            // Build a message map for faster UID matching
            HashMap<String, Message> messageMap = new HashMap<String, Message>();
            boolean handledUidPlus = false;
            for (Message m : messages) {
                messageMap.put(m.getUid(), m);
            }
            // Process response to get the new UIDs
            for (ImapResponse response : responseList) {
                // All "BAD" responses are bad. Only "NO", tagged responses are bad.
                if (response.isBad() || (response.isNo() && response.isTagged())) {
                    String responseText = response.getStatusResponseTextOrEmpty().getString();
                    throw new MessagingException(responseText);
                }
                // Skip untagged responses; they're just status
                if (!response.isTagged()) {
                    continue;
                }
                // No callback provided to report of UID changes; nothing more to do here
                // NOTE: We check this here to catch any server errors
                if (callbacks == null) {
                    continue;
                }
                ImapList copyResponse = response.getListOrEmpty(1);
                String responseCode = copyResponse.getStringOrEmpty(0).getString();
                if (ImapConstants.COPYUID.equals(responseCode)) {
                    handledUidPlus = true;
                    String origIdSet = copyResponse.getStringOrEmpty(2).getString();
                    String newIdSet = copyResponse.getStringOrEmpty(3).getString();
                    String[] origIdArray = ImapUtility.getImapSequenceValues(origIdSet);
                    String[] newIdArray = ImapUtility.getImapSequenceValues(newIdSet);
                    // There has to be a 1:1 mapping between old and new IDs
                    if (origIdArray.length != newIdArray.length) {
                        throw new MessagingException("Set length mis-match; orig IDs \"" +
                                origIdSet + "\"  new IDs \"" + newIdSet + "\"");
                    }
                    for (int i = 0; i < origIdArray.length; i++) {
                        final String id = origIdArray[i];
                        final Message m = messageMap.get(id);
                        if (m != null) {
                            callbacks.onMessageUidChange(m, newIdArray[i]);
                        }
                    }
                }
            }
            // If the server doesn't support UIDPLUS, try a different way to get the new UID(s)
            if (callbacks != null && !handledUidPlus) {
                final ImapFolder newFolder = (ImapFolder)folder;
                try {
                    // Temporarily select the destination folder
                    newFolder.open(OpenMode.READ_WRITE);
                    // Do the search(es) ...
                    for (Message m : messages) {
                        final String searchString =
                                "HEADER Message-Id \"" + m.getMessageId() + "\"";
                        final String[] newIdArray = newFolder.searchForUids(searchString);
                        if (newIdArray.length == 1) {
                            callbacks.onMessageUidChange(m, newIdArray[0]);
                        }
                    }
                } catch (MessagingException e) {
                    // Log, but, don't abort; failures here don't need to be propagated
                    LogUtils.d(Logging.LOG_TAG, "Failed to find message", e);
                } finally {
                    newFolder.close(false);
                }
                // Re-select the original folder
                doSelect();
            }
        } catch (IOException ioe) {
            throw ioExceptionHandler(mConnection, ioe);
        } finally {
            destroyResponses();
        }
    }

    @Override
    public int getMessageCount() {
        synchronized (this) {
            return mMessageCount;
        }
    }

    @Override
    public int getUnreadMessageCount() throws MessagingException {
        checkOpen();
        try {
            int unreadMessageCount = 0;
            final List<ImapResponse> responses = mConnection.executeSimpleCommand(
                    String.format(Locale.US,
                            ImapConstants.STATUS + " \"%s\" (" + ImapConstants.UNSEEN + ")",
                            ImapStore.encodeFolderName(mName, mStore.mPathPrefix)));
            // S: * STATUS mboxname (MESSAGES 231 UIDNEXT 44292)
            for (ImapResponse response : responses) {
                if (response.isDataResponse(0, ImapConstants.STATUS)) {
                    unreadMessageCount = response.getListOrEmpty(2)
                            .getKeyedStringOrEmpty(ImapConstants.UNSEEN).getNumberOrZero();
                }
            }
            return unreadMessageCount;
        } catch (IOException ioe) {
            throw ioExceptionHandler(mConnection, ioe);
        } finally {
            destroyResponses();
        }
    }

    public Map<String, String> getStatuses(String[] statuses) throws MessagingException {
        checkOpen();
        Map<String, String> allReturnStatuses = new HashMap<>();
        try {
            String flags = TextUtils.join(" ", statuses);
            final List<ImapResponse> responses = mConnection.executeSimpleCommand(
                    String.format(Locale.US,
                            ImapConstants.STATUS + " \"%s\" (%s)",
                            ImapStore.encodeFolderName(mName, mStore.mPathPrefix), flags));
            // S: * STATUS mboxname (MESSAGES 231 UIDNEXT 44292)
            for (ImapResponse response : responses) {
                if (response.isDataResponse(0, ImapConstants.STATUS)) {
                    ImapList list = response.getListOrEmpty(2);
                    int count = list.size();
                    for (int i = 0; i < count; i += 2) {
                        String key = list.getStringOrEmpty(i).getString();
                        String value = list.getStringOrEmpty(i + 1).getString();
                        allReturnStatuses.put(key, value);
                    }
                }
            }
        } catch (IOException ioe) {
            throw ioExceptionHandler(mConnection, ioe);
        } finally {
            destroyResponses();
        }
        return allReturnStatuses;
    }

    private void cleanupConnection(ImapConnection connection, boolean close) {
        if (close) {
            connection.close();
        }
        synchronized (this) {
            if (connection == mConnection) {
                if (close) {
                    // To prevent close() from returning the connection to the pool
                    mConnection = null;
                }
                close(false);
            }
        }
    }

    private List<String> getNewMessagesFromUid(String uid) throws MessagingException {
        checkOpen();
        List<String> nextMSNs = new ArrayList<>();
        try {
            final List<ImapResponse> responses = mConnection.executeSimpleCommand(
                    ImapConstants.SEARCH + " " + ImapConstants.UID + " " + uid + ":*");
            // S: * SEARCH 1 2 3
            for (ImapResponse response : responses) {
                if (response.isDataResponse(0, ImapConstants.SEARCH)) {
                    int count = response.size();
                    for (int i = 1; i < count; i++) {
                        nextMSNs.add(response.getStringOrEmpty(i).getString());
                    }
                }
            }
        } catch (IOException ioe) {
            throw ioExceptionHandler(mConnection, ioe);
        } finally {
            destroyResponses();
        }
        return nextMSNs;
    }

    @Override
    public void delete(boolean recurse) {
        throw new Error("ImapStore.delete() not yet implemented");
    }

    String[] getSearchUids(List<ImapResponse> responses) {
        // S: * SEARCH 2 3 6
        final ArrayList<String> uids = new ArrayList<String>();
        for (ImapResponse response : responses) {
            if (!response.isDataResponse(0, ImapConstants.SEARCH)) {
                continue;
            }
            // Found SEARCH response data
            for (int i = 1; i < response.size(); i++) {
                ImapString s = response.getStringOrEmpty(i);
                if (s.isString()) {
                    uids.add(s.getString());
                }
            }
        }
        return uids.toArray(Utility.EMPTY_STRINGS);
    }

    String[] searchForUids(String searchCriteria) throws MessagingException {
        return searchForUids(searchCriteria, true);
    }

    /**
     * I'm not a fan of having a parameter that determines whether to throw exceptions or
     * consume them, but getMessage() for a date range needs to differentiate between
     * a failure and just a legitimate empty result.
     * See b/11183568.
     * TODO:
     * Either figure out how to make getMessage() with a date range work without this
     * exception information, or make all users of searchForUids() handle the ImapException.
     * It's too late in the release cycle to add this risk right now.
     */
    @VisibleForTesting
    String[] searchForUids(String searchCriteria, boolean swallowException)
            throws MessagingException {
        checkOpen();
        try {
            try {
                final String command = ImapConstants.UID_SEARCH + " " + searchCriteria;
                final String[] result = getSearchUids(mConnection.executeSimpleCommand(command));
                LogUtils.d(Logging.LOG_TAG, "searchForUids '" + searchCriteria + "' results: " +
                        result.length);
                return result;
            } catch (ImapException me) {
                LogUtils.d(Logging.LOG_TAG, me, "ImapException in search: " + searchCriteria);
                if (swallowException) {
                    return Utility.EMPTY_STRINGS; // Not found
                } else {
                    throw me;
                }
            } catch (IOException ioe) {
                LogUtils.d(Logging.LOG_TAG, ioe, "IOException in search: " + searchCriteria);
                throw ioExceptionHandler(mConnection, ioe);
            }
        } finally {
            destroyResponses();
        }
    }

    @Override
    @VisibleForTesting
    public Message getMessage(String uid) throws MessagingException {
        checkOpen();

        final String[] uids = searchForUids(ImapConstants.UID + " " + uid);
        for (int i = 0; i < uids.length; i++) {
            if (uids[i].equals(uid)) {
                return new ImapMessage(uid, this);
            }
        }
        return null;
    }

    @VisibleForTesting
    protected static boolean isAsciiString(String str) {
        int len = str.length();
        for (int i = 0; i < len; i++) {
            char c = str.charAt(i);
            if (c >= 128) return false;
        }
        return true;
    }

    /**
     * Retrieve messages based on search parameters.  We search FROM, TO, CC, SUBJECT, and BODY
     * We send: SEARCH OR FROM "foo" (OR TO "foo" (OR CC "foo" (OR SUBJECT "foo" BODY "foo"))), but
     * with the additional CHARSET argument and sending "foo" as a literal (e.g. {3}<CRLF>foo}
     */
    @Override
    @VisibleForTesting
    public Message[] getMessages(SearchParams params, MessageRetrievalListener listener)
            throws MessagingException {
        List<String> commands = new ArrayList<String>();
        final String filter = params.mFilter;
        // All servers MUST accept US-ASCII, so we'll send this as the CHARSET unless we're really
        // dealing with a string that contains non-ascii characters
        String charset = "US-ASCII";
        if (!isAsciiString(filter)) {
            charset = "UTF-8";
        }
        // This is the length of the string in octets (bytes), formatted as a string literal {n}
        final String octetLength = "{" + filter.getBytes().length + "}";
        // Break the command up into pieces ending with the string literal length
        commands.add(ImapConstants.UID_SEARCH + " CHARSET " + charset + " OR FROM " + octetLength);
        commands.add(filter + " (OR TO " + octetLength);
        commands.add(filter + " (OR CC " + octetLength);
        commands.add(filter + " (OR SUBJECT " + octetLength);
        commands.add(filter + " BODY " + octetLength);
        commands.add(filter + ")))");
        return getMessagesInternal(complexSearchForUids(commands), listener);
    }

    /* package */ String[] complexSearchForUids(List<String> commands) throws MessagingException {
        checkOpen();
        try {
            try {
                return getSearchUids(mConnection.executeComplexCommand(commands, false));
            } catch (ImapException e) {
                return Utility.EMPTY_STRINGS; // not found;
            } catch (IOException ioe) {
                throw ioExceptionHandler(mConnection, ioe);
            }
        } finally {
            destroyResponses();
        }
    }

    @Override
    @VisibleForTesting
    public Message[] getMessages(int start, int end, MessageRetrievalListener listener)
            throws MessagingException {
        if (start < 1 || end < 1 || end < start) {
            throw new MessagingException(String.format("Invalid range: %d %d", start, end));
        }
        LogUtils.d(Logging.LOG_TAG, "getMessages number " + start + " - " + end);
        return getMessagesInternal(
                searchForUids(String.format(Locale.US, "%d:%d NOT DELETED", start, end)), listener);
    }

    private String generateDateRangeCommand(final long startDate, final long endDate,
            boolean useQuotes)
            throws MessagingException {
        // Dates must be formatted like: 7-Feb-1994. Time info within a date is not
        // universally supported.
        // XXX can I limit the maximum number of results?
        final SimpleDateFormat formatter = new SimpleDateFormat("dd-LLL-yyyy", Locale.US);
        formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
        final String sinceDateStr = formatter.format(endDate);

        StringBuilder queryParam = new StringBuilder();
        queryParam.append( "1:* ");
        // If the caller requests a startDate of zero, then ignore the BEFORE parameter.
        // This makes sure that we can always query for the newest messages, even if our
        // time is different from the imap server's time.
        if (startDate != 0) {
            final String beforeDateStr = formatter.format(startDate);
            if (startDate < endDate) {
                throw new MessagingException(String.format("Invalid date range: %s - %s",
                        sinceDateStr, beforeDateStr));
            }
            queryParam.append("BEFORE ");
            if (useQuotes) queryParam.append('\"');
            queryParam.append(beforeDateStr);
            if (useQuotes) queryParam.append('\"');
            queryParam.append(" ");
        }
        queryParam.append("SINCE ");
        if (useQuotes) queryParam.append('\"');
        queryParam.append(sinceDateStr);
        if (useQuotes) queryParam.append('\"');

        return queryParam.toString();
    }

    @Override
    @VisibleForTesting
    public Message[] getMessages(long startDate, long endDate, MessageRetrievalListener listener)
            throws MessagingException {
        String [] uids = null;
        String command = generateDateRangeCommand(startDate, endDate, false)
                + " NOT DELETED";
        LogUtils.d(Logging.LOG_TAG, "getMessages dateRange " + command.toString());

        try {
            uids = searchForUids(command.toString(), false);
        } catch (ImapException e) {
            // TODO: This is a last minute hack to make certain servers work. Some servers
            // demand that the date in the date range be surrounded by double quotes, other
            // servers won't accept that. So if we can an ImapException using one method,
            // try the other.
            // See b/11183568
            LogUtils.d(Logging.LOG_TAG, e, "query failed %s, trying alternate",
                    command.toString());
            command = generateDateRangeCommand(startDate, endDate, true)
                    + " NOT DELETED";
            try {
                uids = searchForUids(command, true);
            } catch (ImapException e2) {
                LogUtils.w(Logging.LOG_TAG, e2, "query failed %s, fatal", command);
                uids = null;
            }
        }
        return getMessagesInternal(uids, listener);
    }

    @Override
    @VisibleForTesting
    public Message[] getMessages(String[] uids, MessageRetrievalListener listener)
            throws MessagingException {
        if (uids == null) {
            uids = searchForUids("1:* NOT DELETED");
        }
        return getMessagesInternal(uids, listener);
    }

    public Message[] getMessagesInternal(String[] uids, MessageRetrievalListener listener) {
        final ArrayList<Message> messages = new ArrayList<Message>(uids.length);
        for (int i = 0; i < uids.length; i++) {
            final String uid = uids[i];
            final ImapMessage message = new ImapMessage(uid, this);
            messages.add(message);
            if (listener != null) {
                listener.messageRetrieved(message);
            }
        }
        return messages.toArray(Message.EMPTY_ARRAY);
    }

    @Override
    public void fetch(Message[] messages, FetchProfile fp, MessageRetrievalListener listener)
            throws MessagingException {
        try {
            fetchInternal(messages, fp, listener);
        } catch (RuntimeException e) { // Probably a parser error.
            LogUtils.w(Logging.LOG_TAG, "Exception detected: " + e.getMessage());
            if (mConnection != null) {
                mConnection.logLastDiscourse();
            }
            throw e;
        }
    }

    public void fetchInternal(Message[] messages, FetchProfile fp,
            MessageRetrievalListener listener) throws MessagingException {
        if (messages.length == 0) {
            return;
        }
        checkOpen();
        HashMap<String, Message> messageMap = new HashMap<String, Message>();
        for (Message m : messages) {
            messageMap.put(m.getUid(), m);
        }

        /*
         * Figure out what command we are going to run:
         * FLAGS     - UID FETCH (FLAGS)
         * ENVELOPE  - UID FETCH (INTERNALDATE UID RFC822.SIZE FLAGS BODY.PEEK[
         *                            HEADER.FIELDS (date subject from content-type to cc)])
         * STRUCTURE - UID FETCH (BODYSTRUCTURE)
         * BODY_SANE - UID FETCH (BODY.PEEK[]<0.N>) where N = max bytes returned
         * BODY      - UID FETCH (BODY.PEEK[])
         * Part      - UID FETCH (BODY.PEEK[ID]) where ID = mime part ID
         */

        final LinkedHashSet<String> fetchFields = new LinkedHashSet<String>();

        fetchFields.add(ImapConstants.UID);
        if (fp.contains(FetchProfile.Item.FLAGS)) {
            fetchFields.add(ImapConstants.FLAGS);
        }
        if (fp.contains(FetchProfile.Item.ENVELOPE)) {
            fetchFields.add(ImapConstants.INTERNALDATE);
            fetchFields.add(ImapConstants.RFC822_SIZE);
            fetchFields.add(ImapConstants.FETCH_FIELD_HEADERS);
        }
        if (fp.contains(FetchProfile.Item.STRUCTURE)) {
            fetchFields.add(ImapConstants.BODYSTRUCTURE);
        }

        if (fp.contains(FetchProfile.Item.BODY_SANE)) {
            fetchFields.add(ImapConstants.FETCH_FIELD_BODY_PEEK_SANE);
        }
        if (fp.contains(FetchProfile.Item.BODY)) {
            fetchFields.add(ImapConstants.FETCH_FIELD_BODY_PEEK);
        }

        // TODO Why are we only fetching the first part given?
        final Part fetchPart = fp.getFirstPart();
        if (fetchPart != null) {
            final String[] partIds =
                    fetchPart.getHeader(MimeHeader.HEADER_ANDROID_ATTACHMENT_STORE_DATA);
            // TODO Why can a single part have more than one Id? And why should we only fetch
            // the first id if there are more than one?
            if (partIds != null) {
                fetchFields.add(ImapConstants.FETCH_FIELD_BODY_PEEK_BARE
                        + "[" + partIds[0] + "]");
            }
        }

        try {
            mConnection.sendCommand(String.format(Locale.US,
                    ImapConstants.UID_FETCH + " %s (%s)", ImapStore.joinMessageUids(messages),
                    Utility.combine(fetchFields.toArray(new String[fetchFields.size()]), ' ')
                    ), false);
            ImapResponse response;
            do {
                response = null;
                try {
                    response = mConnection.readResponse();

                    if (!response.isDataResponse(1, ImapConstants.FETCH)) {
                        continue; // Ignore
                    }
                    final ImapList fetchList = response.getListOrEmpty(2);
                    final String uid = fetchList.getKeyedStringOrEmpty(ImapConstants.UID)
                            .getString();
                    if (TextUtils.isEmpty(uid)) continue;

                    ImapMessage message = (ImapMessage) messageMap.get(uid);
                    if (message == null) continue;

                    if (fp.contains(FetchProfile.Item.FLAGS)) {
                        final ImapList flags =
                            fetchList.getKeyedListOrEmpty(ImapConstants.FLAGS);
                        for (int i = 0, count = flags.size(); i < count; i++) {
                            final ImapString flag = flags.getStringOrEmpty(i);
                            if (flag.is(ImapConstants.FLAG_DELETED)) {
                                message.setFlagInternal(Flag.DELETED, true);
                            } else if (flag.is(ImapConstants.FLAG_ANSWERED)) {
                                message.setFlagInternal(Flag.ANSWERED, true);
                            } else if (flag.is(ImapConstants.FLAG_SEEN)) {
                                message.setFlagInternal(Flag.SEEN, true);
                            } else if (flag.is(ImapConstants.FLAG_FLAGGED)) {
                                message.setFlagInternal(Flag.FLAGGED, true);
                            }
                        }
                    }
                    if (fp.contains(FetchProfile.Item.ENVELOPE)) {
                        final Date internalDate = fetchList.getKeyedStringOrEmpty(
                                ImapConstants.INTERNALDATE).getDateOrNull();
                        final int size = fetchList.getKeyedStringOrEmpty(
                                ImapConstants.RFC822_SIZE).getNumberOrZero();
                        final String header = fetchList.getKeyedStringOrEmpty(
                                ImapConstants.BODY_BRACKET_HEADER, true).getString();

                        message.setInternalDate(internalDate);
                        message.setSize(size);
                        message.parse(Utility.streamFromAsciiString(header));
                    }
                    if (fp.contains(FetchProfile.Item.STRUCTURE)) {
                        ImapList bs = fetchList.getKeyedListOrEmpty(
                                ImapConstants.BODYSTRUCTURE);
                        if (!bs.isEmpty()) {
                            try {
                                parseBodyStructure(bs, message, ImapConstants.TEXT);
                            } catch (MessagingException e) {
                                if (Logging.LOGD) {
                                    LogUtils.v(Logging.LOG_TAG, e, "Error handling message");
                                }
                                message.setBody(null);
                            }
                        }
                    }
                    if (fp.contains(FetchProfile.Item.BODY)
                            || fp.contains(FetchProfile.Item.BODY_SANE)) {
                        // Body is keyed by "BODY[]...".
                        // Previously used "BODY[..." but this can be confused with "BODY[HEADER..."
                        // TODO Should we accept "RFC822" as well??
                        ImapString body = fetchList.getKeyedStringOrEmpty("BODY[]", true);
                        InputStream bodyStream = body.getAsStream();
                        message.parse(bodyStream);
                    }
                    if (fetchPart != null) {
                        InputStream bodyStream =
                                fetchList.getKeyedStringOrEmpty("BODY[", true).getAsStream();
                        String encodings[] = fetchPart.getHeader(
                                MimeHeader.HEADER_CONTENT_TRANSFER_ENCODING);

                        String contentTransferEncoding = null;
                        if (encodings != null && encodings.length > 0) {
                            contentTransferEncoding = encodings[0];
                        } else {
                            // According to http://tools.ietf.org/html/rfc2045#section-6.1
                            // "7bit" is the default.
                            contentTransferEncoding = "7bit";
                        }

                        try {
                            // TODO Don't create 2 temp files.
                            // decodeBody creates BinaryTempFileBody, but we could avoid this
                            // if we implement ImapStringBody.
                            // (We'll need to share a temp file.  Protect it with a ref-count.)
                            fetchPart.setBody(decodeBody(bodyStream, contentTransferEncoding,
                                    fetchPart.getSize(), listener));
                        } catch(Exception e) {
                            // TODO: Figure out what kinds of exceptions might actually be thrown
                            // from here. This blanket catch-all is because we're not sure what to
                            // do if we don't have a contentTransferEncoding, and we don't have
                            // time to figure out what exceptions might be thrown.
                            LogUtils.e(Logging.LOG_TAG, "Error fetching body %s", e);
                        }
                    }

                    if (listener != null) {
                        listener.messageRetrieved(message);
                    }
                } finally {
                    destroyResponses();
                }
            } while (!response.isTagged());
        } catch (IOException ioe) {
            throw ioExceptionHandler(mConnection, ioe);
        }
    }

    /**
     * Removes any content transfer encoding from the stream and returns a Body.
     * This code is taken/condensed from MimeUtility.decodeBody
     */
    private static Body decodeBody(InputStream in, String contentTransferEncoding, int size,
            MessageRetrievalListener listener) throws IOException {
        // Get a properly wrapped input stream
        in = MimeUtility.getInputStreamForContentTransferEncoding(in, contentTransferEncoding);
        BinaryTempFileBody tempBody = new BinaryTempFileBody();
        OutputStream out = tempBody.getOutputStream();
        try {
            byte[] buffer = new byte[COPY_BUFFER_SIZE];
            int n = 0;
            int count = 0;
            while (-1 != (n = in.read(buffer))) {
                out.write(buffer, 0, n);
                count += n;
                if (listener != null) {
                    if (size == 0) {
                        // We don't know how big the file is, so just fake it.
                        listener.loadAttachmentProgress((int)Math.ceil(100 * (1-1.0/count)));
                    } else {
                        listener.loadAttachmentProgress(count * 100 / size);
                    }
                }
            }
        } catch (Base64DataException bde) {
            String warning = "\n\n" + ImapService.getMessageDecodeErrorString();
            out.write(warning.getBytes());
        } finally {
            out.close();
        }
        return tempBody;
    }

    @Override
    public Flag[] getPermanentFlags() {
        return PERMANENT_FLAGS;
    }

    /**
     * Handle any untagged responses that the caller doesn't care to handle themselves.
     * @param responses
     */
    private void handleUntaggedResponses(List<ImapResponse> responses) {
        for (ImapResponse response : responses) {
            handleUntaggedResponse(response);
        }
    }

    /**
     * Handle an untagged response that the caller doesn't care to handle themselves.
     * @param response
     */
    private void handleUntaggedResponse(ImapResponse response) {
        if (response.isDataResponse(1, ImapConstants.EXISTS)) {
            synchronized (this) {
                mMessageCount = response.getStringOrEmpty(0).getNumberOrZero();
            }
        }
    }

    private static void parseBodyStructure(ImapList bs, Part part, String id)
            throws MessagingException {
        if (bs.getElementOrNone(0).isList()) {
            /*
             * This is a multipart/*
             */
            MimeMultipart mp = new MimeMultipart();
            for (int i = 0, count = bs.size(); i < count; i++) {
                ImapElement e = bs.getElementOrNone(i);
                if (e.isList()) {
                    /*
                     * For each part in the message we're going to add a new BodyPart and parse
                     * into it.
                     */
                    MimeBodyPart bp = new MimeBodyPart();
                    if (id.equals(ImapConstants.TEXT)) {
                        parseBodyStructure(bs.getListOrEmpty(i), bp, Integer.toString(i + 1));

                    } else {
                        parseBodyStructure(bs.getListOrEmpty(i), bp, id + "." + (i + 1));
                    }
                    mp.addBodyPart(bp);

                } else {
                    if (e.isString()) {
                        mp.setSubType(bs.getStringOrEmpty(i).getString().toLowerCase(Locale.US));
                    }
                    break; // Ignore the rest of the list.
                }
            }
            part.setBody(mp);
        } else {
            /*
             * This is a body. We need to add as much information as we can find out about
             * it to the Part.
             */

            /*
             body type
             body subtype
             body parameter parenthesized list
             body id
             body description
             body encoding
             body size
             */

            final ImapString type = bs.getStringOrEmpty(0);
            final ImapString subType = bs.getStringOrEmpty(1);
            final String mimeType =
                    (type.getString() + "/" + subType.getString()).toLowerCase(Locale.US);

            final ImapList bodyParams = bs.getListOrEmpty(2);
            final ImapString cid = bs.getStringOrEmpty(3);
            final ImapString encoding = bs.getStringOrEmpty(5);
            final int size = bs.getStringOrEmpty(6).getNumberOrZero();

            if (MimeUtility.mimeTypeMatches(mimeType, MimeUtility.MIME_TYPE_RFC822)) {
                // A body type of type MESSAGE and subtype RFC822
                // contains, immediately after the basic fields, the
                // envelope structure, body structure, and size in
                // text lines of the encapsulated message.
                // [MESSAGE, RFC822, [NAME, filename.eml], NIL, NIL, 7BIT, 5974, NIL,
                //     [INLINE, [FILENAME*0, Fwd: Xxx..., FILENAME*1, filename.eml]], NIL]
                /*
                 * This will be caught by fetch and handled appropriately.
                 */
                throw new MessagingException("BODYSTRUCTURE " + MimeUtility.MIME_TYPE_RFC822
                        + " not yet supported.");
            }

            /*
             * Set the content type with as much information as we know right now.
             */
            final StringBuilder contentType = new StringBuilder(mimeType);

            /*
             * If there are body params we might be able to get some more information out
             * of them.
             */
            for (int i = 1, count = bodyParams.size(); i < count; i += 2) {

                // TODO We need to convert " into %22, but
                // because MimeUtility.getHeaderParameter doesn't recognize it,
                // we can't fix it for now.
                contentType.append(String.format(";\n %s=\"%s\"",
                        bodyParams.getStringOrEmpty(i - 1).getString(),
                        bodyParams.getStringOrEmpty(i).getString()));
            }

            part.setHeader(MimeHeader.HEADER_CONTENT_TYPE, contentType.toString());

            // Extension items
            final ImapList bodyDisposition;

            if (type.is(ImapConstants.TEXT) && bs.getElementOrNone(9).isList()) {
                // If media-type is TEXT, 9th element might be: [body-fld-lines] := number
                // So, if it's not a list, use 10th element.
                // (Couldn't find evidence in the RFC if it's ALWAYS 10th element.)
                bodyDisposition = bs.getListOrEmpty(9);
            } else {
                bodyDisposition = bs.getListOrEmpty(8);
            }

            final StringBuilder contentDisposition = new StringBuilder();

            if (bodyDisposition.size() > 0) {
                final String bodyDisposition0Str =
                        bodyDisposition.getStringOrEmpty(0).getString().toLowerCase(Locale.US);
                if (!TextUtils.isEmpty(bodyDisposition0Str)) {
                    contentDisposition.append(bodyDisposition0Str);
                }

                final ImapList bodyDispositionParams = bodyDisposition.getListOrEmpty(1);
                if (!bodyDispositionParams.isEmpty()) {
                    /*
                     * If there is body disposition information we can pull some more
                     * information about the attachment out.
                     */
                    for (int i = 1, count = bodyDispositionParams.size(); i < count; i += 2) {

                        // TODO We need to convert " into %22.  See above.
                        contentDisposition.append(String.format(Locale.US, ";\n %s=\"%s\"",
                                bodyDispositionParams.getStringOrEmpty(i - 1)
                                        .getString().toLowerCase(Locale.US),
                                bodyDispositionParams.getStringOrEmpty(i).getString()));
                    }
                }
            }

            if ((size > 0)
                    && (MimeUtility.getHeaderParameter(contentDisposition.toString(), "size")
                            == null)) {
                contentDisposition.append(String.format(Locale.US, ";\n size=%d", size));
            }

            if (contentDisposition.length() > 0) {
                /*
                 * Set the content disposition containing at least the size. Attachment
                 * handling code will use this down the road.
                 */
                part.setHeader(MimeHeader.HEADER_CONTENT_DISPOSITION,
                        contentDisposition.toString());
            }

            /*
             * Set the Content-Transfer-Encoding header. Attachment code will use this
             * to parse the body.
             */
            if (!encoding.isEmpty()) {
                part.setHeader(MimeHeader.HEADER_CONTENT_TRANSFER_ENCODING,
                        encoding.getString());
            }

            /*
             * Set the Content-ID header.
             */
            if (!cid.isEmpty()) {
                part.setHeader(MimeHeader.HEADER_CONTENT_ID, cid.getString());
            }

            if (size > 0) {
                if (part instanceof ImapMessage) {
                    ((ImapMessage) part).setSize(size);
                } else if (part instanceof MimeBodyPart) {
                    ((MimeBodyPart) part).setSize(size);
                } else {
                    throw new MessagingException("Unknown part type " + part.toString());
                }
            }
            part.setHeader(MimeHeader.HEADER_ANDROID_ATTACHMENT_STORE_DATA, id);
        }

    }

    /**
     * Appends the given messages to the selected folder. This implementation also determines
     * the new UID of the given message on the IMAP server and sets the Message's UID to the
     * new server UID.
     * @param message Message
     * @param noTimeout Set to true on manual syncs, disables the timeout after sending the message
     *                  content to the server
     */
    @Override
    public void appendMessage(final Context context, final Message message, final boolean noTimeout)
            throws MessagingException {
        checkOpen();
        try {
            // Create temp file
            /**
             * We need to know the encoded message size before we upload it, and encoding
             * attachments as Base64, possibly reading from a slow provider, is a non-trivial
             * operation. So we write the contents to a temp file while measuring the size,
             * and then use that temp file and size to do the actual upsync.
             * For context, most classic email clients would store the message in RFC822 format
             * internally, and so would not need to do this on-the-fly.
             */
            final File tempDir = context.getExternalCacheDir();
            final File tempFile = File.createTempFile("IMAPupsync", ".eml", tempDir);
            // Delete here so we don't leave the file lingering. We've got a handle to it so we
            // can still use it.
            final boolean deleteSuccessful = tempFile.delete();
            if (!deleteSuccessful) {
                LogUtils.w(LogUtils.TAG, "Could not delete temp file %s",
                        tempFile.getAbsolutePath());
            }
            final OutputStream tempOut = new FileOutputStream(tempFile);
            // Create output count while writing temp file
            final CountingOutputStream out = new CountingOutputStream(tempOut);
            final EOLConvertingOutputStream eolOut = new EOLConvertingOutputStream(out);
            message.writeTo(eolOut);
            eolOut.flush();
            // Create flag list (most often this will be "\SEEN")
            String flagList = "";
            Flag[] flags = message.getFlags();
            if (flags.length > 0) {
                StringBuilder sb = new StringBuilder();
                for (final Flag flag : flags) {
                    if (flag == Flag.SEEN) {
                        sb.append(" " + ImapConstants.FLAG_SEEN);
                    } else if (flag == Flag.FLAGGED) {
                        sb.append(" " + ImapConstants.FLAG_FLAGGED);
                    }
                }
                if (sb.length() > 0) {
                    flagList = sb.substring(1);
                }
            }

            mConnection.sendCommand(
                    String.format(Locale.US, ImapConstants.APPEND + " \"%s\" (%s) {%d}",
                            ImapStore.encodeFolderName(mName, mStore.mPathPrefix),
                            flagList,
                            out.getCount()), false);
            ImapResponse response;
            do {
                final int socketTimeout = mConnection.mTransport.getSoTimeout();
                try {
                    // Need to set the timeout to unlimited since we might be upsyncing a pretty
                    // big attachment so who knows how long it'll take. It would sure be nice
                    // if this only timed out after the send buffer drained but welp.
                    if (noTimeout) {
                        // For now, only unset the timeout if we're doing a manual sync
                        mConnection.mTransport.setSoTimeout(0);
                    }
                    response = mConnection.readResponse();
                    if (response.isContinuationRequest()) {
                        final OutputStream transportOutputStream =
                                mConnection.mTransport.getOutputStream();
                        IOUtils.copyLarge(new FileInputStream(tempFile), transportOutputStream);
                        transportOutputStream.write('\r');
                        transportOutputStream.write('\n');
                        transportOutputStream.flush();
                    } else if (!response.isTagged()) {
                        handleUntaggedResponse(response);
                    }
                } finally {
                    mConnection.mTransport.setSoTimeout(socketTimeout);
                }
            } while (!response.isTagged());

            // TODO Why not check the response?

                /*
                 * Try to recover the UID of the message from an APPENDUID response.
                 * e.g. 11 OK [APPENDUID 2 238268] APPEND completed
                 */
            final ImapList appendList = response.getListOrEmpty(1);
            if ((appendList.size() >= 3) && appendList.is(0, ImapConstants.APPENDUID)) {
                String serverUid = appendList.getStringOrEmpty(2).getString();
                if (!TextUtils.isEmpty(serverUid)) {
                    message.setUid(serverUid);
                    return;
                }
            }

            /*
             * Try to find the UID of the message we just appended using the
             * Message-ID header.  If there are more than one response, take the
             * last one, as it's most likely the newest (the one we just uploaded).
             */
            final String messageId = message.getMessageId();
            if (messageId == null || messageId.length() == 0) {
                return;
            }
            // Most servers don't care about parenthesis in the search query [and, some
            // fail to work if they are used]
            String[] uids = searchForUids(
                    String.format(Locale.US, "HEADER MESSAGE-ID %s", messageId));
            if (uids.length > 0) {
                message.setUid(uids[0]);
            }
            // However, there's at least one server [AOL] that fails to work unless there
            // are parenthesis, so, try this as a last resort
            uids = searchForUids(String.format(Locale.US, "(HEADER MESSAGE-ID %s)", messageId));
            if (uids.length > 0) {
                message.setUid(uids[0]);
            }
        } catch (IOException ioe) {
            throw ioExceptionHandler(mConnection, ioe);
        } finally {
            destroyResponses();
        }
    }

    @Override
    public Message[] expunge() throws MessagingException {
        checkOpen();
        try {
            handleUntaggedResponses(mConnection.executeSimpleCommand(ImapConstants.EXPUNGE));
        } catch (IOException ioe) {
            throw ioExceptionHandler(mConnection, ioe);
        } finally {
            destroyResponses();
        }
        return null;
    }

    @Override
    public void setFlags(Message[] messages, Flag[] flags, boolean value)
            throws MessagingException {
        checkOpen();

        String allFlags = "";
        if (flags.length > 0) {
            StringBuilder flagList = new StringBuilder();
            for (int i = 0, count = flags.length; i < count; i++) {
                Flag flag = flags[i];
                if (flag == Flag.SEEN) {
                    flagList.append(" " + ImapConstants.FLAG_SEEN);
                } else if (flag == Flag.DELETED) {
                    flagList.append(" " + ImapConstants.FLAG_DELETED);
                } else if (flag == Flag.FLAGGED) {
                    flagList.append(" " + ImapConstants.FLAG_FLAGGED);
                } else if (flag == Flag.ANSWERED) {
                    flagList.append(" " + ImapConstants.FLAG_ANSWERED);
                }
            }
            allFlags = flagList.substring(1);
        }
        try {
            mConnection.executeSimpleCommand(String.format(Locale.US,
                    ImapConstants.UID_STORE + " %s %s" + ImapConstants.FLAGS_SILENT + " (%s)",
                    ImapStore.joinMessageUids(messages),
                    value ? "+" : "-",
                    allFlags));

        } catch (IOException ioe) {
            throw ioExceptionHandler(mConnection, ioe);
        } finally {
            destroyResponses();
        }
    }

    /**
     * Persists this folder. We will always perform the proper database operation (e.g.
     * 'save' or 'update'). As an optimization, if a folder has not been modified, no
     * database operations are performed.
     */
    void save(Context context) {
        final Mailbox mailbox = mMailbox;
        if (!mailbox.isSaved()) {
            mailbox.save(context);
            mHash = mailbox.getHashes();
        } else {
            Object[] hash = mailbox.getHashes();
            if (!Arrays.equals(mHash, hash)) {
                mailbox.update(context, mailbox.toContentValues());
                mHash = hash;  // Save updated hash
            }
        }
    }

    /**
     * Selects the folder for use. Before performing any operations on this folder, it
     * must be selected.
     */
    private void doSelect() throws IOException, MessagingException {
        final List<ImapResponse> responses = mConnection.executeSimpleCommand(
                String.format(Locale.US, ImapConstants.SELECT + " \"%s\"",
                        ImapStore.encodeFolderName(mName, mStore.mPathPrefix)));

        // Assume the folder is opened read-write; unless we are notified otherwise
        mMode = OpenMode.READ_WRITE;
        int messageCount = -1;
        for (ImapResponse response : responses) {
            if (response.isDataResponse(1, ImapConstants.EXISTS)) {
                messageCount = response.getStringOrEmpty(0).getNumberOrZero();
            } else if (response.isOk()) {
                final ImapString responseCode = response.getResponseCodeOrEmpty();
                if (responseCode.is(ImapConstants.READ_ONLY)) {
                    mMode = OpenMode.READ_ONLY;
                } else if (responseCode.is(ImapConstants.READ_WRITE)) {
                    mMode = OpenMode.READ_WRITE;
                }
            } else if (response.isTagged()) { // Not OK
                throw new MessagingException("Can't open mailbox: "
                        + response.getStatusResponseTextOrEmpty());
            }
        }
        if (messageCount == -1) {
            throw new MessagingException("Did not find message count during select");
        }
        mMessageCount = messageCount;
        mExists = true;
    }

    private void checkOpen() throws MessagingException {
        if (!isOpen()) {
            throw new MessagingException("Folder " + mName + " is not open.");
        }
    }

    private MessagingException ioExceptionHandler(ImapConnection connection, IOException ioe) {
        if (DebugUtils.DEBUG) {
            LogUtils.d(Logging.LOG_TAG, ioe, "IO Exception detected: ");
        }
        if (connection != null) {
            cleanupConnection(connection, true);
        }
        return new MessagingException(MessagingException.IOERROR, "IO Error", ioe);
    }

    private ImapIdleChanges extractImapChanges(List<Object> changes) throws MessagingException {
        // Process the changes and fill the idle changes structure.
        // Basically we should look for the next commands in this method:
        //
        //    OK DONE
        //        No more changes
        //    n EXISTS
        //        Indicates the number of messages in the mailbox => handle like
        //        RECENT if the number increased
        //    n EXPUNGE
        //        Indicates a message was completely deleted => a full sync is required
        //    n RECENT
        //        New messages waiting in the server => use UIDNEXT to search for the new messages.
        //        If isn't possible to retrieve the new UID messages, then a full sync is required
        //    n FETCH (UID X FLAGS (...))
        //        a message has changed and requires to fetch only X message
        //        (something change on that item). If UID is not present, a conversion
        //        from MSN to UID is required

        final ImapIdleChanges imapIdleChanges = new ImapIdleChanges();

        int count = changes.size();
        if (Logging.LOGD) {
            for (int i = 0; i < count; i++) {
                ImapResponse change = (ImapResponse) changes.get(i);
                if (Logging.LOGD) {
                    LogUtils.d(Logging.LOG_TAG, "Received: " + change.toString());
                }
            }
        }

        // We can't ask to the server, because the responses will be destroyed. We need
        // to compute and fetch any related after we have all the responses processed
        boolean hasNewMessages = false;
        List<String> msns = new ArrayList<>();
        for (int i = 0; i < count; i++) {
            ImapResponse change = (ImapResponse) changes.get(i);
            if (change.isOk() || change.isNo() || change.isBad()) {
                // No more processing. DONE included
                break;
            }
            try {
                ImapElement element = change.getElementOrNone(1);
                if (element.equals(ImapElement.NONE)) {
                    continue;
                }
                if (!element.isString()) {
                    continue;
                }

                ImapString op = (ImapString) element;
                if (op.is(ImapConstants.DONE)) {
                    break;
                } else if (op.is(ImapConstants.EXISTS)) {
                    int newMessageCount = change.getStringOrEmpty(0).getNumberOrZero();
                    int oldMessageCount;
                    synchronized (this) {
                        oldMessageCount = mMessageCount;
                        mMessageCount = newMessageCount;
                    }
                    if (Logging.LOGD) {
                        LogUtils.d(LOG_TAG, "Got EXISTS idle response, message count now "
                                + newMessageCount + ", was " + oldMessageCount);
                    }
                    if (newMessageCount > oldMessageCount) {
                        hasNewMessages = true;
                    }
                } else if (op.is(ImapConstants.EXPUNGE)) {
                    imapIdleChanges.mRequiredSync = true;
                    synchronized (this) {
                        mMessageCount--;
                    }
                } else if (op.is(ImapConstants.RECENT)) {
                    hasNewMessages = true;
                } else if (op.is(ImapConstants.FETCH)
                        && change.getElementOrNone(2).isList()) {
                    ImapList messageFlags = (ImapList) change.getElementOrNone(2);
                    String uid = ((ImapString) messageFlags.getKeyedStringOrEmpty(
                            ImapConstants.UID, true)).getString();
                    if (!TextUtils.isEmpty(uid) &&
                            !imapIdleChanges.mMessageToFetch.contains(uid)) {
                        imapIdleChanges.mMessageToFetch.add(uid);
                    } else {
                        msns.add(change.getStringOrEmpty(0).getString());
                    }
                } else {
                    if (Logging.LOGD) {
                        LogUtils.w(LOG_TAG, "Unrecognized imap change (" + change
                                + ") for mailbox " + mName);
                    }
                }

            } catch (Exception ex) {
                if (Logging.LOGD) {
                    LogUtils.e(LOG_TAG, ex, "Failure processing imap change (" + change
                            + ") for mailbox " + mName);
                }
            }
        }

        // Check whether UIDVALIDITY changed - if yes, a full sync request is required
        // NOTE: This needs to happen after parsing all responses; otherwise
        //       getStatuses will destroy the response
        Map<String, String> statuses = getStatuses(new String[] { ImapConstants.UIDVALIDITY });
        String oldUidValidity = mIdleStatuses.get(ImapConstants.UIDVALIDITY);
        String newUidValidity = statuses.get(ImapConstants.UIDVALIDITY);
        if (!TextUtils.equals(oldUidValidity, newUidValidity)) {
            imapIdleChanges.mMessageToFetch.clear();
            imapIdleChanges.mRequiredSync = true;
            return imapIdleChanges;
        }

        // Recover the UIDs of new messages in case we don't do a full sync anyway
        if (!imapIdleChanges.mRequiredSync) {
            try {
                // Retrieve new message UIDs
                String uidNext = mIdleStatuses.get(ImapConstants.UIDNEXT);
                if (hasNewMessages && !TextUtils.isEmpty(uidNext)) {
                    msns.addAll(getNewMessagesFromUid(uidNext));
                }

                // Transform MSNs to UIDs
                for (String msn : msns) {
                    String[] uids = searchForUids(String.format(Locale.US, "%s:%s", msn, msn));
                    if (uids.length > 0) {
                        imapIdleChanges.mMessageToFetch.add(uids[0]);
                    } else {
                        throw new MessagingException("Server could not resolve MSN " + msn);
                    }
                }
            } catch (MessagingException ex) {
                // Server doesn't support UID. We have to do a full sync (since
                // we don't know what message changed)
                imapIdleChanges.mMessageToFetch.clear();
                imapIdleChanges.mRequiredSync = true;
            }
        }

        return imapIdleChanges;
    }

    @Override
    public boolean equals(Object o) {
        if (o instanceof ImapFolder) {
            return ((ImapFolder)o).mName.equals(mName);
        }
        return super.equals(o);
    }

    @Override
    public Message createMessage(String uid) {
        return new ImapMessage(uid, this);
    }
}