xref: /packages/apps/Email/emailcommon/src/com/android/emailcommon/utility/Utility.java

/*
 * Copyright (C) 2008 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.emailcommon.utility;

import android.app.Activity;
import android.app.Fragment;
import android.content.ContentResolver;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.CursorWrapper;
import android.graphics.Typeface;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Environment;
import android.os.Handler;
import android.os.Looper;
import android.os.StrictMode;
import android.provider.OpenableColumns;
import android.text.Spannable;
import android.text.SpannableString;
import android.text.SpannableStringBuilder;
import android.text.TextUtils;
import android.text.style.StyleSpan;
import android.util.Base64;
import android.util.Log;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.android.emailcommon.Logging;
import com.android.emailcommon.provider.Account;
import com.android.emailcommon.provider.EmailContent;
import com.android.emailcommon.provider.EmailContent.AccountColumns;
import com.android.emailcommon.provider.EmailContent.Attachment;
import com.android.emailcommon.provider.EmailContent.AttachmentColumns;
import com.android.emailcommon.provider.EmailContent.HostAuthColumns;
import com.android.emailcommon.provider.EmailContent.MailboxColumns;
import com.android.emailcommon.provider.EmailContent.Message;
import com.android.emailcommon.provider.EmailContent.MessageColumns;
import com.android.emailcommon.provider.HostAuth;
import com.android.emailcommon.provider.Mailbox;
import com.android.emailcommon.provider.ProviderUnavailableException;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileDescriptor;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.GregorianCalendar;
import java.util.HashSet;
import java.util.Set;
import java.util.TimeZone;
import java.util.regex.Pattern;

public class Utility {
    public static final Charset UTF_8 = Charset.forName("UTF-8");
    public static final Charset ASCII = Charset.forName("US-ASCII");

    public static final String[] EMPTY_STRINGS = new String[0];
    public static final Long[] EMPTY_LONGS = new Long[0];

    // "GMT" + "+" or "-" + 4 digits
    private static final Pattern DATE_CLEANUP_PATTERN_WRONG_TIMEZONE =
            Pattern.compile("GMT([-+]\\d{4})$");

    private static Handler sMainThreadHandler;

    /**
     * @return a {@link Handler} tied to the main thread.
     */
    public static Handler getMainThreadHandler() {
        if (sMainThreadHandler == null) {
            // No need to synchronize -- it's okay to create an extra Handler, which will be used
            // only once and then thrown away.
            sMainThreadHandler = new Handler(Looper.getMainLooper());
        }
        return sMainThreadHandler;
    }

    public final static String readInputStream(InputStream in, String encoding) throws IOException {
        InputStreamReader reader = new InputStreamReader(in, encoding);
        StringBuffer sb = new StringBuffer();
        int count;
        char[] buf = new char[512];
        while ((count = reader.read(buf)) != -1) {
            sb.append(buf, 0, count);
        }
        return sb.toString();
    }

    public final static boolean arrayContains(Object[] a, Object o) {
        int index = arrayIndex(a, o);
        return (index >= 0);
    }

    public final static int arrayIndex(Object[] a, Object o) {
        for (int i = 0, count = a.length; i < count; i++) {
            if (a[i].equals(o)) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Returns a concatenated string containing the output of every Object's
     * toString() method, each separated by the given separator character.
     */
    public static String combine(Object[] parts, char separator) {
        if (parts == null) {
            return null;
        }
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < parts.length; i++) {
            sb.append(parts[i].toString());
            if (i < parts.length - 1) {
                sb.append(separator);
            }
        }
        return sb.toString();
    }
    public static String base64Decode(String encoded) {
        if (encoded == null) {
            return null;
        }
        byte[] decoded = Base64.decode(encoded, Base64.DEFAULT);
        return new String(decoded);
    }

    public static String base64Encode(String s) {
        if (s == null) {
            return s;
        }
        return Base64.encodeToString(s.getBytes(), Base64.NO_WRAP);
    }

    public static boolean isTextViewNotEmpty(TextView view) {
        return !TextUtils.isEmpty(view.getText());
    }

    public static boolean isPortFieldValid(TextView view) {
        CharSequence chars = view.getText();
        if (TextUtils.isEmpty(chars)) return false;
        Integer port;
        // In theory, we can't get an illegal value here, since the field is monitored for valid
        // numeric input. But this might be used elsewhere without such a check.
        try {
            port = Integer.parseInt(chars.toString());
        } catch (NumberFormatException e) {
            return false;
        }
        return port > 0 && port < 65536;
    }

    /**
     * Validate a hostname name field.
     *
     * Because we just use the {@link URI} class for validation, it'll accept some invalid
     * host names, but it works well enough...
     */
    public static boolean isServerNameValid(TextView view) {
        return isServerNameValid(view.getText().toString());
    }

    public static boolean isServerNameValid(String serverName) {
        serverName = serverName.trim();
        if (TextUtils.isEmpty(serverName)) {
            return false;
        }
        try {
            URI uri = new URI(
                    "http",
                    null,
                    serverName,
                    -1,
                    null, // path
                    null, // query
                    null);
            return true;
        } catch (URISyntaxException e) {
            return false;
        }
    }

    /**
     * Ensures that the given string starts and ends with the double quote character. The string is
     * not modified in any way except to add the double quote character to start and end if it's not
     * already there.
     *
     * TODO: Rename this, because "quoteString()" can mean so many different things.
     *
     * sample -> "sample"
     * "sample" -> "sample"
     * ""sample"" -> "sample"
     * "sample"" -> "sample"
     * sa"mp"le -> "sa"mp"le"
     * "sa"mp"le" -> "sa"mp"le"
     * (empty string) -> ""
     * " -> ""
     */
    public static String quoteString(String s) {
        if (s == null) {
            return null;
        }
        if (!s.matches("^\".*\"$")) {
            return "\"" + s + "\"";
        }
        else {
            return s;
        }
    }

    /**
     * A fast version of  URLDecoder.decode() that works only with UTF-8 and does only two
     * allocations. This version is around 3x as fast as the standard one and I'm using it
     * hundreds of times in places that slow down the UI, so it helps.
     */
    public static String fastUrlDecode(String s) {
        try {
            byte[] bytes = s.getBytes("UTF-8");
            byte ch;
            int length = 0;
            for (int i = 0, count = bytes.length; i < count; i++) {
                ch = bytes[i];
                if (ch == '%') {
                    int h = (bytes[i + 1] - '0');
                    int l = (bytes[i + 2] - '0');
                    if (h > 9) {
                        h -= 7;
                    }
                    if (l > 9) {
                        l -= 7;
                    }
                    bytes[length] = (byte) ((h << 4) | l);
                    i += 2;
                }
                else if (ch == '+') {
                    bytes[length] = ' ';
                }
                else {
                    bytes[length] = bytes[i];
                }
                length++;
            }
            return new String(bytes, 0, length, "UTF-8");
        }
        catch (UnsupportedEncodingException uee) {
            return null;
        }
    }
    private final static String HOSTAUTH_WHERE_CREDENTIALS = HostAuthColumns.ADDRESS + " like ?"
            + " and " + HostAuthColumns.LOGIN + " like ?  ESCAPE '\\'"
            + " and " + HostAuthColumns.PROTOCOL + " not like \"smtp\"";
    private final static String ACCOUNT_WHERE_HOSTAUTH = AccountColumns.HOST_AUTH_KEY_RECV + "=?";

    /**
     * Look for an existing account with the same username & server
     *
     * @param context a system context
     * @param allowAccountId this account Id will not trigger (when editing an existing account)
     * @param hostName the server's address
     * @param userLogin the user's login string
     * @result null = no matching account found.  Account = matching account
     */
    public static Account findExistingAccount(Context context, long allowAccountId,
            String hostName, String userLogin) {
        ContentResolver resolver = context.getContentResolver();
        String userName = userLogin.replace("_", "\\_");
        Cursor c = resolver.query(HostAuth.CONTENT_URI, HostAuth.ID_PROJECTION,
                HOSTAUTH_WHERE_CREDENTIALS, new String[] { hostName, userName }, null);
        if (c == null) throw new ProviderUnavailableException();
        try {
            while (c.moveToNext()) {
                long hostAuthId = c.getLong(HostAuth.ID_PROJECTION_COLUMN);
                // Find account with matching hostauthrecv key, and return it
                Cursor c2 = resolver.query(Account.CONTENT_URI, Account.ID_PROJECTION,
                        ACCOUNT_WHERE_HOSTAUTH, new String[] { Long.toString(hostAuthId) }, null);
                try {
                    while (c2.moveToNext()) {
                        long accountId = c2.getLong(Account.ID_PROJECTION_COLUMN);
                        if (accountId != allowAccountId) {
                            Account account = Account.restoreAccountWithId(context, accountId);
                            if (account != null) {
                                return account;
                            }
                        }
                    }
                } finally {
                    c2.close();
                }
            }
        } finally {
            c.close();
        }

        return null;
    }

    /**
     * Generate a random message-id header for locally-generated messages.
     */
    public static String generateMessageId() {
        StringBuffer sb = new StringBuffer();
        sb.append("<");
        for (int i = 0; i < 24; i++) {
            sb.append(Integer.toString((int)(Math.random() * 35), 36));
        }
        sb.append(".");
        sb.append(Long.toString(System.currentTimeMillis()));
        sb.append("@email.android.com>");
        return sb.toString();
    }

    /**
     * Generate a time in milliseconds from a date string that represents a date/time in GMT
     * @param date string in format 20090211T180303Z (rfc2445, iCalendar).
     * @return the time in milliseconds (since Jan 1, 1970)
     */
    public static long parseDateTimeToMillis(String date) {
        GregorianCalendar cal = parseDateTimeToCalendar(date);
        return cal.getTimeInMillis();
    }

    /**
     * Generate a GregorianCalendar from a date string that represents a date/time in GMT
     * @param date string in format 20090211T180303Z (rfc2445, iCalendar).
     * @return the GregorianCalendar
     */
    public static GregorianCalendar parseDateTimeToCalendar(String date) {
        GregorianCalendar cal = new GregorianCalendar(Integer.parseInt(date.substring(0, 4)),
                Integer.parseInt(date.substring(4, 6)) - 1, Integer.parseInt(date.substring(6, 8)),
                Integer.parseInt(date.substring(9, 11)), Integer.parseInt(date.substring(11, 13)),
                Integer.parseInt(date.substring(13, 15)));
        cal.setTimeZone(TimeZone.getTimeZone("GMT"));
        return cal;
    }

    /**
     * Generate a time in milliseconds from an email date string that represents a date/time in GMT
     * @param date string in format 2010-02-23T16:00:00.000Z (ISO 8601, rfc3339)
     * @return the time in milliseconds (since Jan 1, 1970)
     */
    public static long parseEmailDateTimeToMillis(String date) {
        GregorianCalendar cal = new GregorianCalendar(Integer.parseInt(date.substring(0, 4)),
                Integer.parseInt(date.substring(5, 7)) - 1, Integer.parseInt(date.substring(8, 10)),
                Integer.parseInt(date.substring(11, 13)), Integer.parseInt(date.substring(14, 16)),
                Integer.parseInt(date.substring(17, 19)));
        cal.setTimeZone(TimeZone.getTimeZone("GMT"));
        return cal.getTimeInMillis();
    }

    private static byte[] encode(Charset charset, String s) {
        if (s == null) {
            return null;
        }
        final ByteBuffer buffer = charset.encode(CharBuffer.wrap(s));
        final byte[] bytes = new byte[buffer.limit()];
        buffer.get(bytes);
        return bytes;
    }

    private static String decode(Charset charset, byte[] b) {
        if (b == null) {
            return null;
        }
        final CharBuffer cb = charset.decode(ByteBuffer.wrap(b));
        return new String(cb.array(), 0, cb.length());
    }

    /** Converts a String to UTF-8 */
    public static byte[] toUtf8(String s) {
        return encode(UTF_8, s);
    }

    /** Builds a String from UTF-8 bytes */
    public static String fromUtf8(byte[] b) {
        return decode(UTF_8, b);
    }

    /** Converts a String to ASCII bytes */
    public static byte[] toAscii(String s) {
        return encode(ASCII, s);
    }

    /** Builds a String from ASCII bytes */
    public static String fromAscii(byte[] b) {
        return decode(ASCII, b);
    }

    /**
     * @return true if the input is the first (or only) byte in a UTF-8 character
     */
    public static boolean isFirstUtf8Byte(byte b) {
        // If the top 2 bits is '10', it's not a first byte.
        return (b & 0xc0) != 0x80;
    }

    public static String byteToHex(int b) {
        return byteToHex(new StringBuilder(), b).toString();
    }

    public static StringBuilder byteToHex(StringBuilder sb, int b) {
        b &= 0xFF;
        sb.append("0123456789ABCDEF".charAt(b >> 4));
        sb.append("0123456789ABCDEF".charAt(b & 0xF));
        return sb;
    }

    public static String replaceBareLfWithCrlf(String str) {
        return str.replace("\r", "").replace("\n", "\r\n");
    }

    /**
     * Cancel an {@link AsyncTask}.  If it's already running, it'll be interrupted.
     */
    public static void cancelTaskInterrupt(AsyncTask<?, ?, ?> task) {
        cancelTask(task, true);
    }

    /**
     * Cancel an {@link EmailAsyncTask}.  If it's already running, it'll be interrupted.
     */
    public static void cancelTaskInterrupt(EmailAsyncTask<?, ?, ?> task) {
        if (task != null) {
            task.cancel(true);
        }
    }

    /**
     * Cancel an {@link AsyncTask}.
     *
     * @param mayInterruptIfRunning <tt>true</tt> if the thread executing this
     *        task should be interrupted; otherwise, in-progress tasks are allowed
     *        to complete.
     */
    public static void cancelTask(AsyncTask<?, ?, ?> task, boolean mayInterruptIfRunning) {
        if (task != null && task.getStatus() != AsyncTask.Status.FINISHED) {
            task.cancel(mayInterruptIfRunning);
        }
    }

    public static String getSmallHash(final String value) {
        final MessageDigest sha;
        try {
            sha = MessageDigest.getInstance("SHA-1");
        } catch (NoSuchAlgorithmException impossible) {
            return null;
        }
        sha.update(Utility.toUtf8(value));
        final int hash = getSmallHashFromSha1(sha.digest());
        return Integer.toString(hash);
    }

    /**
     * @return a non-negative integer generated from 20 byte SHA-1 hash.
     */
    /* package for testing */ static int getSmallHashFromSha1(byte[] sha1) {
        final int offset = sha1[19] & 0xf; // SHA1 is 20 bytes.
        return ((sha1[offset]  & 0x7f) << 24)
                | ((sha1[offset + 1] & 0xff) << 16)
                | ((sha1[offset + 2] & 0xff) << 8)
                | ((sha1[offset + 3] & 0xff));
    }

    /**
     * Try to make a date MIME(RFC 2822/5322)-compliant.
     *
     * It fixes:
     * - "Thu, 10 Dec 09 15:08:08 GMT-0700" to "Thu, 10 Dec 09 15:08:08 -0700"
     *   (4 digit zone value can't be preceded by "GMT")
     *   We got a report saying eBay sends a date in this format
     */
    public static String cleanUpMimeDate(String date) {
        if (TextUtils.isEmpty(date)) {
            return date;
        }
        date = DATE_CLEANUP_PATTERN_WRONG_TIMEZONE.matcher(date).replaceFirst("$1");
        return date;
    }

    public static ByteArrayInputStream streamFromAsciiString(String ascii) {
        return new ByteArrayInputStream(toAscii(ascii));
    }

    /**
     * A thread safe way to show a Toast.  Can be called from any thread.
     *
     * @param context context
     * @param resId Resource ID of the message string.
     */
    public static void showToast(Context context, int resId) {
        showToast(context, context.getResources().getString(resId));
    }

    /**
     * A thread safe way to show a Toast.  Can be called from any thread.
     *
     * @param context context
     * @param message Message to show.
     */
    public static void showToast(final Context context, final String message) {
        getMainThreadHandler().post(new Runnable() {
            @Override
            public void run() {
                Toast.makeText(context, message, Toast.LENGTH_LONG).show();
            }
        });
    }

    /**
     * Run {@code r} on a worker thread, returning the AsyncTask
     * @return the AsyncTask; this is primarily for use by unit tests, which require the
     * result of the task
     *
     * @deprecated use {@link EmailAsyncTask#runAsyncParallel} or
     *     {@link EmailAsyncTask#runAsyncSerial}
     */
    @Deprecated
    public static AsyncTask<Void, Void, Void> runAsync(final Runnable r) {
        return new AsyncTask<Void, Void, Void>() {
            @Override protected Void doInBackground(Void... params) {
                r.run();
                return null;
            }
        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
    }

    /**
     * Interface used in {@link #createUniqueFile} instead of {@link File#createNewFile()} to make
     * it testable.
     */
    /* package */ interface NewFileCreator {
        public static final NewFileCreator DEFAULT = new NewFileCreator() {
                    @Override public boolean createNewFile(File f) throws IOException {
                        return f.createNewFile();
                    }
        };
        public boolean createNewFile(File f) throws IOException ;
    }

    /**
     * Creates a new empty file with a unique name in the given directory by appending a hyphen and
     * a number to the given filename.
     *
     * @return a new File object, or null if one could not be created
     */
    public static File createUniqueFile(File directory, String filename) throws IOException {
        return createUniqueFileInternal(NewFileCreator.DEFAULT, directory, filename);
    }

    /* package */ static File createUniqueFileInternal(NewFileCreator nfc,
            File directory, String filename) throws IOException {
        File file = new File(directory, filename);
        if (nfc.createNewFile(file)) {
            return file;
        }
        // Get the extension of the file, if any.
        int index = filename.lastIndexOf('.');
        String format;
        if (index != -1) {
            String name = filename.substring(0, index);
            String extension = filename.substring(index);
            format = name + "-%d" + extension;
        } else {
            format = filename + "-%d";
        }

        for (int i = 2; i < Integer.MAX_VALUE; i++) {
            file = new File(directory, String.format(format, i));
            if (nfc.createNewFile(file)) {
                return file;
            }
        }
        return null;
    }

    public interface CursorGetter<T> {
        T get(Cursor cursor, int column);
    }

    private static final CursorGetter<Long> LONG_GETTER = new CursorGetter<Long>() {
        @Override
        public Long get(Cursor cursor, int column) {
            return cursor.getLong(column);
        }
    };

    private static final CursorGetter<Integer> INT_GETTER = new CursorGetter<Integer>() {
        @Override
        public Integer get(Cursor cursor, int column) {
            return cursor.getInt(column);
        }
    };

    private static final CursorGetter<String> STRING_GETTER = new CursorGetter<String>() {
        @Override
        public String get(Cursor cursor, int column) {
            return cursor.getString(column);
        }
    };

    private static final CursorGetter<byte[]> BLOB_GETTER = new CursorGetter<byte[]>() {
        @Override
        public byte[] get(Cursor cursor, int column) {
            return cursor.getBlob(column);
        }
    };

    /**
     * @return if {@code original} is to the EmailProvider, add "?limit=1".  Otherwise just returns
     * {@code original}.
     *
     * Other providers don't support the limit param.  Also, changing URI passed from other apps
     * can cause permission errors.
     */
    /* package */ static Uri buildLimitOneUri(Uri original) {
        if ("content".equals(original.getScheme()) &&
                EmailContent.AUTHORITY.equals(original.getAuthority())) {
            return EmailContent.uriWithLimit(original, 1);
        }
        return original;
    }

    /**
     * @return a generic in column {@code column} of the first result row, if the query returns at
     * least 1 row.  Otherwise returns {@code defaultValue}.
     */
    public static <T extends Object> T getFirstRowColumn(Context context, Uri uri,
            String[] projection, String selection, String[] selectionArgs, String sortOrder,
            int column, T defaultValue, CursorGetter<T> getter) {
        // Use PARAMETER_LIMIT to restrict the query to the single row we need
        uri = buildLimitOneUri(uri);
        Cursor c = context.getContentResolver().query(uri, projection, selection, selectionArgs,
                sortOrder);
        if (c != null) {
            try {
                if (c.moveToFirst()) {
                    return getter.get(c, column);
                }
            } finally {
                c.close();
            }
        }
        return defaultValue;
    }

    /**
     * {@link #getFirstRowColumn} for a Long with null as a default value.
     */
    public static Long getFirstRowLong(Context context, Uri uri, String[] projection,
            String selection, String[] selectionArgs, String sortOrder, int column) {
        return getFirstRowColumn(context, uri, projection, selection, selectionArgs,
                sortOrder, column, null, LONG_GETTER);
    }

    /**
     * {@link #getFirstRowColumn} for a Long with a provided default value.
     */
    public static Long getFirstRowLong(Context context, Uri uri, String[] projection,
            String selection, String[] selectionArgs, String sortOrder, int column,
            Long defaultValue) {
        return getFirstRowColumn(context, uri, projection, selection, selectionArgs,
                sortOrder, column, defaultValue, LONG_GETTER);
    }

    /**
     * {@link #getFirstRowColumn} for an Integer with null as a default value.
     */
    public static Integer getFirstRowInt(Context context, Uri uri, String[] projection,
            String selection, String[] selectionArgs, String sortOrder, int column) {
        return getFirstRowColumn(context, uri, projection, selection, selectionArgs,
                sortOrder, column, null, INT_GETTER);
    }

    /**
     * {@link #getFirstRowColumn} for an Integer with a provided default value.
     */
    public static Integer getFirstRowInt(Context context, Uri uri, String[] projection,
            String selection, String[] selectionArgs, String sortOrder, int column,
            Integer defaultValue) {
        return getFirstRowColumn(context, uri, projection, selection, selectionArgs,
                sortOrder, column, defaultValue, INT_GETTER);
    }

    /**
     * {@link #getFirstRowColumn} for a String with null as a default value.
     */
    public static String getFirstRowString(Context context, Uri uri, String[] projection,
            String selection, String[] selectionArgs, String sortOrder, int column) {
        return getFirstRowString(context, uri, projection, selection, selectionArgs, sortOrder,
                column, null);
    }

    /**
     * {@link #getFirstRowColumn} for a String with a provided default value.
     */
    public static String getFirstRowString(Context context, Uri uri, String[] projection,
            String selection, String[] selectionArgs, String sortOrder, int column,
            String defaultValue) {
        return getFirstRowColumn(context, uri, projection, selection, selectionArgs,
                sortOrder, column, defaultValue, STRING_GETTER);
    }

    /**
     * {@link #getFirstRowColumn} for a byte array with a provided default value.
     */
    public static byte[] getFirstRowBlob(Context context, Uri uri, String[] projection,
            String selection, String[] selectionArgs, String sortOrder, int column,
            byte[] defaultValue) {
        return getFirstRowColumn(context, uri, projection, selection, selectionArgs, sortOrder,
                column, defaultValue, BLOB_GETTER);
    }

    public static boolean attachmentExists(Context context, Attachment attachment) {
        if (attachment == null) {
            return false;
        } else if (attachment.mContentBytes != null) {
            return true;
        } else if (TextUtils.isEmpty(attachment.mContentUri)) {
            return false;
        }
        try {
            Uri fileUri = Uri.parse(attachment.mContentUri);
            try {
                InputStream inStream = context.getContentResolver().openInputStream(fileUri);
                try {
                    inStream.close();
                } catch (IOException e) {
                    // Nothing to be done if can't close the stream
                }
                return true;
            } catch (FileNotFoundException e) {
                return false;
            }
        } catch (RuntimeException re) {
            Log.w(Logging.LOG_TAG, "attachmentExists RuntimeException=" + re);
            return false;
        }
    }

    /**
     * Check whether the message with a given id has unloaded attachments.  If the message is
     * a forwarded message, we look instead at the messages's source for the attachments.  If the
     * message or forward source can't be found, we return false
     * @param context the caller's context
     * @param messageId the id of the message
     * @return whether or not the message has unloaded attachments
     */
    public static boolean hasUnloadedAttachments(Context context, long messageId) {
        Message msg = Message.restoreMessageWithId(context, messageId);
        if (msg == null) return false;
        Attachment[] atts = Attachment.restoreAttachmentsWithMessageId(context, messageId);
        for (Attachment att: atts) {
            if (!attachmentExists(context, att)) {
                // If the attachment doesn't exist and isn't marked for download, we're in trouble
                // since the outbound message will be stuck indefinitely in the Outbox.  Instead,
                // we'll just delete the attachment and continue; this is far better than the
                // alternative.  In theory, this situation shouldn't be possible.
                if ((att.mFlags & (Attachment.FLAG_DOWNLOAD_FORWARD |
                        Attachment.FLAG_DOWNLOAD_USER_REQUEST)) == 0) {
                    Log.d(Logging.LOG_TAG, "Unloaded attachment isn't marked for download: " +
                            att.mFileName + ", #" + att.mId);
                    Attachment.delete(context, Attachment.CONTENT_URI, att.mId);
                } else if (att.mContentUri != null) {
                    // In this case, the attachment file is gone from the cache; let's clear the
                    // contentUri; this should be a very unusual case
                    ContentValues cv = new ContentValues();
                    cv.putNull(AttachmentColumns.CONTENT_URI);
                    Attachment.update(context, Attachment.CONTENT_URI, att.mId, cv);
                }
                return true;
            }
        }
        return false;
    }

    /**
     * Convenience method wrapping calls to retrieve columns from a single row, via EmailProvider.
     * The arguments are exactly the same as to contentResolver.query().  Results are returned in
     * an array of Strings corresponding to the columns in the projection.  If the cursor has no
     * rows, null is returned.
     */
    public static String[] getRowColumns(Context context, Uri contentUri, String[] projection,
            String selection, String[] selectionArgs) {
        String[] values = new String[projection.length];
        ContentResolver cr = context.getContentResolver();
        Cursor c = cr.query(contentUri, projection, selection, selectionArgs, null);
        try {
            if (c.moveToFirst()) {
                for (int i = 0; i < projection.length; i++) {
                    values[i] = c.getString(i);
                }
            } else {
                return null;
            }
        } finally {
            c.close();
        }
        return values;
    }

    /**
     * Convenience method for retrieving columns from a particular row in EmailProvider.
     * Passed in here are a base uri (e.g. Message.CONTENT_URI), the unique id of a row, and
     * a projection.  This method calls the previous one with the appropriate URI.
     */
    public static String[] getRowColumns(Context context, Uri baseUri, long id,
            String ... projection) {
        return getRowColumns(context, ContentUris.withAppendedId(baseUri, id), projection, null,
                null);
    }

    public static boolean isExternalStorageMounted() {
        return Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);
    }

    /**
     * Class that supports running any operation for each account.
     */
    public abstract static class ForEachAccount extends AsyncTask<Void, Void, Long[]> {
        private final Context mContext;

        public ForEachAccount(Context context) {
            mContext = context;
        }

        @Override
        protected final Long[] doInBackground(Void... params) {
            ArrayList<Long> ids = new ArrayList<Long>();
            Cursor c = mContext.getContentResolver().query(Account.CONTENT_URI,
                    Account.ID_PROJECTION, null, null, null);
            try {
                while (c.moveToNext()) {
                    ids.add(c.getLong(Account.ID_PROJECTION_COLUMN));
                }
            } finally {
                c.close();
            }
            return ids.toArray(EMPTY_LONGS);
        }

        @Override
        protected final void onPostExecute(Long[] ids) {
            if (ids != null && !isCancelled()) {
                for (long id : ids) {
                    performAction(id);
                }
            }
            onFinished();
        }

        /**
         * This method will be called for each account.
         */
        protected abstract void performAction(long accountId);

        /**
         * Called when the iteration is finished.
         */
        protected void onFinished() {
        }
    }

    /**
     * Updates the last seen message key in the mailbox data base for the INBOX of the currently
     * shown account. If the account is {@link Account#ACCOUNT_ID_COMBINED_VIEW}, the INBOX for
     * all accounts are updated.
     * @return an {@link EmailAsyncTask} for test only.
     */
    public static EmailAsyncTask<Void, Void, Void> updateLastSeenMessageKey(final Context context,
            final long accountId) {
        return EmailAsyncTask.runAsyncParallel(new Runnable() {
            private void updateLastSeenMessageKeyForAccount(long accountId) {
                ContentResolver resolver = context.getContentResolver();
                if (accountId == Account.ACCOUNT_ID_COMBINED_VIEW) {
                    Cursor c = resolver.query(
                            Account.CONTENT_URI, EmailContent.ID_PROJECTION, null, null, null);
                    if (c == null) throw new ProviderUnavailableException();
                    try {
                        while (c.moveToNext()) {
                            final long id = c.getLong(EmailContent.ID_PROJECTION_COLUMN);
                            updateLastSeenMessageKeyForAccount(id);
                        }
                    } finally {
                        c.close();
                    }
                } else if (accountId > 0L) {
                    Mailbox mailbox =
                        Mailbox.restoreMailboxOfType(context, accountId, Mailbox.TYPE_INBOX);

                    // mailbox has been removed
                    if (mailbox == null) {
                        return;
                    }
                    // We use the highest _id for the account the mailbox table as the "last seen
                    // message key". We don't care if the message has been read or not. We only
                    // need a point at which we can compare against in the future. By setting this
                    // value, we are claiming that every message before this has potentially been
                    // seen by the user.
                    long messageId = Utility.getFirstRowLong(
                            context,
                            Message.CONTENT_URI,
                            EmailContent.ID_PROJECTION,
                            MessageColumns.MAILBOX_KEY + "=?",
                            new String[] { Long.toString(mailbox.mId) },
                            MessageColumns.ID + " DESC",
                            EmailContent.ID_PROJECTION_COLUMN, 0L);
                    long oldLastSeenMessageId = Utility.getFirstRowLong(
                            context, ContentUris.withAppendedId(Mailbox.CONTENT_URI, mailbox.mId),
                            new String[] { MailboxColumns.LAST_SEEN_MESSAGE_KEY },
                            null, null, null, 0, 0L);
                    // Only update the db if the value has changed
                    if (messageId != oldLastSeenMessageId) {
                        ContentValues values = mailbox.toContentValues();
                        values.put(MailboxColumns.LAST_SEEN_MESSAGE_KEY, messageId);
                        resolver.update(
                                Mailbox.CONTENT_URI,
                                values,
                                EmailContent.ID_SELECTION,
                                new String[] { Long.toString(mailbox.mId) });
                    }
                }
            }

            @Override
            public void run() {
                updateLastSeenMessageKeyForAccount(accountId);
            }
        });
    }

    public static long[] toPrimitiveLongArray(Collection<Long> collection) {
        // Need to do this manually because we're converting to a primitive long array, not
        // a Long array.
        final int size = collection.size();
        final long[] ret = new long[size];
        // Collection doesn't have get(i).  (Iterable doesn't have size())
        int i = 0;
        for (Long value : collection) {
            ret[i++] = value;
        }
        return ret;
    }

    public static Set<Long> toLongSet(long[] array) {
        // Need to do this manually because we're converting from a primitive long array, not
        // a Long array.
        final int size = array.length;
        HashSet<Long> ret = new HashSet<Long>(size);
        for (int i = 0; i < size; i++) {
            ret.add(array[i]);
        }
        return ret;
    }

    /**
     * Workaround for the {@link ListView#smoothScrollToPosition} randomly scroll the view bug
     * if it's called right after {@link ListView#setAdapter}.
     */
    public static void listViewSmoothScrollToPosition(final Activity activity,
            final ListView listView, final int position) {
        // Workarond: delay-call smoothScrollToPosition()
        new Handler().post(new Runnable() {
            @Override
            public void run() {
                if (activity.isFinishing()) {
                    return; // Activity being destroyed
                }
                listView.smoothScrollToPosition(position);
            }
        });
    }

    private static final String[] ATTACHMENT_META_NAME_PROJECTION = {
        OpenableColumns.DISPLAY_NAME
    };
    private static final int ATTACHMENT_META_NAME_COLUMN_DISPLAY_NAME = 0;

    /**
     * @return Filename of a content of {@code contentUri}.  If the provider doesn't provide the
     * filename, returns the last path segment of the URI.
     */
    public static String getContentFileName(Context context, Uri contentUri) {
        String name = getFirstRowString(context, contentUri, ATTACHMENT_META_NAME_PROJECTION, null,
                null, null, ATTACHMENT_META_NAME_COLUMN_DISPLAY_NAME);
        if (name == null) {
            name = contentUri.getLastPathSegment();
        }
        return name;
    }

    /**
     * Append a bold span to a {@link SpannableStringBuilder}.
     */
    public static SpannableStringBuilder appendBold(SpannableStringBuilder ssb, String text) {
        if (!TextUtils.isEmpty(text)) {
            SpannableString ss = new SpannableString(text);
            ss.setSpan(new StyleSpan(Typeface.BOLD), 0, ss.length(),
                    Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
            ssb.append(ss);
        }

        return ssb;
    }

    /**
     * Stringify a cursor for logging purpose.
     */
    public static String dumpCursor(Cursor c) {
        StringBuilder sb = new StringBuilder();
        sb.append("[");
        while (c != null) {
            sb.append(c.getClass()); // Class name may not be available if toString() is overridden
            sb.append("/");
            sb.append(c.toString());
            if (c.isClosed()) {
                sb.append(" (closed)");
            }
            if (c instanceof CursorWrapper) {
                c = ((CursorWrapper) c).getWrappedCursor();
                sb.append(", ");
            } else {
                break;
            }
        }
        sb.append("]");
        return sb.toString();
    }

    /**
     * Cursor wrapper that remembers where it was closed.
     *
     * Use {@link #get} to create a wrapped cursor.
     * USe {@link #getTraceIfAvailable} to get the stack trace.
     * Use {@link #log} to log if/where it was closed.
     */
    public static class CloseTraceCursorWrapper extends CursorWrapper {
        private static final boolean TRACE_ENABLED = false;

        private Exception mTrace;

        private CloseTraceCursorWrapper(Cursor cursor) {
            super(cursor);
        }

        @Override
        public void close() {
            mTrace = new Exception("STACK TRACE");
            super.close();
        }

        public static Exception getTraceIfAvailable(Cursor c) {
            if (c instanceof CloseTraceCursorWrapper) {
                return ((CloseTraceCursorWrapper) c).mTrace;
            } else {
                return null;
            }
        }

        public static void log(Cursor c) {
            if (c == null) {
                return;
            }
            if (c.isClosed()) {
                Log.w(Logging.LOG_TAG, "Cursor was closed here: Cursor=" + c,
                        getTraceIfAvailable(c));
            } else {
                Log.w(Logging.LOG_TAG, "Cursor not closed.  Cursor=" + c);
            }
        }

        public static Cursor get(Cursor original) {
            return TRACE_ENABLED ? new CloseTraceCursorWrapper(original) : original;
        }

        /* package */ static CloseTraceCursorWrapper alwaysCreateForTest(Cursor original) {
            return new CloseTraceCursorWrapper(original);
        }
    }

    /**
     * Test that the given strings are equal in a null-pointer safe fashion.
     */
    public static boolean areStringsEqual(String s1, String s2) {
        return (s1 != null && s1.equals(s2)) || (s1 == null && s2 == null);
    }

    public static void enableStrictMode(boolean enabled) {
        StrictMode.setThreadPolicy(enabled
                ? new StrictMode.ThreadPolicy.Builder().detectAll().build()
                : StrictMode.ThreadPolicy.LAX);
        StrictMode.setVmPolicy(enabled
                ? new StrictMode.VmPolicy.Builder().detectAll().build()
                : StrictMode.VmPolicy.LAX);
    }

    public static String dumpFragment(Fragment f) {
        StringWriter sw = new StringWriter();
        PrintWriter w = new PrintWriter(sw);
        f.dump("", new FileDescriptor(), w, new String[0]);
        return sw.toString();
    }

    /**
     * Builds an "in" expression for SQLite.
     *
     * e.g. "ID" + 1,2,3 -> "ID in (1,2,3)".  If {@code values} is empty or null, it returns an
     * empty string.
     */
    public static String buildInSelection(String columnName, Collection<? extends Number> values) {
        if ((values == null) || (values.size() == 0)) {
            return "";
        }
        StringBuilder sb = new StringBuilder();
        sb.append(columnName);
        sb.append(" in (");
        String sep = "";
        for (Number n : values) {
            sb.append(sep);
            sb.append(n.toString());
            sep = ",";
        }
        sb.append(')');
        return sb.toString();
    }
}