xref: /packages/apps/Calendar/src/com/android/calendar/Utils.java

/*
 * Copyright (C) 2006 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.calendar;

import static android.provider.CalendarContract.EXTRA_EVENT_BEGIN_TIME;

import com.android.calendar.CalendarController.ViewType;

import android.app.Activity;
import android.app.SearchManager;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.graphics.Color;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.text.TextUtils;
import android.text.format.DateFormat;
import android.text.format.DateUtils;
import android.text.format.Time;
import android.util.Log;
import android.widget.SearchView;

import com.android.calendar.CalendarUtils.TimeZoneUtils;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Formatter;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.TimeZone;

public class Utils {
    private static final boolean DEBUG = false;
    private static final String TAG = "CalUtils";

    // Set to 0 until we have UI to perform undo
    public static final long UNDO_DELAY = 0;

    // For recurring events which instances of the series are being modified
    public static final int MODIFY_UNINITIALIZED = 0;
    public static final int MODIFY_SELECTED = 1;
    public static final int MODIFY_ALL_FOLLOWING = 2;
    public static final int MODIFY_ALL = 3;

    // When the edit event view finishes it passes back the appropriate exit
    // code.
    public static final int DONE_REVERT = 1 << 0;
    public static final int DONE_SAVE = 1 << 1;
    public static final int DONE_DELETE = 1 << 2;
    // And should re run with DONE_EXIT if it should also leave the view, just
    // exiting is identical to reverting
    public static final int DONE_EXIT = 1 << 0;

    public static final String OPEN_EMAIL_MARKER = " <";
    public static final String CLOSE_EMAIL_MARKER = ">";

    public static final String INTENT_KEY_DETAIL_VIEW = "DETAIL_VIEW";
    public static final String INTENT_KEY_VIEW_TYPE = "VIEW";
    public static final String INTENT_VALUE_VIEW_TYPE_DAY = "DAY";
    public static final String INTENT_KEY_HOME = "KEY_HOME";

    public static final int MONDAY_BEFORE_JULIAN_EPOCH = Time.EPOCH_JULIAN_DAY - 3;
    public static final int DECLINED_EVENT_ALPHA = 0x66;
    public static final int DECLINED_EVENT_TEXT_ALPHA = 0xC0;

    private static final float SATURATION_ADJUST = 1.3f;
    private static final float INTENSITY_ADJUST = 0.8f;

    // Defines used by the DNA generation code
    static final int DAY_IN_MINUTES = 60 * 24;
    static final int WEEK_IN_MINUTES = DAY_IN_MINUTES * 7;
    // The work day is being counted as 6am to 8pm
    static int WORK_DAY_MINUTES = 14 * 60;
    static int WORK_DAY_START_MINUTES = 6 * 60;
    static int WORK_DAY_END_MINUTES = 20 * 60;
    static int WORK_DAY_END_LENGTH = (24 * 60) - WORK_DAY_END_MINUTES;
    static int CONFLICT_COLOR = 0xFF000000;
    static boolean mMinutesLoaded = false;

    // The name of the shared preferences file. This name must be maintained for
    // historical
    // reasons, as it's what PreferenceManager assigned the first time the file
    // was created.
    static final String SHARED_PREFS_NAME = "com.android.calendar_preferences";

    public static final String APPWIDGET_DATA_TYPE = "vnd.android.data/update";

    static final String MACHINE_GENERATED_ADDRESS = "calendar.google.com";

    private static final TimeZoneUtils mTZUtils = new TimeZoneUtils(SHARED_PREFS_NAME);
    private static boolean mAllowWeekForDetailView = false;
    private static long mTardis = 0;

    public static int getViewTypeFromIntentAndSharedPref(Activity activity) {
        Intent intent = activity.getIntent();
        Bundle extras = intent.getExtras();
        SharedPreferences prefs = GeneralPreferences.getSharedPreferences(activity);

        if (TextUtils.equals(intent.getAction(), Intent.ACTION_EDIT)) {
            return ViewType.EDIT;
        }
        if (extras != null) {
            if (extras.getBoolean(INTENT_KEY_DETAIL_VIEW, false)) {
                // This is the "detail" view which is either agenda or day view
                return prefs.getInt(GeneralPreferences.KEY_DETAILED_VIEW,
                        GeneralPreferences.DEFAULT_DETAILED_VIEW);
            } else if (INTENT_VALUE_VIEW_TYPE_DAY.equals(extras.getString(INTENT_KEY_VIEW_TYPE))) {
                // Not sure who uses this. This logic came from LaunchActivity
                return ViewType.DAY;
            }
        }

        // Default to the last view
        return prefs.getInt(
                GeneralPreferences.KEY_START_VIEW, GeneralPreferences.DEFAULT_START_VIEW);
    }

    /**
     * Gets the intent action for telling the widget to update.
     */
    public static String getWidgetUpdateAction(Context context) {
        return context.getPackageName() + ".APPWIDGET_UPDATE";
    }

    /**
     * Gets the intent action for telling the widget to update.
     */
    public static String getWidgetScheduledUpdateAction(Context context) {
        return context.getPackageName() + ".APPWIDGET_SCHEDULED_UPDATE";
    }

    /**
     * Gets the intent action for telling the widget to update.
     */
    public static String getSearchAuthority(Context context) {
        return context.getPackageName() + ".CalendarRecentSuggestionsProvider";
    }

    /**
     * Writes a new home time zone to the db. Updates the home time zone in the
     * db asynchronously and updates the local cache. Sending a time zone of
     * **tbd** will cause it to be set to the device's time zone. null or empty
     * tz will be ignored.
     *
     * @param context The calling activity
     * @param timeZone The time zone to set Calendar to, or **tbd**
     */
    public static void setTimeZone(Context context, String timeZone) {
        mTZUtils.setTimeZone(context, timeZone);
    }

    /**
     * Gets the time zone that Calendar should be displayed in This is a helper
     * method to get the appropriate time zone for Calendar. If this is the
     * first time this method has been called it will initiate an asynchronous
     * query to verify that the data in preferences is correct. The callback
     * supplied will only be called if this query returns a value other than
     * what is stored in preferences and should cause the calling activity to
     * refresh anything that depends on calling this method.
     *
     * @param context The calling activity
     * @param callback The runnable that should execute if a query returns new
     *            values
     * @return The string value representing the time zone Calendar should
     *         display
     */
    public static String getTimeZone(Context context, Runnable callback) {
        return mTZUtils.getTimeZone(context, callback);
    }

    /**
     * Formats a date or a time range according to the local conventions.
     *
     * @param context the context is required only if the time is shown
     * @param startMillis the start time in UTC milliseconds
     * @param endMillis the end time in UTC milliseconds
     * @param flags a bit mask of options See {@link DateUtils#formatDateRange(Context, Formatter,
     * long, long, int, String) formatDateRange}
     * @return a string containing the formatted date/time range.
     */
    public static String formatDateRange(
            Context context, long startMillis, long endMillis, int flags) {
        return mTZUtils.formatDateRange(context, startMillis, endMillis, flags);
    }

    public static String getSharedPreference(Context context, String key, String defaultValue) {
        SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        return prefs.getString(key, defaultValue);
    }

    public static int getSharedPreference(Context context, String key, int defaultValue) {
        SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        return prefs.getInt(key, defaultValue);
    }

    public static boolean getSharedPreference(Context context, String key, boolean defaultValue) {
        SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        return prefs.getBoolean(key, defaultValue);
    }

    /**
     * Asynchronously sets the preference with the given key to the given value
     *
     * @param context the context to use to get preferences from
     * @param key the key of the preference to set
     * @param value the value to set
     */
    public static void setSharedPreference(Context context, String key, String value) {
        SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        prefs.edit().putString(key, value).apply();
    }

    protected static void tardis() {
        mTardis = System.currentTimeMillis();
    }

    protected static long getTardis() {
        return mTardis;
    }

    static void setSharedPreference(Context context, String key, boolean value) {
        SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        SharedPreferences.Editor editor = prefs.edit();
        editor.putBoolean(key, value);
        editor.apply();
    }

    static void setSharedPreference(Context context, String key, int value) {
        SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        SharedPreferences.Editor editor = prefs.edit();
        editor.putInt(key, value);
        editor.apply();
    }

    /**
     * Save default agenda/day/week/month view for next time
     *
     * @param context
     * @param viewId {@link CalendarController.ViewType}
     */
    static void setDefaultView(Context context, int viewId) {
        SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        SharedPreferences.Editor editor = prefs.edit();

        boolean validDetailView = false;
        if (mAllowWeekForDetailView && viewId == CalendarController.ViewType.WEEK) {
            validDetailView = true;
        } else {
            validDetailView = viewId == CalendarController.ViewType.AGENDA
                    || viewId == CalendarController.ViewType.DAY;
        }

        if (validDetailView) {
            // Record the detail start view
            editor.putInt(GeneralPreferences.KEY_DETAILED_VIEW, viewId);
        }

        // Record the (new) start view
        editor.putInt(GeneralPreferences.KEY_START_VIEW, viewId);
        editor.apply();
    }

    public static MatrixCursor matrixCursorFromCursor(Cursor cursor) {
        MatrixCursor newCursor = new MatrixCursor(cursor.getColumnNames());
        int numColumns = cursor.getColumnCount();
        String data[] = new String[numColumns];
        cursor.moveToPosition(-1);
        while (cursor.moveToNext()) {
            for (int i = 0; i < numColumns; i++) {
                data[i] = cursor.getString(i);
            }
            newCursor.addRow(data);
        }
        return newCursor;
    }

    /**
     * Compares two cursors to see if they contain the same data.
     *
     * @return Returns true of the cursors contain the same data and are not
     *         null, false otherwise
     */
    public static boolean compareCursors(Cursor c1, Cursor c2) {
        if (c1 == null || c2 == null) {
            return false;
        }

        int numColumns = c1.getColumnCount();
        if (numColumns != c2.getColumnCount()) {
            return false;
        }

        if (c1.getCount() != c2.getCount()) {
            return false;
        }

        c1.moveToPosition(-1);
        c2.moveToPosition(-1);
        while (c1.moveToNext() && c2.moveToNext()) {
            for (int i = 0; i < numColumns; i++) {
                if (!TextUtils.equals(c1.getString(i), c2.getString(i))) {
                    return false;
                }
            }
        }

        return true;
    }

    /**
     * If the given intent specifies a time (in milliseconds since the epoch),
     * then that time is returned. Otherwise, the current time is returned.
     */
    public static final long timeFromIntentInMillis(Intent intent) {
        // If the time was specified, then use that. Otherwise, use the current
        // time.
        Uri data = intent.getData();
        long millis = intent.getLongExtra(EXTRA_EVENT_BEGIN_TIME, -1);
        if (millis == -1 && data != null && data.isHierarchical()) {
            List<String> path = data.getPathSegments();
            if (path.size() == 2 && path.get(0).equals("time")) {
                try {
                    millis = Long.valueOf(data.getLastPathSegment());
                } catch (NumberFormatException e) {
                    Log.i("Calendar", "timeFromIntentInMillis: Data existed but no valid time "
                            + "found. Using current time.");
                }
            }
        }
        if (millis <= 0) {
            millis = System.currentTimeMillis();
        }
        return millis;
    }

    /**
     * Formats the given Time object so that it gives the month and year (for
     * example, "September 2007").
     *
     * @param time the time to format
     * @return the string containing the weekday and the date
     */
    public static String formatMonthYear(Context context, Time time) {
        int flags = DateUtils.FORMAT_SHOW_DATE | DateUtils.FORMAT_NO_MONTH_DAY
                | DateUtils.FORMAT_SHOW_YEAR;
        long millis = time.toMillis(true);
        return formatDateRange(context, millis, millis, flags);
    }

    /**
     * Returns a list joined together by the provided delimiter, for example,
     * ["a", "b", "c"] could be joined into "a,b,c"
     *
     * @param things the things to join together
     * @param delim the delimiter to use
     * @return a string contained the things joined together
     */
    public static String join(List<?> things, String delim) {
        StringBuilder builder = new StringBuilder();
        boolean first = true;
        for (Object thing : things) {
            if (first) {
                first = false;
            } else {
                builder.append(delim);
            }
            builder.append(thing.toString());
        }
        return builder.toString();
    }

    /**
     * Returns the week since {@link Time#EPOCH_JULIAN_DAY} (Jan 1, 1970)
     * adjusted for first day of week.
     *
     * This takes a julian day and the week start day and calculates which
     * week since {@link Time#EPOCH_JULIAN_DAY} that day occurs in, starting
     * at 0. *Do not* use this to compute the ISO week number for the year.
     *
     * @param julianDay The julian day to calculate the week number for
     * @param firstDayOfWeek Which week day is the first day of the week,
     *          see {@link Time#SUNDAY}
     * @return Weeks since the epoch
     */
    public static int getWeeksSinceEpochFromJulianDay(int julianDay, int firstDayOfWeek) {
        int diff = Time.THURSDAY - firstDayOfWeek;
        if (diff < 0) {
            diff += 7;
        }
        int refDay = Time.EPOCH_JULIAN_DAY - diff;
        return (julianDay - refDay) / 7;
    }

    /**
     * Takes a number of weeks since the epoch and calculates the Julian day of
     * the Monday for that week.
     *
     * This assumes that the week containing the {@link Time#EPOCH_JULIAN_DAY}
     * is considered week 0. It returns the Julian day for the Monday
     * {@code week} weeks after the Monday of the week containing the epoch.
     *
     * @param week Number of weeks since the epoch
     * @return The julian day for the Monday of the given week since the epoch
     */
    public static int getJulianMondayFromWeeksSinceEpoch(int week) {
        return MONDAY_BEFORE_JULIAN_EPOCH + week * 7;
    }

    /**
     * Get first day of week as android.text.format.Time constant.
     *
     * @return the first day of week in android.text.format.Time
     */
    public static int getFirstDayOfWeek(Context context) {
        SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        String pref = prefs.getString(
                GeneralPreferences.KEY_WEEK_START_DAY, GeneralPreferences.WEEK_START_DEFAULT);

        int startDay;
        if (GeneralPreferences.WEEK_START_DEFAULT.equals(pref)) {
            startDay = Calendar.getInstance().getFirstDayOfWeek();
        } else {
            startDay = Integer.parseInt(pref);
        }

        if (startDay == Calendar.SATURDAY) {
            return Time.SATURDAY;
        } else if (startDay == Calendar.MONDAY) {
            return Time.MONDAY;
        } else {
            return Time.SUNDAY;
        }
    }

    /**
     * @return true when week number should be shown.
     */
    public static boolean getShowWeekNumber(Context context) {
        final SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        return prefs.getBoolean(
                GeneralPreferences.KEY_SHOW_WEEK_NUM, GeneralPreferences.DEFAULT_SHOW_WEEK_NUM);
    }

    /**
     * @return true when declined events should be hidden.
     */
    public static boolean getHideDeclinedEvents(Context context) {
        final SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        return prefs.getBoolean(GeneralPreferences.KEY_HIDE_DECLINED, false);
    }

    public static int getDaysPerWeek(Context context) {
        final SharedPreferences prefs = GeneralPreferences.getSharedPreferences(context);
        return prefs.getInt(GeneralPreferences.KEY_DAYS_PER_WEEK, 7);
    }

    /**
     * Determine whether the column position is Saturday or not.
     *
     * @param column the column position
     * @param firstDayOfWeek the first day of week in android.text.format.Time
     * @return true if the column is Saturday position
     */
    public static boolean isSaturday(int column, int firstDayOfWeek) {
        return (firstDayOfWeek == Time.SUNDAY && column == 6)
                || (firstDayOfWeek == Time.MONDAY && column == 5)
                || (firstDayOfWeek == Time.SATURDAY && column == 0);
    }

    /**
     * Determine whether the column position is Sunday or not.
     *
     * @param column the column position
     * @param firstDayOfWeek the first day of week in android.text.format.Time
     * @return true if the column is Sunday position
     */
    public static boolean isSunday(int column, int firstDayOfWeek) {
        return (firstDayOfWeek == Time.SUNDAY && column == 0)
                || (firstDayOfWeek == Time.MONDAY && column == 6)
                || (firstDayOfWeek == Time.SATURDAY && column == 1);
    }

    /**
     * Convert given UTC time into current local time. This assumes it is for an
     * allday event and will adjust the time to be on a midnight boundary.
     *
     * @param recycle Time object to recycle, otherwise null.
     * @param utcTime Time to convert, in UTC.
     * @param tz The time zone to convert this time to.
     */
    public static long convertAlldayUtcToLocal(Time recycle, long utcTime, String tz) {
        if (recycle == null) {
            recycle = new Time();
        }
        recycle.timezone = Time.TIMEZONE_UTC;
        recycle.set(utcTime);
        recycle.timezone = tz;
        return recycle.normalize(true);
    }

    public static long convertAlldayLocalToUTC(Time recycle, long localTime, String tz) {
        if (recycle == null) {
            recycle = new Time();
        }
        recycle.timezone = tz;
        recycle.set(localTime);
        recycle.timezone = Time.TIMEZONE_UTC;
        return recycle.normalize(true);
    }

    /**
     * Finds and returns the next midnight after "theTime" in milliseconds UTC
     *
     * @param recycle - Time object to recycle, otherwise null.
     * @param theTime - Time used for calculations (in UTC)
     * @param tz The time zone to convert this time to.
     */
    public static long getNextMidnight(Time recycle, long theTime, String tz) {
        if (recycle == null) {
            recycle = new Time();
        }
        recycle.timezone = tz;
        recycle.set(theTime);
        recycle.monthDay ++;
        recycle.hour = 0;
        recycle.minute = 0;
        recycle.second = 0;
        return recycle.normalize(true);
    }

    /**
     * Scan through a cursor of calendars and check if names are duplicated.
     * This travels a cursor containing calendar display names and fills in the
     * provided map with whether or not each name is repeated.
     *
     * @param isDuplicateName The map to put the duplicate check results in.
     * @param cursor The query of calendars to check
     * @param nameIndex The column of the query that contains the display name
     */
    public static void checkForDuplicateNames(
            Map<String, Boolean> isDuplicateName, Cursor cursor, int nameIndex) {
        isDuplicateName.clear();
        cursor.moveToPosition(-1);
        while (cursor.moveToNext()) {
            String displayName = cursor.getString(nameIndex);
            // Set it to true if we've seen this name before, false otherwise
            if (displayName != null) {
                isDuplicateName.put(displayName, isDuplicateName.containsKey(displayName));
            }
        }
    }

    /**
     * Null-safe object comparison
     *
     * @param s1
     * @param s2
     * @return
     */
    public static boolean equals(Object o1, Object o2) {
        return o1 == null ? o2 == null : o1.equals(o2);
    }

    public static void setAllowWeekForDetailView(boolean allowWeekView) {
        mAllowWeekForDetailView  = allowWeekView;
    }

    public static boolean getAllowWeekForDetailView() {
        return mAllowWeekForDetailView;
    }

    public static boolean getConfigBool(Context c, int key) {
        return c.getResources().getBoolean(key);
    }

    public static int getDisplayColorFromColor(int color) {
        // STOPSHIP - Finalize color adjustment algorithm before shipping

        float[] hsv = new float[3];
        Color.colorToHSV(color, hsv);
        hsv[1] = Math.min(hsv[1] * SATURATION_ADJUST, 1.0f);
        hsv[2] = hsv[2] * INTENSITY_ADJUST;
        return Color.HSVToColor(hsv);
    }

    // This takes a color and computes what it would look like blended with
    // white. The result is the color that should be used for declined events.
    public static int getDeclinedColorFromColor(int color) {
        int bg = 0xffffffff;
        int a = DECLINED_EVENT_ALPHA;
        int r = (((color & 0x00ff0000) * a) + ((bg & 0x00ff0000) * (0xff - a))) & 0xff000000;
        int g = (((color & 0x0000ff00) * a) + ((bg & 0x0000ff00) * (0xff - a))) & 0x00ff0000;
        int b = (((color & 0x000000ff) * a) + ((bg & 0x000000ff) * (0xff - a))) & 0x0000ff00;
        return (0xff000000) | ((r | g | b) >> 8);
    }

    // A single strand represents one color of events. Events are divided up by
    // color to make them convenient to draw. The black strand is special in
    // that it holds conflicting events as well as color settings for allday on
    // each day.
    public static class DNAStrand {
        public float[] points;
        public int[] allDays; // color for the allday, 0 means no event
        int position;
        public int color;
        int count;
    }

    // A segment is a single continuous length of time occupied by a single
    // color. Segments should never span multiple days.
    private static class DNASegment {
        int startMinute; // in minutes since the start of the week
        int endMinute;
        int color; // Calendar color or black for conflicts
        int day; // quick reference to the day this segment is on
    }

    /**
     * Converts a list of events to a list of segments to draw. Assumes list is
     * ordered by start time of the events. The function processes events for a
     * range of days from firstJulianDay to firstJulianDay + dayXs.length - 1.
     * The algorithm goes over all the events and creates a set of segments
     * ordered by start time. This list of segments is then converted into a
     * HashMap of strands which contain the draw points and are organized by
     * color. The strands can then be drawn by setting the paint color to each
     * strand's color and calling drawLines on its set of points. The points are
     * set up using the following parameters.
     * <ul>
     * <li>Events between midnight and WORK_DAY_START_MINUTES are compressed
     * into the first 1/8th of the space between top and bottom.</li>
     * <li>Events between WORK_DAY_END_MINUTES and the following midnight are
     * compressed into the last 1/8th of the space between top and bottom</li>
     * <li>Events between WORK_DAY_START_MINUTES and WORK_DAY_END_MINUTES use
     * the remaining 3/4ths of the space</li>
     * <li>All segments drawn will maintain at least minPixels height, except
     * for conflicts in the first or last 1/8th, which may be smaller</li>
     * </ul>
     *
     * @param firstJulianDay The julian day of the first day of events
     * @param events A list of events sorted by start time
     * @param top The lowest y value the dna should be drawn at
     * @param bottom The highest y value the dna should be drawn at
     * @param dayXs An array of x values to draw the dna at, one for each day
     * @param conflictColor the color to use for conflicts
     * @return
     */
    public static HashMap<Integer, DNAStrand> createDNAStrands(int firstJulianDay,
            ArrayList<Event> events, int top, int bottom, int minPixels, int[] dayXs,
            Context context) {

        if (!mMinutesLoaded) {
            if (context == null) {
                Log.wtf(TAG, "No context and haven't loaded parameters yet! Can't create DNA.");
            }
            Resources res = context.getResources();
            CONFLICT_COLOR = res.getColor(R.color.month_dna_conflict_time_color);
            WORK_DAY_START_MINUTES = res.getInteger(R.integer.work_start_minutes);
            WORK_DAY_END_MINUTES = res.getInteger(R.integer.work_end_minutes);
            WORK_DAY_END_LENGTH = DAY_IN_MINUTES - WORK_DAY_END_MINUTES;
            WORK_DAY_MINUTES = WORK_DAY_END_MINUTES - WORK_DAY_START_MINUTES;
            mMinutesLoaded = true;
        }

        if (events == null || events.isEmpty() || dayXs == null || dayXs.length < 1
                || bottom - top < 8 || minPixels < 0) {
            Log.e(TAG,
                    "Bad values for createDNAStrands! events:" + events + " dayXs:"
                            + Arrays.toString(dayXs) + " bot-top:" + (bottom - top) + " minPixels:"
                            + minPixels);
            return null;
        }

        LinkedList<DNASegment> segments = new LinkedList<DNASegment>();
        HashMap<Integer, DNAStrand> strands = new HashMap<Integer, DNAStrand>();
        // add a black strand by default, other colors will get added in
        // the loop
        DNAStrand blackStrand = new DNAStrand();
        blackStrand.color = CONFLICT_COLOR;
        strands.put(CONFLICT_COLOR, blackStrand);
        // the min length is the number of minutes that will occupy
        // MIN_SEGMENT_PIXELS in the 'work day' time slot. This computes the
        // minutes/pixel * minpx where the number of pixels are 3/4 the total
        // dna height: 4*(mins/(px * 3/4))
        int minMinutes = minPixels * 4 * WORK_DAY_MINUTES / (3 * (bottom - top));

        // There are slightly fewer than half as many pixels in 1/6 the space,
        // so round to 2.5x for the min minutes in the non-work area
        int minOtherMinutes = minMinutes * 5 / 2;
        int lastJulianDay = firstJulianDay + dayXs.length - 1;

        Event event = new Event();
        // Go through all the events for the week
        for (Event currEvent : events) {
            // if this event is outside the weeks range skip it
            if (currEvent.endDay < firstJulianDay || currEvent.startDay > lastJulianDay) {
                continue;
            }
            if (currEvent.drawAsAllday()) {
                addAllDayToStrands(currEvent, strands, firstJulianDay, dayXs.length);
                continue;
            }
            // Copy the event over so we can clip its start and end to our range
            currEvent.copyTo(event);
            if (event.startDay < firstJulianDay) {
                event.startDay = firstJulianDay;
                event.startTime = 0;
            }
            // If it starts after the work day make sure the start is at least
            // minPixels from midnight
            if (event.startTime > DAY_IN_MINUTES - minOtherMinutes) {
                event.startTime = DAY_IN_MINUTES - minOtherMinutes;
            }
            if (event.endDay > lastJulianDay) {
                event.endDay = lastJulianDay;
                event.endTime = DAY_IN_MINUTES - 1;
            }
            // If the end time is before the work day make sure it ends at least
            // minPixels after midnight
            if (event.endTime < minOtherMinutes) {
                event.endTime = minOtherMinutes;
            }
            // If the start and end are on the same day make sure they are at
            // least minPixels apart. This only needs to be done for times
            // outside the work day as the min distance for within the work day
            // is enforced in the segment code.
            if (event.startDay == event.endDay &&
                    event.endTime - event.startTime < minOtherMinutes) {
                // If it's less than minPixels in an area before the work
                // day
                if (event.startTime < WORK_DAY_START_MINUTES) {
                    // extend the end to the first easy guarantee that it's
                    // minPixels
                    event.endTime = Math.min(event.startTime + minOtherMinutes,
                            WORK_DAY_START_MINUTES + minMinutes);
                    // if it's in the area after the work day
                } else if (event.endTime > WORK_DAY_END_MINUTES) {
                    // First try shifting the end but not past midnight
                    event.endTime = Math.min(event.endTime + minOtherMinutes, DAY_IN_MINUTES - 1);
                    // if it's still too small move the start back
                    if (event.endTime - event.startTime < minOtherMinutes) {
                        event.startTime = event.endTime - minOtherMinutes;
                    }
                }
            }

            // This handles adding the first segment
            if (segments.size() == 0) {
                addNewSegment(segments, event, strands, firstJulianDay, 0, minMinutes);
                continue;
            }
            // Now compare our current start time to the end time of the last
            // segment in the list
            DNASegment lastSegment = segments.getLast();
            int startMinute = (event.startDay - firstJulianDay) * DAY_IN_MINUTES + event.startTime;
            int endMinute = Math.max((event.endDay - firstJulianDay) * DAY_IN_MINUTES
                    + event.endTime, startMinute + minMinutes);

            if (startMinute < 0) {
                startMinute = 0;
            }
            if (endMinute >= WEEK_IN_MINUTES) {
                endMinute = WEEK_IN_MINUTES - 1;
            }
            // If we start before the last segment in the list ends we need to
            // start going through the list as this may conflict with other
            // events
            if (startMinute < lastSegment.endMinute) {
                int i = segments.size();
                // find the last segment this event intersects with
                while (--i >= 0 && endMinute < segments.get(i).startMinute);

                DNASegment currSegment;
                // for each segment this event intersects with
                for (; i >= 0 && startMinute <= (currSegment = segments.get(i)).endMinute; i--) {
                    // if the segment is already a conflict ignore it
                    if (currSegment.color == CONFLICT_COLOR) {
                        continue;
                    }
                    // if the event ends before the segment and wouldn't create
                    // a segment that is too small split off the right side
                    if (endMinute < currSegment.endMinute - minMinutes) {
                        DNASegment rhs = new DNASegment();
                        rhs.endMinute = currSegment.endMinute;
                        rhs.color = currSegment.color;
                        rhs.startMinute = endMinute + 1;
                        rhs.day = currSegment.day;
                        currSegment.endMinute = endMinute;
                        segments.add(i + 1, rhs);
                        strands.get(rhs.color).count++;
                        if (DEBUG) {
                            Log.d(TAG, "Added rhs, curr:" + currSegment.toString() + " i:"
                                    + segments.get(i).toString());
                        }
                    }
                    // if the event starts after the segment and wouldn't create
                    // a segment that is too small split off the left side
                    if (startMinute > currSegment.startMinute + minMinutes) {
                        DNASegment lhs = new DNASegment();
                        lhs.startMinute = currSegment.startMinute;
                        lhs.color = currSegment.color;
                        lhs.endMinute = startMinute - 1;
                        lhs.day = currSegment.day;
                        currSegment.startMinute = startMinute;
                        // increment i so that we are at the right position when
                        // referencing the segments to the right and left of the
                        // current segment.
                        segments.add(i++, lhs);
                        strands.get(lhs.color).count++;
                        if (DEBUG) {
                            Log.d(TAG, "Added lhs, curr:" + currSegment.toString() + " i:"
                                    + segments.get(i).toString());
                        }
                    }
                    // if the right side is black merge this with the segment to
                    // the right if they're on the same day and overlap
                    if (i + 1 < segments.size()) {
                        DNASegment rhs = segments.get(i + 1);
                        if (rhs.color == CONFLICT_COLOR && currSegment.day == rhs.day
                                && rhs.startMinute <= currSegment.endMinute + 1) {
                            rhs.startMinute = Math.min(currSegment.startMinute, rhs.startMinute);
                            segments.remove(currSegment);
                            strands.get(currSegment.color).count--;
                            // point at the new current segment
                            currSegment = rhs;
                        }
                    }
                    // if the left side is black merge this with the segment to
                    // the left if they're on the same day and overlap
                    if (i - 1 >= 0) {
                        DNASegment lhs = segments.get(i - 1);
                        if (lhs.color == CONFLICT_COLOR && currSegment.day == lhs.day
                                && lhs.endMinute >= currSegment.startMinute - 1) {
                            lhs.endMinute = Math.max(currSegment.endMinute, lhs.endMinute);
                            segments.remove(currSegment);
                            strands.get(currSegment.color).count--;
                            // point at the new current segment
                            currSegment = lhs;
                            // point i at the new current segment in case new
                            // code is added
                            i--;
                        }
                    }
                    // if we're still not black, decrement the count for the
                    // color being removed, change this to black, and increment
                    // the black count
                    if (currSegment.color != CONFLICT_COLOR) {
                        strands.get(currSegment.color).count--;
                        currSegment.color = CONFLICT_COLOR;
                        strands.get(CONFLICT_COLOR).count++;
                    }
                }

            }
            // If this event extends beyond the last segment add a new segment
            if (endMinute > lastSegment.endMinute) {
                addNewSegment(segments, event, strands, firstJulianDay, lastSegment.endMinute,
                        minMinutes);
            }
        }
        weaveDNAStrands(segments, firstJulianDay, strands, top, bottom, dayXs);
        return strands;
    }

    // This figures out allDay colors as allDay events are found
    private static void addAllDayToStrands(Event event, HashMap<Integer, DNAStrand> strands,
            int firstJulianDay, int numDays) {
        DNAStrand strand = getOrCreateStrand(strands, CONFLICT_COLOR);
        // if we haven't initialized the allDay portion create it now
        if (strand.allDays == null) {
            strand.allDays = new int[numDays];
        }

        // For each day this event is on update the color
        int end = Math.min(event.endDay - firstJulianDay, numDays - 1);
        for (int i = Math.max(event.startDay - firstJulianDay, 0); i <= end; i++) {
            if (strand.allDays[i] != 0) {
                // if this day already had a color, it is now a conflict
                strand.allDays[i] = CONFLICT_COLOR;
            } else {
                // else it's just the color of the event
                strand.allDays[i] = event.color;
            }
        }
    }

    // This processes all the segments, sorts them by color, and generates a
    // list of points to draw
    private static void weaveDNAStrands(LinkedList<DNASegment> segments, int firstJulianDay,
            HashMap<Integer, DNAStrand> strands, int top, int bottom, int[] dayXs) {
        // First, get rid of any colors that ended up with no segments
        Iterator<DNAStrand> strandIterator = strands.values().iterator();
        while (strandIterator.hasNext()) {
            DNAStrand strand = strandIterator.next();
            if (strand.count < 1 && strand.allDays == null) {
                strandIterator.remove();
                continue;
            }
            strand.points = new float[strand.count * 4];
            strand.position = 0;
        }
        // Go through each segment and compute its points
        for (DNASegment segment : segments) {
            // Add the points to the strand of that color
            DNAStrand strand = strands.get(segment.color);
            int dayIndex = segment.day - firstJulianDay;
            int dayStartMinute = segment.startMinute % DAY_IN_MINUTES;
            int dayEndMinute = segment.endMinute % DAY_IN_MINUTES;
            int height = bottom - top;
            int workDayHeight = height * 3 / 4;
            int remainderHeight = (height - workDayHeight) / 2;

            int x = dayXs[dayIndex];
            int y0 = 0;
            int y1 = 0;

            y0 = top + getPixelOffsetFromMinutes(dayStartMinute, workDayHeight, remainderHeight);
            y1 = top + getPixelOffsetFromMinutes(dayEndMinute, workDayHeight, remainderHeight);
            if (DEBUG) {
                Log.d(TAG, "Adding " + Integer.toHexString(segment.color) + " at x,y0,y1: " + x
                        + " " + y0 + " " + y1 + " for " + dayStartMinute + " " + dayEndMinute);
            }
            strand.points[strand.position++] = x;
            strand.points[strand.position++] = y0;
            strand.points[strand.position++] = x;
            strand.points[strand.position++] = y1;
        }
    }

    /**
     * Compute a pixel offset from the top for a given minute from the work day
     * height and the height of the top area.
     */
    private static int getPixelOffsetFromMinutes(int minute, int workDayHeight,
            int remainderHeight) {
        int y;
        if (minute < WORK_DAY_START_MINUTES) {
            y = minute * remainderHeight / WORK_DAY_START_MINUTES;
        } else if (minute < WORK_DAY_END_MINUTES) {
            y = remainderHeight + (minute - WORK_DAY_START_MINUTES) * workDayHeight
                    / WORK_DAY_MINUTES;
        } else {
            y = remainderHeight + workDayHeight + (minute - WORK_DAY_END_MINUTES) * remainderHeight
                    / WORK_DAY_END_LENGTH;
        }
        return y;
    }

    /**
     * Add a new segment based on the event provided. This will handle splitting
     * segments across day boundaries and ensures a minimum size for segments.
     */
    private static void addNewSegment(LinkedList<DNASegment> segments, Event event,
            HashMap<Integer, DNAStrand> strands, int firstJulianDay, int minStart, int minMinutes) {
        if (event.startDay > event.endDay) {
            Log.wtf(TAG, "Event starts after it ends: " + event.toString());
        }
        // If this is a multiday event split it up by day
        if (event.startDay != event.endDay) {
            Event lhs = new Event();
            lhs.color = event.color;
            lhs.startDay = event.startDay;
            // the first day we want the start time to be the actual start time
            lhs.startTime = event.startTime;
            lhs.endDay = lhs.startDay;
            lhs.endTime = DAY_IN_MINUTES - 1;
            // Nearly recursive iteration!
            while (lhs.startDay != event.endDay) {
                addNewSegment(segments, lhs, strands, firstJulianDay, minStart, minMinutes);
                // The days in between are all day, even though that shouldn't
                // actually happen due to the allday filtering
                lhs.startDay++;
                lhs.endDay = lhs.startDay;
                lhs.startTime = 0;
                minStart = 0;
            }
            // The last day we want the end time to be the actual end time
            lhs.endTime = event.endTime;
            event = lhs;
        }
        // Create the new segment and compute its fields
        DNASegment segment = new DNASegment();
        int dayOffset = (event.startDay - firstJulianDay) * DAY_IN_MINUTES;
        int endOfDay = dayOffset + DAY_IN_MINUTES - 1;
        // clip the start if needed
        segment.startMinute = Math.max(dayOffset + event.startTime, minStart);
        // and extend the end if it's too small, but not beyond the end of the
        // day
        int minEnd = Math.min(segment.startMinute + minMinutes, endOfDay);
        segment.endMinute = Math.max(dayOffset + event.endTime, minEnd);
        if (segment.endMinute > endOfDay) {
            segment.endMinute = endOfDay;
        }

        segment.color = event.color;
        segment.day = event.startDay;
        segments.add(segment);
        // increment the count for the correct color or add a new strand if we
        // don't have that color yet
        DNAStrand strand = getOrCreateStrand(strands, segment.color);
        strand.count++;
    }

    /**
     * Try to get a strand of the given color. Create it if it doesn't exist.
     */
    private static DNAStrand getOrCreateStrand(HashMap<Integer, DNAStrand> strands, int color) {
        DNAStrand strand = strands.get(color);
        if (strand == null) {
            strand = new DNAStrand();
            strand.color = color;
            strand.count = 0;
            strands.put(strand.color, strand);
        }
        return strand;
    }

    /**
     * Sends an intent to launch the top level Calendar view.
     *
     * @param context
     */
    public static void returnToCalendarHome(Context context) {
        Intent launchIntent = new Intent(context, AllInOneActivity.class);
        launchIntent.setAction(Intent.ACTION_DEFAULT);
        launchIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        launchIntent.putExtra(INTENT_KEY_HOME, true);
        context.startActivity(launchIntent);
    }

    /**
     * This sets up a search view to use Calendar's search suggestions provider
     * and to allow refining the search.
     *
     * @param view The {@link SearchView} to set up
     * @param act The activity using the view
     */
    public static void setUpSearchView(SearchView view, Activity act) {
        SearchManager searchManager = (SearchManager) act.getSystemService(Context.SEARCH_SERVICE);
        view.setSearchableInfo(searchManager.getSearchableInfo(act.getComponentName()));
        view.setQueryRefinementEnabled(true);
    }

    /**
     * Given a context and a time in millis since unix epoch figures out the
     * correct week of the year for that time.
     *
     * @param millisSinceEpoch
     * @return
     */
    public static int getWeekNumberFromTime(long millisSinceEpoch, Context context) {
        Time weekTime = new Time(getTimeZone(context, null));
        weekTime.set(millisSinceEpoch);
        weekTime.normalize(true);
        int firstDayOfWeek = getFirstDayOfWeek(context);
        // if the date is on Saturday or Sunday and the start of the week
        // isn't Monday we may need to shift the date to be in the correct
        // week
        if (weekTime.weekDay == Time.SUNDAY
                && (firstDayOfWeek == Time.SUNDAY || firstDayOfWeek == Time.SATURDAY)) {
            weekTime.monthDay++;
            weekTime.normalize(true);
        } else if (weekTime.weekDay == Time.SATURDAY && firstDayOfWeek == Time.SATURDAY) {
            weekTime.monthDay += 2;
            weekTime.normalize(true);
        }
        return weekTime.getWeekNumber();
    }

    /**
     * Formats a day of the week string. This is either just the name of the day
     * or a combination of yesterday/today/tomorrow and the day of the week.
     *
     * @param julianDay The julian day to get the string for
     * @param todayJulianDay The julian day for today's date
     * @param millis A utc millis since epoch time that falls on julian day
     * @param context The calling context, used to get the timezone and do the
     *            formatting
     * @return
     */
    public static String getDayOfWeekString(int julianDay, int todayJulianDay, long millis,
            Context context) {
        getTimeZone(context, null);
        int flags = DateUtils.FORMAT_SHOW_WEEKDAY;
        String dayViewText;
        if (julianDay == todayJulianDay) {
            dayViewText = context.getString(R.string.agenda_today,
                    mTZUtils.formatDateRange(context, millis, millis, flags).toString());
        } else if (julianDay == todayJulianDay - 1) {
            dayViewText = context.getString(R.string.agenda_yesterday,
                    mTZUtils.formatDateRange(context, millis, millis, flags).toString());
        } else if (julianDay == todayJulianDay + 1) {
            dayViewText = context.getString(R.string.agenda_tomorrow,
                    mTZUtils.formatDateRange(context, millis, millis, flags).toString());
        } else {
            dayViewText = mTZUtils.formatDateRange(context, millis, millis, flags).toString();
        }
        dayViewText = dayViewText.toUpperCase();
        return dayViewText;
    }

    // Calculate the time until midnight + 1 second and set the handler to
    // do run the runnable
    public static void setMidnightUpdater(Handler h, Runnable r, String timezone) {
        if (h == null || r == null || timezone == null) {
            return;
        }
        long now = System.currentTimeMillis();
        Time time = new Time(timezone);
        time.set(now);
        long runInMillis = (24 * 3600 - time.hour * 3600 - time.minute * 60 -
                time.second + 1) * 1000;
        h.removeCallbacks(r);
        h.postDelayed(r, runInMillis);
    }

    // Stop the midnight update thread
    public static void resetMidnightUpdater(Handler h, Runnable r) {
        if (h == null || r == null) {
            return;
        }
        h.removeCallbacks(r);
    }

    /**
     * Returns a string description of the specified time interval.
     */
    public static String getDisplayedDatetime(long startMillis, long endMillis, long currentMillis,
            String localTimezone, boolean allDay, Context context) {
        // Configure date/time formatting.
        int flagsDate = DateUtils.FORMAT_SHOW_DATE | DateUtils.FORMAT_SHOW_WEEKDAY;
        int flagsTime = DateUtils.FORMAT_SHOW_TIME;
        if (DateFormat.is24HourFormat(context)) {
            flagsTime |= DateUtils.FORMAT_24HOUR;
        }

        Time currentTime = new Time(localTimezone);
        currentTime.set(currentMillis);
        Resources resources = context.getResources();
        String datetimeString = null;
        if (allDay) {
            // All day events require special timezone adjustment.
            long localStartMillis = convertAlldayUtcToLocal(null, startMillis, localTimezone);
            long localEndMillis = convertAlldayUtcToLocal(null, endMillis, localTimezone);
            if (singleDayEvent(localStartMillis, localEndMillis, currentTime.gmtoff)) {
                // If possible, use "Today" or "Tomorrow" instead of a full date string.
                int todayOrTomorrow = isTodayOrTomorrow(context.getResources(),
                        localStartMillis, currentMillis, currentTime.gmtoff);
                if (TODAY == todayOrTomorrow) {
                    datetimeString = resources.getString(R.string.today);
                } else if (TOMORROW == todayOrTomorrow) {
                    datetimeString = resources.getString(R.string.tomorrow);
                }
            }
            if (datetimeString == null) {
                // For multi-day allday events or single-day all-day events that are not
                // today or tomorrow, use framework formatter.
                Formatter f = new Formatter(new StringBuilder(50), Locale.getDefault());
                datetimeString = DateUtils.formatDateRange(context, f, startMillis,
                        endMillis, flagsDate, Time.TIMEZONE_UTC).toString();
            }
        } else {
            if (singleDayEvent(startMillis, endMillis, currentTime.gmtoff)) {
                // Format the time.
                String timeString = Utils.formatDateRange(context, startMillis, endMillis,
                        flagsTime);

                // If possible, use "Today" or "Tomorrow" instead of a full date string.
                int todayOrTomorrow = isTodayOrTomorrow(context.getResources(), startMillis,
                        currentMillis, currentTime.gmtoff);
                if (TODAY == todayOrTomorrow) {
                    // Example: "Today at 1:00pm - 2:00 pm"
                    datetimeString = resources.getString(R.string.today_at_time_fmt,
                            timeString);
                } else if (TOMORROW == todayOrTomorrow) {
                    // Example: "Tomorrow at 1:00pm - 2:00 pm"
                    datetimeString = resources.getString(R.string.tomorrow_at_time_fmt,
                            timeString);
                } else {
                    // Format the full date. Example: "Thursday, April 12, 1:00pm - 2:00pm"
                    String dateString = Utils.formatDateRange(context, startMillis, endMillis,
                            flagsDate);
                    datetimeString = resources.getString(R.string.date_time_fmt, dateString,
                            timeString);
                }
            } else {
                // For multiday events, shorten day/month names.
                // Example format: "Fri Apr 6, 5:00pm - Sun, Apr 8, 6:00pm"
                int flagsDatetime = flagsDate | flagsTime | DateUtils.FORMAT_ABBREV_MONTH |
                        DateUtils.FORMAT_ABBREV_WEEKDAY;
                datetimeString = Utils.formatDateRange(context, startMillis, endMillis,
                        flagsDatetime);
            }
        }
        return datetimeString;
    }

    /**
     * Returns the timezone to display in the event info, if the local timezone is different
     * from the event timezone.  Otherwise returns null.
     */
    public static String getDisplayedTimezone(long startMillis, String localTimezone,
            String eventTimezone) {
        String tzDisplay = null;
        if (!TextUtils.equals(localTimezone, eventTimezone)) {
            // Figure out if this is in DST
            TimeZone tz = TimeZone.getTimeZone(localTimezone);
            if (tz == null || tz.getID().equals("GMT")) {
                tzDisplay = localTimezone;
            } else {
                Time startTime = new Time(localTimezone);
                startTime.set(startMillis);
                tzDisplay = tz.getDisplayName(startTime.isDst != 0, TimeZone.SHORT);
            }
        }
        return tzDisplay;
    }

    /**
     * Returns whether the specified time interval is in a single day.
     */
    private static boolean singleDayEvent(long startMillis, long endMillis, long localGmtOffset) {
        if (startMillis == endMillis) {
            return true;
        }

        // An event ending at midnight should still be a single-day event, so check
        // time end-1.
        int startDay = Time.getJulianDay(startMillis, localGmtOffset);
        int endDay = Time.getJulianDay(endMillis - 1, localGmtOffset);
        return startDay == endDay;
    }

    // Using int constants as a return value instead of an enum to minimize resources.
    private static final int TODAY = 1;
    private static final int TOMORROW = 2;
    private static final int NONE = 0;

    /**
     * Returns TODAY or TOMORROW if applicable.  Otherwise returns NONE.
     */
    private static int isTodayOrTomorrow(Resources r, long dayMillis,
            long currentMillis, long localGmtOffset) {
        int startDay = Time.getJulianDay(dayMillis, localGmtOffset);
        int currentDay = Time.getJulianDay(currentMillis, localGmtOffset);

        int days = startDay - currentDay;
        if (days == 1) {
            return TOMORROW;
        } else if (days == 0) {
            return TODAY;
        } else {
            return NONE;
        }
    }

    /**
     * Create an intent for emailing attendees of an event.
     *
     * @param resources The resources for translating strings.
     * @param eventTitle The title of the event to use as the email subject.
     * @param toEmails The list of emails for the 'to' line.
     * @param ccEmails The list of emails for the 'cc' line.
     * @param ownerAccount The owner account to use as the email sender.
     */
    public static Intent createEmailAttendeesIntent(Resources resources, String eventTitle,
            List<String> toEmails, List<String> ccEmails, String ownerAccount) {
        List<String> toList = toEmails;
        List<String> ccList = ccEmails;
        if (toEmails.size() <= 0) {
            if (ccEmails.size() <= 0) {
                // TODO: Return a SEND intent if no one to email to, to at least populate
                // a draft email with the subject (and no recipients).
                throw new IllegalArgumentException("Both toEmails and ccEmails are null.");
            }

            // Email app does not work with no "to" recipient.  Move all 'cc' to 'to'
            // in this case.
            toList = ccEmails;
            ccList = null;
        }

        // Use the event title as the email subject (prepended with 'Re: ').
        String subject = null;
        if (eventTitle != null) {
            subject = resources.getString(R.string.email_subject_prefix) + eventTitle;
        }

        // Use the SENDTO intent with a 'mailto' URI, because using SEND will cause
        // the picker to show apps like text messaging, which does not make sense
        // for email addresses.  We put all data in the URI instead of using the extra
        // Intent fields (ie. EXTRA_CC, etc) because some email apps might not handle
        // those (though gmail does).
        Uri.Builder uriBuilder = new Uri.Builder();
        uriBuilder.scheme("mailto");

        // We will append the first email to the 'mailto' field later (because the
        // current state of the Email app requires it).  Add the remaining 'to' values
        // here.  When the email codebase is updated, we can simplify this.
        if (toList.size() > 1) {
            for (int i = 1; i < toList.size(); i++) {
                // The Email app requires repeated parameter settings instead of
                // a single comma-separated list.
                uriBuilder.appendQueryParameter("to", toList.get(i));
            }
        }

        // Add the subject parameter.
        if (subject != null) {
            uriBuilder.appendQueryParameter("subject", subject);
        }

        // Add the cc parameters.
        if (ccList != null && ccList.size() > 0) {
            for (String email : ccList) {
                uriBuilder.appendQueryParameter("cc", email);
            }
        }

        // Insert the first email after 'mailto:' in the URI manually since Uri.Builder
        // doesn't seem to have a way to do this.
        String uri = uriBuilder.toString();
        if (uri.startsWith("mailto:")) {
            StringBuilder builder = new StringBuilder(uri);
            builder.insert(7, Uri.encode(toList.get(0)));
            uri = builder.toString();
        }

        // Start the email intent.  Email from the account of the calendar owner in case there
        // are multiple email accounts.
        Intent emailIntent = new Intent(android.content.Intent.ACTION_SENDTO, Uri.parse(uri));
        emailIntent.putExtra("fromAccountString", ownerAccount);
        return Intent.createChooser(emailIntent, resources.getString(R.string.email_picker_label));
    }

    /**
     * Example fake email addresses used as attendee emails are resources like conference rooms,
     * or another calendar, etc.  These all end in "calendar.google.com".
     */
    public static boolean isValidEmail(String email) {
        return email != null && !email.endsWith(MACHINE_GENERATED_ADDRESS);
    }
}