/*
 * Copyright (C) 2015 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.settingslib.datetime;

import android.content.Context;
import android.content.res.XmlResourceParser;
import android.icu.text.TimeZoneFormat;
import android.icu.text.TimeZoneNames;
import android.support.annotation.VisibleForTesting;
import android.support.v4.text.BidiFormatter;
import android.support.v4.text.TextDirectionHeuristicsCompat;
import android.text.SpannableString;
import android.text.SpannableStringBuilder;
import android.text.TextUtils;
import android.text.format.DateUtils;
import android.text.style.TtsSpan;
import android.util.Log;
import android.view.View;

import com.android.settingslib.R;

import libcore.util.TimeZoneFinder;

import org.xmlpull.v1.XmlPullParserException;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.TimeZone;

ZoneGetter is the utility class to get time zone and zone list, and both of them have display
name in time zone. In this class, we will keep consistency about display names for all
the methods.
The display name chosen for each zone entry depends on whether the zone is one associated
with the country of the user's chosen locale. For "local" zones we prefer the "long name"
(e.g. "Europe/London" -> "British Summer Time" for people in the UK). For "non-local"
zones we prefer the exemplar location (e.g. "Europe/London" -> "London" for English
speakers from outside the UK). This heuristic is based on the fact that people are
typically familiar with their local timezones and exemplar locations don't always match
modern-day expectations for people living in the country covered. Large countries like
China that mostly use a single timezone (olson id: "Asia/Shanghai") may not live near
"Shanghai" and prefer the long name over the exemplar location. The only time we don't
follow this policy for local zones is when Android supplies multiple olson IDs to choose
from and the use of a zone's long name leads to ambiguity. For example, at the time of
writing Android lists 5 olson ids for Australia which collapse to 2 different zone names
in winter but 4 different zone names in summer. The ambiguity leads to the users
selecting the wrong olson ids.
/**
 * ZoneGetter is the utility class to get time zone and zone list, and both of them have display
 * name in time zone. In this class, we will keep consistency about display names for all
 * the methods.
 *
 * The display name chosen for each zone entry depends on whether the zone is one associated
 * with the country of the user's chosen locale. For "local" zones we prefer the "long name"
 * (e.g. "Europe/London" -> "British Summer Time" for people in the UK). For "non-local"
 * zones we prefer the exemplar location (e.g. "Europe/London" -> "London" for English
 * speakers from outside the UK). This heuristic is based on the fact that people are
 * typically familiar with their local timezones and exemplar locations don't always match
 * modern-day expectations for people living in the country covered. Large countries like
 * China that mostly use a single timezone (olson id: "Asia/Shanghai") may not live near
 * "Shanghai" and prefer the long name over the exemplar location. The only time we don't
 * follow this policy for local zones is when Android supplies multiple olson IDs to choose
 * from and the use of a zone's long name leads to ambiguity. For example, at the time of
 * writing Android lists 5 olson ids for Australia which collapse to 2 different zone names
 * in winter but 4 different zone names in summer. The ambiguity leads to the users
 * selecting the wrong olson ids.
 *
 */
public class ZoneGetter {
    private static final String TAG = "ZoneGetter";

    public static final String KEY_ID = "id";  // value: String

    
Deprecated:
Use KEY_DISPLAY_LABEL instead./**
     * @deprecated Use {@link #KEY_DISPLAY_LABEL} instead.
     */
    @Deprecated
    public static final String KEY_DISPLAYNAME = "name";  // value: String

    public static final String KEY_DISPLAY_LABEL = "display_label"; // value: CharSequence

    
Deprecated:
Use KEY_OFFSET_LABEL instead./**
     * @deprecated Use {@link #KEY_OFFSET_LABEL} instead.
     */
    @Deprecated
    public static final String KEY_GMT = "gmt";  // value: String
    public static final String KEY_OFFSET = "offset";  // value: int (Integer)
    public static final String KEY_OFFSET_LABEL = "offset_label";  // value: CharSequence

    private static final String XMLTAG_TIMEZONE = "timezone";

    public static CharSequence getTimeZoneOffsetAndName(Context context, TimeZone tz, Date now) {
        Locale locale = context.getResources().getConfiguration().locale;
        TimeZoneFormat tzFormatter = TimeZoneFormat.getInstance(locale);
        CharSequence gmtText = getGmtOffsetText(tzFormatter, locale, tz, now);
        TimeZoneNames timeZoneNames = TimeZoneNames.getInstance(locale);
        String zoneNameString = getZoneLongName(timeZoneNames, tz, now);
        if (zoneNameString == null) {
            return gmtText;
        }

        // We don't use punctuation here to avoid having to worry about localizing that too!
        return TextUtils.concat(gmtText, " ", zoneNameString);
    }

    public static List<Map<String, Object>> getZonesList(Context context) {
        final Locale locale = context.getResources().getConfiguration().locale;
        final Date now = new Date();
        final TimeZoneNames timeZoneNames = TimeZoneNames.getInstance(locale);
        final ZoneGetterData data = new ZoneGetterData(context);

        // Work out whether the display names we would show by default would be ambiguous.
        final boolean useExemplarLocationForLocalNames =
                shouldUseExemplarLocationForLocalNames(data, timeZoneNames);

        // Generate the list of zone entries to return.
        List<Map<String, Object>> zones = new ArrayList<Map<String, Object>>();
        for (int i = 0; i < data.zoneCount; i++) {
            TimeZone tz = data.timeZones[i];
            CharSequence gmtOffsetText = data.gmtOffsetTexts[i];

            CharSequence displayName = getTimeZoneDisplayName(data, timeZoneNames,
                    useExemplarLocationForLocalNames, tz, data.olsonIdsToDisplay[i]);
            if (TextUtils.isEmpty(displayName)) {
                displayName = gmtOffsetText;
            }

            int offsetMillis = tz.getOffset(now.getTime());
            Map<String, Object> displayEntry =
                    createDisplayEntry(tz, gmtOffsetText, displayName, offsetMillis);
            zones.add(displayEntry);
        }
        return zones;
    }

    private static Map<String, Object> createDisplayEntry(
            TimeZone tz, CharSequence gmtOffsetText, CharSequence displayName, int offsetMillis) {
        Map<String, Object> map = new HashMap<>();
        map.put(KEY_ID, tz.getID());
        map.put(KEY_DISPLAYNAME, displayName.toString());
        map.put(KEY_DISPLAY_LABEL, displayName);
        map.put(KEY_GMT, gmtOffsetText.toString());
        map.put(KEY_OFFSET_LABEL, gmtOffsetText);
        map.put(KEY_OFFSET, offsetMillis);
        return map;
    }

    private static List<String> readTimezonesToDisplay(Context context) {
        List<String> olsonIds = new ArrayList<String>();
        try (XmlResourceParser xrp = context.getResources().getXml(R.xml.timezones)) {
            while (xrp.next() != XmlResourceParser.START_TAG) {
                continue;
            }
            xrp.next();
            while (xrp.getEventType() != XmlResourceParser.END_TAG) {
                while (xrp.getEventType() != XmlResourceParser.START_TAG) {
                    if (xrp.getEventType() == XmlResourceParser.END_DOCUMENT) {
                        return olsonIds;
                    }
                    xrp.next();
                }
                if (xrp.getName().equals(XMLTAG_TIMEZONE)) {
                    String olsonId = xrp.getAttributeValue(0);
                    olsonIds.add(olsonId);
                }
                while (xrp.getEventType() != XmlResourceParser.END_TAG) {
                    xrp.next();
                }
                xrp.next();
            }
        } catch (XmlPullParserException xppe) {
            Log.e(TAG, "Ill-formatted timezones.xml file");
        } catch (java.io.IOException ioe) {
            Log.e(TAG, "Unable to read timezones.xml file");
        }
        return olsonIds;
    }

    private static boolean shouldUseExemplarLocationForLocalNames(ZoneGetterData data,
            TimeZoneNames timeZoneNames) {
        final Set<CharSequence> localZoneNames = new HashSet<>();
        final Date now = new Date();
        for (int i = 0; i < data.zoneCount; i++) {
            final String olsonId = data.olsonIdsToDisplay[i];
            if (data.localZoneIds.contains(olsonId)) {
                final TimeZone tz = data.timeZones[i];
                CharSequence displayName = getZoneLongName(timeZoneNames, tz, now);
                if (displayName == null) {
                    displayName = data.gmtOffsetTexts[i];
                }
                final boolean nameIsUnique = localZoneNames.add(displayName);
                if (!nameIsUnique) {
                    return true;
                }
            }
        }

        return false;
    }

    private static CharSequence getTimeZoneDisplayName(ZoneGetterData data,
            TimeZoneNames timeZoneNames, boolean useExemplarLocationForLocalNames, TimeZone tz,
            String olsonId) {
        final Date now = new Date();
        final boolean isLocalZoneId = data.localZoneIds.contains(olsonId);
        final boolean preferLongName = isLocalZoneId && !useExemplarLocationForLocalNames;
        String displayName;

        if (preferLongName) {
            displayName = getZoneLongName(timeZoneNames, tz, now);
        } else {
            // Canonicalize the zone ID for ICU. It will only return valid strings for zone IDs
            // that match ICUs zone IDs (which are similar but not guaranteed the same as those
            // in timezones.xml). timezones.xml and related files uses the IANA IDs. ICU IDs are
            // stable and IANA IDs have changed over time so they have drifted.
            // See http://bugs.icu-project.org/trac/ticket/13070 / http://b/36469833.
            String canonicalZoneId = android.icu.util.TimeZone.getCanonicalID(tz.getID());
            if (canonicalZoneId == null) {
                canonicalZoneId = tz.getID();
            }
            displayName = timeZoneNames.getExemplarLocationName(canonicalZoneId);
            if (displayName == null || displayName.isEmpty()) {
                // getZoneExemplarLocation can return null. Fall back to the long name.
                displayName = getZoneLongName(timeZoneNames, tz, now);
            }
        }

        return displayName;
    }

    
Returns the long name for the timezone for the given locale at the time specified. Can return null. /**
     * Returns the long name for the timezone for the given locale at the time specified.
     * Can return {@code null}.
     */
    private static String getZoneLongName(TimeZoneNames names, TimeZone tz, Date now) {
        final TimeZoneNames.NameType nameType =
                tz.inDaylightTime(now) ? TimeZoneNames.NameType.LONG_DAYLIGHT
                        : TimeZoneNames.NameType.LONG_STANDARD;
        return names.getDisplayName(tz.getID(), nameType, now.getTime());
    }

    private static void appendWithTtsSpan(SpannableStringBuilder builder, CharSequence content,
            TtsSpan span) {
        int start = builder.length();
        builder.append(content);
        builder.setSpan(span, start, builder.length(), 0);
    }

    // Input must be positive. minDigits must be 1 or 2.
    private static String formatDigits(int input, int minDigits, String localizedDigits) {
        final int tens = input / 10;
        final int units = input % 10;
        StringBuilder builder = new StringBuilder(minDigits);
        if (input >= 10 || minDigits == 2) {
            builder.append(localizedDigits.charAt(tens));
        }
        builder.append(localizedDigits.charAt(units));
        return builder.toString();
    }

    
Get the GMT offset text label for the given time zone, in the format "GMT-08:00". This will
also add TTS spans to give hints to the text-to-speech engine for the type of data it is.
Params:
tzFormatter – The timezone formatter to use.
locale – The locale which the string is displayed in. This should be the same as the
              locale of the time zone formatter.
tz – Time zone to get the GMT offset from.
now – The current time, used to tell whether daylight savings is active.
Returns:
A CharSequence suitable for display as the offset label of tz./**
     * Get the GMT offset text label for the given time zone, in the format "GMT-08:00". This will
     * also add TTS spans to give hints to the text-to-speech engine for the type of data it is.
     *
     * @param tzFormatter The timezone formatter to use.
     * @param locale The locale which the string is displayed in. This should be the same as the
     *               locale of the time zone formatter.
     * @param tz Time zone to get the GMT offset from.
     * @param now The current time, used to tell whether daylight savings is active.
     * @return A CharSequence suitable for display as the offset label of {@code tz}.
     */
    public static CharSequence getGmtOffsetText(TimeZoneFormat tzFormatter, Locale locale,
            TimeZone tz, Date now) {
        final SpannableStringBuilder builder = new SpannableStringBuilder();

        final String gmtPattern = tzFormatter.getGMTPattern();
        final int placeholderIndex = gmtPattern.indexOf("{0}");
        final String gmtPatternPrefix, gmtPatternSuffix;
        if (placeholderIndex == -1) {
            // Bad pattern. Replace with defaults.
            gmtPatternPrefix = "GMT";
            gmtPatternSuffix = "";
        } else {
            gmtPatternPrefix = gmtPattern.substring(0, placeholderIndex);
            gmtPatternSuffix = gmtPattern.substring(placeholderIndex + 3); // After the "{0}".
        }

        if (!gmtPatternPrefix.isEmpty()) {
            appendWithTtsSpan(builder, gmtPatternPrefix,
                    new TtsSpan.TextBuilder(gmtPatternPrefix).build());
        }

        int offsetMillis = tz.getOffset(now.getTime());
        final boolean negative = offsetMillis < 0;
        final TimeZoneFormat.GMTOffsetPatternType patternType;
        if (negative) {
            offsetMillis = -offsetMillis;
            patternType = TimeZoneFormat.GMTOffsetPatternType.NEGATIVE_HM;
        } else {
            patternType = TimeZoneFormat.GMTOffsetPatternType.POSITIVE_HM;
        }
        final String gmtOffsetPattern = tzFormatter.getGMTOffsetPattern(patternType);
        final String localizedDigits = tzFormatter.getGMTOffsetDigits();

        final int offsetHours = (int) (offsetMillis / DateUtils.HOUR_IN_MILLIS);
        final int offsetMinutes = (int) (offsetMillis / DateUtils.MINUTE_IN_MILLIS);
        final int offsetMinutesRemaining = Math.abs(offsetMinutes) % 60;

        for (int i = 0; i < gmtOffsetPattern.length(); i++) {
            char c = gmtOffsetPattern.charAt(i);
            if (c == '+' || c == '-' || c == '\u2212' /* MINUS SIGN */) {
                final String sign = String.valueOf(c);
                appendWithTtsSpan(builder, sign, new TtsSpan.VerbatimBuilder(sign).build());
            } else if (c == 'H' || c == 'm') {
                final int numDigits;
                if (i + 1 < gmtOffsetPattern.length() && gmtOffsetPattern.charAt(i + 1) == c) {
                    numDigits = 2;
                    i++; // Skip the next formatting character.
                } else {
                    numDigits = 1;
                }
                final int number;
                final String unit;
                if (c == 'H') {
                    number = offsetHours;
                    unit = "hour";
                } else { // c == 'm'
                    number = offsetMinutesRemaining;
                    unit = "minute";
                }
                appendWithTtsSpan(builder, formatDigits(number, numDigits, localizedDigits),
                        new TtsSpan.MeasureBuilder().setNumber(number).setUnit(unit).build());
            } else {
                builder.append(c);
            }
        }

        if (!gmtPatternSuffix.isEmpty()) {
            appendWithTtsSpan(builder, gmtPatternSuffix,
                    new TtsSpan.TextBuilder(gmtPatternSuffix).build());
        }

        CharSequence gmtText = new SpannableString(builder);

        // Ensure that the "GMT+" stays with the "00:00" even if the digits are RTL.
        final BidiFormatter bidiFormatter = BidiFormatter.getInstance();
        boolean isRtl = TextUtils.getLayoutDirectionFromLocale(locale) == View.LAYOUT_DIRECTION_RTL;
        gmtText = bidiFormatter.unicodeWrap(gmtText,
                isRtl ? TextDirectionHeuristicsCompat.RTL : TextDirectionHeuristicsCompat.LTR);
        return gmtText;
    }

    @VisibleForTesting
    public static final class ZoneGetterData {
        public final String[] olsonIdsToDisplay;
        public final CharSequence[] gmtOffsetTexts;
        public final TimeZone[] timeZones;
        public final Set<String> localZoneIds;
        public final int zoneCount;

        public ZoneGetterData(Context context) {
            final Locale locale = context.getResources().getConfiguration().locale;
            final TimeZoneFormat tzFormatter = TimeZoneFormat.getInstance(locale);
            final Date now = new Date();
            final List<String> olsonIdsToDisplayList = readTimezonesToDisplay(context);

            // Load all the data needed to display time zones
            zoneCount = olsonIdsToDisplayList.size();
            olsonIdsToDisplay = new String[zoneCount];
            timeZones = new TimeZone[zoneCount];
            gmtOffsetTexts = new CharSequence[zoneCount];
            for (int i = 0; i < zoneCount; i++) {
                final String olsonId = olsonIdsToDisplayList.get(i);
                olsonIdsToDisplay[i] = olsonId;
                final TimeZone tz = TimeZone.getTimeZone(olsonId);
                timeZones[i] = tz;
                gmtOffsetTexts[i] = getGmtOffsetText(tzFormatter, locale, tz, now);
            }

            // Create a lookup of local zone IDs.
            final List<String> zoneIds = lookupTimeZoneIdsByCountry(locale.getCountry());
            localZoneIds = new HashSet<>(zoneIds);
        }

        @VisibleForTesting
        public List<String> lookupTimeZoneIdsByCountry(String country) {
            return TimeZoneFinder.getInstance().lookupTimeZoneIdsByCountry(country);
        }
    }
}