/*
 * 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 android.text.format;

import android.content.Context;
import android.provider.Settings;
import android.text.SpannableStringBuilder;
import android.text.Spanned;
import android.text.SpannedString;

import com.android.internal.R;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Locale;
import java.util.TimeZone;
import java.text.SimpleDateFormat;

/**
    Utility class for producing strings with formatted date/time.

    <p>
    Most callers should avoid supplying their own format strings to this
    class' {@code format} methods and rely on the correctly localized ones
    supplied by the system. This class' factory methods return
    appropriately-localized {@link java.text.DateFormat} instances, suitable
    for both formatting and parsing dates. For the canonical documentation
    of format strings, see {@link java.text.SimpleDateFormat}.
    </p>
    <p>
    The format methods in this class takes as inputs a format string and a representation of a date/time.
    The format string controls how the output is generated.
    This class only supports a subset of the full Unicode specification.
    Use {@link java.text.SimpleDateFormat} if you need more.
    Formatting characters may be repeated in order to get more detailed representations
    of that field.  For instance, the format character &apos;M&apos; is used to
    represent the month.  Depending on how many times that character is repeated
    you get a different representation.
    </p>
    <p>
    For the month of September:<br/>
    M -&gt; 9<br/>
    MM -&gt; 09<br/>
    MMM -&gt; Sep<br/>
    MMMM -&gt; September
    </p>
    <p>
    The effects of the duplication vary depending on the nature of the field.
    See the notes on the individual field formatters for details.  For purely numeric
    fields such as <code>HOUR</code> adding more copies of the designator will
    zero-pad the value to that number of characters.
    </p>
    <p>
    For 7 minutes past the hour:<br/>
    m -&gt; 7<br/>
    mm -&gt; 07<br/>
    mmm -&gt; 007<br/>
    mmmm -&gt; 0007
    </p>
    <p>
    Examples for April 6, 1970 at 3:23am:<br/>
    &quot;MM/dd/yy h:mmaa&quot; -&gt; &quot;04/06/70 3:23am&quot<br/>
    &quot;MMM dd, yyyy h:mmaa&quot; -&gt; &quot;Apr 6, 1970 3:23am&quot<br/>
    &quot;MMMM dd, yyyy h:mmaa&quot; -&gt; &quot;April 6, 1970 3:23am&quot<br/>
    &quot;E, MMMM dd, yyyy h:mmaa&quot; -&gt; &quot;Mon, April 6, 1970 3:23am&<br/>
    &quot;EEEE, MMMM dd, yyyy h:mmaa&quot; -&gt; &quot;Monday, April 6, 1970 3:23am&quot;<br/>
    &quot;&apos;Noteworthy day: &apos;M/d/yy&quot; -&gt; &quot;Noteworthy day: 4/6/70&quot;
 */

public class DateFormat {
    /**
        Text in the format string that should be copied verbatim rather that
        interpreted as formatting codes must be surrounded by the <code>QUOTE</code>
        character.  If you need to embed a literal <code>QUOTE</code> character in
        the output text then use two in a row.
     */
    public  static final char    QUOTE                  =    '\'';
    
    /**
        This designator indicates whether the <code>HOUR</code> field is before
        or after noon.  The output is lower-case.
     
        Examples:
        a -> a or p
        aa -> am or pm
     */
    public  static final char    AM_PM                  =    'a';

    /**
        This designator indicates whether the <code>HOUR</code> field is before
        or after noon.  The output is capitalized.
     
        Examples:
        A -> A or P
        AA -> AM or PM
     */
    public  static final char    CAPITAL_AM_PM          =    'A';

    /**
        This designator indicates the day of the month.
         
        Examples for the 9th of the month:
        d -> 9
        dd -> 09
     */
    public  static final char    DATE                   =    'd';

    /**
        This designator indicates the name of the day of the week.
     
        Examples for Sunday:
        E -> Sun
        EEEE -> Sunday
     */
    public  static final char    DAY                    =    'E';

    /**
        This designator indicates the hour of the day in 12 hour format.
     
        Examples for 3pm:
        h -> 3
        hh -> 03
     */
    public  static final char    HOUR                   =    'h';

    /**
        This designator indicates the hour of the day in 24 hour format.
     
        Example for 3pm:
        k -> 15

        Examples for midnight:
        k -> 0
        kk -> 00
     */
    public  static final char    HOUR_OF_DAY            =    'k';

    /**
        This designator indicates the minute of the hour.
     
        Examples for 7 minutes past the hour:
        m -> 7
        mm -> 07
     */
    public  static final char    MINUTE                 =    'm';

    /**
        This designator indicates the month of the year. See also
        {@link #STANDALONE_MONTH}.
     
        Examples for September:
        M -> 9
        MM -> 09
        MMM -> Sep
        MMMM -> September
     */
    public  static final char    MONTH                  =    'M';

    /**
        This designator indicates the standalone month of the year,
        necessary in some format strings in some languages. For
        example, Russian distinguishes between the "June" in
        "June" and that in "June 2010".
     */
    public  static final char    STANDALONE_MONTH       =    'L';

    /**
        This designator indicates the seconds of the minute.
     
        Examples for 7 seconds past the minute:
        s -> 7
        ss -> 07
     */
    public  static final char    SECONDS                =    's';

    /**
        This designator indicates the offset of the timezone from GMT.
     
        Example for US/Pacific timezone:
        z -> -0800
        zz -> PST
     */
    public  static final char    TIME_ZONE              =    'z';

    /**
        This designator indicates the year.
     
        Examples for 2006
        y -> 06
        yyyy -> 2006
     */
    public  static final char    YEAR                   =    'y';


    private static final Object sLocaleLock = new Object();
    private static Locale sIs24HourLocale;
    private static boolean sIs24Hour;


    /**
     * Returns true if user preference is set to 24-hour format.
     * @param context the context to use for the content resolver
     * @return true if 24 hour time format is selected, false otherwise.
     */
    public static boolean is24HourFormat(Context context) {
        String value = Settings.System.getString(context.getContentResolver(),
                Settings.System.TIME_12_24);

        if (value == null) {
            Locale locale = context.getResources().getConfiguration().locale;

            synchronized (sLocaleLock) {
                if (sIs24HourLocale != null && sIs24HourLocale.equals(locale)) {
                    return sIs24Hour;
                }
            }

            java.text.DateFormat natural =
                java.text.DateFormat.getTimeInstance(
                    java.text.DateFormat.LONG, locale);

            if (natural instanceof SimpleDateFormat) {
                SimpleDateFormat sdf = (SimpleDateFormat) natural;
                String pattern = sdf.toPattern();

                if (pattern.indexOf('H') >= 0) {
                    value = "24";
                } else {
                    value = "12";
                }
            } else {
                value = "12";
            }

            synchronized (sLocaleLock) {
                sIs24HourLocale = locale;
                sIs24Hour = value.equals("24");
            }

            return sIs24Hour;
        }

        return value.equals("24");
    }

    /**
     * Returns a {@link java.text.DateFormat} object that can format the time according
     * to the current locale and the user's 12-/24-hour clock preference.
     * @param context the application context
     * @return the {@link java.text.DateFormat} object that properly formats the time.
     */
    public static java.text.DateFormat getTimeFormat(Context context) {
        boolean b24 = is24HourFormat(context);
        int res;

        if (b24) {
            res = R.string.twenty_four_hour_time_format;
        } else {
            res = R.string.twelve_hour_time_format;
        }

        return new java.text.SimpleDateFormat(context.getString(res));
    }

    /**
     * Returns a {@link java.text.DateFormat} object that can format the date 
     * in short form (such as 12/31/1999) according
     * to the current locale and the user's date-order preference.
     * @param context the application context
     * @return the {@link java.text.DateFormat} object that properly formats the date.
     */
    public static java.text.DateFormat getDateFormat(Context context) {
        String value = Settings.System.getString(context.getContentResolver(),
                Settings.System.DATE_FORMAT);

        return getDateFormatForSetting(context, value);
    }

    /**
     * Returns a {@link java.text.DateFormat} object to format the date
     * as if the date format setting were set to <code>value</code>,
     * including null to use the locale's default format.
     * @param context the application context
     * @param value the date format setting string to interpret for
     *              the current locale
     * @hide
     */
    public static java.text.DateFormat getDateFormatForSetting(Context context,
                                                               String value) {
        String format = getDateFormatStringForSetting(context, value);

        return new java.text.SimpleDateFormat(format);
    }

    private static String getDateFormatStringForSetting(Context context, String value) {
        if (value != null) {
            int month = value.indexOf('M');
            int day = value.indexOf('d');
            int year = value.indexOf('y');

            if (month >= 0 && day >= 0 && year >= 0) {
                String template = context.getString(R.string.numeric_date_template);
                if (year < month && year < day) {
                    if (month < day) {
                        value = String.format(template, "yyyy", "MM", "dd");
                    } else {
                        value = String.format(template, "yyyy", "dd", "MM");
                    }
                } else if (month < day) {
                    if (day < year) {
                        value = String.format(template, "MM", "dd", "yyyy");
                    } else { // unlikely
                        value = String.format(template, "MM", "yyyy", "dd");
                    }
                } else { // day < month
                    if (month < year) {
                        value = String.format(template, "dd", "MM", "yyyy");
                    } else { // unlikely
                        value = String.format(template, "dd", "yyyy", "MM");
                    }
                }

                return value;
            }
        }

        /*
         * The setting is not set; use the default.
         * We use a resource string here instead of just DateFormat.SHORT
         * so that we get a four-digit year instead a two-digit year.
         */
        value = context.getString(R.string.numeric_date_format);
        return value;
    }
    
    /**
     * Returns a {@link java.text.DateFormat} object that can format the date
     * in long form (such as December 31, 1999) for the current locale.
     * @param context the application context
     * @return the {@link java.text.DateFormat} object that formats the date in long form.
     */
    public static java.text.DateFormat getLongDateFormat(Context context) {
        return java.text.DateFormat.getDateInstance(java.text.DateFormat.LONG);
    }

    /**
     * Returns a {@link java.text.DateFormat} object that can format the date
     * in medium form (such as Dec. 31, 1999) for the current locale.
     * @param context the application context
     * @return the {@link java.text.DateFormat} object that formats the date in long form.
     */
    public static java.text.DateFormat getMediumDateFormat(Context context) {
        return java.text.DateFormat.getDateInstance(java.text.DateFormat.MEDIUM);
    }

    /**
     * Gets the current date format stored as a char array. The array will contain
     * 3 elements ({@link #DATE}, {@link #MONTH}, and {@link #YEAR}) in the order    
     * specified by the user's format preference.  Note that this order is
     * only appropriate for all-numeric dates; spelled-out (MEDIUM and LONG)
     * dates will generally contain other punctuation, spaces, or words,
     * not just the day, month, and year, and not necessarily in the same
     * order returned here.
     */    
    public static char[] getDateFormatOrder(Context context) {
        char[] order = new char[] {DATE, MONTH, YEAR};
        String value = getDateFormatString(context);
        int index = 0;
        boolean foundDate = false;
        boolean foundMonth = false;
        boolean foundYear = false;

        for (char c : value.toCharArray()) {
            if (!foundDate && (c == DATE)) {
                foundDate = true;
                order[index] = DATE;
                index++;
            }

            if (!foundMonth && (c == MONTH || c == STANDALONE_MONTH)) {
                foundMonth = true;
                order[index] = MONTH;
                index++;
            }

            if (!foundYear && (c == YEAR)) {
                foundYear = true;
                order[index] = YEAR;
                index++;
            }
        }
        return order;
    }
    
    private static String getDateFormatString(Context context) {
        String value = Settings.System.getString(context.getContentResolver(),
                Settings.System.DATE_FORMAT);

        return getDateFormatStringForSetting(context, value);
    }

    /**
     * Given a format string and a time in milliseconds since Jan 1, 1970 GMT, returns a 
     * CharSequence containing the requested date.
     * @param inFormat the format string, as described in {@link android.text.format.DateFormat}
     * @param inTimeInMillis in milliseconds since Jan 1, 1970 GMT
     * @return a {@link CharSequence} containing the requested text
     */
    public static CharSequence format(CharSequence inFormat, long inTimeInMillis) {
        return format(inFormat, new Date(inTimeInMillis));
    }

    /**
     * Given a format string and a {@link java.util.Date} object, returns a CharSequence containing
     * the requested date.
     * @param inFormat the format string, as described in {@link android.text.format.DateFormat}
     * @param inDate the date to format
     * @return a {@link CharSequence} containing the requested text
     */
    public static CharSequence format(CharSequence inFormat, Date inDate) {
        Calendar    c = new GregorianCalendar();
        
        c.setTime(inDate);
        
        return format(inFormat, c);
    }

    /**
     * Indicates whether the specified format string contains seconds.
     * 
     * Always returns false if the input format is null.
     * 
     * @param inFormat the format string, as described in {@link android.text.format.DateFormat}
     *                 
     * @return true if the format string contains {@link #SECONDS}, false otherwise
     * 
     * @hide
     */
    public static boolean hasSeconds(CharSequence inFormat) {
        if (inFormat == null) return false;

        final int length = inFormat.length();

        int c;
        int count;

        for (int i = 0; i < length; i += count) {
            count = 1;
            c = inFormat.charAt(i);

            if (c == QUOTE) {
                count = skipQuotedText(inFormat, i, length);
            } else if (c == SECONDS) {
                return true;
            }
        }

        return false;
    }

    private static int skipQuotedText(CharSequence s, int i, int len) {
        if (i + 1 < len && s.charAt(i + 1) == QUOTE) {
            return 2;
        }

        int count = 1;
        // skip leading quote
        i++;

        while (i < len) {
            char c = s.charAt(i);

            if (c == QUOTE) {
                count++;
                //  QUOTEQUOTE -> QUOTE
                if (i + 1 < len && s.charAt(i + 1) == QUOTE) {
                    i++;
                } else {
                    break;
                }
            } else {
                i++;
                count++;
            }
        }

        return count;
    }

    /**
     * Given a format string and a {@link java.util.Calendar} object, returns a CharSequence 
     * containing the requested date.
     * @param inFormat the format string, as described in {@link android.text.format.DateFormat}
     * @param inDate the date to format
     * @return a {@link CharSequence} containing the requested text
     */
    public static CharSequence format(CharSequence inFormat, Calendar inDate) {
        SpannableStringBuilder      s = new SpannableStringBuilder(inFormat);
        int             c;
        int             count;

        int len = inFormat.length();

        for (int i = 0; i < len; i += count) {
            int temp;

            count = 1;
            c = s.charAt(i);

            if (c == QUOTE) {
                count = appendQuotedText(s, i, len);
                len = s.length();
                continue;
            }

            while ((i + count < len) && (s.charAt(i + count) == c)) {
                count++;
            }

            String replacement;

            switch (c) {
                case AM_PM:
                    replacement = DateUtils.getAMPMString(inDate.get(Calendar.AM_PM));
                    break;
                                        
                case CAPITAL_AM_PM:
                    //FIXME: this is the same as AM_PM? no capital?
                    replacement = DateUtils.getAMPMString(inDate.get(Calendar.AM_PM));
                    break;
                
                case DATE:
                    replacement = zeroPad(inDate.get(Calendar.DATE), count);
                    break;
                    
                case DAY:
                    temp = inDate.get(Calendar.DAY_OF_WEEK);
                    replacement = DateUtils.getDayOfWeekString(temp,
                                                               count < 4 ? 
                                                               DateUtils.LENGTH_MEDIUM : 
                                                               DateUtils.LENGTH_LONG);
                    break;
                    
                case HOUR:
                    temp = inDate.get(Calendar.HOUR);

                    if (0 == temp)
                        temp = 12;
                    
                    replacement = zeroPad(temp, count);
                    break;
                    
                case HOUR_OF_DAY:
                    replacement = zeroPad(inDate.get(Calendar.HOUR_OF_DAY), count);
                    break;
                    
                case MINUTE:
                    replacement = zeroPad(inDate.get(Calendar.MINUTE), count);
                    break;
                    
                case MONTH:
                case STANDALONE_MONTH:
                    replacement = getMonthString(inDate, count, c);
                    break;

                case SECONDS:
                    replacement = zeroPad(inDate.get(Calendar.SECOND), count);
                    break;
                    
                case TIME_ZONE:
                    replacement = getTimeZoneString(inDate, count);
                    break;
                    
                case YEAR:
                    replacement = getYearString(inDate, count);
                    break;

                default:
                    replacement = null;
                    break;
            }
            
            if (replacement != null) {
                s.replace(i, i + count, replacement);
                count = replacement.length(); // CARE: count is used in the for loop above
                len = s.length();
            }
        }
        
        if (inFormat instanceof Spanned)
            return new SpannedString(s);
        else
            return s.toString();
    }
    
    private static String getMonthString(Calendar inDate, int count, int kind) {
        boolean standalone = (kind == STANDALONE_MONTH);
        int month = inDate.get(Calendar.MONTH);
        
        if (count >= 4) {
            return standalone
                ? DateUtils.getStandaloneMonthString(month, DateUtils.LENGTH_LONG)
                : DateUtils.getMonthString(month, DateUtils.LENGTH_LONG);
        } else if (count == 3) {
            return standalone
                ? DateUtils.getStandaloneMonthString(month, DateUtils.LENGTH_MEDIUM)
                : DateUtils.getMonthString(month, DateUtils.LENGTH_MEDIUM);
        } else {
            // Calendar.JANUARY == 0, so add 1 to month.
            return zeroPad(month+1, count);
        }
    }
        
    private static String getTimeZoneString(Calendar inDate, int count) {
        TimeZone tz = inDate.getTimeZone();
        
        if (count < 2) { // FIXME: shouldn't this be <= 2 ?
            return formatZoneOffset(inDate.get(Calendar.DST_OFFSET) +
                                    inDate.get(Calendar.ZONE_OFFSET),
                                    count);
        } else {
            boolean dst = inDate.get(Calendar.DST_OFFSET) != 0;
            return tz.getDisplayName(dst, TimeZone.SHORT);
        }
    }

    private static String formatZoneOffset(int offset, int count) {
        offset /= 1000; // milliseconds to seconds
        StringBuilder tb = new StringBuilder();

        if (offset < 0) {
            tb.insert(0, "-");
            offset = -offset;
        } else {
            tb.insert(0, "+");
        }

        int hours = offset / 3600;
        int minutes = (offset % 3600) / 60;

        tb.append(zeroPad(hours, 2));
        tb.append(zeroPad(minutes, 2));
        return tb.toString();
    }
    
    private static String getYearString(Calendar inDate, int count) {
        int year = inDate.get(Calendar.YEAR);
        return (count <= 2) ? zeroPad(year % 100, 2)
                            : String.format(Locale.getDefault(), "%d", year);
    }
   
    private static int appendQuotedText(SpannableStringBuilder s, int i, int len) {
        if (i + 1 < len && s.charAt(i + 1) == QUOTE) {
            s.delete(i, i + 1);
            return 1;
        }

        int count = 0;

        // delete leading quote
        s.delete(i, i + 1);
        len--;

        while (i < len) {
            char c = s.charAt(i);

            if (c == QUOTE) {
                //  QUOTEQUOTE -> QUOTE
                if (i + 1 < len && s.charAt(i + 1) == QUOTE) {

                    s.delete(i, i + 1);
                    len--;
                    count++;
                    i++;
                } else {
                    //  Closing QUOTE ends quoted text copying
                    s.delete(i, i + 1);
                    break;
                }
            } else {
                i++;
                count++;
            }
        }

        return count;
    }

    private static String zeroPad(int inValue, int inMinDigits) {
        return String.format(Locale.getDefault(), "%0" + inMinDigits + "d", inValue);
    }
}