/*
 * 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 libcore.icu;

import com.ibm.icu.impl.JavaTimeZone;
import com.ibm.icu.util.Calendar;
import com.ibm.icu.util.GregorianCalendar;
import com.ibm.icu.util.ULocale;

/**
 * Common methods and constants for the various ICU formatters used to support
 * android.text.format.DateUtils.
 */
public final class DateUtilsBridge {
  // These are all public API in DateUtils. There are others, but they're either for use with
  // other methods (like FORMAT_ABBREV_RELATIVE), don't internationalize (like FORMAT_CAP_AMPM),
  // or have never been implemented anyway.
  public static final int FORMAT_SHOW_TIME       = 0x00001;
  public static final int FORMAT_SHOW_WEEKDAY    = 0x00002;
  public static final int FORMAT_SHOW_YEAR       = 0x00004;
  public static final int FORMAT_NO_YEAR         = 0x00008;
  public static final int FORMAT_SHOW_DATE       = 0x00010;
  public static final int FORMAT_NO_MONTH_DAY    = 0x00020;
  public static final int FORMAT_12HOUR          = 0x00040;
  public static final int FORMAT_24HOUR          = 0x00080;
  public static final int FORMAT_UTC             = 0x02000;
  public static final int FORMAT_ABBREV_TIME     = 0x04000;
  public static final int FORMAT_ABBREV_WEEKDAY  = 0x08000;
  public static final int FORMAT_ABBREV_MONTH    = 0x10000;
  public static final int FORMAT_NUMERIC_DATE    = 0x20000;
  public static final int FORMAT_ABBREV_RELATIVE = 0x40000;
  public static final int FORMAT_ABBREV_ALL      = 0x80000;

  /**
   * Creates an immutable ICU timezone backed by the specified libcore timezone data. At the time of
   * writing the libcore implementation is faster but restricted to 1902 - 2038.
   * Callers must not modify the {@code tz} after calling this method.
   */
  public static com.ibm.icu.util.TimeZone icuTimeZone(java.util.TimeZone tz) {
    JavaTimeZone javaTimeZone = new JavaTimeZone(tz, null);
    javaTimeZone.freeze(); // Optimization - allows the timezone to be copied cheaply.
    return javaTimeZone;
  }

  public static Calendar createIcuCalendar(com.ibm.icu.util.TimeZone icuTimeZone, ULocale icuLocale,
      long timeInMillis) {
    Calendar calendar = new GregorianCalendar(icuTimeZone, icuLocale);
    calendar.setTimeInMillis(timeInMillis);
    return calendar;
  }

  public static String toSkeleton(Calendar calendar, int flags) {
    return toSkeleton(calendar, calendar, flags);
  }

  public static String toSkeleton(Calendar startCalendar, Calendar endCalendar, int flags) {
    if ((flags & FORMAT_ABBREV_ALL) != 0) {
      flags |= FORMAT_ABBREV_MONTH | FORMAT_ABBREV_TIME | FORMAT_ABBREV_WEEKDAY;
    }

    String monthPart = "MMMM";
    if ((flags & FORMAT_NUMERIC_DATE) != 0) {
      monthPart = "M";
    } else if ((flags & FORMAT_ABBREV_MONTH) != 0) {
      monthPart = "MMM";
    }

    String weekPart = "EEEE";
    if ((flags & FORMAT_ABBREV_WEEKDAY) != 0) {
      weekPart = "EEE";
    }

    String timePart = "j"; // "j" means choose 12 or 24 hour based on current locale.
    if ((flags & FORMAT_24HOUR) != 0) {
      timePart = "H";
    } else if ((flags & FORMAT_12HOUR) != 0) {
      timePart = "h";
    }

    // If we've not been asked to abbreviate times, or we're using the 24-hour clock (where it
    // never makes sense to leave out the minutes), include minutes. This gets us times like
    // "4 PM" while avoiding times like "16" (for "16:00").
    if ((flags & FORMAT_ABBREV_TIME) == 0 || (flags & FORMAT_24HOUR) != 0) {
      timePart += "m";
    } else {
      // Otherwise, we're abbreviating a 12-hour time, and should only show the minutes
      // if they're not both "00".
      if (!(onTheHour(startCalendar) && onTheHour(endCalendar))) {
        timePart = timePart + "m";
      }
    }

    if (fallOnDifferentDates(startCalendar, endCalendar)) {
      flags |= FORMAT_SHOW_DATE;
    }

    if (fallInSameMonth(startCalendar, endCalendar) && (flags & FORMAT_NO_MONTH_DAY) != 0) {
      flags &= (~FORMAT_SHOW_WEEKDAY);
      flags &= (~FORMAT_SHOW_TIME);
    }

    if ((flags & (FORMAT_SHOW_DATE | FORMAT_SHOW_TIME | FORMAT_SHOW_WEEKDAY)) == 0) {
      flags |= FORMAT_SHOW_DATE;
    }

    // If we've been asked to show the date, work out whether we think we should show the year.
    if ((flags & FORMAT_SHOW_DATE) != 0) {
      if ((flags & FORMAT_SHOW_YEAR) != 0) {
        // The caller explicitly wants us to show the year.
      } else if ((flags & FORMAT_NO_YEAR) != 0) {
        // The caller explicitly doesn't want us to show the year, even if we otherwise would.
      } else if (!fallInSameYear(startCalendar, endCalendar) || !isThisYear(startCalendar)) {
        flags |= FORMAT_SHOW_YEAR;
      }
    }

    StringBuilder builder = new StringBuilder();
    if ((flags & (FORMAT_SHOW_DATE | FORMAT_NO_MONTH_DAY)) != 0) {
      if ((flags & FORMAT_SHOW_YEAR) != 0) {
        builder.append("y");
      }
      builder.append(monthPart);
      if ((flags & FORMAT_NO_MONTH_DAY) == 0) {
        builder.append("d");
      }
    }
    if ((flags & FORMAT_SHOW_WEEKDAY) != 0) {
      builder.append(weekPart);
    }
    if ((flags & FORMAT_SHOW_TIME) != 0) {
      builder.append(timePart);
    }
    return builder.toString();
  }

  public static int dayDistance(Calendar c1, Calendar c2) {
    return c2.get(Calendar.JULIAN_DAY) - c1.get(Calendar.JULIAN_DAY);
  }

  private static boolean onTheHour(Calendar c) {
    return c.get(Calendar.MINUTE) == 0 && c.get(Calendar.SECOND) == 0;
  }

  private static boolean fallOnDifferentDates(Calendar c1, Calendar c2) {
    return c1.get(Calendar.YEAR) != c2.get(Calendar.YEAR) ||
        c1.get(Calendar.MONTH) != c2.get(Calendar.MONTH) ||
        c1.get(Calendar.DAY_OF_MONTH) != c2.get(Calendar.DAY_OF_MONTH);
  }

  private static boolean fallInSameMonth(Calendar c1, Calendar c2) {
    return c1.get(Calendar.MONTH) == c2.get(Calendar.MONTH);
  }

  private static boolean fallInSameYear(Calendar c1, Calendar c2) {
    return c1.get(Calendar.YEAR) == c2.get(Calendar.YEAR);
  }

  private static boolean isThisYear(Calendar c) {
    Calendar now = (Calendar) c.clone();
    now.setTimeInMillis(System.currentTimeMillis());
    return c.get(Calendar.YEAR) == now.get(Calendar.YEAR);
  }
}