/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you 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 org.apache.logging.log4j.core.util.datetime;

import java.text.DateFormat;
import java.text.FieldPosition;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/**
 * <p>FastDateFormat is a fast and thread-safe version of
 * {@link java.text.SimpleDateFormat}.</p>
 *
 * <p>To obtain an instance of FastDateFormat, use one of the static factory methods:
 * {@link #getInstance(String, TimeZone, Locale)}, {@link #getDateInstance(int, TimeZone, Locale)},
 * {@link #getTimeInstance(int, TimeZone, Locale)}, or {@link #getDateTimeInstance(int, int, TimeZone, Locale)}
 * </p>
 *
 * <p>Since FastDateFormat is thread safe, you can use a static member instance:</p>
 * <code>
 *   private static final FastDateFormat DATE_FORMATTER = FastDateFormat.getDateTimeInstance(FastDateFormat.LONG, FastDateFormat.SHORT);
 * </code>
 *
 * <p>This class can be used as a direct replacement to
 * {@code SimpleDateFormat} in most formatting and parsing situations.
 * This class is especially useful in multi-threaded server environments.
 * {@code SimpleDateFormat} is not thread-safe in any JDK version,
 * nor will it be as Sun have closed the bug/RFE.
 * </p>
 *
 * <p>All patterns are compatible with
 * SimpleDateFormat (except time zones and some year patterns - see below).</p>
 *
 * <p>Since 3.2, FastDateFormat supports parsing as well as printing.</p>
 *
 * <p>Java 1.4 introduced a new pattern letter, {@code 'Z'}, to represent
 * time zones in RFC822 format (eg. {@code +0800} or {@code -1100}).
 * This pattern letter can be used here (on all JDK versions).</p>
 *
 * <p>In addition, the pattern {@code 'ZZ'} has been made to represent
 * ISO 8601 extended format time zones (eg. {@code +08:00} or {@code -11:00}).
 * This introduces a minor incompatibility with Java 1.4, but at a gain of
 * useful functionality.</p>
 *
 * <p>Javadoc cites for the year pattern: <i>For formatting, if the number of
 * pattern letters is 2, the year is truncated to 2 digits; otherwise it is
 * interpreted as a number.</i> Starting with Java 1.7 a pattern of 'Y' or
 * 'YYY' will be formatted as '2003', while it was '03' in former Java
 * versions. FastDateFormat implements the behavior of Java 7.</p>
 *
 * <p>
 * Copied and modified from <a href="https://commons.apache.org/proper/commons-lang/">Apache Commons Lang</a>.
 * </p>
 *
 * @since Apache Commons Lang 2.0
 */
public class FastDateFormat extends Format implements DatePrinter {

    /**
     * FULL locale dependent date or time style.
     */
    public static final int FULL = DateFormat.FULL;

    /**
     * LONG locale dependent date or time style.
     */
    public static final int LONG = DateFormat.LONG;

    /**
     * MEDIUM locale dependent date or time style.
     */
    public static final int MEDIUM = DateFormat.MEDIUM;

    /**
     * SHORT locale dependent date or time style.
     */
    public static final int SHORT = DateFormat.SHORT;

    private static final FormatCache<FastDateFormat> cache = new FormatCache<FastDateFormat>() {
        @Override
        protected FastDateFormat createInstance(final String pattern, final TimeZone timeZone, final Locale locale) {
            return new FastDateFormat(pattern, timeZone, locale);
        }
    };

    private final FastDatePrinter printer;

    // -----------------------------------------------------------------------
    /**
     * <p>Gets a formatter instance using the default pattern in the
     * default locale.</p>
     *
     * @return a date/time formatter
     */
    public static FastDateFormat getInstance() {
        return cache.getInstance();
    }

    /**
     * <p>Gets a formatter instance using the specified pattern in the
     * default locale.</p>
     *
     * @param pattern  {@link java.text.SimpleDateFormat} compatible
     *  pattern
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     */
    public static FastDateFormat getInstance(final String pattern) {
        return cache.getInstance(pattern, null, null);
    }

    /**
     * <p>Gets a formatter instance using the specified pattern and
     * time zone.</p>
     *
     * @param pattern  {@link java.text.SimpleDateFormat} compatible
     *  pattern
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     */
    public static FastDateFormat getInstance(final String pattern, final TimeZone timeZone) {
        return cache.getInstance(pattern, timeZone, null);
    }

    /**
     * <p>Gets a formatter instance using the specified pattern and
     * locale.</p>
     *
     * @param pattern  {@link java.text.SimpleDateFormat} compatible
     *  pattern
     * @param locale  optional locale, overrides system locale
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     */
    public static FastDateFormat getInstance(final String pattern, final Locale locale) {
        return cache.getInstance(pattern, null, locale);
    }

    /**
     * <p>Gets a formatter instance using the specified pattern, time zone
     * and locale.</p>
     *
     * @param pattern  {@link java.text.SimpleDateFormat} compatible
     *  pattern
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @param locale  optional locale, overrides system locale
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     *  or {@code null}
     */
    public static FastDateFormat getInstance(final String pattern, final TimeZone timeZone, final Locale locale) {
        return cache.getInstance(pattern, timeZone, locale);
    }

    // -----------------------------------------------------------------------
    /**
     * <p>Gets a date formatter instance using the specified style in the
     * default time zone and locale.</p>
     *
     * @param style  date style: FULL, LONG, MEDIUM, or SHORT
     * @return a localized standard date formatter
     * @throws IllegalArgumentException if the Locale has no date
     *  pattern defined
     * @since 2.1
     */
    public static FastDateFormat getDateInstance(final int style) {
        return cache.getDateInstance(style, null, null);
    }

    /**
     * <p>Gets a date formatter instance using the specified style and
     * locale in the default time zone.</p>
     *
     * @param style  date style: FULL, LONG, MEDIUM, or SHORT
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date formatter
     * @throws IllegalArgumentException if the Locale has no date
     *  pattern defined
     * @since 2.1
     */
    public static FastDateFormat getDateInstance(final int style, final Locale locale) {
        return cache.getDateInstance(style, null, locale);
    }

    /**
     * <p>Gets a date formatter instance using the specified style and
     * time zone in the default locale.</p>
     *
     * @param style  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @return a localized standard date formatter
     * @throws IllegalArgumentException if the Locale has no date
     *  pattern defined
     * @since 2.1
     */
    public static FastDateFormat getDateInstance(final int style, final TimeZone timeZone) {
        return cache.getDateInstance(style, timeZone, null);
    }

    /**
     * <p>Gets a date formatter instance using the specified style, time
     * zone and locale.</p>
     *
     * @param style  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date formatter
     * @throws IllegalArgumentException if the Locale has no date
     *  pattern defined
     */
    public static FastDateFormat getDateInstance(final int style, final TimeZone timeZone, final Locale locale) {
        return cache.getDateInstance(style, timeZone, locale);
    }

    // -----------------------------------------------------------------------
    /**
     * <p>Gets a time formatter instance using the specified style in the
     * default time zone and locale.</p>
     *
     * @param style  time style: FULL, LONG, MEDIUM, or SHORT
     * @return a localized standard time formatter
     * @throws IllegalArgumentException if the Locale has no time
     *  pattern defined
     * @since 2.1
     */
    public static FastDateFormat getTimeInstance(final int style) {
        return cache.getTimeInstance(style, null, null);
    }

    /**
     * <p>Gets a time formatter instance using the specified style and
     * locale in the default time zone.</p>
     *
     * @param style  time style: FULL, LONG, MEDIUM, or SHORT
     * @param locale  optional locale, overrides system locale
     * @return a localized standard time formatter
     * @throws IllegalArgumentException if the Locale has no time
     *  pattern defined
     * @since 2.1
     */
    public static FastDateFormat getTimeInstance(final int style, final Locale locale) {
        return cache.getTimeInstance(style, null, locale);
    }

    /**
     * <p>Gets a time formatter instance using the specified style and
     * time zone in the default locale.</p>
     *
     * @param style  time style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted time
     * @return a localized standard time formatter
     * @throws IllegalArgumentException if the Locale has no time
     *  pattern defined
     * @since 2.1
     */
    public static FastDateFormat getTimeInstance(final int style, final TimeZone timeZone) {
        return cache.getTimeInstance(style, timeZone, null);
    }

    /**
     * <p>Gets a time formatter instance using the specified style, time
     * zone and locale.</p>
     *
     * @param style  time style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted time
     * @param locale  optional locale, overrides system locale
     * @return a localized standard time formatter
     * @throws IllegalArgumentException if the Locale has no time
     *  pattern defined
     */
    public static FastDateFormat getTimeInstance(final int style, final TimeZone timeZone, final Locale locale) {
        return cache.getTimeInstance(style, timeZone, locale);
    }

    // -----------------------------------------------------------------------
    /**
     * <p>Gets a date/time formatter instance using the specified style
     * in the default time zone and locale.</p>
     *
     * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT
     * @return a localized standard date/time formatter
     * @throws IllegalArgumentException if the Locale has no date/time
     *  pattern defined
     * @since 2.1
     */
    public static FastDateFormat getDateTimeInstance(final int dateStyle, final int timeStyle) {
        return cache.getDateTimeInstance(dateStyle, timeStyle, null, null);
    }

    /**
     * <p>Gets a date/time formatter instance using the specified style and
     * locale in the default time zone.</p>
     *
     * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date/time formatter
     * @throws IllegalArgumentException if the Locale has no date/time
     *  pattern defined
     * @since 2.1
     */
    public static FastDateFormat getDateTimeInstance(final int dateStyle, final int timeStyle, final Locale locale) {
        return cache.getDateTimeInstance(dateStyle, timeStyle, null, locale);
    }

    /**
     * <p>Gets a date/time formatter instance using the specified style and
     * time zone in the default locale.</p>
     *
     * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @return a localized standard date/time formatter
     * @throws IllegalArgumentException if the Locale has no date/time
     *  pattern defined
     * @since 2.1
     */
    public static FastDateFormat getDateTimeInstance(
            final int dateStyle, final int timeStyle, final TimeZone timeZone) {
        return getDateTimeInstance(dateStyle, timeStyle, timeZone, null);
    }
    /**
     * <p>Gets a date/time formatter instance using the specified style,
     * time zone and locale.</p>
     *
     * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date/time formatter
     * @throws IllegalArgumentException if the Locale has no date/time
     *  pattern defined
     */
    public static FastDateFormat getDateTimeInstance(
            final int dateStyle, final int timeStyle, final TimeZone timeZone, final Locale locale) {
        return cache.getDateTimeInstance(dateStyle, timeStyle, timeZone, locale);
    }

    // Constructor
    // -----------------------------------------------------------------------
    /**
     * <p>Constructs a new FastDateFormat.</p>
     *
     * @param pattern  {@link java.text.SimpleDateFormat} compatible pattern
     * @param timeZone  non-null time zone to use
     * @param locale  non-null locale to use
     * @throws NullPointerException if pattern, timeZone, or locale is null.
     */
    protected FastDateFormat(final String pattern, final TimeZone timeZone, final Locale locale) {
        this(pattern, timeZone, locale, null);
    }

    // Constructor
    // -----------------------------------------------------------------------
    /**
     * <p>Constructs a new FastDateFormat.</p>
     *
     * @param pattern  {@link java.text.SimpleDateFormat} compatible pattern
     * @param timeZone  non-null time zone to use
     * @param locale  non-null locale to use
     * @param centuryStart The start of the 100 year period to use as the "default century" for 2 digit year parsing.  If centuryStart is null, defaults to now - 80 years
     * @throws NullPointerException if pattern, timeZone, or locale is null.
     */
    protected FastDateFormat(
            final String pattern, final TimeZone timeZone, final Locale locale, final Date centuryStart) {
        printer = new FastDatePrinter(pattern, timeZone, locale);
    }

    // Format methods
    // -----------------------------------------------------------------------
    /**
     * <p>Formats a {@code Date}, {@code Calendar} or
     * {@code Long} (milliseconds) object.</p>
     * This method is an implementation of {@link Format#format(Object, StringBuilder, FieldPosition)}
     *
     * @param obj  the object to format
     * @param toAppendTo  the buffer to append to
     * @param pos  the position - ignored
     * @return the buffer passed in
     */
    @Override
    public StringBuilder format(final Object obj, final StringBuilder toAppendTo, final FieldPosition pos) {
        return toAppendTo.append(printer.format(obj));
    }

    /**
     * <p>Formats a millisecond {@code long} value.</p>
     *
     * @param millis  the millisecond value to format
     * @return the formatted string
     * @since 2.1
     */
    @Override
    public String format(final long millis) {
        return printer.format(millis);
    }

    /**
     * <p>Formats a {@code Date} object using a {@code GregorianCalendar}.</p>
     *
     * @param date  the date to format
     * @return the formatted string
     */
    @Override
    public String format(final Date date) {
        return printer.format(date);
    }

    /**
     * <p>Formats a {@code Calendar} object.</p>
     *
     * @param calendar  the calendar to format
     * @return the formatted string
     */
    @Override
    public String format(final Calendar calendar) {
        return printer.format(calendar);
    }

    /**
     * <p>Formats a millisecond {@code long} value into the
     * supplied {@code StringBuffer}.</p>
     *
     * @param millis  the millisecond value to format
     * @param buf  the buffer to format into
     * @return the specified string buffer
     * @since 3.5
     */
    @Override
    public <B extends Appendable> B format(final long millis, final B buf) {
        return printer.format(millis, buf);
    }

    /**
     * <p>Formats a {@code Date} object into the
     * supplied {@code StringBuffer} using a {@code GregorianCalendar}.</p>
     *
     * @param date  the date to format
     * @param buf  the buffer to format into
     * @return the specified string buffer
     * @since 3.5
     */
    @Override
    public <B extends Appendable> B format(final Date date, final B buf) {
        return printer.format(date, buf);
    }

    /**
     * <p>Formats a {@code Calendar} object into the
     * supplied {@code StringBuffer}.</p>
     *
     * @param calendar  the calendar to format
     * @param buf  the buffer to format into
     * @return the specified string buffer
     * @since 3.5
     */
    @Override
    public <B extends Appendable> B format(final Calendar calendar, final B buf) {
        return printer.format(calendar, buf);
    }

    // Accessors
    // -----------------------------------------------------------------------
    /**
     * <p>Gets the pattern used by this formatter.</p>
     *
     * @return the pattern, {@link java.text.SimpleDateFormat} compatible
     */
    @Override
    public String getPattern() {
        return printer.getPattern();
    }

    /**
     * <p>Gets the time zone used by this formatter.</p>
     *
     * <p>This zone is always used for {@code Date} formatting. </p>
     *
     * @return the time zone
     */
    @Override
    public TimeZone getTimeZone() {
        return printer.getTimeZone();
    }

    /**
     * <p>Gets the locale used by this formatter.</p>
     *
     * @return the locale
     */
    @Override
    public Locale getLocale() {
        return printer.getLocale();
    }

    /**
     * <p>Gets an estimate for the maximum string length that the
     * formatter will produce.</p>
     *
     * <p>The actual formatted length will almost always be less than or
     * equal to this amount.</p>
     *
     * @return the maximum formatted length
     */
    public int getMaxLengthEstimate() {
        return printer.getMaxLengthEstimate();
    }

    // Basics
    // -----------------------------------------------------------------------
    /**
     * <p>Compares two objects for equality.</p>
     *
     * @param obj  the object to compare to
     * @return {@code true} if equal
     */
    @Override
    public boolean equals(final Object obj) {
        if (!(obj instanceof FastDateFormat)) {
            return false;
        }
        final FastDateFormat other = (FastDateFormat) obj;
        // no need to check parser, as it has same invariants as printer
        return printer.equals(other.printer);
    }

    /**
     * <p>Returns a hash code compatible with equals.</p>
     *
     * @return a hash code compatible with equals
     */
    @Override
    public int hashCode() {
        return printer.hashCode();
    }

    /**
     * <p>Gets a debugging string version of this formatter.</p>
     *
     * @return a debugging string
     */
    @Override
    public String toString() {
        return "FastDateFormat[" + printer.getPattern() + "," + printer.getLocale() + ","
                + printer.getTimeZone().getID() + "]";
    }
}
