server/container/util-java8/src/main/java/org/apache/james/util/date/ImapDateTimeFormatter.java

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 * 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   *
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package org.apache.james.util.date;

import static java.time.temporal.ChronoField.DAY_OF_MONTH;
import static java.time.temporal.ChronoField.DAY_OF_WEEK;
import static java.time.temporal.ChronoField.HOUR_OF_DAY;
import static java.time.temporal.ChronoField.MINUTE_OF_HOUR;
import static java.time.temporal.ChronoField.MONTH_OF_YEAR;
import static java.time.temporal.ChronoField.SECOND_OF_MINUTE;
import static java.time.temporal.ChronoField.YEAR;

import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.format.SignStyle;

import com.google.common.collect.ImmutableMap;

public class ImapDateTimeFormatter {

    private static final int INITIAL_YEAR = 1970;

    public static DateTimeFormatter rfc5322() {
        return new DateTimeFormatterBuilder()
                .parseCaseInsensitive()
                .parseLenient()
                .optionalStart()
                    .appendText(DAY_OF_WEEK, dayOfWeek())
                    .appendLiteral(", ")
                .optionalEnd()
                .appendValue(DAY_OF_MONTH, 1, 2, SignStyle.NOT_NEGATIVE)
                .appendLiteral(' ')
                .appendText(MONTH_OF_YEAR, monthOfYear())
                .appendLiteral(' ')
                .appendValueReduced(YEAR, 2, 4, INITIAL_YEAR)
                .appendLiteral(' ')
                .appendValue(HOUR_OF_DAY, 2)
                .appendLiteral(':')
                .appendValue(MINUTE_OF_HOUR, 2)
                .optionalStart()
                    .appendLiteral(':')
                    .appendValue(SECOND_OF_MINUTE, 2)
                .optionalEnd()
                .appendLiteral(' ')
                .appendOffset("+HHMM", "GMT")
                .toFormatter();
    }

    private static ImmutableMap<Long, String> monthOfYear() {
        return ImmutableMap.<Long, String> builder()
                .put(1L, "Jan")
                .put(2L, "Feb")
                .put(3L, "Mar")
                .put(4L, "Apr")
                .put(5L, "May")
                .put(6L, "Jun")
                .put(7L, "Jul")
                .put(8L, "Aug")
                .put(9L, "Sep")
                .put(10L, "Oct")
                .put(11L, "Nov")
                .put(12L, "Dec")
                .build();
    }

    private static ImmutableMap<Long, String> dayOfWeek() {
        return ImmutableMap.<Long, String> builder()
                .put(1L, "Mon")
                .put(2L, "Tue")
                .put(3L, "Wed")
                .put(4L, "Thu")
                .put(5L, "Fri")
                .put(6L, "Sat")
                .put(7L, "Sun")
                .build();
    }

}