com.google.ical.values.VcalRewriter Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of recurrence Show documentation
Show all versions of recurrence Show documentation
Contains the RFC 2445 support.
/**
* Copyright (C) 2015, 2016 Dirk Lemmermann Software & Consulting (dlsc.com)
*
* This file is part of CalendarFX.
*/
// Copyright (C) 2006 Google Inc.
//
// 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.google.ical.values;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* converts vcal recurrence rules to ical.
*
* @author [email protected] (Mike Samuel)
*/
final class VcalRewriter {
private static final String DATE = "[0-9]{8,}(?:T[0-9]{6}Z?)?";
/**
* http://www.imc.org/pdi/vcal-10.txt
*
* Grammar
* {} 0 or more
* [] 0 or 1
*
* start ::= <daily> [<enddate>] |
* <weekly> [<enddate>] |
* <monthlybypos> [<enddate>] |
* <monthlybyday> [<enddate>] |
* <yearlybymonth> [<enddate>] |
* <yearlybyday> [<enddate>]
* digit ::= <0|1|2|3|4|5|6|7|8|9>
* digits ::= <digit> {<digits>}
* enddate ::= ISO 8601_date_time value(e.g., 19940712T101530Z)
* interval ::= <digits>
* duration ::= #<digits>
* lastday ::= LD
* plus ::= +
* minus ::= -
* daynumber ::= <1-31> [<plus>|<minus>]| <lastday>
* daynumberlist ::= daynumber {<daynumberlist>}
* month ::= <1-12>
* monthlist ::= <month> {<monthlist>}
* day ::= <1-366>
* daylist ::= <day> {<daylist>}
* occurrence ::= <1-5><plus> | <1-5><minus>
* occurrencelist ::= <occurrence> {<occurrencelist>}
* weekday ::= <SU|MO|TU|WE|TH|FR|SA>
* weekdaylist ::= <weekday> {<weekdaylist>}
* daily ::= D<interval> [<duration>]
* weekly ::= W<interval> [<weekdaylist>] [<duration>]
* monthlybypos ::= MP<interval> [<occurrencelist> <weekdaylist>]
* [<duration>]
* monthlybyday ::= MD<interval> [<daynumberlist>] [<duration>]
* yearlybymonth ::= YM<interval> [<monthlist>] [<duration>]
* yearlybyday ::= YD<interval> [<daylist>] [<duration>]
*
*
* Glossary
* enddate Controls when a repeating event terminates. The enddate is
* the last time an event can occur.
* interval Defines the frequency in which a rule repeats.
* duration Controls the number of events a rule generates.
* lastday Can be used as a replacement to daynumber to indicate the
* last day of the month.
* daynumber A number representing a day of the month.
* month A number representing a month of the year.
* day A number representing a day of the year.
* occurrence Controls which week of the month a particular weekday event
* occurs.
* weekday A symbol representing a day of the week.
* daily Defines a rule that repeats on a daily basis.
* weekly Defines a rule that repeats on a weekly basis.
* monthlybypos Defines a rule that repeats on a monthly basis on a
* relative day and week.
* monthlybyday Defines a rule that repeats on a monthly basis on an
* absolute day.
* yearlybymonth Defines a rule that repeats on specific months of the year.
* yearlybyday Defines a rule that repeats on specific days of the year.
*
*
* Policies
* The duration portion of a rule defines the total number of events the rule
* generates, including the first event.
* Information, not contained in the rule, necessary to determine the next
* event time and date is derived from the Start Time entry attribute.
* If an end date and a duration is specified in the rule, the recurring event
* ceases when the end date is reached or the number of events indicated in
* the duration occur; whichever comes first.
* If the duration or an end date is not established in the rule (e.g., D4)
* the event occurs twice. That is D4 is equivalent to D4 #2.
* A duration of #0 means repeat this event forever.
* Using the occurrence specifier 5+ (e.g. 5th Friday) or 5- (e.g. 5th from
* last Friday) in a month that does not contain 5 weeks does not generate an
* event and thus does not count against the duration. The same applies to
* providing a day of the month that does not occur in the month. For example
* the 30th or 31st .
* The start time and date of an entry must be synchronized with one of the
* repeating events defined by its recurrence rule. The following is not
* allowed:
*
* Initial Appt Date: 7/1/94 (Friday)
* Recurrence Rule: W1 MO TH #5
*
* The following is acceptable:
*
* Initial Appt Date: 7/1/94 (Friday)
* Recurrence Rule: W1 MO FR #5 or W1 #5
* If the optional <occurrencelist> and <weekdaylist> information is missing
* from a <monthlybypos> occurrence the information is derived from the entry
* attributes. The <occurrence> used in the recurring event is a count from
* the beginning of the month to the entry date and the <weekday> used is the
* day of the week the entry is scheduled to occur on.
*
*/
private static final Pattern VCAL_RRULE = Pattern.compile(
"^"
// name and parameters
+ "("
+ "(?:RRULE|EXRULE)"
+ "(?:;[\\w-]+="
+ "(?:\"[^\"]*\""
+ "|[^;:\"]*)"
+ ")*"
+ ":"
+ ")"
// frequency
+ "("
+ "D" // daily
+ "|W" // weekly
+ "|M[DP]" // monthly by day or by position
+ "|Y[DM]" // yearly by day or by month
+ ")"
+ "([0-9]*)" // interval
// frequency modifier
+ "("
+ "(?:\\s+"
+ "(?:MO|TU|WE|TH|FR|SA|SU|LD|(?:[0-9]{1,3}[+-]?))"
+ ")*"
+ ")"
// duration
+ "(?:\\s+"
+ "(?:"
+ "#([0-9]+)" // count
+ "|(" + DATE + ")" // until
+ ")"
+ ")?"
+ "$",
Pattern.CASE_INSENSITIVE
);
private static final Pattern WHITESPACE = Pattern.compile("\\s+");
/**
* rewrite a vcal rrule to an ical rrule.
* http://www.shuchow.com/vCalAddendum.html
*/
static String rewriteRule(String vcalText) {
Matcher m = VCAL_RRULE.matcher(vcalText.trim());
if (!m.matches()) {
return vcalText;
}
StringBuilder sb = new StringBuilder();
String nameAndParams = m.group(1),
freq = m.group(2).toUpperCase(),
interval = m.group(3),
modifier = m.group(4).trim().toUpperCase(),
count = m.group(5),
until = m.group(6);
sb.append(nameAndParams);
Frequency f;
switch (freq.charAt(0)) {
case 'Y':
f = Frequency.YEARLY;
break;
case 'M':
f = Frequency.MONTHLY;
break;
case 'W':
f = Frequency.WEEKLY;
break;
case 'D':
f = Frequency.DAILY;
break;
default:
throw new AssertionError();
}
sb.append("FREQ=").append(f.name());
if (!"".equals(interval) && !"1".equals(interval)) {
sb.append(";INTERVAL=").append(interval);
}
if (!"".equals(modifier)) {
String[] parts = WHITESPACE.split(modifier);
for (int i = 0; i < parts.length; ++i) {
String p = parts[i];
char lastchar = p.charAt(p.length() - 1);
switch (lastchar) {
case '+':
parts[i] = p.substring(0, p.length() - 1);
break;
case '-':
parts[i] = lastchar + p.substring(0, p.length() - 1);
break;
}
if (p.equals("LD")) {
parts[i] = "-1";
} // abbrev for last day
}
switch (f) {
case YEARLY:
if ('D' == freq.charAt(1)) {
sb.append(";BYYEARDAY=");
join(sb, ",", parts);
} else {
sb.append(";BYMONTH=");
join(sb, ",", parts);
}
break;
case MONTHLY:
if ('P' == freq.charAt(1)) { // byday (position)
int pos = 0;
boolean comma = false;
sb.append(";BYDAY=");
for (int i = 0; i < parts.length; ++i) {
if (Character.isLetter(parts[i].charAt(0))) {
// a day name
if (i > pos) {
for (int j = pos; j < i; ++j) {
// week number followed by day of week
if (comma) {
sb.append(',');
} else {
comma = true;
}
sb.append(parts[j]).append(parts[i]);
}
} else {
if (comma) {
sb.append(',');
} else {
comma = true;
}
sb.append(parts[i]);
}
pos = i + 1;
}
}
} else { // bymonthday
sb.append(";BYMONTHDAY=");
join(sb, ",", parts);
}
break;
case WEEKLY:
sb.append(";BYDAY=");
join(sb, ",", parts);
break;
default:
}
}
if (null != count) {
if ("0".equals(count)) {
// means forever
} else {
sb.append(";COUNT=").append(count);
}
} else if (null != until) {
until = until.toUpperCase();
sb.append(";UNTIL=").append(until);
// treat as UTC if not already
if (!until.endsWith("Z") && until.indexOf('T') >= 0) {
sb.append('Z');
}
}
return sb.toString();
}
private static void join(StringBuilder out, String delim, String[] parts) {
if (0 != parts.length) {
out.append(parts[0]);
for (int i = 1; i < parts.length; ++i) {
out.append(delim).append(parts[i]);
}
}
}
private VcalRewriter() {
// uninstantiable
}
}