com.google.ical.values.VcalRewriter Maven / Gradle / Ivy
The newest version!
// 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
}
}