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/*
 * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH
 * under one or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information regarding copyright
 * ownership. Camunda licenses this file to you under the Apache License,
 * Version 2.0; 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.camunda.bpm.engine.impl.calendar;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.List;

import javax.xml.datatype.DatatypeFactory;
import javax.xml.datatype.Duration;

import org.camunda.bpm.engine.impl.ProcessEngineLogger;
import org.camunda.bpm.engine.impl.util.ClockUtil;
import org.camunda.bpm.engine.impl.util.EngineUtilLogger;

/**
 * helper class for parsing ISO8601 duration format (also recurring) and computing next timer date
 */
public class DurationHelper {

  public static final String PnW_PATTERN = "P\\d+W";
  private static final int MS_PER_WEEK = 7 * 24 * 60 * 60 * 1000;
  private static final EngineUtilLogger LOG = ProcessEngineLogger.UTIL_LOGGER;

  Date start;

  Date end;

  Duration period;

  boolean isRepeat;

  int times;

  long repeatOffset;

  DatatypeFactory datatypeFactory;

  public DurationHelper(String expressions) throws Exception {
    this(expressions, null);
  }
  
  public DurationHelper(String expressions, Date startDate) throws Exception {
    List expression = new ArrayList();
    if(expressions != null) {
      expression = Arrays.asList(expressions.split("/"));
    }
    datatypeFactory = DatatypeFactory.newInstance();

    if (expression.size() > 3 || expression.isEmpty()) {
      throw LOG.cannotParseDuration(expressions);
    }
    if (expression.get(0).startsWith("R")) {
      isRepeat = true;
      times = expression.get(0).length() ==  1 ? Integer.MAX_VALUE : Integer.parseInt(expression.get(0).substring(1));
      expression = expression.subList(1, expression.size());
    }

    if (isDuration(expression.get(0))) {
      period = parsePeriod(expression.get(0));
      end = expression.size() == 1 ? null : DateTimeUtil.parseDate(expression.get(1));
    } else {
      start = DateTimeUtil.parseDate(expression.get(0));
      if (isDuration(expression.get(1))) {
        period = parsePeriod(expression.get(1));
      } else {
        end = DateTimeUtil.parseDate(expression.get(1));
        period = datatypeFactory.newDuration(end.getTime()-start.getTime());
      }
    }
    if (start == null && end == null) {
      start = startDate == null ? ClockUtil.getCurrentTime() : startDate;
    }
  }

  public Date getDateAfter() {
    return getDateAfter(null);
  }
  
  public Date getDateAfter(Date date) {
    if (isRepeat) {
      return getDateAfterRepeat(date == null ? ClockUtil.getCurrentTime() : date);
    }
    //TODO: is this correct?
    if (end != null) {
      return end;
    }
    return add(start, period);
  }

  public int getTimes() {
    return times;
  }

  public boolean isRepeat() {
    return isRepeat;
  }

  private Date getDateAfterRepeat(Date date) {
    // use date without the current offset for due date calculation to get the
    // next due date as it would be without any modifications, later add offset
    Date dateWithoutOffset = new Date(date.getTime() - repeatOffset);
    if (start != null) {
      Date cur = start;
      for (int i = 0; i < times && !cur.after(dateWithoutOffset); i++) {
        cur = add(cur, period);
      }
      if (cur.before(dateWithoutOffset)) {
        return null;
      }
      // add offset to calculated due date
      return repeatOffset == 0L ? cur : new Date(cur.getTime() + repeatOffset);
    }
    Date cur = add(end, period.negate());
    Date next = end;

    for (int i=0;i