/* Copyright 2002-2018 CS Systèmes d'Information
    * Licensed to CS Systèmes d'Information (CS) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * CS 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.orekit.propagation;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  
  import org.orekit.attitudes.AttitudeProvider;
  import org.orekit.errors.OrekitException;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.frames.Frame;
  import org.orekit.propagation.events.EventDetector;
  import org.orekit.propagation.sampling.OrekitFixedStepHandler;
  import org.orekit.propagation.sampling.OrekitStepHandler;
  import org.orekit.propagation.sampling.OrekitStepNormalizer;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.utils.TimeStampedPVCoordinates;
  
  /** Common handling of {@link Propagator} methods for analytical propagators.
   * <p>
   * This abstract class allows to provide easily the full set of {@link Propagator}
   * methods, including all propagation modes support and discrete events support for
   * any simple propagation method.
   * </p>
   * @author Luc Maisonobe
   */
  public abstract class AbstractPropagator implements Propagator {
  
      /** Propagation mode. */
      private int mode;
  
      /** Fixed step size. */
      private double fixedStepSize;
  
      /** Step handler. */
      private OrekitStepHandler stepHandler;
  
      /** Start date. */
      private AbsoluteDate startDate;
  
      /** Attitude provider. */
      private AttitudeProvider attitudeProvider;
  
      /** Additional state providers. */
      private final List<AdditionalStateProvider> additionalStateProviders;
  
      /** Initial state. */
      private SpacecraftState initialState;
  
      /** Build a new instance.
       */
      protected AbstractPropagator() {
          mode                     = SLAVE_MODE;
          stepHandler              = null;
          fixedStepSize            = Double.NaN;
          additionalStateProviders = new ArrayList<AdditionalStateProvider>();
      }
  
      /** Set a start date.
       * @param startDate start date
       */
      protected void setStartDate(final AbsoluteDate startDate) {
          this.startDate = startDate;
      }
  
      /** Get the start date.
       * @return start date
       */
      protected AbsoluteDate getStartDate() {
          return startDate;
      }
  
      /**  {@inheritDoc} */
      public AttitudeProvider getAttitudeProvider() {
          return attitudeProvider;
      }
  
      /**  {@inheritDoc} */
      public void setAttitudeProvider(final AttitudeProvider attitudeProvider) {
          this.attitudeProvider = attitudeProvider;
      }
  
     /** {@inheritDoc} */
     public SpacecraftState getInitialState() throws OrekitException {
         return initialState;
     }
 
     /** {@inheritDoc} */
     public int getMode() {
         return mode;
     }
 
     /** {@inheritDoc} */
     public Frame getFrame() {
         return initialState.getFrame();
     }
 
     /** {@inheritDoc} */
     public void resetInitialState(final SpacecraftState state) throws OrekitException {
         initialState = state;
         setStartDate(state.getDate());
     }
 
     /** {@inheritDoc} */
     public void setSlaveMode() {
         mode          = SLAVE_MODE;
         stepHandler   = null;
         fixedStepSize = Double.NaN;
     }
 
     /** {@inheritDoc} */
     public void setMasterMode(final double h,
                               final OrekitFixedStepHandler handler) {
         setMasterMode(new OrekitStepNormalizer(h, handler));
         fixedStepSize = h;
     }
 
     /** {@inheritDoc} */
     public void setMasterMode(final OrekitStepHandler handler) {
         mode          = MASTER_MODE;
         stepHandler   = handler;
         fixedStepSize = Double.NaN;
     }
 
     /** {@inheritDoc} */
     public void setEphemerisMode() {
         mode          = EPHEMERIS_GENERATION_MODE;
         stepHandler   = null;
         fixedStepSize = Double.NaN;
     }
 
     /** {@inheritDoc} */
     @Override
     public void setEphemerisMode(final OrekitStepHandler handler) {
         mode          = EPHEMERIS_GENERATION_MODE;
         stepHandler   = handler;
         fixedStepSize = Double.NaN;
     }
 
     /** {@inheritDoc} */
     public void addAdditionalStateProvider(final AdditionalStateProvider additionalStateProvider)
         throws OrekitException {
 
         // check if the name is already used
         if (isAdditionalStateManaged(additionalStateProvider.getName())) {
             // this additional state is already registered, complain
             throw new OrekitException(OrekitMessages.ADDITIONAL_STATE_NAME_ALREADY_IN_USE,
                                       additionalStateProvider.getName());
         }
 
         // this is really a new name, add it
         additionalStateProviders.add(additionalStateProvider);
 
     }
 
     /** {@inheritDoc} */
     public List<AdditionalStateProvider> getAdditionalStateProviders() {
         return Collections.unmodifiableList(additionalStateProviders);
     }
 
     /** Update state by adding all additional states.
      * @param original original state
      * @return updated state, with all additional states included
      * @exception OrekitException if one of the providers throws one
      * @see #addAdditionalStateProvider(AdditionalStateProvider)
      */
     protected SpacecraftState updateAdditionalStates(final SpacecraftState original)
         throws OrekitException {
 
         // start with original state,
         // which may already contain additional states, for example in interpolated ephemerides
         SpacecraftState updated = original;
 
         if (initialState != null) {
             // there is an initial state
             // (null initial states occur for example in interpolated ephemerides)
             // copy the additional states present in initialState but otherwise not managed
             for (final Map.Entry<String, double[]> initial : initialState.getAdditionalStates().entrySet()) {
                 if (!isAdditionalStateManaged(initial.getKey())) {
                     // this additional state was in the initial state, but is unknown to the propagator
                     // we simply copy its initial value as is
                     updated = updated.addAdditionalState(initial.getKey(), initial.getValue());
                 }
             }
         }
 
         // update the additional states managed by providers
         for (final AdditionalStateProvider provider : additionalStateProviders) {
             updated = updated.addAdditionalState(provider.getName(),
                                                  provider.getAdditionalState(updated));
         }
 
         return updated;
 
     }
 
     /** {@inheritDoc} */
     public boolean isAdditionalStateManaged(final String name) {
         for (final AdditionalStateProvider provider : additionalStateProviders) {
             if (provider.getName().equals(name)) {
                 return true;
             }
         }
         return false;
     }
 
     /** {@inheritDoc} */
     public String[] getManagedAdditionalStates() {
         final String[] managed = new String[additionalStateProviders.size()];
         for (int i = 0; i < managed.length; ++i) {
             managed[i] = additionalStateProviders.get(i).getName();
         }
         return managed;
     }
 
     /** Get the fixed step size.
      * @return fixed step size (or NaN if there are no fixed step size).
      */
     protected double getFixedStepSize() {
         return fixedStepSize;
     }
 
     /** Get the step handler.
      * @return step handler
      */
     protected OrekitStepHandler getStepHandler() {
         return stepHandler;
     }
 
     /** {@inheritDoc} */
     public abstract BoundedPropagator getGeneratedEphemeris();
 
     /** {@inheritDoc} */
     public abstract <T extends EventDetector> void addEventDetector(T detector);
 
     /** {@inheritDoc} */
     public abstract Collection<EventDetector> getEventsDetectors();
 
     /** {@inheritDoc} */
     public abstract void clearEventsDetectors();
 
     /** {@inheritDoc} */
     public SpacecraftState propagate(final AbsoluteDate target) throws OrekitException {
         if (startDate == null) {
             startDate = getInitialState().getDate();
         }
         return propagate(startDate, target);
     }
 
     /** {@inheritDoc} */
     public TimeStampedPVCoordinates getPVCoordinates(final AbsoluteDate date, final Frame frame)
         throws OrekitException {
         return propagate(date).getPVCoordinates(frame);
     }
 
 }