/* Copyright 2002-2025 CS GROUP
    * Licensed to CS GROUP (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.forces.maneuvers.trigger;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.Field;
  import org.hipparchus.ode.events.Action;
  import org.orekit.propagation.FieldSpacecraftState;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.propagation.events.EventDetector;
  import org.orekit.propagation.events.FieldEventDetector;
  import org.orekit.propagation.events.handlers.EventHandler;
  import org.orekit.propagation.events.handlers.FieldEventHandler;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.FieldAbsoluteDate;
  import org.orekit.utils.TimeSpanMap;
  
  /** Base class for triggers.
   * @author Luc Maisonobe
   * @since 11.1
   */
  public abstract class AbstractManeuverTriggers implements ResettableManeuverTriggers {
  
      /** Firing time spans. */
      private TimeSpanMap<Boolean> firings;
  
      /** Propagation direction. */
      private boolean forward;
  
      /** Resetters for the maneuver triggers. */
      private final List<ManeuverTriggersResetter> resetters;
  
      /** Cached field-based resetters. */
      private final Map<Field<? extends CalculusFieldElement<?>>, List<FieldManeuverTriggersResetter<?>>> fieldResetters;
  
      /** Simple constructor.
       */
      protected AbstractManeuverTriggers() {
          this.firings        = new TimeSpanMap<>(Boolean.FALSE);
          this.resetters      = new ArrayList<>();
          this.fieldResetters = new HashMap<>();
      }
  
      /** {@inheritDoc} */
      @Override
      public void init(final SpacecraftState initialState, final AbsoluteDate target) {
  
          forward = target.isAfterOrEqualTo(initialState);
          firings = new TimeSpanMap<>(Boolean.FALSE);
          initializeResetters(initialState, target);
  
          if (isFiringOnInitialState(initialState, forward)) {
              if (forward) {
                  firings.addValidAfter(Boolean.TRUE, initialState.getDate(), false);
              } else {
                  firings.addValidBefore(Boolean.TRUE, initialState.getDate(), false);
              }
          }
  
      }
  
      /** {@inheritDoc} */
      @SuppressWarnings("unchecked")
      @Override
      public <T extends CalculusFieldElement<T>> void init(final FieldSpacecraftState<T> initialState, final FieldAbsoluteDate<T> target) {
  
          forward = target.isAfterOrEqualTo(initialState);
          firings = new TimeSpanMap<>(Boolean.FALSE);
          // check if we already have resetters for this field
          final List<FieldManeuverTriggersResetter<?>> list = fieldResetters.get(initialState.getDate().getField());
          if (list != null) {
              for (FieldManeuverTriggersResetter<?> r : list) {
                  ((FieldManeuverTriggersResetter<T>) r).init(initialState, target);
              }
          }
  
          if (isFiringOnInitialState(initialState.toSpacecraftState(), forward)) {
              if (forward) {
                  firings.addValidAfter(Boolean.TRUE, initialState.getDate().toAbsoluteDate(), false);
              } else {
                 firings.addValidBefore(Boolean.TRUE, initialState.getDate().toAbsoluteDate(), false);
             }
         }
 
     }
 
     /**
      * Method to check if the thruster is firing on initialization. can be called by
      * sub classes
      *
      * @param initialState initial spacecraft state
      * @param isForward if true, propagation will be in the forward direction
      * @return true if firing in propagation direction
      */
     protected abstract boolean isFiringOnInitialState(SpacecraftState initialState, boolean isForward);
 
     /** {@inheritDoc} */
     @Override
     public boolean isFiring(final AbsoluteDate date, final double[] parameters) {
         return firings.get(date);
     }
 
     /** {@inheritDoc} */
     @Override
     public <S extends CalculusFieldElement<S>> boolean isFiring(final FieldAbsoluteDate<S> date, final S[] parameters) {
         return firings.get(date.toAbsoluteDate());
     }
 
     /** Get the firings detected during last propagation.
      * @return firings detected during last propagation
      */
     public TimeSpanMap<Boolean> getFirings() {
         return firings;
     }
 
     /** {@inheritDoc} */
     @Override
     public void addResetter(final ManeuverTriggersResetter resetter) {
         resetters.add(resetter);
     }
 
     /** {@inheritDoc} */
     @Override
     public <T extends CalculusFieldElement<T>> void addResetter(final Field<T> field, final FieldManeuverTriggersResetter<T> resetter) {
 
         // check if we already have resetters for this field
         final List<FieldManeuverTriggersResetter<?>> list = fieldResetters.computeIfAbsent(field, k -> new ArrayList<>());
 
         // add the resetter to the list
         list.add(resetter);
 
     }
 
     /** Initialize resetters.
      * @param initialState initial state
      * @param target target date for the propagation
      */
     protected void initializeResetters(final SpacecraftState initialState, final AbsoluteDate target) {
         for (final ManeuverTriggersResetter r : resetters) {
             r.init(initialState, target);
         }
     }
 
     /** Notify resetters.
      * @param state spacecraft state at trigger date (before applying the maneuver)
      * @param start if true, the trigger is the start of the maneuver
      */
     protected void notifyResetters(final SpacecraftState state, final boolean start) {
         for (final ManeuverTriggersResetter r : resetters) {
             r.maneuverTriggered(state, start);
         }
     }
 
     /** Apply resetters.
      * @param state spacecraft state at trigger date
      * @return reset state
      */
     protected SpacecraftState applyResetters(final SpacecraftState state) {
         SpacecraftState reset = state;
         for (final ManeuverTriggersResetter r : resetters) {
             reset = r.resetState(reset);
         }
         return reset;
     }
 
     /** Initialize resetters.
      * @param initialState initial state
      * @param target target date for the propagation
      * @param <T> type of the field elements
      */
     protected <T extends CalculusFieldElement<T>> void initializeResetters(final FieldSpacecraftState<T> initialState, final FieldAbsoluteDate<T> target) {
         final List<FieldManeuverTriggersResetter<?>> list = fieldResetters.get(initialState.getDate().getField());
         if (list != null) {
             for (final FieldManeuverTriggersResetter<?> r : list) {
                 @SuppressWarnings("unchecked")
                 final FieldManeuverTriggersResetter<T> tr = (FieldManeuverTriggersResetter<T>) r;
                 tr.init(initialState, target);
             }
         }
     }
 
     /** Notify resetters.
      * @param state spacecraft state at trigger date (before applying the maneuver)
      * @param start if true, the trigger is the start of the maneuver
      * @param <T> type of the field elements
      */
     protected <T extends CalculusFieldElement<T>> void notifyResetters(final FieldSpacecraftState<T> state, final boolean start) {
         final List<FieldManeuverTriggersResetter<?>> list = fieldResetters.get(state.getDate().getField());
         if (list != null) {
             for (final FieldManeuverTriggersResetter<?> r : list) {
                 @SuppressWarnings("unchecked")
                 final FieldManeuverTriggersResetter<T> tr = (FieldManeuverTriggersResetter<T>) r;
                 tr.maneuverTriggered(state, start);
             }
         }
     }
 
     /** Apply resetters.
      * @param state spacecraft state at trigger date
      * @param <T> type of the field elements
      * @return reset state
      */
     protected <T extends CalculusFieldElement<T>> FieldSpacecraftState<T>
         applyResetters(final FieldSpacecraftState<T> state) {
         FieldSpacecraftState<T> reset = state;
         final List<FieldManeuverTriggersResetter<?>> list = fieldResetters.get(state.getDate().getField());
         if (list != null) {
             for (final FieldManeuverTriggersResetter<?> r : list) {
                 @SuppressWarnings("unchecked")
                 final FieldManeuverTriggersResetter<T> tr = (FieldManeuverTriggersResetter<T>) r;
                 reset = tr.resetState(reset);
             }
         }
         return reset;
     }
 
     /** Local abstract handler for triggers, with a cache for the reset.
      * @since 13.1
      */
     protected abstract class TriggerHandler implements EventHandler {
 
         /** Propagation direction. */
         private boolean forward;
 
         /** Last evaluated state for cache. */
         private SpacecraftState lastState;
 
         /** Last reset state for cache. */
         private SpacecraftState lastResetState;
 
         /** {@inheritDoc} */
         @Override
         public void init(final SpacecraftState initialState, final AbsoluteDate target, final EventDetector detector) {
             forward = target.isAfterOrEqualTo(initialState);
             lastState = null;
             lastResetState = null;
             initializeResetters(initialState, target);
         }
 
         /**
          * Determines the action (reset state or derivatives only).
          * @param detector event detector
          * @param oldState state before reset if any
          * @return action
          */
         protected Action determineAction(final EventDetector detector, final SpacecraftState oldState) {
             final SpacecraftState resetState = resetState(detector, oldState);
             if (resetState == oldState) {
                 return Action.RESET_DERIVATIVES;
             } else {
                 return Action.RESET_STATE;
             }
         }
 
         /** {@inheritDoc} */
         @Override
         public SpacecraftState resetState(final EventDetector detector, final SpacecraftState oldState) {
             if (lastState != oldState) {
                 lastResetState = applyResetters(oldState);
                 lastState = oldState;
             }
             return lastResetState;
         }
 
         /**
          * Getter for flag.
          * @return flag on backward propagation
          */
         protected boolean isForward() {
             return forward;
         }
     }
 
     /** Local abstract handler for triggers, with a cache for the reset.
      * @param <S> type of the field elements
      * @since 13.1
      */
     protected abstract class FieldTriggerHandler<S extends CalculusFieldElement<S>> implements FieldEventHandler<S> {
 
         /** Propagation direction. */
         private boolean forward;
 
         /** Last evaluated state for cache. */
         private FieldSpacecraftState<S> lastState;
 
         /** Last reset state for cache. */
         private FieldSpacecraftState<S> lastResetState;
 
         /** {@inheritDoc} */
         @Override
         public void init(final FieldSpacecraftState<S> initialState,
                          final FieldAbsoluteDate<S> target,
                          final FieldEventDetector<S> detector) {
             forward = target.isAfterOrEqualTo(initialState);
             lastState = null;
             lastResetState = null;
             initializeResetters(initialState, target);
         }
 
         /**
          * Determines the action (reset state or derivatives only).
          * @param detector event detector
          * @param oldState state before reset if any
          * @return action
          */
         protected Action determineAction(final FieldEventDetector<S> detector, final FieldSpacecraftState<S> oldState) {
             final FieldSpacecraftState<S> resetState = resetState(detector, oldState);
             if (resetState == oldState) {
                 return Action.RESET_DERIVATIVES;
             } else {
                 return Action.RESET_STATE;
             }
         }
 
         /** {@inheritDoc} */
         @Override
         public FieldSpacecraftState<S> resetState(final FieldEventDetector<S> detector, final FieldSpacecraftState<S> oldState) {
             if (lastState != oldState) {
                 lastResetState = applyResetters(oldState);
                 lastState = oldState;
             }
             return lastResetState;
         }
 
         /**
          * Getter for flag.
          * @return flag on backward propagation
          */
         protected boolean isForward() {
             return forward;
         }
     }
 }