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package org.apache.commons.math3.ode;

import java.util.Collection;

import org.apache.commons.math3.RealFieldElement;
import org.apache.commons.math3.analysis.solvers.BracketedRealFieldUnivariateSolver;
import org.apache.commons.math3.exception.MaxCountExceededException;
import org.apache.commons.math3.exception.NoBracketingException;
import org.apache.commons.math3.exception.NumberIsTooSmallException;
import org.apache.commons.math3.ode.events.FieldEventHandler;
import org.apache.commons.math3.ode.sampling.FieldStepHandler;

This interface represents a first order integrator for
differential equations.
The classes which are devoted to solve first order differential equations should implement this interface. The problems which can be handled should implement the FirstOrderDifferentialEquations interface.
Type parameters:
<T> – the type of the field elements
See Also:
FirstOrderFieldDifferentialEquations
Since:
3.6/** This interface represents a first order integrator for
 * differential equations.

 * <p>The classes which are devoted to solve first order differential
 * equations should implement this interface. The problems which can
 * be handled should implement the {@link
 * FirstOrderDifferentialEquations} interface.</p>
 *
 * @see FirstOrderFieldDifferentialEquations
 * @param <T> the type of the field elements
 * @since 3.6
 */

public interface FirstOrderFieldIntegrator<T extends RealFieldElement<T>> {

    
Get the name of the method.
Returns:
name of the method/** Get the name of the method.
     * @return name of the method
     */
    String getName();

    
Add a step handler to this integrator.
The handler will be called by the integrator for each accepted
step.
Params:
handler – handler for the accepted steps
See Also:
getStepHandlers()
clearStepHandlers()/** Add a step handler to this integrator.
     * <p>The handler will be called by the integrator for each accepted
     * step.</p>
     * @param handler handler for the accepted steps
     * @see #getStepHandlers()
     * @see #clearStepHandlers()
     */
    void addStepHandler(FieldStepHandler<T> handler);

    
Get all the step handlers that have been added to the integrator.
See Also:
addStepHandler(FieldStepHandler)
clearStepHandlers()
Returns:
an unmodifiable collection of the added events handlers/** Get all the step handlers that have been added to the integrator.
     * @return an unmodifiable collection of the added events handlers
     * @see #addStepHandler(FieldStepHandler)
     * @see #clearStepHandlers()
     */
    Collection<FieldStepHandler<T>> getStepHandlers();

    
Remove all the step handlers that have been added to the integrator.
See Also:
addStepHandler(FieldStepHandler)
getStepHandlers()/** Remove all the step handlers that have been added to the integrator.
     * @see #addStepHandler(FieldStepHandler)
     * @see #getStepHandlers()
     */
    void clearStepHandlers();

    
Add an event handler to the integrator.

The default solver is a 5th order FieldBracketingNthOrderBrentSolver. 
Params:
handler – event handler
maxCheckInterval – maximal time interval between switching
function checks (this interval prevents missing sign changes in
case the integration steps becomes very large)
convergence – convergence threshold in the event time search
maxIterationCount – upper limit of the iteration count in
the event time search events.
See Also:
addEventHandler(FieldEventHandler, double, double, int, BracketedRealFieldUnivariateSolver)
getEventHandlers()
clearEventHandlers()/** Add an event handler to the integrator.
     * <p>
     * The default solver is a 5<sup>th</sup> order {@link
     * org.apache.commons.math3.analysis.solvers.FieldBracketingNthOrderBrentSolver}.
     * </p>
     * @param handler event handler
     * @param maxCheckInterval maximal time interval between switching
     * function checks (this interval prevents missing sign changes in
     * case the integration steps becomes very large)
     * @param convergence convergence threshold in the event time search
     * @param maxIterationCount upper limit of the iteration count in
     * the event time search events.
     * @see #addEventHandler(FieldEventHandler, double, double, int,
     * org.apache.commons.math3.analysis.solvers.BracketedRealFieldUnivariateSolver)
     * @see #getEventHandlers()
     * @see #clearEventHandlers()
     */
    void addEventHandler(FieldEventHandler<T>  handler, double maxCheckInterval,
                         double convergence, int maxIterationCount);

    
Add an event handler to the integrator.
Params:
handler – event handler
maxCheckInterval – maximal time interval between switching
function checks (this interval prevents missing sign changes in
case the integration steps becomes very large)
convergence – convergence threshold in the event time search
maxIterationCount – upper limit of the iteration count in
the event time search events.
solver – solver to use to locate the event
See Also:
addEventHandler(FieldEventHandler, double, double, int)
getEventHandlers()
clearEventHandlers()/** Add an event handler to the integrator.
     * @param handler event handler
     * @param maxCheckInterval maximal time interval between switching
     * function checks (this interval prevents missing sign changes in
     * case the integration steps becomes very large)
     * @param convergence convergence threshold in the event time search
     * @param maxIterationCount upper limit of the iteration count in
     * the event time search events.
     * @param solver solver to use to locate the event
     * @see #addEventHandler(FieldEventHandler, double, double, int)
     * @see #getEventHandlers()
     * @see #clearEventHandlers()
     */
    void addEventHandler(FieldEventHandler<T>  handler, double maxCheckInterval,
                         double convergence, int maxIterationCount,
                         BracketedRealFieldUnivariateSolver<T> solver);

    
Get all the event handlers that have been added to the integrator.
See Also:
addEventHandler(FieldEventHandler, double, double, int)
clearEventHandlers()
Returns:
an unmodifiable collection of the added events handlers/** Get all the event handlers that have been added to the integrator.
     * @return an unmodifiable collection of the added events handlers
     * @see #addEventHandler(FieldEventHandler, double, double, int)
     * @see #clearEventHandlers()
     */
    Collection<FieldEventHandler<T> > getEventHandlers();

    
Remove all the event handlers that have been added to the integrator.
See Also:
addEventHandler(FieldEventHandler, double, double, int)
getEventHandlers()/** Remove all the event handlers that have been added to the integrator.
     * @see #addEventHandler(FieldEventHandler, double, double, int)
     * @see #getEventHandlers()
     */
    void clearEventHandlers();

    
Get the current value of the step start time ti.
This method can be called during integration (typically by the object implementing the 
differential equations problem) if the value of the current step that is attempted is needed.
The result is undefined if the method is called outside of
calls to integrate.
Returns:
current value of the state at step start time ti/** Get the current value of the step start time t<sub>i</sub>.
     * <p>This method can be called during integration (typically by
     * the object implementing the {@link FirstOrderDifferentialEquations
     * differential equations} problem) if the value of the current step that
     * is attempted is needed.</p>
     * <p>The result is undefined if the method is called outside of
     * calls to <code>integrate</code>.</p>
     * @return current value of the state at step start time t<sub>i</sub>
     */
    FieldODEStateAndDerivative<T> getCurrentStepStart();

    
Get the current signed value of the integration stepsize.
This method can be called during integration (typically by the object implementing the 
differential equations problem) if the signed value of the current stepsize that is tried is needed.
The result is undefined if the method is called outside of
calls to integrate.
Returns:
current signed value of the stepsize/** Get the current signed value of the integration stepsize.
     * <p>This method can be called during integration (typically by
     * the object implementing the {@link FirstOrderDifferentialEquations
     * differential equations} problem) if the signed value of the current stepsize
     * that is tried is needed.</p>
     * <p>The result is undefined if the method is called outside of
     * calls to <code>integrate</code>.</p>
     * @return current signed value of the stepsize
     */
    T getCurrentSignedStepsize();

    
Set the maximal number of differential equations function evaluations.
The purpose of this method is to avoid infinite loops which can occur
for example when stringent error constraints are set or when lots of
discrete events are triggered, thus leading to many rejected steps.
Params:
maxEvaluations – maximal number of function evaluations (negative
values are silently converted to maximal integer value, thus representing
almost unlimited evaluations)/** Set the maximal number of differential equations function evaluations.
     * <p>The purpose of this method is to avoid infinite loops which can occur
     * for example when stringent error constraints are set or when lots of
     * discrete events are triggered, thus leading to many rejected steps.</p>
     * @param maxEvaluations maximal number of function evaluations (negative
     * values are silently converted to maximal integer value, thus representing
     * almost unlimited evaluations)
     */
    void setMaxEvaluations(int maxEvaluations);

    
Get the maximal number of functions evaluations.
Returns:
maximal number of functions evaluations/** Get the maximal number of functions evaluations.
     * @return maximal number of functions evaluations
     */
    int getMaxEvaluations();

    
Get the number of evaluations of the differential equations function.

The number of evaluations corresponds to the last call to the
integrate method. It is 0 if the method has not been called yet.

Returns:
number of evaluations of the differential equations function/** Get the number of evaluations of the differential equations function.
     * <p>
     * The number of evaluations corresponds to the last call to the
     * <code>integrate</code> method. It is 0 if the method has not been called yet.
     * </p>
     * @return number of evaluations of the differential equations function
     */
    int getEvaluations();

    
Integrate the differential equations up to the given time.
This method solves an Initial Value Problem (IVP).
Since this method stores some internal state variables made available in its public interface during integration (getCurrentSignedStepsize()), it is not thread-safe.
Params:
equations – differential equations to integrate
initialState – initial state (time, primary and secondary state vectors)
finalTime – target time for the integration (can be set to a value smaller than t0 for backward integration)
Throws:
NumberIsTooSmallException – if integration step is too small
MaxCountExceededException – if the number of functions evaluations is exceeded
NoBracketingException – if the location of an event cannot be bracketed
Returns:
final state, its time will be the same as finalTime if integration reached its target, but may be different if some FieldEventHandler stops it at some point./** Integrate the differential equations up to the given time.
     * <p>This method solves an Initial Value Problem (IVP).</p>
     * <p>Since this method stores some internal state variables made
     * available in its public interface during integration ({@link
     * #getCurrentSignedStepsize()}), it is <em>not</em> thread-safe.</p>
     * @param equations differential equations to integrate
     * @param initialState initial state (time, primary and secondary state vectors)
     * @param finalTime target time for the integration
     * (can be set to a value smaller than {@code t0} for backward integration)
     * @return final state, its time will be the same as {@code finalTime} if
     * integration reached its target, but may be different if some {@link
     * org.apache.commons.math3.ode.events.FieldEventHandler} stops it at some point.
     * @exception NumberIsTooSmallException if integration step is too small
     * @exception MaxCountExceededException if the number of functions evaluations is exceeded
     * @exception NoBracketingException if the location of an event cannot be bracketed
     */
    FieldODEStateAndDerivative<T> integrate(FieldExpandableODE<T> equations,
                                            FieldODEState<T> initialState, T finalTime)
        throws NumberIsTooSmallException, MaxCountExceededException, NoBracketingException;

}