package org.opentrafficsim.base.parameters;
   
   import java.io.Serializable;
   import java.lang.reflect.Field;
   import java.util.HashMap;
   import java.util.Map;
   import java.util.Set;
   
   import org.djunits.unit.DimensionlessUnit;
  import org.djunits.value.vdouble.scalar.Dimensionless;
  import org.djutils.exceptions.Throw;
  import org.djutils.reflection.ClassUtil;
  
  /**
   * Implementation of {@link Parameters} with methods to initialize the set of parameters.
   * <p>
   * Copyright (c) 2013-2019 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="http://opentrafficsim.org/docs/current/license.html">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version Apr 13, 2016 <br>
   * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   */
  public class ParameterSet implements Parameters, Serializable
  {
  
      /** */
      private static final long serialVersionUID = 20160400L;
  
      /** Object to recognize that no value was set previously. */
      private static final Empty EMPTY = new Empty();
  
      /** Whether to copy internal data on write. */
      private boolean copyOnWrite = false;
  
      /** List of parameters. */
      private Map<ParameterType<?>, Object> parameters;
  
      /** List of parameters with values before last set. */
      private Map<ParameterType<?>, Object> previous;
  
      /**
       * Construct a new, empty Parameters set.
       */
      public ParameterSet()
      {
          this.parameters = new HashMap<>();
          this.previous = new HashMap<>();
      }
  
      /**
       * Constructor which creates a copy of the input set.
       * @param parameters Parameters; input set to copy into the new Parameters object
       */
      public ParameterSet(final Parameters parameters)
      {
          if (parameters instanceof ParameterSet)
          {
              ParameterSet parameterSet = (ParameterSet) parameters;
              this.parameters = parameterSet.parameters;
              this.previous = parameterSet.previous;
              this.copyOnWrite = true;
              parameterSet.copyOnWrite = true;
          }
          else
          {
              parameters.setAllIn(this);
          }
      }
  
      /** {@inheritDoc} */
      @Override
      public final <T> void setParameter(final ParameterType<T> parameterType, final T value) throws ParameterException
      {
          Throw.when(value == null, ParameterException.class,
                  "Parameter of type '%s' was assigned a null value, this is not allowed.", parameterType.getId());
          saveSetParameter(parameterType, value, false);
      }
  
      /** {@inheritDoc} */
      @Override
      public final <T> void setParameterResettable(final ParameterType<T> parameterType, final T value) throws ParameterException
      {
          Throw.when(value == null, ParameterException.class,
                  "Parameter of type '%s' was assigned a null value, this is not allowed.", parameterType.getId());
          saveSetParameter(parameterType, value, true);
      }
  
      /**
       * Sets a parameter value while checking conditions.
       * @param parameterType ParameterType&lt;T&gt;; the parameter type
       * @param value T; new value for the parameter
       * @param resettable boolean; whether the parameter set should be resettable
       * @param <T> Class of the value
       * @throws ParameterException If the value does not comply with constraints.
       */
      private <T> void saveSetParameter(final ParameterType<T> parameterType, final T value, final boolean resettable)
              throws ParameterException
      {
         parameterType.check(value, this);
         parameterType.checkConstraint(value);
         checkCopyOnWrite();
         if (resettable)
         {
             Object prevValue = this.parameters.get(parameterType);
             if (prevValue == null)
             {
                 // remember that there was no value before this set
                 this.previous.put(parameterType, EMPTY);
             }
             else
             {
                 this.previous.put(parameterType, prevValue);
             }
         }
         else
         {
             // no reset after non-resettale set
             this.previous.remove(parameterType);
         }
         this.parameters.put(parameterType, value);
     }
 
     /** {@inheritDoc} */
     @Override
     public final void resetParameter(final ParameterType<?> parameterType) throws ParameterException
     {
         checkCopyOnWrite();
         Object prevValue = this.previous.remove(parameterType);
         Throw.when(prevValue == null, ParameterException.class,
                 "Reset on parameter of type '%s' could not be performed, it was not set resettable.", parameterType.getId());
         if (prevValue instanceof Empty)
         {
             // no value was set before last set, so make parameter type not set
             this.parameters.remove(parameterType);
         }
         else
         {
             this.parameters.put(parameterType, prevValue);
         }
     }
 
     /**
      * Copy the internal data if needed.
      */
     private void checkCopyOnWrite()
     {
         if (this.copyOnWrite)
         {
             this.parameters = new HashMap<>(this.parameters);
             this.previous = new HashMap<>(this.previous);
             this.copyOnWrite = false;
         }
     }
 
     /** {@inheritDoc} */
     @Override
     @SuppressWarnings("checkstyle:designforextension")
     public <T> T getParameter(final ParameterType<T> parameterType) throws ParameterException
     {
         @SuppressWarnings("unchecked")
         // set methods guarantee matching of parameter type and value
         T result = (T) this.parameters.get(parameterType);
         Throw.when(result == null, ParameterException.class, "Could not get parameter of type '%s' as it was not set.",
                 parameterType.getId());
         return result;
     }
 
     /** {@inheritDoc} */
     @Override
     @SuppressWarnings("unchecked")
     public final <T> T getParameterOrNull(final ParameterType<T> parameterType)
     {
         // set methods guarantee matching of parameter type and value
         return (T) this.parameters.get(parameterType);
     }
 
     /** {@inheritDoc} */
     @Override
     public final boolean contains(final ParameterType<?> parameterType)
     {
         return this.parameters.containsKey(parameterType);
     }
 
     /**
      * Returns a safe copy of the parameters.
      * @return Map&lt;AbstractParameterType&lt;?&gt;&gt;; a safe copy of the parameters, e.g., for printing
      */
     public final Map<ParameterType<?>, Object> getParameters()
     {
         return new HashMap<>(this.parameters);
     }
 
     /**
      * Sets the default value of a parameter. Default value sets are not resettable.
      * @param parameter ParameterType&lt;T&gt;; the parameter to set the default value of
      * @param <T> Class of the value
      * @return Parameters; this set of parameters (for method chaining)
      * @throws ParameterException if the parameter type has no default value
      */
     public final <T> ParameterSet setDefaultParameter(final ParameterType<T> parameter) throws ParameterException
     {
         T defaultValue = parameter.getDefaultValue();
         try
         {
             saveSetParameter(parameter, defaultValue, false);
         }
         catch (ParameterException pe)
         {
             // should not happen, default value and parameter type are connected
             throw new RuntimeException(pe);
         }
         return this;
     }
 
     /**
      * Sets the default values of all accessible parameters defined in the given class. Default value sets are not
      * resettable.<br>
      * @param clazz Class&lt;?&gt;; class with parameters
      * @return Parameters; this set of parameters (for method chaining)
      */
     public final ParameterSet setDefaultParameters(final Class<?> clazz)
     {
         return setDefaultParametersLocal(clazz);
     }
 
     /**
      * Sets the default values of all accessible parameters defined in the given class. Default value sets are not resettable.
      * @param clazz Class&lt;?&gt;; class with parameters
      * @param <T> Class of the value
      * @return this set of parameters (for method chaining)
      */
     @SuppressWarnings("unchecked")
     private <T> ParameterSet setDefaultParametersLocal(final Class<?> clazz)
     {
         // set all default values using reflection
         Set<Field> fields = ClassUtil.getAllFields(clazz);
 
         for (Field field : fields)
         {
             if (ParameterType.class.isAssignableFrom(field.getType()))
             {
                 try
                 {
                     field.setAccessible(true);
                     ParameterType<T> p = (ParameterType<T>) field.get(clazz);
                     saveSetParameter(p, p.getDefaultValue(), false);
                 }
                 catch (IllegalArgumentException iare)
                 {
                     // should not happen, field and clazz are related
                     throw new RuntimeException(iare);
                 }
                 catch (IllegalAccessException iace)
                 {
                     // parameter type not public
                     throw new RuntimeException(iace);
                 }
                 catch (ParameterException pe)
                 {
                     // do not set parameter without default value
                     throw new RuntimeException(pe);
                 }
             }
         }
         return this;
     }
 
     /** {@inheritDoc} */
     @Override
     public final void setAllIn(final Parameters params)
     {
         if (params instanceof ParameterSet)
         {
             ParameterSet parameterSet = (ParameterSet) params;
             parameterSet.checkCopyOnWrite();
             parameterSet.parameters.putAll(this.parameters);
         }
         else
         {
             setAllOneByOne(params);
         }
     }
 
     /**
      * Sets the parameters of this set in the given set.
      * @param params Parameters; parameters to set the values in
      * @param <T> parameter value type
      */
     @SuppressWarnings("unchecked")
     private <T> void setAllOneByOne(final Parameters params)
     {
         for (ParameterType<?> parameterType : this.parameters.keySet())
         {
             try
             {
                 params.setParameter((ParameterType<T>) parameterType, (T) this.parameters.get(parameterType));
             }
             catch (ParameterException exception)
             {
                 throw new RuntimeException(exception); // should not happen
             }
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public final String toString()
     {
         StringBuilder out = new StringBuilder("Parameters [");
         String sep = "";
         for (ParameterType<?> apt : this.parameters.keySet())
         {
             try
             {
                 out.append(sep).append(apt.getId()).append("=").append(apt.printValue(this));
                 sep = ", ";
             }
             catch (ParameterException pe)
             {
                 // We know the parameter has been set as we get the keySet from parameters
                 throw new RuntimeException(pe);
             }
         }
         out.append("]");
         return out.toString();
     }
 
     /**
      * Class of object to put in the internal Map of Parameters to indicate that no value was set.
      */
     private static class Empty extends Dimensionless
     {
         /** */
         private static final long serialVersionUID = 20160414L;
 
         /**
          * Constructor for Empty.
          */
         Empty()
         {
             super(Double.NaN, DimensionlessUnit.SI);
         }
     }
 
 }