package com.google.sitebricks.conversion;



import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

import java.util.Collection;



import org.mvel2.ConversionHandler;

import org.mvel2.DataConversion;



import com.google.common.primitives.Primitives;

import com.google.inject.Inject;

import com.google.sitebricks.conversion.generics.Generics;



/**

 * @author John Patterson (jdpatterson@gmail.com)

 */

public class MvelConversionHandlers {



  private TypeConverter delegate;

  private ConverterRegistry registry;



  @Inject

  public void prepare(ConverterRegistry registry, TypeConverter delegate) {

    this.registry = registry;

    this.delegate = delegate;



    Collection<Converter<?, ?>> converters = registry.getConvertersBySource().values();

    for (Converter<?, ?> converter : converters) {

      ParameterizedType converterType = (ParameterizedType) Generics.getExactSuperType(

          converter.getClass(), Converter.class);



      Type[] converterParameters = converterType.getActualTypeArguments();

      registerMvelHandler(converterParameters[0]);

      registerMvelHandler(converterParameters[1]);

    }

  }



  private void registerMvelHandler(Type targetType) {

    Class<?> targetClass = Generics.erase(targetType);

    SitebricksConversionHandler targetHandler = new SitebricksConversionHandler(targetType);

    DataConversion.addConversionHandler(targetClass, targetHandler);

    if (Primitives.isWrapperType(targetClass)) {

      DataConversion.addConversionHandler(Primitives.unwrap(targetClass), targetHandler);

    }

  }



  private class SitebricksConversionHandler implements ConversionHandler {

    private final Type targetType;



    public SitebricksConversionHandler(Type targetType) {

      this.targetType = targetType;

    }



    @Override

    public Object convertFrom(Object in) {

      return delegate.convert(in, targetType);

    }



    @SuppressWarnings("unchecked")

    @Override

    public boolean canConvertFrom(@SuppressWarnings("rawtypes") Class cls) {

      if (cls == targetType)

        return true;

      

      // check that there is a converter registered for this source type

      return registry.converter(Primitives.wrap(cls), targetType) != null;

    }

  }

}