package demo;

import java.beans.PropertyDescriptor;
import java.util.Collections;
import java.util.Set;

import javax.persistence.Entity;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalConverter;
import org.springframework.core.convert.converter.GenericConverter;
import org.springframework.stereotype.Component;

@Component
public class FieldMappingObjectConverter implements GenericConverter, ConditionalConverter {

	@Override
	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {

		//only for entities?
		//TODO check if source type is a entity managed by Spring Data
		if (!sourceType.hasAnnotation(Entity.class)) {
			return false;
		}

		if (targetType.getType().isInterface()) {
			return false;
		}

		return isCompatibleProjectionType(sourceType, targetType);
	}

	private boolean isCompatibleProjectionType(TypeDescriptor sourceType, TypeDescriptor targetType) {

		// TODO perform more sophisticated compatibility check, e.g. take matching fields into account, or mapping annotations...

		PropertyDescriptor[] targetPds = new BeanWrapperImpl(targetType.getClass()).getPropertyDescriptors();
		PropertyDescriptor[] sourcePds = new BeanWrapperImpl(sourceType.getClass()).getPropertyDescriptors();

		for (PropertyDescriptor pdt : targetPds) {

			boolean found = false;
			for (PropertyDescriptor pds : sourcePds) {
				found |= pdt.getName().equals(pds.getName());
			}

			if (!found) {
				return false;
			}
		}

		return true;
	}

	@Override
	public Set<ConvertiblePair> getConvertibleTypes() {
		return Collections.singleton(new ConvertiblePair(Object.class, Object.class));
	}

	@Override
	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {

		//TODO more sophisticated bean creation and copying...
		Object target = BeanUtils.instantiateClass(targetType.getObjectType());
		BeanUtils.copyProperties(source, target);

		return target;
	}
}