package org.openecomp.sdc.be.view;

import java.io.IOException;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;

import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * A class that is then responsible for converting a message payload with a dedicated mixin from an instance of a specific Java type into a json representation.
 */
@Provider
@Produces(MediaType.APPLICATION_JSON)
public class MixinModelWriter implements MessageBodyWriter<Object> {

    @Override
    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return hasResponseViewAndMixinTargetAnnotations(annotations) && mediaType.isCompatible(MediaType.APPLICATION_JSON_TYPE);
    }

    @Override
    public long getSize(Object object, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return -1;
    }

    @Override
    public void writeTo(Object object, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException {
        ObjectMapper objectMapper = new ObjectMapper();
        List<MixinSourceTarget> mixinSourceTargets = getMixinSourceTarget(annotations);
        mixinSourceTargets.forEach(mixinSourceTarget -> objectMapper.addMixIn(mixinSourceTarget.getTarget(), mixinSourceTarget.getMixinSource()));
        objectMapper.writeValue(entityStream, object);
    }

    private List<MixinSourceTarget> getMixinSourceTarget(Annotation[] annotations) {
        return Stream.of(annotations)
                .filter(annotation -> annotation.annotationType().equals(ResponseView.class))
                .map(annotation -> (ResponseView) annotation)
                .flatMap(responseView -> Stream.of(responseView.mixin()))
                .map(mixinClass -> new MixinSourceTarget(mixinClass, mixinClass.getAnnotation(MixinTarget.class).target()))
                .collect(Collectors.toList());
    }

    private boolean hasResponseViewAndMixinTargetAnnotations(Annotation[] annotations) {
        return Stream.of(annotations)
                .filter(annotation -> annotation.annotationType().equals(ResponseView.class))
                .map(annotation -> (ResponseView) annotation)
                .flatMap(responseView -> Stream.of(responseView.mixin()))
                .anyMatch(mixinClass -> Objects.nonNull(mixinClass.getAnnotation(MixinTarget.class)));
    }
}