package feign.optionals;

import feign.Response;

import feign.Util;

import feign.codec.Decoder;

import java.io.IOException;

import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

import java.util.Objects;

import java.util.Optional;

public final class OptionalDecoder implements Decoder {

final Decoder delegate;

public OptionalDecoder(Decoder delegate) {

Objects.requireNonNull(delegate, "Decoder must not be null. ");

this.delegate = delegate;

}

@Override public Object decode(Response response, Type type) throws IOException {

if(!isOptional(type)) {

return delegate.decode(response, type);

}

if(response.status() == 404) {

return Optional.empty();

}

Type enclosedType = Util.resolveLastTypeParameter(type, Optional.class);

return Optional.of(delegate.decode(response, enclosedType));

}

static boolean isOptional(Type type) {

if(!(type instanceof ParameterizedType)) {

return false;

}

ParameterizedType parameterizedType = (ParameterizedType) type;

return parameterizedType.getRawType().equals(Optional.class);

}

}