/**
 * Copyright (c) 2015-2016 the original author or authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.jmnarloch.spring.boot.rxjava.mvc;

import io.jmnarloch.spring.boot.rxjava.async.ObservableDeferredResult;
import org.springframework.core.MethodParameter;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.async.WebAsyncUtils;
import org.springframework.web.method.support.AsyncHandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;
import io.reactivex.Observable;

/**
 * A specialized {@link AsyncHandlerMethodReturnValueHandler} that handles {@link Observable} return types.
 *
 * @author Jakub Narloch
 * @see ObservableDeferredResult
 */
public class ObservableReturnValueHandler implements AsyncHandlerMethodReturnValueHandler {

    @Override
    public boolean isAsyncReturnValue(Object returnValue, MethodParameter returnType) {
        return returnValue != null && supportsReturnType(returnType);
    }

    @Override
    public boolean supportsReturnType(MethodParameter returnType) {
        return Observable.class.isAssignableFrom(returnType.getParameterType());
    }

    @SuppressWarnings("unchecked")
    @Override
    public void handleReturnValue(Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {

        if (returnValue == null) {
            mavContainer.setRequestHandled(true);
            return;
        }

        final Observable<?> observable = Observable.class.cast(returnValue);
        WebAsyncUtils.getAsyncManager(webRequest)
                .startDeferredResultProcessing(new ObservableDeferredResult(observable), mavContainer);
    }
}