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Contains the entire NEBA core implementation, i.e. the framework that interprets the NEBA API annotations and provides implementations for the service and lifecycle callback interfaces provided in the NEBA API. This package must not export anything as its implementation details are entirely private.
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/**
 * Copyright 2013 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.neba.core.mvc;

import io.neba.api.annotations.ResourceParam;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.resource.Resource;
import org.apache.sling.api.resource.ResourceResolver;
import org.springframework.core.MethodParameter;
import org.springframework.web.bind.MissingServletRequestParameterException;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.ModelAndViewContainer;

import static org.apache.commons.lang.StringUtils.isEmpty;
import static org.apache.sling.api.resource.ResourceUtil.isNonExistingResource;

/**
 * Supports {@link io.neba.api.annotations.ResourceModel} arguments of a
 * {@link org.springframework.web.bind.annotation.RequestMapping}.
 * 

 *
 * Example:

 * 
 * 
 *  @{@link org.springframework.web.bind.annotation.RequestMapping}(...)
 *  public void myHandlerMethod(@{@link io.neba.api.annotations.ResourceParam} MyModel model, ...) {
 *      ...
 *  }
 * 
 * 
 *
 * This will expect a String parameter "model", which is a path to a JCR resource adapting to "MyModel". This argument resolver
 * will resolve the path and adapt to the desired model. Unless the resource param is not
 * {@link io.neba.api.annotations.ResourceParam#required() required}, an exception will be thrown
 * if the parameter is missing, the path is unresolvable or the resource cannot be adapted to the desired model,
 * i.e. the resulting model instance is guaranteed not to be null.
 *
 * @author Olaf Otto
 */
public class ResourceParamArgumentResolver implements HandlerMethodArgumentResolver {
    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return getParameterAnnotation(parameter) != null;
    }

    private ResourceParam getParameterAnnotation(MethodParameter parameter) {
        return parameter.getParameterAnnotation(ResourceParam.class);
    }

    @Override
    public Object resolveArgument(MethodParameter parameter,
                                 ModelAndViewContainer container,
                                 NativeWebRequest webRequest,
                                 WebDataBinderFactory binderFactory) throws Exception {

        final Object nativeRequest = webRequest.getNativeRequest();

        if (!(nativeRequest instanceof SlingHttpServletRequest)) {
            throw new IllegalStateException("Expected a " + SlingHttpServletRequest.class.getName() +
                                            " request, but got: " + nativeRequest + ".");
        }

        final SlingHttpServletRequest request = (SlingHttpServletRequest) nativeRequest;
        final ResourceParam resourceParam = getParameterAnnotation(parameter);
        final String parameterName = resolveParameterName(parameter, resourceParam);
        final boolean required = resourceParam.required() && isEmpty(resourceParam.defaultValue());
        final String resourcePath = resolveResourcePath(request, resourceParam, parameterName, required);

        if (resourcePath == null) {
            return null;
        }

        // We must resolve (and not use getResource()) as the resource path may be mapped.
        ResourceResolver resolver = request.getResourceResolver();
        Resource resource = resolver.resolve(request, resourcePath);

        if (resource == null || isNonExistingResource(resource)) {
            if (required) {
                throw new UnresolvableResourceException("Unable to resolve resource " + resourcePath +
                                                        " for the required parameter '" + parameterName + "'.");
            }
            return null;
        }

        if (parameter.getParameterType().isAssignableFrom(Resource.class)) {
            return resource;
        }

        Object adapted = resource.adaptTo(parameter.getParameterType());
        if (adapted == null && required) {
                throw new MissingAdapterException("Unable to adapt " + resource + " to " + parameter.getParameterType() +
                                                  " for required parameter '" + parameterName + "'.");
        }

        return adapted;
    }

    private String resolveResourcePath(SlingHttpServletRequest request,
                                       ResourceParam resourceParam,
                                       String parameterName,
                                       boolean required) throws MissingServletRequestParameterException {

        String resourcePath = request.getParameter(parameterName);
        if (isEmpty(resourcePath)) {
            resourcePath = resourceParam.defaultValue();
        }

        if (isEmpty(resourcePath)) {
            if (required) {
                throw new MissingServletRequestParameterException(parameterName, String.class.getSimpleName());
            }
            return null;
        }

        if (!isEmpty(resourceParam.append())) {
            resourcePath += resourceParam.append();
        }
        return resourcePath;
    }

    private String resolveParameterName(MethodParameter parameter, ResourceParam param) {
        String parameterName = param.value();
        if (isEmpty(parameterName)) {
            parameterName = parameter.getParameterName();
        }
        return parameterName;
    }
}