/*
 * Copyright (c) 2016, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
 *
 * WSO2 Inc. licenses this file to you 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 org.wso2.carbon.device.mgt.jaxrs.exception;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.cxf.interceptor.Fault;
import org.apache.cxf.jaxrs.lifecycle.ResourceProvider;
import org.apache.cxf.jaxrs.model.ClassResourceInfo;
import org.apache.cxf.jaxrs.model.OperationResourceInfo;
import org.apache.cxf.message.Message;
import org.apache.cxf.message.MessageContentsList;
import org.apache.cxf.phase.AbstractPhaseInterceptor;
import org.apache.cxf.phase.Phase;

import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
import javax.validation.executable.ExecutableValidator;
import java.lang.reflect.Method;
import java.util.List;
import java.util.Set;

public class ValidationInterceptor extends AbstractPhaseInterceptor<Message> {
    private Log log = LogFactory.getLog(getClass());
    private Validator validator = null; //validator interface is thread-safe

    public ValidationInterceptor() {
        super(Phase.PRE_INVOKE);
        ValidatorFactory defaultFactory = Validation.buildDefaultValidatorFactory();
        validator = defaultFactory.getValidator();
        if (validator == null) {
            log.warn("Bean Validation provider could not be found, no validation will be performed");
        } else {
            log.debug("Validation In-Interceptor initialized successfully");
        }
    }

    @Override
    public void handleMessage(Message message) throws Fault {
        final OperationResourceInfo operationResource = message.getExchange().get(OperationResourceInfo.class);
        if (operationResource == null) {
            log.info("OperationResourceInfo is not available, skipping validation");
            return;
        }

        final ClassResourceInfo classResource = operationResource.getClassResourceInfo();
        if (classResource == null) {
            log.info("ClassResourceInfo is not available, skipping validation");
            return;
        }

        final ResourceProvider resourceProvider = classResource.getResourceProvider();
        if (resourceProvider == null) {
            log.info("ResourceProvider is not available, skipping validation");
            return;
        }

        final List<Object> arguments = MessageContentsList.getContentsList(message);
        final Method method = operationResource.getAnnotatedMethod();
        final Object instance = resourceProvider.getInstance(message);
        if (method != null && arguments != null) {
            //validate the parameters(arguments) over the invoked method
            validate(method, arguments.toArray(), instance);

            //validate the fields of each argument
            for (Object arg : arguments) {
                if (arg != null)
                    validate(arg);
            }
        }

    }

    public <T> void validate(final Method method, final Object[] arguments, final T instance) {
        if (validator == null) {
            log.warn("Bean Validation provider could not be found, no validation will be performed");
            return;
        }

        ExecutableValidator methodValidator = validator.forExecutables();
        Set<ConstraintViolation<T>> violations = methodValidator.validateParameters(instance,
                method, arguments);

        if (!violations.isEmpty()) {
            throw new ConstraintViolationException(violations);
        }
    }

    public <T> void validate(final T object) {
        if (validator == null) {
            log.warn("Bean Validation provider could be found, no validation will be performed");
            return;
        }

        Set<ConstraintViolation<T>> violations = validator.validate(object);

        if (!violations.isEmpty()) {
            throw new ConstraintViolationException(violations);
        }
    }

    public void handleFault(org.apache.cxf.message.Message messageParam) {
    }
}
