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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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.apache.struts2;

import org.apache.struts2.config.Configuration;
import org.apache.struts2.config.ConfigurationException;
import org.apache.struts2.config.entities.ActionConfig;
import org.apache.struts2.config.entities.UnknownHandlerConfig;
import org.apache.struts2.inject.Container;
import org.apache.struts2.inject.Inject;
import org.apache.struts2.result.Result;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Set;

/**
 * Default implementation of UnknownHandlerManager
 *
 * @see UnknownHandlerManager
 */
public class DefaultUnknownHandlerManager implements UnknownHandlerManager {

    private Container container;

    protected ArrayList unknownHandlers;

    @Inject
    public void setContainer(Container container) {
        this.container = container;
        try {
            build();
        } catch (Exception e) {
            throw new ConfigurationException(e);
        }
    }

    /**
     * Builds a list of UnknownHandlers in the order specified by the configured "unknown-handler-stack".
     * If "unknown-handler-stack" was not configured, all UnknownHandlers will be returned, in no specific order
     *
     * @throws Exception in case of any error
     */
    protected void build() throws Exception {
        Configuration configuration = container.getInstance(Configuration.class);
        ObjectFactory factory = container.getInstance(ObjectFactory.class);

        if (configuration != null && container != null) {
            List unkownHandlerStack = configuration.getUnknownHandlerStack();
            unknownHandlers = new ArrayList<>();

            if (unkownHandlerStack != null && !unkownHandlerStack.isEmpty()) {
                //get UnknownHandlers in the specified order
                for (UnknownHandlerConfig unknownHandlerConfig : unkownHandlerStack) {
                    UnknownHandler uh = factory.buildUnknownHandler(unknownHandlerConfig.getName(), new HashMap<>());
                    unknownHandlers.add(uh);
                }
            } else {
                //add all available UnknownHandlers
                Set unknownHandlerNames = container.getInstanceNames(UnknownHandler.class);
                for (String unknownHandlerName : unknownHandlerNames) {
                    UnknownHandler uh = container.getInstance(UnknownHandler.class, unknownHandlerName);
                    unknownHandlers.add(uh);
                }
            }
        }
    }

    /**
     * Iterate over UnknownHandlers and return the result of the first one that can handle it
     *
     * @param actionContext the action context
     * @param actionName the action name
     * @param actionConfig  the action config
     * @param resultCode the result code
     */
    public Result handleUnknownResult(ActionContext actionContext, String actionName, ActionConfig actionConfig, String resultCode) {
        for (UnknownHandler unknownHandler : unknownHandlers) {
            Result result = unknownHandler.handleUnknownResult(actionContext, actionName, actionConfig, resultCode);
            if (result != null) {
                return result;
            }
        }

        return null;
    }

    /**
     * Iterate over UnknownHandlers and return the result of the first one that can handle it.
     * Must throw an exception if method cannot be handled.
     *
     * @param action the action
     * @param methodName the method name
     * @throws NoSuchMethodException if method con not be handled
     */
    public Object handleUnknownMethod(Object action, String methodName) throws NoSuchMethodException {
        for (UnknownHandler unknownHandler : unknownHandlers) {
            Object result = unknownHandler.handleUnknownActionMethod(action, methodName);
            if (result != null) {
                return result;
            }
        }

        if (unknownHandlers.isEmpty()) {
            throw new NoSuchMethodException(String.format("No UnknownHandlers defined to handle method [%s]", methodName));
        } else {
            throw new NoSuchMethodException(String.format("None of defined UnknownHandlers can handle method [%s]", methodName));
        }
    }

    /**
     * Iterate over UnknownHandlers and return the result of the first one that can handle it
     *
     * @param namespace the namespace
     * @param actionName the action name
     */
    public ActionConfig handleUnknownAction(String namespace, String actionName) {
        for (UnknownHandler unknownHandler : unknownHandlers) {
            ActionConfig result = unknownHandler.handleUnknownAction(namespace, actionName);
            if (result != null) {
                return result;
            }
        }

        return null;
    }

    public boolean hasUnknownHandlers() {
        return unknownHandlers != null && !unknownHandlers.isEmpty();
    }

    public List getUnknownHandlers() {
        return unknownHandlers;
    }

}