/**
 * 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.fineract.commands.provider;

import com.google.common.base.Preconditions;
import java.util.HashMap;
import lombok.NoArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.fineract.commands.annotation.CommandType;
import org.apache.fineract.commands.exception.UnsupportedCommandException;
import org.apache.fineract.commands.handler.NewCommandSourceHandler;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * {@link CommandHandlerProvider} provides {@link NewCommandSourceHandler}s for a given entity and action. <br>
 * <br>
 * A {@link NewCommandSourceHandler} can be registered and the annotation {@link CommandType} is used to determine the
 * entity and the action the handler is capable to process.
 *
 * @author Markus Geiss
 * @version 1.0
 * @since 15.06
 * @see NewCommandSourceHandler
 * @see CommandType
 */
@Component
@NoArgsConstructor
@Slf4j
public class CommandHandlerProvider implements ApplicationContextAware, InitializingBean {

    private final HashMap<String, String> registeredHandlers = new HashMap<>();
    private ApplicationContext applicationContext;

    @Override
    public void afterPropertiesSet() throws Exception {
        initializeHandlerRegistry();
    }

    private void initializeHandlerRegistry() {
        final String[] commandHandlerBeans = applicationContext.getBeanNamesForAnnotation(CommandType.class);
        if (ArrayUtils.isNotEmpty(commandHandlerBeans)) {
            for (final String commandHandlerName : commandHandlerBeans) {
                log.debug("Register command handler '{}' ...", commandHandlerName);
                final CommandType commandType = applicationContext.findAnnotationOnBean(commandHandlerName, CommandType.class);
                try {
                    if (commandType != null) {
                        registeredHandlers.put(commandType.entity() + "|" + commandType.action(), commandHandlerName);
                    } else {
                        log.error("Unable to register command handler '{}'!", commandHandlerName);
                    }
                } catch (final Throwable th) {
                    log.error("Unable to register command handler '{}'!", commandHandlerName, th);
                }
            }
        }
    }

    /**
     * Returns a handler for the given entity and action.<br>
     * <br>
     * Throws an {@link UnsupportedCommandException} if no handler for the given entity, action combination can be
     * found.
     *
     * @param entity
     *            the entity to lookup the handler, must be given.
     * @param action
     *            the action to lookup the handler, must be given.
     */
    public NewCommandSourceHandler getHandler(final String entity, final String action) {
        Preconditions.checkArgument(StringUtils.isNoneEmpty(entity), "An entity must be given!");
        Preconditions.checkArgument(StringUtils.isNoneEmpty(action), "An action must be given!");

        final String key = entity + "|" + action;
        if (!registeredHandlers.containsKey(key)) {
            throw new UnsupportedCommandException(key);
        }
        return (NewCommandSourceHandler) applicationContext.getBean(registeredHandlers.get(key));
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }
}