/*-
 * ============LICENSE_START=======================================================
 * SDC
 * ================================================================================
 * Copyright (C) 2017 AT&T Intellectual Property. All rights reserved.
 * ================================================================================
 * 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.
 * ============LICENSE_END=========================================================
 * Modifications copyright (c) 2019 Nokia
 * ================================================================================
 */
package org.openecomp.sdc.common.impl;

import java.util.Arrays;
import java.util.stream.Collectors;
import lombok.AllArgsConstructor;
import org.openecomp.sdc.common.api.ConfigurationListener;
import org.openecomp.sdc.common.api.ConfigurationSource;
import org.openecomp.sdc.common.api.Constants;
import org.openecomp.sdc.common.api.exception.LoadConfigurationException;
import org.openecomp.sdc.common.util.YamlToObjectConverter;
import org.openecomp.sdc.exception.YamlConversionException;

/**
 * Read configuration from file system
 *
 * @author esofer
 */
@AllArgsConstructor
public class FSConfigurationSource implements ConfigurationSource {

    private final ConfigFileChangeListener changeListener;
    private final String appConfigDir;

    /**
     * convert camel case string to list of words separated by "-" where each word is in lower case format. For example, MyClass will be calculated to
     * be my-class.yaml .
     *
     * @param className
     * @return file name based on the class name
     */
    static <T> String calculateFileName(Class<T> className) {
        String[] words = className.getSimpleName().split("(?=\\p{Upper})");
        return Arrays.stream(words).map(String::toLowerCase)
            .collect(Collectors.collectingAndThen(Collectors.joining("-"), str -> str + Constants.YAML_SUFFIX));
    }

    /*
     * get and watch configuration changes. The file name we looking for is the lower case of the class name separated by "-".
     *
     * (non-Javadoc)
     *
     * @see org.openecomp.sdc.common.api.ConfigurationSource#getAndWatchConfiguration (java.lang.Class, org.openecomp.sdc.common.api.ConfigurationListener)
     */
    public <T> T getAndWatchConfiguration(final Class<T> className, final ConfigurationListener configurationListener) {
        final String configFileName = calculateFileName(className);
        T object;
        try {
            object = (new YamlToObjectConverter()).convert(this.appConfigDir, className, configFileName);
        } catch (final YamlConversionException e) {
            final String errorMsg = String.format("Could not load '%s' in '%s' for class '%s'", configFileName, appConfigDir, className);
            throw new LoadConfigurationException(errorMsg, e);
        }
        if (configurationListener != null && changeListener != null) {
            changeListener.register(configFileName, configurationListener);
        }
        return object;
    }

    public <T> void addWatchConfiguration(Class<T> className, ConfigurationListener configurationListener) {
        if (configurationListener != null && changeListener != null) {
            changeListener.register(calculateFileName(className), configurationListener);
        }
    }
}