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/**
 * An implementation of {@link ConfigProvider} that simply uses a Properties file.
 */
public class FileConfigProvider implements ConfigProvider {

    private static final Logger log = LoggerFactory.getLogger(FileConfigProvider.class);

    public final static String FILE_NAME = "filename";

    private Properties properties;

    /**
     * Configure this class with the initialization parameters
     */
    public void configure(Map<String, ?> configs) {
        String fileName = (String) configs.get(FILE_NAME);
        try {
            (FileReader fileReader = new FileReader(fileName);) {
            properties = new Properties();
            properties.load(fileReader);
        } catch (IOException e) {
            throw new ConfigException("File name " + fileName + " not found for FileConfigProvider");
        }
    }

    /**
     * Transform the configs by resolving all indirect references
     */
    public Map<String, String> transform(ConfigContext ctx, Map<String, String> configs) {
        Map<String, String> newConfigs = new HashMap<>();
        for (Map.Entry<String, String> config : configs.entrySet()) {
            String value = properties.getProperty(config.getValue());
            if (value != null) {
                log.info("Replacing {} for key {}", config.getValue(), config.getKey());
                newConfigs.put(config.getKey(), value);
            }
        }
        return newConfigs;
    }

    public void close() {
    }
}