import java.util.Map;
import java.util.TreeMap;
import org.jetbrains.annotations.NotNull;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
import org.springframework.boot.context.event.ApplicationPreparedEvent;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.core.env.EnumerablePropertySource;
import org.springframework.core.env.PropertySource;

public class PropertiesLogger implements ApplicationListener<ApplicationEvent> {
  private static final Logger logger = LoggerFactory.getLogger(ConfigurationLogger.class);
  private Map<String, Object> configurationProperties = new TreeMap<>();

  @Override
  public void onApplicationEvent(@NotNull ApplicationEvent event) {
    if (event instanceof ApplicationEnvironmentPreparedEvent) {
      onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
    }else if( event instanceof ApplicationPreparedEvent){
      logProperties((ApplicationPreparedEvent)event);
    }
  }

  private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {
    for (PropertySource<?> source : event.getEnvironment().getPropertySources()) {
      if (source instanceof EnumerablePropertySource) {
        for (String key : ((EnumerablePropertySource) source).getPropertyNames()) {
          Object value = source.getProperty(key);
          if (!configurationProperties.containsKey(key)) {
            configurationProperties.put(key, value);
          }
        }
      }
    }
  }

  private void logProperties(ApplicationPreparedEvent event) {
    logger.debug("Application started with following parameters: ");
    for( Map.Entry<String, Object> entry : configurationProperties.entrySet()){
      logger.debug("{} :: {}", entry.getKey(), entry.getValue());
    }
  }
}