package ca.uhn.hl7v2;
   
   import java.io.IOException;
   import java.io.InputStream;
   import java.util.Properties;
   
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
   import org.w3c.dom.DOMImplementation;
  
  import ca.uhn.hl7v2.util.XMLUtils;
  
  /**
   * Class to log the HAPI version when HAPI is first used (mostly for troubleshooting purposes)
   */
  public class VersionLogger {
  
  	private static boolean ourInitialized = false;
  	private static String ourVersion;
  	private static final Logger LOG = LoggerFactory.getLogger(VersionLogger.class);
  
  	/**
  	 * Non-instantiable
  	 */
  	private VersionLogger() {
  		// nothing
  	}
  
  	/**
  	 * Logs the HAPI version on the first time this method is invoked, does nothing afterwards
  	 */
  	public static void init() {
  		if (!ourInitialized) {
  			printHapiVersion();
  			checkStructureLibraries();
  			checkDOMImplementation();
  			ourInitialized = true;
  		}
  	}
  
  	private static void checkDOMImplementation() {
  		try {
  			// Check if proper XML support is available
  			DOMImplementation impl = XMLUtils.getDOMImpl();
  			if (impl == null) {
  				LOG.warn("DOM Level 3 (Load and Save) is NOT supported by the XML library found first on your classpath!");
  				LOG.warn("XML parsing and encoding as well as working with Conformance Profiles will fail.");
  			}
  		} catch (Throwable e) {
  			LOG.warn("Error occured while trying to retrieve a DOMImplementation.", e);
  			LOG.warn("XML parsing and encoding as well as working with Conformance Profiles will fail.");
  		}
  	}
  
  	private static void checkStructureLibraries() {
  		// Check if any structures are present
  		StringBuilder sb = new StringBuilder();
  		for (Version v : Version.availableVersions()) {
  			sb.append(v.getVersion());
  			sb.append(sb.length() > 0 ? ", " : "");
  		}
  		if (sb.length() == 0) {
  			LOG.warn("No HL7 structure libraries found on the classpath!");
  		} else {
  			LOG.info("Default Structure libraries found for HL7 versions {}", sb.toString());
  		}
  	}
  
  	private static void printHapiVersion() {
          try (InputStream is = VersionLogger.class
                  .getResourceAsStream("/ca/uhn/hl7v2/hapi-version.properties")) {
              Properties p = new Properties();
              p.load(is);
              ourVersion = p.getProperty("version");
              LOG.info("HAPI version is: " + ourVersion);
          } catch (IOException e) {
              LOG.warn("Unable to determine HAPI version information", e);
          }
          // ignore
      }
  
  	/**
  	 * @return Returns the current version of HAPI
  	 */
  	public static String getVersion() {
  		return ourVersion;
  	}
  
  }