/**
    * Logback: the reliable, generic, fast and flexible logging framework.
    * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
    * <p>
    * This program and the accompanying materials are dual-licensed under
    * either the terms of the Eclipse Public License v1.0 as published by
    * the Eclipse Foundation
    * <p>
    * or (per the licensee's choosing)
   * <p>
   * under the terms of the GNU Lesser General Public License version 2.1
   * as published by the Free Software Foundation.
   */
  package ch.qos.logback.core.util;
  
  import java.lang.module.ModuleDescriptor;
  import java.util.Optional;
  
  /**
   * @author Ceki G&uuml;lc&uuml;
   */
  public class EnvUtil {
  
      private EnvUtil() {
      }
  
  
      /**
       * <p>Returns the current version of logback, or null if data is not
       * available.
       * </p>
       *
       * @since 1.3.0
       * @return current version or null if missing version data
       */
      static public String logbackVersion() {
          String moduleVersion = getVersionOfLogbackCoreByModule();
          if (moduleVersion != null)
              return moduleVersion;
  
          Package pkg = EnvUtil.class.getPackage();
          if (pkg == null) {
              return null;
          }
          return pkg.getImplementationVersion();
      }
  
      /**
       * <p>Returns the current version of logback via class.getModule() or null if data is not
       * available.
       * </p>
       *
       * @since 1.3.0
       * @return current version or null if missing version data
       */
      static private String getVersionOfLogbackCoreByModule() {
          Module module = EnvUtil.class.getModule();
          if (module == null)
              return null;
  
          ModuleDescriptor md = module.getDescriptor();
          if (md == null)
              return null;
          Optional<String> opt = md.rawVersion();
          return opt.orElse(null);
      }
  
      static public int getJDKVersion(String javaVersionStr) {
          int version = 0;
  
          for (char ch : javaVersionStr.toCharArray()) {
              if (Character.isDigit(ch)) {
                  version = (version * 10) + (ch - 48);
              } else if (version == 1) {
                  version = 0;
              } else {
                  break;
              }
          }
          return version;
      }
  
      static private boolean isJDK_N_OrHigher(int n) {
          String javaVersionStr = System.getProperty("java.version", "");
          if (javaVersionStr.isEmpty())
              return false;
  
          int version = getJDKVersion(javaVersionStr);
          return version > 0 && n <= version;
      }
  
      static public boolean isJDK5() {
          return isJDK_N_OrHigher(5);
      }
  
      static public boolean isJDK6OrHigher() {
          return isJDK_N_OrHigher(6);
      }
  
     static public boolean isJDK7OrHigher() {
         return isJDK_N_OrHigher(7);
     }
 
     static public boolean isJDK16OrHigher() {
         return isJDK_N_OrHigher(16);
     }
 
     static public boolean isJDK18OrHigher() {
         return isJDK_N_OrHigher(18);
     }
 
     /**
      * @since logback 1.3.12/1.4.12
      * @return true if runtime JDK is version 21 or higher
      */
     static public boolean isJDK21OrHigher() {
         return isJDK_N_OrHigher(21);
     }
 
     static public boolean isJaninoAvailable() {
         ClassLoader classLoader = EnvUtil.class.getClassLoader();
         try {
             Class<?> bindingClass = classLoader.loadClass("org.codehaus.janino.ScriptEvaluator");
             return (bindingClass != null);
         } catch (ClassNotFoundException e) {
             return false;
         }
     }
 
     public static boolean isMacOs() {
         String os = System.getProperty("os.name");
         // expected value is "Mac OS X"
         return os.toLowerCase().contains("mac");
     }
 
     public static boolean isWindows() {
         String os = System.getProperty("os.name");
         return os.startsWith("Windows");
     }
 
     static public boolean isClassAvailable(Class callerClass, String className) {
         ClassLoader classLoader = Loader.getClassLoaderOfClass(callerClass);
         try {
             Class<?> bindingClass = classLoader.loadClass(className);
             return (bindingClass != null);
         } catch (ClassNotFoundException e) {
             return false;
         }
     }
 
 }