package com.atlassian.plugin.osgi.util;
   
   import com.atlassian.plugin.osgi.hostcomponents.HostComponentRegistration;
   import com.atlassian.plugin.osgi.container.PackageScannerConfiguration;
   import com.atlassian.plugin.util.ClassLoaderUtils;
   
   import java.util.*;
   import java.util.jar.Manifest;
   import java.io.IOException;
  import java.io.InputStream;
  
  import org.twdata.pkgscanner.ExportPackage;
  import org.twdata.pkgscanner.PackageScanner;
  import static org.twdata.pkgscanner.PackageScanner.jars;
  import static org.twdata.pkgscanner.PackageScanner.include;
  import static org.twdata.pkgscanner.PackageScanner.exclude;
  import static org.twdata.pkgscanner.PackageScanner.packages;
  import org.osgi.framework.Version;
  import org.osgi.framework.Constants;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import aQute.lib.osgi.Clazz;
  import aQute.lib.osgi.Analyzer;
  import aQute.lib.osgi.Jar;
  
  /**
   * Utilities to help create OSGi headers
   */
  public class OsgiHeaderUtil
  {
      static Log log = LogFactory.getLog(OsgiHeaderUtil.class);
  
      /**
       * Finds all referred packages for host component registrations by scanning their declared interfaces' bytecode.
       *
       * @param registrations A list of host component registrations
       * @return The referred packages in a format compatible with an OSGi header
       * @throws IOException If there are any problems scanning bytecode
       */
      public static String findReferredPackages(List<HostComponentRegistration> registrations) throws IOException
      {
          StringBuffer sb = new StringBuffer();
          Set<String> referredPackages = new HashSet<String>();
          Set<String> referredClasses = new HashSet<String>();
          if (registrations == null)
          {
              sb.append(",");
          }
          else
          {
              for (HostComponentRegistration reg : registrations)
              {
                  for (String inf : reg.getMainInterfaces())
                  {
                      String clsName = inf.replace('.','/')+".class";
                      crawlReferenceTree(clsName, referredClasses, referredPackages, 1);
                  }
              }
              for (String pkg : referredPackages)
              {
                  sb.append(pkg).append(",");
              }
          }
          return sb.toString();
      }
  
      /**
       * This will crawl the class interfaces to the desired level.
       *
       * @param className name of the class.
       * @param scannedClasses set of classes that have been scanned.
       * @param packageImports set of imports that have been found.
       * @param level depth of scan (recursion).
       * @throws IOException error loading a class.
       */
      static void crawlReferenceTree(String className, Set<String> scannedClasses, Set<String> packageImports, int level) throws IOException
      {
          if (level <= 0)
          {
              return;
          }
  
          if (className.startsWith("java/"))
              return;
  
          if (scannedClasses.contains(className))
              return;
          else
              scannedClasses.add(className);
  
          if (log.isDebugEnabled())
              log.debug("Crawling "+className);
  
          InputStream in = ClassLoaderUtils.getResourceAsStream(className, OsgiHeaderUtil.class);
          if (in == null)
          {
              log.error("Cannot find interface "+className);
              return;
          }
         Clazz clz = new Clazz(className, in);
         packageImports.addAll(clz.getReferred().keySet());
 
         Set<String> referredClasses = clz.getReferredClasses();
         for (String ref : referredClasses)
             crawlReferenceTree(ref, scannedClasses, packageImports, level-1);
 
     }
 
     /**
      * Determines framework exports taking into account host components and package scanner configuration.
      *
      * @param regs The list of host component registrations
      * @param packageScannerConfig The configuration for the package scanning
      * @return A list of exports, in a format compatible with OSGi headers
      */
     public static String determineExports(List<HostComponentRegistration> regs, PackageScannerConfiguration packageScannerConfig){
         String exports = null;
 
         StringBuilder origExports = new StringBuilder();
         origExports.append("org.osgi.framework; version=1.3.0,");
         origExports.append("org.osgi.service.packageadmin; version=1.2.0," );
         origExports.append("org.osgi.service.startlevel; version=1.0.0,");
         origExports.append("org.osgi.service.url; version=1.0.0,");
         origExports.append("org.osgi.util; version=1.3.0,");
         origExports.append("org.osgi.util.tracker; version=1.3.0,");
         origExports.append("host.service.command; version=1.0.0,");
         origExports.append("javax.swing.tree,javax.swing,org.xml.sax,org.xml.sax.helpers,");
         origExports.append("javax.xml,javax.xml.parsers,javax.xml.transform,javax.xml.transform.sax,");
         origExports.append("javax.xml.transform.stream,javax.xml.transform.dom,org.w3c.dom,javax.naming,javax.naming.spi,");
         origExports.append("javax.swing.border,javax.swing.event,javax.swing.text,");
 
         Collection<ExportPackage> exportList = generateExports(packageScannerConfig);
         constructAutoExports(origExports, exportList);
 
 
         try
         {
             origExports.append(findReferredPackages(regs));
 
             Analyzer analyzer = new Analyzer();
             analyzer.setJar(new Jar("somename.jar"));
             
             // we pretend the exports are imports for the sake of the bnd tool, which would otherwise cut out
             // exports that weren't actually in the jar
             analyzer.setProperty(Constants.IMPORT_PACKAGE, origExports.toString());
             Manifest mf = analyzer.calcManifest();
 
             exports = mf.getMainAttributes().getValue(Constants.IMPORT_PACKAGE);
         } catch (IOException ex)
         {
             log.error("Unable to calculate necessary exports based on host components", ex);
             exports = origExports.toString();
         }
 
         if (log.isDebugEnabled()) {
             log.debug("Exports:\n"+exports.replaceAll(",", "\r\n"));
         }
         return exports;
     }
 
     static void constructAutoExports(StringBuilder sb, Collection<ExportPackage> packageExports) {
 
         for (Iterator<ExportPackage> i = packageExports.iterator(); i.hasNext(); ) {
             ExportPackage pkg = i.next();
             sb.append(pkg.getPackageName());
             if (pkg.getVersion() != null) {
                 try {
                     Version.parseVersion(pkg.getVersion());
                     sb.append(";version=").append(pkg.getVersion());
                 } catch (IllegalArgumentException ex) {
                     log.info("Unable to parse version: "+pkg.getVersion());
                 }
             }
             sb.append(",");
         }
     }
 
     static Collection<ExportPackage> generateExports(PackageScannerConfiguration packageScannerConfig)
     {
         String[] arrType = new String[0];
         Collection<ExportPackage> exports = new PackageScanner()
            .select(
                jars(
                        include(packageScannerConfig.getJarIncludes().toArray(arrType)),
                        exclude(packageScannerConfig.getJarExcludes().toArray(arrType))),
                packages(
                        include(packageScannerConfig.getPackageIncludes().toArray(arrType)),
                        exclude(packageScannerConfig.getPackageExcludes().toArray(arrType)))
            )
            .withMappings(packageScannerConfig.getPackageVersions())
            .scan();
         return exports;
     }
 }