package com.atlassian.plugin.main;
   
   import com.atlassian.plugin.osgi.container.PackageScannerConfiguration;
   import com.atlassian.plugin.osgi.container.impl.DefaultPackageScannerConfiguration;
   
   import javax.servlet.ServletContext;
   import java.util.ArrayList;
   import java.util.Arrays;
   import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import static java.util.Collections.unmodifiableList;
  import static java.util.Collections.unmodifiableMap;
  
  /**
   * The builder for {@link PackageScannerConfiguration} instances that additionally performs validation and default creation.
   * For a usage example, see the package javadocs.
   * <p>
   * Not thread-safe. Instances of this class should be thread and preferably method local.
   *
   * @since 2.2
   */
  public class PackageScannerConfigurationBuilder {
      /**
       * Static factory for creating a new builder.
       *
       * @return a new builder.
       */
      public static PackageScannerConfigurationBuilder packageScannerConfiguration() {
          return new PackageScannerConfigurationBuilder();
      }
  
      private String hostVersion;
      private final List<String> jarIncludes = new ArrayList<>();
      private final List<String> jarExcludes = new ArrayList<>();
      private final List<String> packageIncludes = new ArrayList<>();
      private final List<String> packageExcludes = new ArrayList<>();
      private final Map<String, String> packageVersions = new HashMap<>();
      private ServletContext servletContext;
  
      /**
       * Default constructor. Uses a DefaultPackageScannerConfiguration as the template.
       */
      public PackageScannerConfigurationBuilder() {
          copy(new DefaultPackageScannerConfiguration());
      }
  
      /**
       * Copy constructor. Use the supplied PackageScannerConfiguration as a template.
       *
       * @param packageScannerConfiguration
       */
      public PackageScannerConfigurationBuilder(final PackageScannerConfiguration packageScannerConfiguration) {
          copy(packageScannerConfiguration);
      }
  
      private void copy(final PackageScannerConfiguration config) {
          hostVersion = config.getCurrentHostVersion();
          packageIncludes.addAll(config.getPackageIncludes());
          packageExcludes.addAll(config.getPackageExcludes());
          jarIncludes.addAll(config.getJarIncludes());
          jarExcludes.addAll(config.getJarExcludes());
          packageVersions.putAll(config.getPackageVersions());
          servletContext = config.getServletContext();
      }
  
      /**
       * Sets the current host version.
       *
       * @param hostVersion the version to set
       * @return this
       * @see PackageScannerConfiguration#getCurrentHostVersion()
       */
      public PackageScannerConfigurationBuilder hostVersion(final String hostVersion) {
          this.hostVersion = hostVersion;
          return this;
      }
  
      /**
       * Sets the {@link ServletContext} used to lookup jars as some application servers need it to lookup jar files.
       *
       * @param servletContext the servlet context
       * @return this
       * @see PackageScannerConfiguration#getServletContext()
       */
      public PackageScannerConfigurationBuilder servletContext(final ServletContext servletContext) {
          this.servletContext = servletContext;
          return this;
      }
  
      /**
       * Sets a list of package expressions to expose to plugins.
       *
       * @param pkgs A list of package expressions, where the '*' character matches any character including subpackages
       * @return this
       * @see PackageScannerConfiguration#getPackageIncludes()
       */
      public PackageScannerConfigurationBuilder packagesToInclude(final String... pkgs) {
         packageIncludes.addAll(Arrays.asList(pkgs));
         return this;
     }
 
     /**
      * Sets a list of package expressions to hide from plugins.
      *
      * @param pkgs A list of package expressions, where the '*' character matches any character including subpackages
      * @return this
      * @see PackageScannerConfiguration#getPackageExcludes()
      */
     public PackageScannerConfigurationBuilder packagesToExclude(final String... pkgs) {
         packageExcludes.addAll(Arrays.asList(pkgs));
         return this;
     }
 
     /**
      * Sets which packages should be exposed as which versions.
      *
      * @param packageToVersion A map of package names to version names. No wildcards allowed, and the version names
      *                         must match the expected OSGi versioning scheme.
      * @return this
      * @see PackageScannerConfiguration#getPackageVersions()
      */
     public PackageScannerConfigurationBuilder packagesVersions(final Map<String, String> packageToVersion) {
         packageVersions.putAll(packageToVersion);
         return this;
     }
 
     /**
      * Sets a list of jar expressions to expose to plugins.
      *
      * @param jars A list of jars expressions, where the '*' character matches any character
      * @return this
      * @see PackageScannerConfiguration#getJarIncludes()
      */
     public PackageScannerConfigurationBuilder jarsToInclude(final String... jars) {
         jarIncludes.addAll(Arrays.asList(jars));
         return this;
     }
 
     /**
      * Sets a list of jar expressions to hide from plugins.
      *
      * @param jars A list of jars expressions, where the '*' character matches any character
      * @return this
      * @see PackageScannerConfiguration#getJarExcludes()
      */
     public PackageScannerConfigurationBuilder jarsToExclude(final String... jars) {
         jarExcludes.addAll(Arrays.asList(jars));
         return this;
     }
 
     /**
      * Builds a {@link PackageScannerConfiguration} instance by processing the configuration that
      * was previously set and setting any defaults where not explicitly specified.
      *
      * @return A valid {@link PackageScannerConfiguration} instance to pass to {@link AtlassianPlugins}
      */
     public PackageScannerConfiguration build() {
         return new ImmutablePackageScannerConfiguration(this);
     }
 
     //
     // inner classes
     //
 
     /**
      * Immutable and thread-safe implementation of the {@link PackageScannerConfiguration} returned by a
      * {@link PackageScannerConfigurationBuilder}
      */
     private static final class ImmutablePackageScannerConfiguration implements PackageScannerConfiguration {
         private final String hostVersion;
         private final List<String> jarIncludes;
         private final List<String> jarExcludes;
         private final List<String> packageIncludes;
         private final List<String> packageExcludes;
         private final Map<String, String> packageVersions;
         private final ServletContext servletContext;
 
         ImmutablePackageScannerConfiguration(final PackageScannerConfigurationBuilder builder) {
             hostVersion = builder.hostVersion;
             jarIncludes = unmodifiableList(new ArrayList<>(builder.jarIncludes));
             jarExcludes = unmodifiableList(new ArrayList<>(builder.jarExcludes));
             packageIncludes = unmodifiableList(new ArrayList<>(builder.packageIncludes));
             packageExcludes = unmodifiableList(new ArrayList<>(builder.packageExcludes));
             packageVersions = unmodifiableMap(new HashMap<>(builder.packageVersions));
             servletContext = builder.servletContext;
         }
 
         public List<String> getJarIncludes() {
             return jarIncludes;
         }
 
         public List<String> getJarExcludes() {
             return jarExcludes;
         }
 
         public List<String> getPackageIncludes() {
             return packageIncludes;
         }
 
         public List<String> getPackageExcludes() {
             return packageExcludes;
         }
 
         public Map<String, String> getPackageVersions() {
             return packageVersions;
         }
 
         public String getCurrentHostVersion() {
             return hostVersion;
         }
 
         public ServletContext getServletContext() {
             return servletContext;
         }
     }
 }