package org.apache.maven.plugins.shade.resource.rule;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *  http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  import static java.lang.annotation.ElementType.METHOD;
  import static java.lang.annotation.RetentionPolicy.RUNTIME;
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertNotNull;
  import static org.junit.Assert.assertTrue;
  import static org.junit.Assert.fail;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.lang.annotation.Retention;
  import java.lang.annotation.Target;
  import java.nio.charset.StandardCharsets;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.jar.JarEntry;
  import java.util.jar.JarInputStream;
  import java.util.jar.JarOutputStream;
  
  import org.apache.maven.plugins.shade.relocation.Relocator;
  import org.apache.maven.plugins.shade.resource.ResourceTransformer;
  import org.codehaus.plexus.component.configurator.ComponentConfigurationException;
  import org.codehaus.plexus.component.configurator.converters.ConfigurationConverter;
  import org.codehaus.plexus.component.configurator.converters.lookup.ConverterLookup;
  import org.codehaus.plexus.component.configurator.converters.lookup.DefaultConverterLookup;
  import org.codehaus.plexus.component.configurator.expression.DefaultExpressionEvaluator;
  import org.codehaus.plexus.configuration.DefaultPlexusConfiguration;
  import org.codehaus.plexus.configuration.PlexusConfiguration;
  import org.junit.rules.TestRule;
  import org.junit.runner.Description;
  import org.junit.runners.model.Statement;
  
  public class TransformerTesterRule implements TestRule
  {
      @Override
      public Statement apply( final Statement base, final Description description )
      {
          return new Statement()
          {
              @Override
              public void evaluate() throws Throwable
              {
                  final TransformerTest spec = description.getAnnotation( TransformerTest.class );
                  if ( spec == null )
                  {
                      base.evaluate();
                      return;
                  }
  
                  final Map<String, String> jar;
                  try
                  {
                      final ResourceTransformer transformer = createTransformer(spec);
                      visit(spec, transformer);
                      jar = captureOutput(transformer);
                  }
                  catch ( final Exception ex )
                  {
                      if ( Exception.class.isAssignableFrom( spec.expectedException() ) )
                      {
                          assertTrue(
                                  ex.getClass().getName(),
                                  spec.expectedException().isAssignableFrom( ex.getClass() ) );
                          return;
                      }
                      else
                      {
                          throw ex;
                      }
                  }
                  asserts(spec, jar);
              }
          };
      }
  
      private void asserts( final TransformerTest spec, final Map<String, String> jar)
      {
         if ( spec.strictMatch() && jar.size() != spec.expected().length )
         {
             fail( "Strict match test failed: " + jar );
         }
         for ( final Resource expected : spec.expected() )
         {
             final String content = jar.get( expected.path() );
             assertNotNull( expected.path(), content );
             assertTrue(
                     expected.path() + ", expected=" + expected.content() + ", actual=" + content,
                     content.replace( System.lineSeparator(), "\n" ) .matches( expected.content() ) );
         }
     }
 
     private Map<String, String> captureOutput(final ResourceTransformer transformer ) throws IOException
     {
         final ByteArrayOutputStream out = new ByteArrayOutputStream();
         try ( final JarOutputStream jar = new JarOutputStream( out ) )
         {
             transformer.modifyOutputStream( jar );
         }
 
         final Map<String, String> created = new HashMap<>();
         try ( final JarInputStream jar = new JarInputStream( new ByteArrayInputStream( out.toByteArray() ) ) )
         {
             JarEntry entry;
             while ( ( entry = jar.getNextJarEntry() ) != null )
             {
                 created.put( entry.getName(), read( jar ) );
             }
         }
         return created;
     }
 
     private void visit( final TransformerTest spec, final ResourceTransformer transformer ) throws IOException
     {
         for ( final Resource resource : spec.visited() )
         {
             if ( transformer.canTransformResource( resource.path() ))
             {
                 transformer.processResource(
                         resource.path(),
                         new ByteArrayInputStream( resource.content().getBytes(StandardCharsets.UTF_8) ),
                         Collections.<Relocator>emptyList() );
             }
         }
     }
 
     private String read(final JarInputStream jar) throws IOException
     {
         final StringBuilder builder = new StringBuilder();
         final byte[] buffer = new byte[512];
         int read;
         while ( (read = jar.read(buffer) ) >= 0 )
         {
             builder.append( new String( buffer, 0, read ) );
         }
         return builder.toString();
     }
 
     private ResourceTransformer createTransformer(final TransformerTest spec)
     {
         final ConverterLookup lookup = new DefaultConverterLookup();
         try
         {
             final ConfigurationConverter converter = lookup.lookupConverterForType( spec.transformer() );
             final PlexusConfiguration configuration = new DefaultPlexusConfiguration( "configuration" );
             for ( final Property property : spec.configuration() )
             {
                 configuration.addChild( property.name(), property.value() );
             }
             return ResourceTransformer.class.cast(
                     converter.fromConfiguration( lookup, configuration,  spec.transformer(), spec.transformer(),
                         Thread.currentThread().getContextClassLoader(),
                         new DefaultExpressionEvaluator() ) );
         }
         catch (final ComponentConfigurationException e)
         {
             throw new IllegalStateException(e);
         }
     }
 
     /**
      * Enables to describe a test without having to implement the logic itself.
      */
     @Target(METHOD)
     @Retention(RUNTIME)
     public @interface TransformerTest
     {
         /**
          * @return the list of resource the transformer will process.
          */
         Resource[] visited();
 
         /**
          * @return the expected output created by the transformer.
          */
         Resource[] expected();
 
         /**
          * @return true if only expected resources must be found.
          */
         boolean strictMatch() default true;
 
         /**
          * @return type of transformer to use.
          */
         Class<?> transformer();
 
         /**
          * @return transformer configuration.
          */
         Property[] configuration();
 
         /**
          * @return if set to an exception class it ensures it is thrown during the processing.
          */
         Class<?> expectedException() default Object.class;
     }
 
     @Target(METHOD)
     @Retention(RUNTIME)
     public @interface Property
     {
         String name();
         String value();
     }
 
     @Target(METHOD)
     @Retention(RUNTIME)
     public @interface Resource
     {
         String path();
         String content();
     }
 }