/*
    * 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.
   */
  package org.apache.maven.shared.dependency.analyzer.asm;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.UncheckedIOException;
  import java.util.Set;
  
  import org.apache.maven.shared.dependency.analyzer.ClassFileVisitor;
  import org.apache.maven.shared.dependency.analyzer.ClassesPatterns;
  import org.apache.maven.shared.dependency.analyzer.DependencyUsage;
  import org.objectweb.asm.AnnotationVisitor;
  import org.objectweb.asm.ClassReader;
  import org.objectweb.asm.ClassVisitor;
  import org.objectweb.asm.FieldVisitor;
  import org.objectweb.asm.MethodVisitor;
  import org.objectweb.asm.signature.SignatureVisitor;
  
  /**
   * Computes the set of classes referenced by visited class files, using
   * <a href="DependencyVisitor.html">DependencyVisitor</a>.
   *
   * @author <a href="mailto:markhobson@gmail.com">Mark Hobson</a>
   * @see #getDependencies()
   */
  public class DependencyClassFileVisitor implements ClassFileVisitor {
      private static final int BUF_SIZE = 8192;
  
      private final ResultCollector resultCollector = new ResultCollector();
  
      private final ClassesPatterns excludedClasses;
  
      /**
       * <p>Constructor for DependencyClassFileVisitor.</p>
       */
      public DependencyClassFileVisitor(ClassesPatterns excludedClasses) {
          this.excludedClasses = excludedClasses;
      }
  
      /**
       * <p>Constructor for DependencyClassFileVisitor.</p>
       */
      public DependencyClassFileVisitor() {
          this(new ClassesPatterns());
      }
  
      /**
       * Visits a class.
       *
       * @param className the name of the class being visited
       * @param in the {@link java.io.InputStream} to read the byte code from
       * @throws VisitClassException if the .class file is corrupt
       * @throws UncheckedIOException if an I/O error occurs while reading the class file
       */
      @Override
      public void visitClass(String className, InputStream in) {
          try {
              byte[] byteCode = toByteArray(in);
  
              if (excludedClasses.isMatch(className)) {
                  return;
              }
  
              ClassReader reader = new ClassReader(byteCode);
  
              final Set<String> constantPoolClassRefs = ConstantPoolParser.getConstantPoolClassReferences(byteCode);
              for (String string : constantPoolClassRefs) {
                  resultCollector.addName(className, string);
              }
  
              AnnotationVisitor annotationVisitor = new DefaultAnnotationVisitor(resultCollector, className);
              SignatureVisitor signatureVisitor = new DefaultSignatureVisitor(resultCollector, className);
              FieldVisitor fieldVisitor = new DefaultFieldVisitor(annotationVisitor, resultCollector, className);
              MethodVisitor methodVisitor =
                      new DefaultMethodVisitor(annotationVisitor, signatureVisitor, resultCollector, className);
              ClassVisitor classVisitor = new DefaultClassVisitor(
                      signatureVisitor, annotationVisitor, fieldVisitor, methodVisitor, resultCollector, className);
  
              reader.accept(classVisitor, 0);
          } catch (IOException exception) {
              throw new UncheckedIOException(exception);
         } catch (IndexOutOfBoundsException e) {
             // some bug inside ASM causes an IOB exception.
             // this happens when the class isn't valid.
             throw new VisitClassException("Unable to process: " + className, e);
         } catch (UnknownConstantPoolTypeException | IllegalArgumentException e) {
             throw new VisitClassException("Byte code of '" + className + "' is corrupt", e);
         }
     }
 
     private byte[] toByteArray(InputStream in) throws IOException {
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         byte[] buffer = new byte[BUF_SIZE];
         int i;
         while ((i = in.read(buffer)) > 0) {
             out.write(buffer, 0, i);
         }
         return out.toByteArray();
     }
 
     /**
      * <p>getDependencies.</p>
      *
      * @return the set of classes referenced by visited class files
      */
     public Set<String> getDependencies() {
         return resultCollector.getDependencies();
     }
 
     /**
      * <p>getDependencyUsages.</p>
      *
      * @return the set of classes referenced by visited class files, paired with
      *     classes declaring the references
      */
     public Set<DependencyUsage> getDependencyUsages() {
         return resultCollector.getDependencyUsages();
     }
 }