/*
    * MIT License
    * Copyright (c) 2006-2025 JMockit developers
    * See LICENSE file for full license text.
    */
   package mockit.internal.state;
   
   import edu.umd.cs.findbugs.annotations.NonNull;
   import edu.umd.cs.findbugs.annotations.Nullable;
  
  import java.lang.instrument.ClassFileTransformer;
  import java.security.ProtectionDomain;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.WeakHashMap;
  
  import mockit.internal.startup.Startup;
  
  /**
   * Holds a map of internal class names to the corresponding class files (bytecode arrays), for the classes that have
   * already been loaded during the test run. These classfiles are not necessarily the same as those stored in the
   * corresponding ".class" files available from the runtime classpath. If any third-party {@link ClassFileTransformer}s
   * are active, those original classfiles may have been modified before being loaded by the JVM. JMockit installs a
   * <code>ClassFileTransformer</code> of its own which saves all potentially modified classfiles here.
   * <p>
   * This bytecode cache allows classes to be mocked and un-mocked correctly, even in the presence of other bytecode
   * modification agents such as the AspectJ load-time weaver.
   */
  public final class CachedClassfiles implements ClassFileTransformer {
      @NonNull
      public static final CachedClassfiles INSTANCE = new CachedClassfiles();
  
      @NonNull
      private final Map<ClassLoader, Map<String, byte[]>> classLoadersAndClassfiles;
      @Nullable
      private Class<?> classBeingCached;
  
      private CachedClassfiles() {
          classLoadersAndClassfiles = new WeakHashMap<>(2);
      }
  
      @Nullable
      @Override
      public byte[] transform(@Nullable ClassLoader loader, String classDesc,
              @Nullable Class<?> classBeingRedefinedOrRetransformed, @Nullable ProtectionDomain protectionDomain,
              @NonNull byte[] classfileBuffer) {
          // can be null for Java 8 lambdas
          if (classDesc != null && classBeingRedefinedOrRetransformed != null
                  && classBeingRedefinedOrRetransformed == classBeingCached) {
              addClassfile(loader, classDesc, classfileBuffer);
              classBeingCached = null;
          }
  
          return null;
      }
  
      private void addClassfile(@Nullable ClassLoader loader, @NonNull String classDesc, @NonNull byte[] classfile) {
          Map<String, byte[]> classfiles = getClassfiles(loader);
          classfiles.put(classDesc, classfile);
      }
  
      @NonNull
      private Map<String, byte[]> getClassfiles(@Nullable ClassLoader loader) {
          return classLoadersAndClassfiles.computeIfAbsent(loader, k -> new HashMap<>(100));
      }
  
      @Nullable
      private byte[] findClassfile(@NonNull Class<?> aClass) {
          String className = aClass.getName();
  
          // Discards an invalid numerical suffix from a synthetic Java 8 class, if detected.
          int p = className.indexOf('/');
          if (p > 0) {
              className = className.substring(0, p);
          }
  
          Map<String, byte[]> classfiles = getClassfiles(aClass.getClassLoader());
          return classfiles.get(className.replace('.', '/'));
      }
  
      @Nullable
      public static synchronized byte[] getClassfile(@NonNull String classDesc) {
          return INSTANCE.findClassfile(classDesc);
      }
  
      @Nullable
      private byte[] findClassfile(@NonNull String classDesc) {
          byte[] classfile = null;
  
          for (Map<String, byte[]> classfiles : classLoadersAndClassfiles.values()) {
              classfile = classfiles.get(classDesc);
  
              if (classfile != null) {
                  return classfile;
              }
          }
  
          Class<?> desiredClass = Startup.getClassIfLoaded(classDesc);
  
         if (desiredClass != null) {
             classBeingCached = desiredClass;
             Startup.retransformClass(desiredClass);
             ClassLoader classLoader = desiredClass.getClassLoader();
             classfile = INSTANCE.findClassfile(classLoader, classDesc);
         }
 
         return classfile;
     }
 
     @Nullable
     private synchronized byte[] findClassfile(@Nullable ClassLoader loader, @NonNull String classDesc) {
         Map<String, byte[]> classfiles = getClassfiles(loader);
         return classfiles.get(classDesc);
     }
 
     @Nullable
     public static synchronized byte[] getClassfile(@NonNull Class<?> aClass) {
         byte[] cached = INSTANCE.findClassfile(aClass);
         if (cached != null) {
             return cached;
         }
 
         INSTANCE.classBeingCached = aClass;
         Startup.retransformClass(aClass);
         return INSTANCE.findClassfile(aClass);
     }
 
     @Nullable
     public static byte[] getClassfile(@Nullable ClassLoader loader, @NonNull String internalClassName) {
         return INSTANCE.findClassfile(loader, internalClassName);
     }
 
     public static void addClassfile(@NonNull Class<?> aClass, @NonNull byte[] classfile) {
         INSTANCE.addClassfile(aClass.getClassLoader(), aClass.getName().replace('.', '/'), classfile);
     }
 }