// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
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// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
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//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
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package org.objectweb.asm.tree.analysis;

import java.util.List;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;

/**
 * An extended {@link BasicVerifier} that performs more precise verifications. This verifier
 * computes exact class types, instead of using a single "object reference" type (as done in {@link
 * BasicVerifier}).
 *
 * @author Eric Bruneton
 * @author Bing Ran
 */
public class SimpleVerifier extends BasicVerifier {

  /** The type of the class that is verified. */
  private final Type currentClass;

  /** The type of the super class of the class that is verified. */
  private final Type currentSuperClass;

  /** The types of the interfaces directly implemented by the class that is verified. */
  private final List<Type> currentClassInterfaces;

  /** Whether the class that is verified is an interface. */
  private final boolean isInterface;

  /** The loader to use to load the referenced classes. */
  private ClassLoader loader = getClass().getClassLoader();

  /**
   * Constructs a new {@link SimpleVerifier}. <i>Subclasses must not use this constructor</i>.
   * Instead, they must use the {@link #SimpleVerifier(int, Type, Type, List, boolean)} version.
   */
  public SimpleVerifier() {
    this(null, null, false);
  }

  /**
   * Constructs a new {@link SimpleVerifier} to verify a specific class. This class will not be
   * loaded into the JVM since it may be incorrect. <i>Subclasses must not use this constructor</i>.
   * Instead, they must use the {@link #SimpleVerifier(int, Type, Type, List, boolean)} version.
   *
   * @param currentClass the type of the class to be verified.
   * @param currentSuperClass the type of the super class of the class to be verified.
   * @param isInterface whether the class to be verifier is an interface.
   */
  public SimpleVerifier(
      final Type currentClass, final Type currentSuperClass, final boolean isInterface) {
    this(currentClass, currentSuperClass, null, isInterface);
  }

  /**
   * Constructs a new {@link SimpleVerifier} to verify a specific class. This class will not be
   * loaded into the JVM since it may be incorrect. <i>Subclasses must not use this constructor</i>.
   * Instead, they must use the {@link #SimpleVerifier(int, Type, Type, List, boolean)} version.
   *
   * @param currentClass the type of the class to be verified.
   * @param currentSuperClass the type of the super class of the class to be verified.
   * @param currentClassInterfaces the types of the interfaces directly implemented by the class to
   *     be verified.
   * @param isInterface whether the class to be verifier is an interface.
   */
  public SimpleVerifier(
      final Type currentClass,
      final Type currentSuperClass,
      final List<Type> currentClassInterfaces,
      final boolean isInterface) {
    this(
        /* latest api = */ ASM9,
        currentClass,
        currentSuperClass,
        currentClassInterfaces,
        isInterface);
    if (getClass() != SimpleVerifier.class) {
      throw new IllegalStateException();
    }
  }

  /**
   * Constructs a new {@link SimpleVerifier} to verify a specific class. This class will not be
   * loaded into the JVM since it may be incorrect.
   *
   * @param api the ASM API version supported by this verifier. Must be one of the {@code
   *     ASM}<i>x</i> values in {@link Opcodes}.
   * @param currentClass the type of the class to be verified.
   * @param currentSuperClass the type of the super class of the class to be verified.
   * @param currentClassInterfaces the types of the interfaces directly implemented by the class to
   *     be verified.
   * @param isInterface whether the class to be verifier is an interface.
   */
  protected SimpleVerifier(
      final int api,
      final Type currentClass,
      final Type currentSuperClass,
      final List<Type> currentClassInterfaces,
      final boolean isInterface) {
    super(api);
    this.currentClass = currentClass;
    this.currentSuperClass = currentSuperClass;
    this.currentClassInterfaces = currentClassInterfaces;
    this.isInterface = isInterface;
  }

  /**
   * Sets the <code>ClassLoader</code> to be used in {@link #getClass}.
   *
   * @param loader the <code>ClassLoader</code> to use.
   */
  public void setClassLoader(final ClassLoader loader) {
    this.loader = loader;
  }

  @Override
  public BasicValue newValue(final Type type) {
    if (type == null) {
      return BasicValue.UNINITIALIZED_VALUE;
    }

    boolean isArray = type.getSort() == Type.ARRAY;
    if (isArray) {
      switch (type.getElementType().getSort()) {
        case Type.BOOLEAN:
        case Type.CHAR:
        case Type.BYTE:
        case Type.SHORT:
          return new BasicValue(type);
        default:
          break;
      }
    }

    BasicValue value = super.newValue(type);
    if (BasicValue.REFERENCE_VALUE.equals(value)) {
      if (isArray) {
        value = newValue(type.getElementType());
        StringBuilder descriptor = new StringBuilder();
        for (int i = 0; i < type.getDimensions(); ++i) {
          descriptor.append('[');
        }
        descriptor.append(value.getType().getDescriptor());
        value = new BasicValue(Type.getType(descriptor.toString()));
      } else {
        value = new BasicValue(type);
      }
    }
    return value;
  }

  @Override
  protected boolean isArrayValue(final BasicValue value) {
    Type type = value.getType();
    return type != null && (type.getSort() == Type.ARRAY || type.equals(NULL_TYPE));
  }

  @Override
  protected BasicValue getElementValue(final BasicValue objectArrayValue) throws AnalyzerException {
    Type arrayType = objectArrayValue.getType();
    if (arrayType != null) {
      if (arrayType.getSort() == Type.ARRAY) {
        return newValue(Type.getType(arrayType.getDescriptor().substring(1)));
      } else if (arrayType.equals(NULL_TYPE)) {
        return objectArrayValue;
      }
    }
    throw new AssertionError();
  }

  @Override
  protected boolean isSubTypeOf(final BasicValue value, final BasicValue expected) {
    Type expectedType = expected.getType();
    Type type = value.getType();
    switch (expectedType.getSort()) {
      case Type.INT:
      case Type.FLOAT:
      case Type.LONG:
      case Type.DOUBLE:
        return type.equals(expectedType);
      case Type.ARRAY:
      case Type.OBJECT:
        if (type.equals(NULL_TYPE)) {
          return true;
        } else if (type.getSort() == Type.OBJECT || type.getSort() == Type.ARRAY) {
          if (isAssignableFrom(expectedType, type)) {
            return true;
          } else if (getClass(expectedType).isInterface()) {
            // The merge of class or interface types can only yield class types (because it is not
            // possible in general to find an unambiguous common super interface, due to multiple
            // inheritance). Because of this limitation, we need to relax the subtyping check here
            // if 'value' is an interface.
            return Object.class.isAssignableFrom(getClass(type));
          } else {
            return false;
          }
        } else {
          return false;
        }
      default:
        throw new AssertionError();
    }
  }

  @Override
  public BasicValue merge(final BasicValue value1, final BasicValue value2) {
    if (!value1.equals(value2)) {
      Type type1 = value1.getType();
      Type type2 = value2.getType();
      if (type1 != null
          && (type1.getSort() == Type.OBJECT || type1.getSort() == Type.ARRAY)
          && type2 != null
          && (type2.getSort() == Type.OBJECT || type2.getSort() == Type.ARRAY)) {
        if (type1.equals(NULL_TYPE)) {
          return value2;
        }
        if (type2.equals(NULL_TYPE)) {
          return value1;
        }
        if (isAssignableFrom(type1, type2)) {
          return value1;
        }
        if (isAssignableFrom(type2, type1)) {
          return value2;
        }
        int numDimensions = 0;
        if (type1.getSort() == Type.ARRAY
            && type2.getSort() == Type.ARRAY
            && type1.getDimensions() == type2.getDimensions()
            && type1.getElementType().getSort() == Type.OBJECT
            && type2.getElementType().getSort() == Type.OBJECT) {
          numDimensions = type1.getDimensions();
          type1 = type1.getElementType();
          type2 = type2.getElementType();
        }
        while (true) {
          if (type1 == null || isInterface(type1)) {
            return newArrayValue(Type.getObjectType("java/lang/Object"), numDimensions);
          }
          type1 = getSuperClass(type1);
          if (isAssignableFrom(type1, type2)) {
            return newArrayValue(type1, numDimensions);
          }
        }
      }
      return BasicValue.UNINITIALIZED_VALUE;
    }
    return value1;
  }

  private BasicValue newArrayValue(final Type type, final int dimensions) {
    if (dimensions == 0) {
      return newValue(type);
    } else {
      StringBuilder descriptor = new StringBuilder();
      for (int i = 0; i < dimensions; ++i) {
        descriptor.append('[');
      }
      descriptor.append(type.getDescriptor());
      return newValue(Type.getType(descriptor.toString()));
    }
  }

  /**
   * Returns whether the given type corresponds to the type of an interface. The default
   * implementation of this method loads the class and uses the reflection API to return its result
   * (unless the given type corresponds to the class being verified).
   *
   * @param type a type.
   * @return whether 'type' corresponds to an interface.
   */
  protected boolean isInterface(final Type type) {
    if (currentClass != null && currentClass.equals(type)) {
      return isInterface;
    }
    return getClass(type).isInterface();
  }

  /**
   * Returns the type corresponding to the super class of the given type. The default implementation
   * of this method loads the class and uses the reflection API to return its result (unless the
   * given type corresponds to the class being verified).
   *
   * @param type a type.
   * @return the type corresponding to the super class of 'type'.
   */
  protected Type getSuperClass(final Type type) {
    if (currentClass != null && currentClass.equals(type)) {
      return currentSuperClass;
    }
    Class<?> superClass = getClass(type).getSuperclass();
    return superClass == null ? null : Type.getType(superClass);
  }

  /**
   * Returns whether the class corresponding to the first argument is either the same as, or is a
   * superclass or superinterface of the class corresponding to the second argument. The default
   * implementation of this method loads the classes and uses the reflection API to return its
   * result (unless the result can be computed from the class being verified, and the types of its
   * super classes and implemented interfaces).
   *
   * @param type1 a type.
   * @param type2 another type.
   * @return whether the class corresponding to 'type1' is either the same as, or is a superclass or
   *     superinterface of the class corresponding to 'type2'.
   */
  protected boolean isAssignableFrom(final Type type1, final Type type2) {
    if (type1.equals(type2)) {
      return true;
    }
    if (currentClass != null && currentClass.equals(type1)) {
      if (getSuperClass(type2) == null) {
        return false;
      } else {
        if (isInterface) {
          return type2.getSort() == Type.OBJECT || type2.getSort() == Type.ARRAY;
        }
        return isAssignableFrom(type1, getSuperClass(type2));
      }
    }
    if (currentClass != null && currentClass.equals(type2)) {
      if (isAssignableFrom(type1, currentSuperClass)) {
        return true;
      }
      if (currentClassInterfaces != null) {
        for (Type currentClassInterface : currentClassInterfaces) {
          if (isAssignableFrom(type1, currentClassInterface)) {
            return true;
          }
        }
      }
      return false;
    }
    return getClass(type1).isAssignableFrom(getClass(type2));
  }

  /**
   * Loads the class corresponding to the given type. The class is loaded with the class loader
   * specified with {@link #setClassLoader}, or with the class loader of this class if no class
   * loader was specified.
   *
   * @param type a type.
   * @return the class corresponding to 'type'.
   */
  protected Class<?> getClass(final Type type) {
    try {
      if (type.getSort() == Type.ARRAY) {
        return Class.forName(type.getDescriptor().replace('/', '.'), false, loader);
      }
      return Class.forName(type.getClassName(), false, loader);
    } catch (ClassNotFoundException e) {
      throw new TypeNotPresentException(e.toString(), e);
    }
  }
}
