// 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
// are met:
// 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
//    documentation and/or other materials provided with the distribution.
// 3. Neither the name of the copyright holders nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
package io.ebean.enhance.asm.commons;

import io.ebean.enhance.asm.*;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * A {@link MethodVisitor} to insert before, after and around advices in methods and constructors.
 * For constructors, the code keeps track of the elements on the stack in order to detect when the
 * super class constructor is called (note that there can be multiple such calls in different
 * branches). {@code onMethodEnter} is called after each super class constructor call, because the
 * object cannot be used before it is properly initialized.
 *
 * @author Eugene Kuleshov
 * @author Eric Bruneton
 */
public abstract class AdviceAdapter extends GeneratorAdapter implements Opcodes {

  /** The "uninitialized this" value. */
  private static final Object UNINITIALIZED_THIS = new Object();

  /** Any value other than "uninitialized this". */
  private static final Object OTHER = new Object();

  /** Prefix of the error message when invalid opcodes are found. */
  private static final String INVALID_OPCODE = "Invalid opcode ";

  /** The access flags of the visited method. */
  protected int methodAccess;

  /** The descriptor of the visited method. */
  protected String methodDesc;

  /** Whether the visited method is a constructor. */
  private final boolean isConstructor;

  /**
   * Whether the super class constructor has been called (if the visited method is a constructor),
   * at the current instruction. There can be multiple call sites to the super constructor (e.g. for
   * Java code such as {@code super(expr ? value1 : value2);}), in different branches. When scanning
   * the bytecode linearly, we can move from one branch where the super constructor has been called
   * to another where it has not been called yet. Therefore, this value can change from false to
   * true, and vice-versa.
   */
  private boolean superClassConstructorCalled;

  /**
   * The values on the current execution stack frame (long and double are represented by two
   * elements). Each value is either {@link #UNINITIALIZED_THIS} (for the uninitialized this value),
   * or {@link #OTHER} (for any other value). This field is only maintained for constructors, in
   * branches where the super class constructor has not been called yet.
   */
  private List<Object> stackFrame;

  /**
   * The stack map frames corresponding to the labels of the forward jumps made *before* the super
   * class constructor has been called (note that the Java Virtual Machine forbids backward jumps
   * before the super class constructor is called). Note that by definition (cf. the 'before'), when
   * we reach a label from this map, {@link #superClassConstructorCalled} must be reset to false.
   * This field is only maintained for constructors.
   */
  private Map<Label, List<Object>> forwardJumpStackFrames;

  /**
   * Constructs a new {@link AdviceAdapter}.
   *
   * @param api the ASM API version implemented by this visitor. Must be one of the {@code
   *     ASM}<i>x</i> values in {@link Opcodes}.
   * @param methodVisitor the method visitor to which this adapter delegates calls.
   * @param access the method's access flags (see {@link Opcodes}).
   * @param name the method's name.
   * @param descriptor the method's descriptor (see {@link Type Type}).
   */
  protected AdviceAdapter(
      final int api,
      final MethodVisitor methodVisitor,
      final int access,
      final String name,
      final String descriptor) {
    super(api, methodVisitor, access, name, descriptor);
    methodAccess = access;
    methodDesc = descriptor;
    isConstructor = "<init>".equals(name);
  }

  @Override
  public void visitCode() {
    super.visitCode();
    if (isConstructor) {
      stackFrame = new ArrayList<>();
      forwardJumpStackFrames = new HashMap<>();
    } else {
      onMethodEnter();
    }
  }

  @Override
  public void visitLabel(final Label label) {
    super.visitLabel(label);
    if (isConstructor && forwardJumpStackFrames != null) {
      List<Object> labelStackFrame = forwardJumpStackFrames.get(label);
      if (labelStackFrame != null) {
        stackFrame = labelStackFrame;
        superClassConstructorCalled = false;
        forwardJumpStackFrames.remove(label);
      }
    }
  }

  @Override
  public void visitInsn(final int opcode) {
    if (isConstructor && !superClassConstructorCalled) {
      int stackSize;
      switch (opcode) {
        case IRETURN:
        case FRETURN:
        case ARETURN:
        case LRETURN:
        case DRETURN:
          throw new IllegalArgumentException("Invalid return in constructor");
        case RETURN: // empty stack
          onMethodExit(opcode);
          endConstructorBasicBlockWithoutSuccessor();
          break;
        case ATHROW: // 1 before n/a after
          popValue();
          onMethodExit(opcode);
          endConstructorBasicBlockWithoutSuccessor();
          break;
        case NOP:
        case LALOAD: // remove 2 add 2
        case DALOAD: // remove 2 add 2
        case LNEG:
        case DNEG:
        case FNEG:
        case INEG:
        case L2D:
        case D2L:
        case F2I:
        case I2B:
        case I2C:
        case I2S:
        case I2F:
        case ARRAYLENGTH:
          break;
        case ACONST_NULL:
        case ICONST_M1:
        case ICONST_0:
        case ICONST_1:
        case ICONST_2:
        case ICONST_3:
        case ICONST_4:
        case ICONST_5:
        case FCONST_0:
        case FCONST_1:
        case FCONST_2:
        case F2L: // 1 before 2 after
        case F2D:
        case I2L:
        case I2D:
          pushValue(OTHER);
          break;
        case LCONST_0:
        case LCONST_1:
        case DCONST_0:
        case DCONST_1:
          pushValue(OTHER);
          pushValue(OTHER);
          break;
        case IALOAD: // remove 2 add 1
        case FALOAD: // remove 2 add 1
        case AALOAD: // remove 2 add 1
        case BALOAD: // remove 2 add 1
        case CALOAD: // remove 2 add 1
        case SALOAD: // remove 2 add 1
        case POP:
        case IADD:
        case FADD:
        case ISUB:
        case LSHL: // 3 before 2 after
        case LSHR: // 3 before 2 after
        case LUSHR: // 3 before 2 after
        case L2I: // 2 before 1 after
        case L2F: // 2 before 1 after
        case D2I: // 2 before 1 after
        case D2F: // 2 before 1 after
        case FSUB:
        case FMUL:
        case FDIV:
        case FREM:
        case FCMPL: // 2 before 1 after
        case FCMPG: // 2 before 1 after
        case IMUL:
        case IDIV:
        case IREM:
        case ISHL:
        case ISHR:
        case IUSHR:
        case IAND:
        case IOR:
        case IXOR:
        case MONITORENTER:
        case MONITOREXIT:
          popValue();
          break;
        case POP2:
        case LSUB:
        case LMUL:
        case LDIV:
        case LREM:
        case LADD:
        case LAND:
        case LOR:
        case LXOR:
        case DADD:
        case DMUL:
        case DSUB:
        case DDIV:
        case DREM:
          popValue();
          popValue();
          break;
        case IASTORE:
        case FASTORE:
        case AASTORE:
        case BASTORE:
        case CASTORE:
        case SASTORE:
        case LCMP: // 4 before 1 after
        case DCMPL:
        case DCMPG:
          popValue();
          popValue();
          popValue();
          break;
        case LASTORE:
        case DASTORE:
          popValue();
          popValue();
          popValue();
          popValue();
          break;
        case DUP:
          pushValue(peekValue());
          break;
        case DUP_X1:
          stackSize = stackFrame.size();
          stackFrame.add(stackSize - 2, stackFrame.get(stackSize - 1));
          break;
        case DUP_X2:
          stackSize = stackFrame.size();
          stackFrame.add(stackSize - 3, stackFrame.get(stackSize - 1));
          break;
        case DUP2:
          stackSize = stackFrame.size();
          stackFrame.add(stackSize - 2, stackFrame.get(stackSize - 1));
          stackFrame.add(stackSize - 2, stackFrame.get(stackSize - 1));
          break;
        case DUP2_X1:
          stackSize = stackFrame.size();
          stackFrame.add(stackSize - 3, stackFrame.get(stackSize - 1));
          stackFrame.add(stackSize - 3, stackFrame.get(stackSize - 1));
          break;
        case DUP2_X2:
          stackSize = stackFrame.size();
          stackFrame.add(stackSize - 4, stackFrame.get(stackSize - 1));
          stackFrame.add(stackSize - 4, stackFrame.get(stackSize - 1));
          break;
        case SWAP:
          stackSize = stackFrame.size();
          stackFrame.add(stackSize - 2, stackFrame.get(stackSize - 1));
          stackFrame.remove(stackSize);
          break;
        default:
          throw new IllegalArgumentException(INVALID_OPCODE + opcode);
      }
    } else {
      switch (opcode) {
        case RETURN:
        case IRETURN:
        case FRETURN:
        case ARETURN:
        case LRETURN:
        case DRETURN:
        case ATHROW:
          onMethodExit(opcode);
          break;
        default:
          break;
      }
    }
    super.visitInsn(opcode);
  }

  @Override
  public void visitVarInsn(final int opcode, final int varIndex) {
    super.visitVarInsn(opcode, varIndex);
    if (isConstructor && !superClassConstructorCalled) {
      switch (opcode) {
        case ILOAD:
        case FLOAD:
          pushValue(OTHER);
          break;
        case LLOAD:
        case DLOAD:
          pushValue(OTHER);
          pushValue(OTHER);
          break;
        case ALOAD:
          pushValue(varIndex == 0 ? UNINITIALIZED_THIS : OTHER);
          break;
        case ASTORE:
        case ISTORE:
        case FSTORE:
          popValue();
          break;
        case LSTORE:
        case DSTORE:
          popValue();
          popValue();
          break;
        case RET:
          endConstructorBasicBlockWithoutSuccessor();
          break;
        default:
          throw new IllegalArgumentException(INVALID_OPCODE + opcode);
      }
    }
  }

  @Override
  public void visitFieldInsn(
      final int opcode, final String owner, final String name, final String descriptor) {
    super.visitFieldInsn(opcode, owner, name, descriptor);
    if (isConstructor && !superClassConstructorCalled) {
      char firstDescriptorChar = descriptor.charAt(0);
      boolean longOrDouble = firstDescriptorChar == 'J' || firstDescriptorChar == 'D';
      switch (opcode) {
        case GETSTATIC:
          pushValue(OTHER);
          if (longOrDouble) {
            pushValue(OTHER);
          }
          break;
        case PUTSTATIC:
          popValue();
          if (longOrDouble) {
            popValue();
          }
          break;
        case PUTFIELD:
          popValue();
          popValue();
          if (longOrDouble) {
            popValue();
          }
          break;
        case GETFIELD:
          if (longOrDouble) {
            pushValue(OTHER);
          }
          break;
        default:
          throw new IllegalArgumentException(INVALID_OPCODE + opcode);
      }
    }
  }

  @Override
  public void visitIntInsn(final int opcode, final int operand) {
    super.visitIntInsn(opcode, operand);
    if (isConstructor && !superClassConstructorCalled && opcode != NEWARRAY) {
      pushValue(OTHER);
    }
  }

  @Override
  public void visitLdcInsn(final Object value) {
    super.visitLdcInsn(value);
    if (isConstructor && !superClassConstructorCalled) {
      pushValue(OTHER);
      if (value instanceof Double
          || value instanceof Long
          || (value instanceof ConstantDynamic && ((ConstantDynamic) value).getSize() == 2)) {
        pushValue(OTHER);
      }
    }
  }

  @Override
  public void visitMultiANewArrayInsn(final String descriptor, final int numDimensions) {
    super.visitMultiANewArrayInsn(descriptor, numDimensions);
    if (isConstructor && !superClassConstructorCalled) {
      for (int i = 0; i < numDimensions; i++) {
        popValue();
      }
      pushValue(OTHER);
    }
  }

  @Override
  public void visitTypeInsn(final int opcode, final String type) {
    super.visitTypeInsn(opcode, type);
    // ANEWARRAY, CHECKCAST or INSTANCEOF don't change stack.
    if (isConstructor && !superClassConstructorCalled && opcode == NEW) {
      pushValue(OTHER);
    }
  }

  @Override
  public void visitMethodInsn(
      final int opcodeAndSource,
      final String owner,
      final String name,
      final String descriptor,
      final boolean isInterface) {
    if (api < Opcodes.ASM5 && (opcodeAndSource & Opcodes.SOURCE_DEPRECATED) == 0) {
      // Redirect the call to the deprecated version of this method.
      super.visitMethodInsn(opcodeAndSource, owner, name, descriptor, isInterface);
      return;
    }
    super.visitMethodInsn(opcodeAndSource, owner, name, descriptor, isInterface);
    int opcode = opcodeAndSource & ~Opcodes.SOURCE_MASK;

    doVisitMethodInsn(opcode, name, descriptor);
  }

  private void doVisitMethodInsn(final int opcode, final String name, final String descriptor) {
    if (isConstructor && !superClassConstructorCalled) {
      for (Type argumentType : Type.getArgumentTypes(descriptor)) {
        popValue();
        if (argumentType.getSize() == 2) {
          popValue();
        }
      }
      switch (opcode) {
        case INVOKEINTERFACE:
        case INVOKEVIRTUAL:
          popValue();
          break;
        case INVOKESPECIAL:
          Object value = popValue();
          if (value == UNINITIALIZED_THIS
              && !superClassConstructorCalled
              && name.equals("<init>")) {
            superClassConstructorCalled = true;
            onMethodEnter();
          }
          break;
        default:
          break;
      }

      Type returnType = Type.getReturnType(descriptor);
      if (returnType != Type.VOID_TYPE) {
        pushValue(OTHER);
        if (returnType.getSize() == 2) {
          pushValue(OTHER);
        }
      }
    }
  }

  @Override
  public void visitInvokeDynamicInsn(
      final String name,
      final String descriptor,
      final Handle bootstrapMethodHandle,
      final Object... bootstrapMethodArguments) {
    super.visitInvokeDynamicInsn(name, descriptor, bootstrapMethodHandle, bootstrapMethodArguments);
    doVisitMethodInsn(Opcodes.INVOKEDYNAMIC, name, descriptor);
  }

  @Override
  public void visitJumpInsn(final int opcode, final Label label) {
    super.visitJumpInsn(opcode, label);
    if (isConstructor && !superClassConstructorCalled) {
      switch (opcode) {
        case IFEQ:
        case IFNE:
        case IFLT:
        case IFGE:
        case IFGT:
        case IFLE:
        case IFNULL:
        case IFNONNULL:
          popValue();
          break;
        case IF_ICMPEQ:
        case IF_ICMPNE:
        case IF_ICMPLT:
        case IF_ICMPGE:
        case IF_ICMPGT:
        case IF_ICMPLE:
        case IF_ACMPEQ:
        case IF_ACMPNE:
          popValue();
          popValue();
          break;
        case JSR:
          pushValue(OTHER);
          break;
        case GOTO:
          endConstructorBasicBlockWithoutSuccessor();
          break;
        default:
          break;
      }
      addForwardJump(label);
    }
  }

  @Override
  public void visitLookupSwitchInsn(final Label dflt, final int[] keys, final Label[] labels) {
    super.visitLookupSwitchInsn(dflt, keys, labels);
    if (isConstructor && !superClassConstructorCalled) {
      popValue();
      addForwardJumps(dflt, labels);
      endConstructorBasicBlockWithoutSuccessor();
    }
  }

  @Override
  public void visitTableSwitchInsn(
      final int min, final int max, final Label dflt, final Label... labels) {
    super.visitTableSwitchInsn(min, max, dflt, labels);
    if (isConstructor && !superClassConstructorCalled) {
      popValue();
      addForwardJumps(dflt, labels);
      endConstructorBasicBlockWithoutSuccessor();
    }
  }

  @Override
  public void visitTryCatchBlock(
      final Label start, final Label end, final Label handler, final String type) {
    super.visitTryCatchBlock(start, end, handler, type);
    // By definition of 'forwardJumpStackFrames', 'handler' should be pushed only if there is an
    // instruction between 'start' and 'end' at which the super class constructor is not yet
    // called. Unfortunately, try catch blocks must be visited before their labels, so we have no
    // way to know this at this point. Instead, we suppose that the super class constructor has not
    // been called at the start of *any* exception handler. If this is wrong, normally there should
    // not be a second super class constructor call in the exception handler (an object can't be
    // initialized twice), so this is not issue (in the sense that there is no risk to emit a wrong
    // 'onMethodEnter').
    if (isConstructor && !forwardJumpStackFrames.containsKey(handler)) {
      List<Object> handlerStackFrame = new ArrayList<>();
      handlerStackFrame.add(OTHER);
      forwardJumpStackFrames.put(handler, handlerStackFrame);
    }
  }

  private void addForwardJumps(final Label dflt, final Label[] labels) {
    addForwardJump(dflt);
    for (Label label : labels) {
      addForwardJump(label);
    }
  }

  private void addForwardJump(final Label label) {
    if (forwardJumpStackFrames.containsKey(label)) {
      return;
    }
    forwardJumpStackFrames.put(label, new ArrayList<>(stackFrame));
  }

  private void endConstructorBasicBlockWithoutSuccessor() {
    // The next instruction is not reachable from this instruction. If it is dead code, we
    // should not try to simulate stack operations, and there is no need to insert advices
    // here. If it is reachable with a backward jump, the only possible case is that the super
    // class constructor has already been called (backward jumps are forbidden before it is
    // called). If it is reachable with a forward jump, there are two sub-cases. Either the
    // super class constructor has already been called when reaching the next instruction, or
    // it has not been called. But in this case there must be a forwardJumpStackFrames entry
    // for a Label designating the next instruction, and superClassConstructorCalled will be
    // reset to false there. We can therefore always reset this field to true here.
    superClassConstructorCalled = true;
  }

  private Object popValue() {
    return stackFrame.remove(stackFrame.size() - 1);
  }

  private Object peekValue() {
    return stackFrame.get(stackFrame.size() - 1);
  }

  private void pushValue(final Object value) {
    stackFrame.add(value);
  }

  /**
   * Generates the "before" advice for the visited method. The default implementation of this method
   * does nothing. Subclasses can use or change all the local variables, but should not change state
   * of the stack. This method is called at the beginning of the method or after super class
   * constructor has been called (in constructors).
   */
  protected void onMethodEnter() {}

  /**
   * Generates the "after" advice for the visited method. The default implementation of this method
   * does nothing. Subclasses can use or change all the local variables, but should not change state
   * of the stack. This method is called at the end of the method, just before return and athrow
   * instructions. The top element on the stack contains the return value or the exception instance.
   * For example:
   *
   * <pre>
   * public void onMethodExit(final int opcode) {
   *   if (opcode == RETURN) {
   *     visitInsn(ACONST_NULL);
   *   } else if (opcode == ARETURN || opcode == ATHROW) {
   *     dup();
   *   } else {
   *     if (opcode == LRETURN || opcode == DRETURN) {
   *       dup2();
   *     } else {
   *       dup();
   *     }
   *     box(Type.getReturnType(this.methodDesc));
   *   }
   *   visitIntInsn(SIPUSH, opcode);
   *   visitMethodInsn(INVOKESTATIC, owner, "onExit", "(Ljava/lang/Object;I)V");
   * }
   *
   * // An actual call back method.
   * public static void onExit(final Object exitValue, final int opcode) {
   *   ...
   * }
   * </pre>
   *
   * @param opcode one of {@link Opcodes#RETURN}, {@link Opcodes#IRETURN}, {@link Opcodes#FRETURN},
   *     {@link Opcodes#ARETURN}, {@link Opcodes#LRETURN}, {@link Opcodes#DRETURN} or {@link
   *     Opcodes#ATHROW}.
   */
  protected void onMethodExit(final int opcode) {}
}