/*******************************************************************************
 * Copyright (c) 2013 IBM Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package com.ibm.wala.cast.ir.ssa;

import java.util.Collection;
import java.util.Collections;

import com.ibm.wala.ssa.SSAInstruction;
import com.ibm.wala.ssa.SSAInstructionFactory;
import com.ibm.wala.ssa.SymbolTable;
import com.ibm.wala.types.FieldReference;
import com.ibm.wala.types.TypeReference;
import com.ibm.wala.util.debug.Assertions;

/**
 * IR instruction to check whether a field is defined on some object. The field
 * is represented either by a {@link FieldReference} or by a local value number.  
 */
public class AstIsDefinedInstruction extends SSAInstruction {
  /**
   * name of the field.  If non-null, fieldVal should be -1.
   */
  private final FieldReference fieldRef;

  /**
   * value number holding the field string.  If non-negative,
   * fieldRef should be null.
   */
  private final int fieldVal;

  /**
   * the base pointer
   */
  private final int rval;

  /**
   * gets 1 if the field is defined, 0 otherwise.
   */
  private final int lval;

  /**
   * This constructor should only be used from {@link SSAInstruction#copyForSSA(SSAInstructionFactory, int[], int[])}
   */
  public AstIsDefinedInstruction(int iindex, int lval, int rval, int fieldVal, FieldReference fieldRef) {
    super(iindex);
    this.lval = lval;
    this.rval = rval;
    this.fieldVal = fieldVal;
    this.fieldRef = fieldRef;
  }

  public AstIsDefinedInstruction(int iindex, int lval, int rval, FieldReference fieldRef) {
    super(iindex);
    this.lval = lval;
    this.rval = rval;
    this.fieldVal = -1;
    this.fieldRef = fieldRef;
  }

  public AstIsDefinedInstruction(int iindex, int lval, int rval, int fieldVal) {
    super(iindex);
    this.lval = lval;
    this.rval = rval;
    this.fieldVal = fieldVal;
    this.fieldRef = null;
  }

  public AstIsDefinedInstruction(int iindex, int lval, int rval) {
    super(iindex);
    this.lval = lval;
    this.rval = rval;
    this.fieldVal = -1;
    this.fieldRef = null;
  }

  @Override
  public SSAInstruction copyForSSA(SSAInstructionFactory insts, int[] defs, int[] uses) {
    assert fieldVal == -1 || fieldRef == null;

    return ((AstInstructionFactory) insts).IsDefinedInstruction(iindex, (defs == null) ? lval : defs[0], (uses == null) ? rval : uses[0],
        (uses == null || fieldVal == -1) ? fieldVal : uses[1], fieldRef);
  }

  @Override
  public String toString(SymbolTable symbolTable) {
    if (fieldVal == -1 && fieldRef == null) {
      return getValueString(symbolTable, lval) + " = isDefined(" + getValueString(symbolTable, rval) + ")";
    } else if (fieldVal == -1) {
      return getValueString(symbolTable, lval) + " = isDefined(" + getValueString(symbolTable, rval) + "," + fieldRef.getName()
          + ")";
    } else if (fieldRef == null) {
      return getValueString(symbolTable, lval) + " = isDefined(" + getValueString(symbolTable, rval) + ","
          + getValueString(symbolTable, fieldVal) + ")";
    } else {
      Assertions.UNREACHABLE();
      return null;
    }
  }

  @Override
  public void visit(IVisitor v) {
    ((AstInstructionVisitor) v).visitIsDefined(this);
  }

  @Override
  public Collection<TypeReference> getExceptionTypes() {
    return Collections.emptySet();
  }

  @Override
  public boolean hasDef() {
    return true;
  }

  @Override
  public int getDef() {
    return lval;
  }

  @Override
  public int getDef(int i) {
    assert i == 0;

    return lval;
  }

  @Override
  public int getNumberOfDefs() {
    return 1;
  }

  @Override
  public int getNumberOfUses() {
    return (fieldVal == -1) ? 1 : 2;
  }

  @Override
  public int getUse(int j) {
    if (j == 0) {
      return rval;
    } else if (j == 1 && fieldVal != -1) {
      return fieldVal;
    } else {
      Assertions.UNREACHABLE();
      return -1;
    }
  }

  @Override
  public boolean isFallThrough() {
    return true;
  }

  @Override
  public int hashCode() {
    return 3077 * fieldVal * rval;
  }

  public FieldReference getFieldRef() {
    return fieldRef;
  }
}