/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

/*

 * Copyright 2001-2004 The Apache Software Foundation.

 *

 * Licensed 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.

 */

/*

 * $Id: Expression.java,v 1.2.4.1 2005/09/01 14:17:51 pvedula Exp $

 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import java.util.Vector;

import com.sun.org.apache.bcel.internal.generic.BranchHandle;

import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;

import com.sun.org.apache.bcel.internal.generic.GOTO_W;

import com.sun.org.apache.bcel.internal.generic.IFEQ;

import com.sun.org.apache.bcel.internal.generic.InstructionHandle;

import com.sun.org.apache.bcel.internal.generic.InstructionList;

import com.sun.org.apache.xalan.internal.xsltc.compiler.util.BooleanType;

import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;

import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ErrorMsg;

import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;

import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodType;

import com.sun.org.apache.xalan.internal.xsltc.compiler.util.NodeSetType;

import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;

import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;

/**

 * @author Jacek Ambroziak

 * @author Santiago Pericas-Geertsen

 * @author Morten Jorgensen

 * @author Erwin Bolwidt <ejb@klomp.org>

 */

abstract class Expression extends SyntaxTreeNode {

    /**

     * The type of this expression. It is set after calling

     * <code>typeCheck()</code>.

     */

    protected Type _type;

    /**

     * Instruction handles that comprise the true list.

     */

    protected FlowList _trueList = new FlowList();

    /**

     * Instruction handles that comprise the false list.

     */

    protected FlowList _falseList = new FlowList();

    public Type getType() {

        return _type;

    }

    public abstract String toString();

    public boolean hasPositionCall() {

        return false;           // default should be 'false' for StepPattern

    }

    public boolean hasLastCall() {

        return false;

    }

    /**

     * Returns an object representing the compile-time evaluation

     * of an expression. We are only using this for function-available

     * and element-available at this time.

     */

    public Object evaluateAtCompileTime() {

        return null;

    }

    /**

     * Type check all the children of this node.

     */

    public Type typeCheck(SymbolTable stable) throws TypeCheckError {

        return typeCheckContents(stable);

    }

    /**

     * Translate this node into JVM bytecodes.

     */

    public void translate(ClassGenerator classGen, MethodGenerator methodGen) {

        ErrorMsg msg = new ErrorMsg(ErrorMsg.NOT_IMPLEMENTED_ERR,

                                    getClass(), this);

        getParser().reportError(FATAL, msg);

    }

    /**

     * Translate this node into a fresh instruction list.

     * The original instruction list is saved and restored.

     */

    public final InstructionList compile(ClassGenerator classGen,

                                         MethodGenerator methodGen) {

        final InstructionList result, save = methodGen.getInstructionList();

        methodGen.setInstructionList(result = new InstructionList());

        translate(classGen, methodGen);

        methodGen.setInstructionList(save);

        return result;

    }

    /**

     * Redefined by expressions of type boolean that use flow lists.

     */

    public void translateDesynthesized(ClassGenerator classGen,

                                       MethodGenerator methodGen) {

        translate(classGen, methodGen);

        if (_type instanceof BooleanType) {

            desynthesize(classGen, methodGen);

        }

    }

    /**

     * If this expression is of type node-set and it is not a variable

     * reference, then call setStartNode() passing the context node.

     */

    public void startIterator(ClassGenerator classGen,

                                   MethodGenerator methodGen) {

        // Ignore if type is not node-set

        if (_type instanceof NodeSetType == false) {

            return;

        }

        // setStartNode() should not be called if expr is a variable ref

        Expression expr = this;

        if (expr instanceof CastExpr) {

            expr = ((CastExpr) expr).getExpr();

        }

        if (expr instanceof VariableRefBase == false) {

            final InstructionList il = methodGen.getInstructionList();

            il.append(methodGen.loadContextNode());

            il.append(methodGen.setStartNode());

        }

    }

    /**

     * Synthesize a boolean expression, i.e., either push a 0 or 1 onto the

     * operand stack for the next statement to succeed. Returns the handle

     * of the instruction to be backpatched.

     */

    public void synthesize(ClassGenerator classGen, MethodGenerator methodGen) {

        final ConstantPoolGen cpg = classGen.getConstantPool();

        final InstructionList il = methodGen.getInstructionList();

        _trueList.backPatch(il.append(ICONST_1));

        final BranchHandle truec = il.append(new GOTO_W(null));

        _falseList.backPatch(il.append(ICONST_0));

        truec.setTarget(il.append(NOP));

    }

    public void desynthesize(ClassGenerator classGen,

                             MethodGenerator methodGen) {

        final InstructionList il = methodGen.getInstructionList();

        _falseList.add(il.append(new IFEQ(null)));

    }

    public FlowList getFalseList() {

        return _falseList;

    }

    public FlowList getTrueList() {

        return _trueList;

    }

    public void backPatchFalseList(InstructionHandle ih) {

        _falseList.backPatch(ih);

    }

    public void backPatchTrueList(InstructionHandle ih) {

        _trueList.backPatch(ih);

    }

    /**

     * Search for a primop in the symbol table that matches the method type

     * <code>ctype</code>. Two methods match if they have the same arity.

     * If a primop is overloaded then the "closest match" is returned. The

     * first entry in the vector of primops that has the right arity is

     * considered to be the default one.

     */

    public MethodType lookupPrimop(SymbolTable stable, String op,

                                   MethodType ctype) {

        MethodType result = null;

        final Vector primop = stable.lookupPrimop(op);

        if (primop != null) {

            final int n = primop.size();

            int minDistance = Integer.MAX_VALUE;

            for (int i = 0; i < n; i++) {

                final MethodType ptype = (MethodType) primop.elementAt(i);

                // Skip if different arity

                if (ptype.argsCount() != ctype.argsCount()) {

                    continue;

                }

                // The first method with the right arity is the default

                if (result == null) {

                    result = ptype;             // default method

                }

                // Check if better than last one found

                final int distance = ctype.distanceTo(ptype);

                if (distance < minDistance) {

                    minDistance = distance;

                    result = ptype;

                }

            }

        }

        return result;

    }

}