/*
 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
 */
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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: ForEach.java,v 1.2.4.1 2005/09/01 15:23:46 pvedula Exp $
 */

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

import java.util.Enumeration;
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;
import com.sun.org.apache.bcel.internal.generic.IFGT;
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.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.NodeSetType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.NodeType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ReferenceType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ResultTreeType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Util;
import java.util.Iterator;

Author:
Jacek Ambroziak, Santiago Pericas-Geertsen, Morten Jorgensen/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 * @author Morten Jorgensen
 */
final class ForEach extends Instruction {

    private Expression _select;
    private Type       _type;

    public void display(int indent) {
        indent(indent);
        Util.println("ForEach");
        indent(indent + IndentIncrement);
        Util.println("select " + _select.toString());
        displayContents(indent + IndentIncrement);
    }

    public void parseContents(Parser parser) {
        _select = parser.parseExpression(this, "select", null);

        parseChildren(parser);

        // make sure required attribute(s) have been set
        if (_select.isDummy()) {
            reportError(this, parser, ErrorMsg.REQUIRED_ATTR_ERR, "select");
        }
    }

    public Type typeCheck(SymbolTable stable) throws TypeCheckError {
        _type = _select.typeCheck(stable);

        if (_type instanceof ReferenceType || _type instanceof NodeType) {
            _select = new CastExpr(_select, Type.NodeSet);
            typeCheckContents(stable);
            return Type.Void;
        }
        if (_type instanceof NodeSetType||_type instanceof ResultTreeType) {
            typeCheckContents(stable);
            return Type.Void;
        }
        throw new TypeCheckError(this);
    }

    public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
        final ConstantPoolGen cpg = classGen.getConstantPool();
        final InstructionList il = methodGen.getInstructionList();

        // Save current node and current iterator on the stack
        il.append(methodGen.loadCurrentNode());
        il.append(methodGen.loadIterator());

        // Collect sort objects associated with this instruction
        final Vector sortObjects = new Vector();
        Iterator<SyntaxTreeNode> children = elements();
        while (children.hasNext()) {
            final Object child = children.next();
            if (child instanceof Sort) {
                sortObjects.addElement(child);
            }
        }

        if ((_type != null) && (_type instanceof ResultTreeType)) {
            // Store existing DOM on stack - must be restored when loop is done
            il.append(methodGen.loadDOM());

            // <xsl:sort> cannot be applied to a result tree - issue warning
            if (sortObjects.size() > 0) {
                ErrorMsg msg = new ErrorMsg(ErrorMsg.RESULT_TREE_SORT_ERR,this);
                getParser().reportError(WARNING, msg);
            }

            // Put the result tree on the stack (DOM)
            _select.translate(classGen, methodGen);
            // Get an iterator for the whole DOM - excluding the root node
            _type.translateTo(classGen, methodGen, Type.NodeSet);
            // Store the result tree as the default DOM
            il.append(SWAP);
            il.append(methodGen.storeDOM());
        }
        else {
            // Compile node iterator
            if (sortObjects.size() > 0) {
                Sort.translateSortIterator(classGen, methodGen,
                                           _select, sortObjects);
            }
            else {
                _select.translate(classGen, methodGen);
            }

            if (_type instanceof ReferenceType == false) {
                il.append(methodGen.loadContextNode());
                il.append(methodGen.setStartNode());
            }
        }


        // Overwrite current iterator
        il.append(methodGen.storeIterator());

        // Give local variables (if any) default values before starting loop
        initializeVariables(classGen, methodGen);

        final BranchHandle nextNode = il.append(new GOTO(null));
        final InstructionHandle loop = il.append(NOP);

        translateContents(classGen, methodGen);

        nextNode.setTarget(il.append(methodGen.loadIterator()));
        il.append(methodGen.nextNode());
        il.append(DUP);
        il.append(methodGen.storeCurrentNode());
        il.append(new IFGT(loop));

        // Restore current DOM (if result tree was used instead for this loop)
        if ((_type != null) && (_type instanceof ResultTreeType)) {
            il.append(methodGen.storeDOM());
        }

        // Restore current node and current iterator from the stack
        il.append(methodGen.storeIterator());
        il.append(methodGen.storeCurrentNode());
    }

    
The code that is generated by nested for-each loops can appear to some
JVMs as if it is accessing un-initialized variables. We must add some
code that pushes the default variable value on the stack and pops it
into the variable slot. This is done by the Variable.initialize()
method. The code that we compile for this loop looks like this:
          initialize iterator
          initialize variables <-- HERE!!!
          goto   Iterate
 Loop:    :
          : (code for  contents)
          :
 Iterate: node = iterator.next();
          if (node != END) goto Loop
/**
     * The code that is generated by nested for-each loops can appear to some
     * JVMs as if it is accessing un-initialized variables. We must add some
     * code that pushes the default variable value on the stack and pops it
     * into the variable slot. This is done by the Variable.initialize()
     * method. The code that we compile for this loop looks like this:
     *
     *           initialize iterator
     *           initialize variables <-- HERE!!!
     *           goto   Iterate
     *  Loop:    :
     *           : (code for <xsl:for-each> contents)
     *           :
     *  Iterate: node = iterator.next();
     *           if (node != END) goto Loop
     */
    public void initializeVariables(ClassGenerator classGen,
                                   MethodGenerator methodGen) {
        final int n = elementCount();
        for (int i = 0; i < n; i++) {
            final Object child = getContents().get(i);
            if (child instanceof Variable) {
                Variable var = (Variable)child;
                var.initialize(classGen, methodGen);
            }
        }
    }

}