/*
 * 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: VariableBase.java,v 1.5 2005/09/28 13:48:18 pvedula Exp $
 */

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

import java.util.Vector;

import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.Instruction;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.bcel.internal.generic.INVOKESPECIAL;
import com.sun.org.apache.bcel.internal.generic.LocalVariableGen;
import com.sun.org.apache.bcel.internal.generic.NEW;
import com.sun.org.apache.bcel.internal.generic.PUSH;
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.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Util;
import com.sun.org.apache.xml.internal.utils.XML11Char;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 * @author Morten Jorgensen
 * @author Erwin Bolwidt <ejb@klomp.org>
 * @author John Howard <JohnH@schemasoft.com>
 */
class VariableBase extends TopLevelElement {

    protected QName       _name;            // The name of the variable.
    protected String      _escapedName;        // The escaped qname of the variable.
    protected Type        _type;            // The type of this variable.
    protected boolean     _isLocal;         // True if the variable is local.
    protected LocalVariableGen _local;      // Reference to JVM variable
    protected Instruction _loadInstruction; // Instruction to load JVM variable
    protected Instruction _storeInstruction; // Instruction to load JVM variable
    protected Expression  _select;          // Reference to variable expression
    protected String      select;           // Textual repr. of variable expr.

    // References to this variable (when local)
    protected Vector      _refs = new Vector(2);

    // Dependencies to other variables/parameters (for globals only)
    protected Vector      _dependencies = null;

    // Used to make sure parameter field is not added twice
    protected boolean    _ignore = false;

    /**
     * Disable this variable/parameter
     */
    public void disable() {
        _ignore = true;
    }

    /**
     * Add a reference to this variable. Called by VariableRef when an
     * expression contains a reference to this variable.
     */
    public void addReference(VariableRefBase vref) {
        _refs.addElement(vref);
    }

    /**
     * Remove a reference to this variable. Called by VariableRef when this
     * variable goes out of scope.
     */
    public void removeReference(VariableRefBase vref) {
        _refs.remove(vref);
    }

    /**
     * When a variable is overriden by another, e.g. via xsl:import,
     * its references need to be copied or otherwise it may be
     * compiled away as dead code. This method can be used for that
     * purpose.
     */
    public void copyReferences(VariableBase var) {
        final int size = _refs.size();
        for (int i = 0; i < size; i++) {
            var.addReference((VariableRefBase) _refs.get(i));
        }
    }

    /**
     * Map this variable to a register
     */
    public void mapRegister(MethodGenerator methodGen) {
        if (_local == null) {
            final InstructionList il = methodGen.getInstructionList();
            final String name = getEscapedName(); // TODO: namespace ?
            final com.sun.org.apache.bcel.internal.generic.Type varType = _type.toJCType();
            _local = methodGen.addLocalVariable2(name, varType, il.getEnd());
        }
    }

    /**
     * Remove the mapping of this variable to a register.
     * Called when we leave the AST scope of the variable's declaration
     */
    public void unmapRegister(MethodGenerator methodGen) {
        if (_refs.isEmpty() && (_local != null)) {
            _local.setEnd(methodGen.getInstructionList().getEnd());
            methodGen.removeLocalVariable(_local);
            _refs = null;
            _local = null;
        }
    }

    /**
     * Returns an instruction for loading the value of this variable onto
     * the JVM stack.
     */
    public Instruction loadInstruction() {
        final Instruction instr = _loadInstruction;
        if (_loadInstruction == null) {
            _loadInstruction = _type.LOAD(_local.getIndex());
        }
        return _loadInstruction;
    }

    /**
     * Returns an instruction for storing a value from the JVM stack
     * into this variable.
     */
    public Instruction storeInstruction() {
        final Instruction instr = _storeInstruction;
        if (_storeInstruction == null) {
            _storeInstruction = _type.STORE(_local.getIndex());
        }
        return _storeInstruction;
    }

    /**
     * Returns the expression from this variable's select attribute (if any)
     */
    public Expression getExpression() {
        return(_select);
    }

    /**
     * Display variable as single string
     */
    public String toString() {
        return("variable("+_name+")");
    }

    /**
     * Display variable in a full AST dump
     */
    public void display(int indent) {
        indent(indent);
        System.out.println("Variable " + _name);
        if (_select != null) {
            indent(indent + IndentIncrement);
            System.out.println("select " + _select.toString());
        }
        displayContents(indent + IndentIncrement);
    }

    /**
     * Returns the type of the variable
     */
    public Type getType() {
        return _type;
    }

    /**
     * Returns the name of the variable or parameter as it will occur in the
     * compiled translet.
     */
    public QName getName() {
        return _name;
    }

    /**
     * Returns the escaped qname of the variable or parameter
     */
    public String getEscapedName() {
        return _escapedName;
    }

    /**
     * Set the name of the variable or paremeter. Escape all special chars.
     */
    public void setName(QName name) {
        _name = name;
        _escapedName = Util.escape(name.getStringRep());
    }

    /**
     * Returns the true if the variable is local
     */
    public boolean isLocal() {
        return _isLocal;
    }

    /**
     * Parse the contents of the <xsl:decimal-format> element.
     */
    public void parseContents(Parser parser) {
        // Get the 'name attribute
        String name = getAttribute("name");

        if (name.length() > 0) {
            if (!XML11Char.isXML11ValidQName(name)) {
                ErrorMsg err = new ErrorMsg(ErrorMsg.INVALID_QNAME_ERR, name, this);
                parser.reportError(Constants.ERROR, err);
            }
            setName(parser.getQNameIgnoreDefaultNs(name));
        }
        else
            reportError(this, parser, ErrorMsg.REQUIRED_ATTR_ERR, "name");

        // Check whether variable/param of the same name is already in scope
        VariableBase other = parser.lookupVariable(_name);
        if ((other != null) && (other.getParent() == getParent())) {
            reportError(this, parser, ErrorMsg.VARIABLE_REDEF_ERR, name);
        }

        select = getAttribute("select");
        if (select.length() > 0) {
            _select = getParser().parseExpression(this, "select", null);
            if (_select.isDummy()) {
                reportError(this, parser, ErrorMsg.REQUIRED_ATTR_ERR, "select");
                return;
            }
        }

        // Children must be parsed first -> static scoping
        parseChildren(parser);
    }

    /**
     * Compile the value of the variable, which is either in an expression in
     * a 'select' attribute, or in the variable elements body
     */
    public void translateValue(ClassGenerator classGen,
                               MethodGenerator methodGen) {
        // Compile expression is 'select' attribute if present
        if (_select != null) {
            _select.translate(classGen, methodGen);
            // Create a CachedNodeListIterator for select expressions
            // in a variable or parameter.
            if (_select.getType() instanceof NodeSetType) {
                final ConstantPoolGen cpg = classGen.getConstantPool();
                final InstructionList il = methodGen.getInstructionList();

                final int initCNI = cpg.addMethodref(CACHED_NODE_LIST_ITERATOR_CLASS,
                                            "<init>",
                                            "("
                                            +NODE_ITERATOR_SIG
                                            +")V");
                il.append(new NEW(cpg.addClass(CACHED_NODE_LIST_ITERATOR_CLASS)));
                il.append(DUP_X1);
                il.append(SWAP);

                il.append(new INVOKESPECIAL(initCNI));
            }
            _select.startIterator(classGen, methodGen);
        }
        // If not, compile result tree from parameter body if present.
        else if (hasContents()) {
            compileResultTree(classGen, methodGen);
        }
        // If neither are present then store empty string in variable
        else {
            final ConstantPoolGen cpg = classGen.getConstantPool();
            final InstructionList il = methodGen.getInstructionList();
            il.append(new PUSH(cpg, Constants.EMPTYSTRING));
        }
    }

}
