/*
 * 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.
 */

package org.apache.xerces.impl.dtd.models;

import org.apache.xerces.impl.dtd.XMLContentSpec;
import org.apache.xerces.xni.QName;

SimpleContentModel is a derivative of the abstract content model base
class that handles a small set of simple content models that are just
way overkill to give the DFA treatment.

This class handles the following scenarios:

 a
 a?
 a*
 a+
 a,b
 a|b


These all involve a unary operation with one element type, or a binary
operation with two elements. These are very simple and can be checked
in a simple way without a DFA and without the overhead of setting up a
DFA for such a simple check.
@xerces.internal
Version:
$Id: SimpleContentModel.java 699892 2008-09-28 21:08:27Z mrglavas $/**
 * SimpleContentModel is a derivative of the abstract content model base
 * class that handles a small set of simple content models that are just
 * way overkill to give the DFA treatment.
 * <p>
 * This class handles the following scenarios:
 * <ul>
 * <li> a
 * <li> a?
 * <li> a*
 * <li> a+
 * <li> a,b
 * <li> a|b
 * </ul>
 * <p>
 * These all involve a unary operation with one element type, or a binary
 * operation with two elements. These are very simple and can be checked
 * in a simple way without a DFA and without the overhead of setting up a
 * DFA for such a simple check.
 * 
 * @xerces.internal

 * 
 * @version $Id: SimpleContentModel.java 699892 2008-09-28 21:08:27Z mrglavas $
 */
public class SimpleContentModel
    implements ContentModelValidator {

    //
    // Constants
    //

    
CHOICE /** CHOICE */
    public static final short CHOICE = -1;

    
SEQUENCE /** SEQUENCE */
    public static final short SEQUENCE = -1;

    //
    // Data
    //


    
The element decl pool indices of the first (and optional second)
child node. The operation code tells us whether the second child
is used or not.
/**
     * The element decl pool indices of the first (and optional second)
     * child node. The operation code tells us whether the second child
     * is used or not.
     */
    private final QName fFirstChild = new QName();

    
The element decl pool indices of the first (and optional second)
child node. The operation code tells us whether the second child
is used or not.
/**
     * The element decl pool indices of the first (and optional second)
     * child node. The operation code tells us whether the second child
     * is used or not.
     */
    private final QName fSecondChild = new QName();

    
The operation that this object represents. Since this class only
does simple contents, there is only ever a single operation
involved (i.e. the children of the operation are always one or
two leafs.) This is one of the XMLDTDParams.CONTENTSPECNODE_XXX values.
/**
     * The operation that this object represents. Since this class only
     * does simple contents, there is only ever a single operation
     * involved (i.e. the children of the operation are always one or
     * two leafs.) This is one of the XMLDTDParams.CONTENTSPECNODE_XXX values.
     */
    private final int fOperator;

    /* this is the EquivClassComparator object */
    //private EquivClassComparator comparator = null;
    

    //
    // Constructors
    //

    
Constructs a simple content model.
Params:
operator – The content model operator.
firstChild – qualified name of the first child
secondChild – qualified name of the second child/**
     * Constructs a simple content model.
     *
     * @param operator The content model operator.
     * @param firstChild qualified name of the first child
     * @param secondChild qualified name of the second child
     *
     */
    public SimpleContentModel(short operator, QName firstChild, QName secondChild) {
        //
        //  Store away the children and operation. This is all we need to
        //  do the content model check.
        //
        //  The operation is one of the ContentSpecNode.NODE_XXX values!
        //
        fFirstChild.setValues(firstChild);
        if (secondChild != null) {
            fSecondChild.setValues(secondChild);
        }
        else {
            fSecondChild.clear();
        }
        fOperator = operator;
    }

    //
    // ContentModelValidator methods
    //

    
Check that the specified content is valid according to this
content model. This method can also be called to do 'what if' 
testing of content models just to see if they would be valid.

A value of -1 in the children array indicates a PCDATA node. All other 
indexes will be positive and represent child elements. The count can be
zero, since some elements have the EMPTY content model and that must be 
confirmed.
Params:
children – The children of this element.  Each integer is an index within
                the StringPool of the child element name.  An index
                of -1 is used to indicate an occurrence of non-whitespace character
                data.
offset – Offset into the array where the children starts.
length – The number of entries in the children array.
Returns:
The value -1 if fully valid, else the 0 based index of the child
        that first failed. If the value returned is equal to the number
        of children, then the specified children are valid but additional
        content is required to reach a valid ending state./**
     * Check that the specified content is valid according to this
     * content model. This method can also be called to do 'what if' 
     * testing of content models just to see if they would be valid.
     * <p>
     * A value of -1 in the children array indicates a PCDATA node. All other 
     * indexes will be positive and represent child elements. The count can be
     * zero, since some elements have the EMPTY content model and that must be 
     * confirmed.
     *
     * @param children The children of this element.  Each integer is an index within
     *                 the <code>StringPool</code> of the child element name.  An index
     *                 of -1 is used to indicate an occurrence of non-whitespace character
     *                 data.
     * @param offset Offset into the array where the children starts.
     * @param length The number of entries in the <code>children</code> array.
     *
     * @return The value -1 if fully valid, else the 0 based index of the child
     *         that first failed. If the value returned is equal to the number
     *         of children, then the specified children are valid but additional
     *         content is required to reach a valid ending state.
     *
     */
    public int validate(QName[] children, int offset, int length) {

        //
        //  According to the type of operation, we do the correct type of
        //  content check.
        //
        switch(fOperator)
        {
            case XMLContentSpec.CONTENTSPECNODE_LEAF :
                // If there is not a child, then report an error at index 0
                if (length == 0)
                    return 0;

                // If the 0th child is not the right kind, report an error at 0
                if (children[offset].rawname != fFirstChild.rawname) {
                    return 0;
                }

                // If more than one child, report an error at index 1
                if (length > 1)
                    return 1;
                break;

            case XMLContentSpec.CONTENTSPECNODE_ZERO_OR_ONE :
                //
                //  If there is one child, make sure its the right type. If not,
                //  then its an error at index 0.
                //
                if (length == 1) {
                    if (children[offset].rawname != fFirstChild.rawname) {
                        return 0;
                    }
                }

                //
                //  If the child count is greater than one, then obviously
                //  bad, so report an error at index 1.
                //
                if (length > 1)
                    return 1;
                break;

            case XMLContentSpec.CONTENTSPECNODE_ZERO_OR_MORE :
                //
                //  If the child count is zero, that's fine. If its more than
                //  zero, then make sure that all children are of the element
                //  type that we stored. If not, report the index of the first
                //  failed one.
                //
                if (length > 0)
                {
                    for (int index = 0; index < length; index++) {
                        if (children[offset + index].rawname != fFirstChild.rawname) {
                            return index;
                        }
                    }
                }
                break;

            case XMLContentSpec.CONTENTSPECNODE_ONE_OR_MORE :
                //
                //  If the child count is zero, that's an error so report
                //  an error at index 0.
                //
                if (length == 0)
                    return 0;

                //
                //  Otherwise we have to check them all to make sure that they
                //  are of the correct child type. If not, then report the index
                //  of the first one that is not.
                //
                for (int index = 0; index < length; index++) {
                    if (children[offset + index].rawname != fFirstChild.rawname) {
                        return index;
                    }
                }
                break;

            case XMLContentSpec.CONTENTSPECNODE_CHOICE :
                //
                //  There must be one and only one child, so if the element count
                //  is zero, return an error at index 0.
                //
                if (length == 0)
                    return 0;

                // If the zeroth element isn't one of our choices, error at 0
                if ((children[offset].rawname != fFirstChild.rawname) &&
                    (children[offset].rawname != fSecondChild.rawname)) {
                    return 0;
                }

                // If there is more than one element, then an error at 1
                if (length > 1)
                    return 1;
                break;

            case XMLContentSpec.CONTENTSPECNODE_SEQ :
                //
                //  There must be two children and they must be the two values
                //  we stored, in the stored order.
                //
                if (length == 2) {
                    if (children[offset].rawname != fFirstChild.rawname) {
                        return 0;
                    }
                    if (children[offset + 1].rawname != fSecondChild.rawname) {
                        return 1;
                    }
                }
                else {
                    if (length > 2) {
                        return 2;
                    }

                    return length;
                }

                break;

            default :
                throw new RuntimeException("ImplementationMessages.VAL_CST");
        }

        // We survived, so return success status
        return -1;
    } // validate

} // class SimpleContentModel