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/*
 * Copyright (c) 2001-2013 Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
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 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 */

package com.sun.msv.reader.trex;

import com.sun.msv.grammar.Expression;
import com.sun.msv.grammar.ReferenceExp;
import com.sun.msv.reader.ExpressionOwner;
import com.sun.msv.reader.GrammarReader;
import com.sun.msv.reader.SimpleState;
import com.sun.msv.reader.State;
import com.sun.msv.util.StartTagInfo;

/**
 * parses <define> declaration.
 * 
 * @author Kohsuke KAWAGUCHI
 */
public abstract class DefineState extends SimpleState implements ExpressionOwner {

    /**
     * expression object that is being created.
     * See {@link #castPattern} and {@link #annealPattern} methods
     * for how will a pattern be created.
     */
    protected Expression exp = null; // or Expression.epsilon if  is allowed.
    
    /**
     * Container to which the expression will be assigned.
     */
    private ReferenceExp ref;
    
    /**
     * Obtains a {@link ReferenceExp} that represents the target
     * pattern block.
     * 
     * @return null
     *      If there was an error in the input, this method may
     *      return null.
     */
    public final ReferenceExp getRef() {
        return ref;
    }
    /** receives a Pattern object that is contained in this element. */
    public final void onEndChild( Expression child ) {
        if( exp==null ) { // first one.
            exp = child;
        } else {
            exp = reader.pool.createSequence(exp,child);
        }
    }
    
    protected void startSelf() {
        super.startSelf();
        ref = getReference();
    }

    
    protected void endSelf() {
        if( exp==null ) {
            reader.reportError( GrammarReader.ERR_MISSING_CHILD_EXPRESSION );
            exp = Expression.nullSet;
            // recover by assuming some pattern.
        }

        if(ref==null)    return;    // error. abort.
        
        final TREXBaseReader reader = (TREXBaseReader)this.reader;
        final String combine = startTag.getCollapsedAttribute("combine");
        
        exp = callInterceptExpression(exp);
        
        // combine two patterns
        Expression newexp = doCombine( ref, exp, combine );
        if( newexp==null )
            reader.reportError( TREXBaseReader.ERR_BAD_COMBINE, combine );
            // recover by ignoring this definition
        else
            ref.exp = newexp;
    
        reader.setDeclaredLocationOf(ref);

        ((ExpressionOwner)parentState).onEndChild(ref);
    }

    
    protected State createChildState( StartTagInfo tag ) {
        return reader.createExpressionChildState(this,tag);
    }

    /**
     * 
     * @return null in case of error.
     */
    protected ReferenceExp getReference() {
        final String name = startTag.getCollapsedAttribute("name");
        
        if(name==null) {
            // name attribute is required.
            reader.reportError( TREXBaseReader.ERR_MISSING_ATTRIBUTE,
                "ref","name");
            return null;
        }
        
        final TREXBaseReader reader = (TREXBaseReader)this.reader;
        return reader.grammar.namedPatterns.getOrCreate(name);
    }
    
    
    /**
     * combines two expressions into one as specified by the combine parameter,
     * and returns a new expression.
     * 
     * If the combine parameter is invalid, then return null.
     */
    protected abstract Expression doCombine( ReferenceExp baseExp, Expression newExp, String combine );
}