/*
 * (c) Copyright 2009-2011 by Volker Bergmann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, is permitted under the terms of the
 * GNU General Public License.
 *
 * For redistributing this software or a derivative work under a license other
 * than the GPL-compatible Free Software License as defined by the Free
 * Software Foundation or approved by OSI, you must first obtain a commercial
 * license to this software product from Volker Bergmann.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * WITHOUT A WARRANTY OF ANY KIND. ALL EXPRESS OR IMPLIED CONDITIONS,
 * REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE
 * HEREBY EXCLUDED. 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, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

package org.databene.benerator.sample;

import java.util.HashMap;
import java.util.Map;

import org.databene.benerator.Generator;
import org.databene.benerator.GeneratorContext;
import org.databene.benerator.IllegalGeneratorStateException;
import org.databene.benerator.InvalidGeneratorSetupException;
import org.databene.benerator.util.UnsafeNonNullGenerator;
import org.databene.benerator.wrapper.ProductWrapper;
import org.databene.commons.ConfigurationError;
import org.databene.commons.ParseException;
import org.databene.commons.StringUtil;
import org.databene.script.DatabeneScriptParser;
import org.databene.script.WeightedTransition;

/**
 * Generates states as configured by a state machine.<br/>
 * <br/>
 * Created at 17.07.2009 05:41:47
 * @since 0.6.0
 * @author Volker Bergmann
 */

public class StateGenerator<E> extends UnsafeNonNullGenerator<E> {
	
	private Class<E> generatedType;
	private Map<E, AttachedWeightSampleGenerator<E>> transitionsGenerators;
	private E nextState;
	
	// initialization --------------------------------------------------------------------------------------------------

    public StateGenerator() {
	    this((String) null);
    }
    
    @SuppressWarnings("unchecked")
    public StateGenerator(String transitionSpec) {
	    this((Class<E>) Object.class);
	    setTransitions(transitionSpec);
    }
    
    public StateGenerator(Class<E> generatedType) {
	    this.generatedType = generatedType;
	    this.transitionsGenerators = new HashMap<E, AttachedWeightSampleGenerator<E>>();
	    this.nextState = null;
    }
    
    @SuppressWarnings("unchecked")
    public void setTransitions(String transitionSpec) {
		if (StringUtil.isEmpty(transitionSpec)) {
			transitionsGenerators.clear();
			return;
		}
    	try {
    		WeightedTransition[] ts = DatabeneScriptParser.parseTransitionList(transitionSpec);
	    	for (WeightedTransition t : ts)
	    		addTransition((E) t.getFrom(), (E) t.getTo(), t.getWeight());
    	} catch (ParseException e) {
    		throw new ConfigurationError("Error parsing state machine specification: " + transitionSpec, e);
        }
    }

    public void addTransition(E from, E to, double weight) {
    	AttachedWeightSampleGenerator<E> subGenerator = transitionsGenerators.get(from);
    	if (subGenerator == null) {
    		subGenerator = new AttachedWeightSampleGenerator<E>(generatedType);
    		transitionsGenerators.put(from, subGenerator);
    	}
    	subGenerator.addSample(to, weight);
    }
    
    // Generator interface implementation ------------------------------------------------------------------------------

    public Class<E> getGeneratedType() {
	    return generatedType;
    }
    
    @Override
    public void init(GeneratorContext context) throws InvalidGeneratorSetupException {
    	assertNotInitialized();
        boolean hasEndTransition = false;
        for (AttachedWeightSampleGenerator<E> tmp : transitionsGenerators.values())
        	if (tmp.containsSample(null)) {
        		hasEndTransition = true;
        		break;
        	}
        if (!hasEndTransition)
        	throw new InvalidGeneratorSetupException("No final state defined for " + this);
    	for (Generator<E> tmp : transitionsGenerators.values())
    		tmp.init(context);
    	AttachedWeightSampleGenerator<E> gen = this.transitionsGenerators.get(null);
        nextState = gen.generate(getResultWrapper()).unwrap();
        super.init(context);
    }
	
	@Override
	public E generate() {
    	if (nextState == null)
    		return null;
    	E result = nextState;
    	AttachedWeightSampleGenerator<E> transitionGenerator = transitionsGenerators.get(nextState);
	    ProductWrapper<E> wrapper = transitionGenerator.generate(getResultWrapper());
		nextState = (wrapper != null ? wrapper.unwrap() : null);
		return result;
    }

    @Override
    public void reset() throws IllegalGeneratorStateException {
    	AttachedWeightSampleGenerator<E> transitionGenerator = this.transitionsGenerators.get(null);
	    ProductWrapper<E> wrapper = transitionGenerator.generate(getResultWrapper());
		nextState = (wrapper != null ? wrapper.unwrap() : null);
        super.reset();
    }
    
    @Override
    public void close() {
    	super.close();
    }
    
    // java.lang.Object overrides --------------------------------------------------------------------------------------
    
    @Override
    public String toString() {
        return getClass().getSimpleName() + transitionsGenerators;
    }

}