/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2016 Open Source Geospatial Foundation (OSGeo)
 *    (C) 2014-2016 Boundless Spatial
 *    
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License as published by the Free Software Foundation;
 *    version 2.1 of the License.
 *
 *    This library is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    Lesser General Public License for more details.
 */
package org.geotools.ysld.validate;

import java.util.ArrayList;
import java.util.List;

import org.yaml.snakeyaml.events.AliasEvent;
import org.yaml.snakeyaml.events.ScalarEvent;
import org.yaml.snakeyaml.events.SequenceEndEvent;
import org.yaml.snakeyaml.events.SequenceStartEvent;

/**
 * Validator for Tuples
 * <p>
 * This Validator is stateful, reset it before re-using it.
 * 
 * @author Kevin Smith, Boundless
 *
 */
public class TupleValidator extends StatefulValidator {

    enum State {
        NEW, STARTED, DONE
    }

    State state = State.NEW;

    int valuesValidated = 0;

    List<ScalarValidator> subValidators;

    public TupleValidator(List<? extends ScalarValidator> subValidators) {
        super();
        this.subValidators = new ArrayList<>(subValidators);
    }

    @Override
    public void sequence(SequenceStartEvent evt, YsldValidateContext context) {
        if (state == State.NEW) {
            state = State.STARTED;
        } else {
            context.error("Unexpected Start of Sequence", evt.getStartMark());
        }
    }

    @Override
    public void endSequence(SequenceEndEvent evt, YsldValidateContext context) {
        if (state != State.STARTED) {
            context.error("Unexpected End of Sequence", evt.getStartMark());
        } else if (valuesValidated != getSubValidators().size()) {
            context.error(String.format("Expected tuple of size %d but was %d",
                    getSubValidators().size(), valuesValidated), evt.getStartMark());
        }
        state = State.DONE;
        context.pop();
    }

    protected List<ScalarValidator> getSubValidators() {
        return subValidators;
    }

    @Override
    public void scalar(ScalarEvent evt, YsldValidateContext context) {
        String val = evt.getValue();
        switch (state) {
        case STARTED:
            try {
                context.push(getSubValidators().get(valuesValidated));

                context.peek().scalar(evt, context);
            } catch (IndexOutOfBoundsException ex) {
                // Do nothing, this will be detected when valuesValidated is too large.
            }
            valuesValidated++;
            break;
        default:
            context.error(String.format("Unexpected scalar '%s'", val), evt.getStartMark());
            break;
        }
    }

    public TupleValidator clone() {
        return new TupleValidator(this.subValidators);
    }

    @Override
    void reset() {
        if (state == State.NEW || state == State.DONE) {
            state = State.NEW;
            valuesValidated = 0; 
        } else {
            throw new IllegalStateException(
                    "TupleValidator.reset() called in invalid state: " + state.toString());
        }

    }

    @Override
    public void alias(AliasEvent evt, YsldValidateContext context) {
        switch (state) {
        case NEW:
            // Can't validate this so just move on.
            state = State.DONE;
            context.pop();
            break;
        case STARTED:
            // Can't validate this so just move on.
            valuesValidated++;
            break;
        default:
            context.error(String.format("Unexpected alias '%s'", evt.getAnchor()),
                    evt.getStartMark());
            break;
        }
    }

}