/*
 *    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 org.yaml.snakeyaml.events.AliasEvent;
import org.yaml.snakeyaml.events.Event;
import org.yaml.snakeyaml.events.MappingEndEvent;
import org.yaml.snakeyaml.events.MappingStartEvent;
import org.yaml.snakeyaml.events.ScalarEvent;
import org.yaml.snakeyaml.events.SequenceEndEvent;
import org.yaml.snakeyaml.events.SequenceStartEvent;

/**
 * Validator which accepts a YAML subtree and then removes itself from the stack.
 *
 * This Validator is stateful, do not re-use it.
 */
public class PermissiveValidator extends StatefulValidator {

    enum State {
        NEW, STARTED, DONE
    }

    int depth = 0;

    State state = State.NEW;

    private void start(Event evt, YsldValidateContext context) {
        if (state == State.NEW) {
            state = State.STARTED;
        }
        depth++;
    }

    private void end(Event evt, YsldValidateContext context) {
        if (state == State.STARTED) {
            depth--;
            if (depth == 0) {
                state = State.DONE;
                context.pop();
            }
        } else {
            context.error(
                    "Unexpected End of "
                            + ((evt instanceof MappingEndEvent) ? "Mapping" : "Sequence"),
                    evt.getStartMark());
        }
    }

    @Override
    public void mapping(MappingStartEvent evt, YsldValidateContext context) {
        start(evt, context);
    }

    @Override
    public void scalar(ScalarEvent evt, YsldValidateContext context) {
        if (state == State.NEW) {
            context.pop();
            state = State.DONE;
        }
    }

    @Override
    public void sequence(SequenceStartEvent evt, YsldValidateContext context) {
        start(evt, context);
    }

    @Override
    public void endMapping(MappingEndEvent evt, YsldValidateContext context) {
        end(evt, context);
    }

    @Override
    public void endSequence(SequenceEndEvent evt, YsldValidateContext context) {
        end(evt, context);
    }

    @Override
    void reset() {
        state = State.NEW;
        depth = 0;
    }

    @Override
    public void alias(AliasEvent evt, YsldValidateContext context) {
        switch (state) {
        case NEW:
            state = State.DONE;
            context.pop();
            break;
        case STARTED:
            break;
        default:
            context.error(String.format("Unexpected alias '%s'", evt.getAnchor()),
                    evt.getStartMark());
            break;
        }
    }
}