com.github.parboiled1.grappa.run.EventBasedParseRunner Maven / Gradle / Ivy

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/*
 * Copyright (C) 2015 Francis Galiegue 
 *
 * Licensed 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 com.github.parboiled1.grappa.run;

import com.github.parboiled1.grappa.buffers.InputBuffer;
import com.github.parboiled1.grappa.internal.NonFinalForTesting;
import com.github.parboiled1.grappa.matchers.base.Matcher;
import com.google.common.base.Preconditions;
import com.google.common.eventbus.EventBus;
import org.parboiled.MatchHandler;
import org.parboiled.MatcherContext;
import org.parboiled.Rule;
import org.parboiled.support.ParsingResult;

import javax.annotation.ParametersAreNonnullByDefault;

/**
 * The most basic of all {@link ParseRunner} implementations. It runs a rule
 * against a given input text and builds a corresponding {@link ParsingResult}
 * instance. However, it does not report any parse errors nor recover from them.
 * Instead it simply marks the ParsingResult as "unmatched" if the input is not
 * valid with regard to the rule grammar.It never causes the parser to perform
 * more than one parsing run and is the fastest way to determine whether a given
 * input conforms to the rule grammar.
 */
@SuppressWarnings("DesignForExtension")
@ParametersAreNonnullByDefault
@NonFinalForTesting
public class EventBasedParseRunner
    extends AbstractParseRunner
    implements MatchHandler
{
    private final EventBus bus = new EventBus();
    /**
     * Creates a new BasicParseRunner instance for the given rule.
     *
     * @param rule the parser rule
     */
    public EventBasedParseRunner(final Rule rule)
    {
        super(rule);
    }

    public final void registerListener(final ParseRunnerListener listener)
    {
        bus.register(listener);
    }

    @Override
    public ParsingResult run(final InputBuffer inputBuffer)
    {
        Preconditions.checkNotNull(inputBuffer, "inputBuffer");
        resetValueStack();

        final MatcherContext rootContext
            = createRootContext(inputBuffer, this);
        bus.post(new PreParseEvent<>(rootContext));
        final boolean matched = rootContext.runMatcher();
        final ParsingResult result
            = createParsingResult(matched, rootContext);
        bus.post(new PostParseEvent<>(result));
        return result;
    }

    @Override
    public  boolean match(final MatcherContext context)
    {
        final Matcher matcher = context.getMatcher();

        final PreMatchEvent preMatchEvent = new PreMatchEvent<>(context);
        bus.post(preMatchEvent);

        // FIXME: is there any case at all where context.getMatcher() is null?
        @SuppressWarnings("ConstantConditions")
        final boolean match = matcher.match(context);

        final MatchContextEvent postMatchEvent = match
            ? new MatchSuccessEvent<>(context)
            : new MatchFailureEvent<>(context);
        bus.post(postMatchEvent);

        return match;
    }
}