AttemptElement.java

/* 
 * 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 org.esigate.extension.parallelesi;

import java.io.IOException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

import org.esigate.parser.future.FutureElementType;
import org.esigate.parser.future.FutureParserContext;
import org.esigate.parser.future.StringBuilderFutureAppendable;

/**
 * Implementation of the <esi:attempt/> tag. This tag must be enclosed by a <esi:try/>
 * 
 * <p>
 * This is the implementation for the FutureParser. This tag depends on the behavior of its children : the tag behavior
 * is deferred until all previous tags (including children) have been applied.
 * 
 */
class AttemptElement extends BaseElement {

    public static final FutureElementType TYPE = new BaseElementType("<esi:attempt", "</esi:attempt") {
        @Override
        public AttemptElement newInstance() {
            return new AttemptElement();
        }
    };

    private static final class AttemptTask implements Future<CharSequence> {
        private TryElement parent;
        private Future<CharSequence> buffer;

        private AttemptTask(TryElement parent, Future<CharSequence> buf) {
            this.parent = parent;
            this.buffer = buf;
        }

        @Override
        public boolean cancel(boolean mayInterruptIfRunning) {
            return false;
        }

        @Override
        public boolean isCancelled() {
            return false;
        }

        @Override
        public boolean isDone() {
            return true;
        }

        @Override
        public CharSequence get() throws InterruptedException, ExecutionException {
            // Requires completion of all Future objects inside this tag, in
            // order to trigger any error.
            CharSequence content = this.buffer.get();

            // If creating content was successful, return it.
            if (this.parent != null && !this.parent.hasErrors()) {
                return content;
            }

            // If there was an error, discard content.
            return "";
        }

        @Override
        public CharSequence get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException {
            return get();
        }
    }

    private StringBuilderFutureAppendable buf = new StringBuilderFutureAppendable();

    AttemptElement() {
    }

    @Override
    public void characters(Future<CharSequence> csq) {
        this.buf.enqueueAppend(csq);
    }

    @Override
    public void onTagEnd(String tag, FutureParserContext ctx) throws IOException {
        TryElement parent = ctx.findAncestor(TryElement.class);
        if (parent != null) {
            parent.setWrite(true);
            ctx.getCurrent().characters(new AttemptTask(ctx.findAncestor(TryElement.class), this.buf));
            parent.setWrite(false);
        }
    }
}