PartialSegment.java

/*
 * Copyright 2013 Martin Kouba
 *
 * 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.trimou.engine.segment;

import java.util.List;
import java.util.concurrent.atomic.AtomicReference;

import org.trimou.annotations.Internal;
import org.trimou.engine.MustacheTagType;
import org.trimou.engine.context.ExecutionContext;
import org.trimou.engine.parser.Template;
import org.trimou.exception.MustacheException;
import org.trimou.exception.MustacheProblem;

/**
 * Partial segment.
 *
 * @author Martin Kouba
 */
@Internal
public class PartialSegment extends AbstractSegment {

    private final TextSegment indentation;

    /**
     * Cache the partial template if possible, i.e. if the cache is enabled, no
     * expiration timeout is set and debug mode is not enabled
     */
    private final AtomicReference<Template> cachedPartialTemplate;

    private volatile List<List<Segment>> cachedPartialLines;

    /**
     *
     * @param text
     * @param origin
     * @param indentation
     */
    public PartialSegment(String text, Origin origin, String indentation) {
        super(text, origin);
        this.indentation = indentation != null ? new TextSegment(indentation,
                new Origin(origin.getTemplate())) : null;
        this.cachedPartialTemplate = Segments
                .isTemplateCachingAllowed(getEngineConfiguration()) ? new AtomicReference<>()
                : null;
    }

    @Override
    public SegmentType getType() {
        return SegmentType.PARTIAL;
    }

    @Override
    public Appendable execute(Appendable appendable, ExecutionContext context) {

        Template partialTemplate = Segments.getTemplate(cachedPartialTemplate,
                getText(), getEngine(), getTemplate());

        if (partialTemplate == null) {
            throw new MustacheException(
                    MustacheProblem.RENDER_INVALID_PARTIAL_KEY,
                    "No partial found for the given key: %s %s", getText(),
                    getOrigin());
        }

        if (indentation == null) {
            appendable = partialTemplate.getRootSegment().execute(appendable, context);
        } else {
            prependIndentation(appendable, context.setTemplateInvocation(partialTemplate), partialTemplate);
        }
        return appendable;
    }

    @Override
    public String getLiteralBlock() {
        return getTagLiteral(MustacheTagType.PARTIAL.getCommand() + getText());
    }

    @Override
    protected String getSegmentName() {
        return getText();
    }

    private void prependIndentation(Appendable appendable,
            ExecutionContext context, Template partialTemplate) {

        List<List<Segment>> partialLines;

        if (cachedPartialTemplate != null) {
            partialLines = cachedPartialLines;
            if (partialLines == null) {
                synchronized (this) {
                    partialLines = cachedPartialLines;
                    if (partialLines == null) {
                        partialLines = getPartialLines(partialTemplate);
                        cachedPartialLines = partialLines;
                    }
                }
            }
        } else {
            partialLines = getPartialLines(partialTemplate);
        }

        for (List<Segment> line : partialLines) {
            for (Segment segment : line) {
                segment.execute(appendable, context);
            }
        }
    }

    private List<List<Segment>> getPartialLines(Template partialTemplate) {
        List<List<Segment>> partialLines = Segments
                .readSegmentLinesBeforeRendering(partialTemplate
                        .getRootSegment());
        for (List<Segment> line : partialLines) {
            line.add(0, indentation);
        }
        return partialLines;
    }

}