com.metreeca.mark.steps.LinkRewriterExtension Maven / Gradle / Ivy

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/*
 * Copyright © 2019-2020 Metreeca srl
 *
 * 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.metreeca.mark.steps;

import com.vladsch.flexmark.html.*;
import com.vladsch.flexmark.html.renderer.LinkResolverBasicContext;
import com.vladsch.flexmark.html.renderer.ResolvedLink;
import com.vladsch.flexmark.util.ast.Node;
import com.vladsch.flexmark.util.data.MutableDataHolder;

import java.util.Optional;
import java.util.Set;
import java.util.regex.Pattern;

final class LinkRewriterExtension implements HtmlRenderer.HtmlRendererExtension {

	public static LinkRewriterExtension create() {
		return new LinkRewriterExtension();
	}


	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

	private static final Pattern URLPattern=Pattern.compile("(?<=^|/)(index|([^/#]*))\\.md(#[^/#]*)?$");


	static String plain(final String url) {
		return url == null ? null : URLPattern.matcher(url).replaceAll("$1.html$3");
	}

	static String smart(final String url) {
		return url == null ? null : Optional.of(URLPattern.matcher(url).replaceAll("$2$3"))
				.filter(smart -> !smart.isEmpty())
				.orElse(".");
	}


	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

	@Override public void rendererOptions(final MutableDataHolder options) {}

	@Override public void extend(final HtmlRenderer.Builder htmlRendererBuilder, final String rendererType) {
		htmlRendererBuilder.linkResolverFactory(new LinkRewriterFactory());
	}


	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

	private static final class LinkRewriterFactory implements LinkResolverFactory {

		@Override public Set> getAfterDependents() { return null; }

		@Override public Set> getBeforeDependents() { return null; }

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

		@Override public LinkResolver apply(final LinkResolverBasicContext context) {
			return new LinkRewriter(context);
		}

	}

	private static final class LinkRewriter implements LinkResolver {

		private final boolean smart;
		private final boolean external;


		private LinkRewriter(final LinkResolverBasicContext context) {
			smart=Markdown.SmartLinks.get(context.getOptions());
			external=Markdown.ExternalLinks.get(context.getOptions());
		}


		@Override public ResolvedLink resolveLink(
				final Node node, final LinkResolverBasicContext context, final ResolvedLink link
		) {

			final String url=link.getUrl();
			final String target=link.getTarget();

			return link
					.withUrl(smart ? smart(url) : plain(url))
					.withTarget(external && url.startsWith("http") && target == null ? "_blank" : target);

		}

	}

}