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A minimalist Maven plugin for static site generation
There is a newer version: 0.9.1
/*
 * 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.metreeca.mark.Mark;

import com.vladsch.flexmark.ast.Heading;
import com.vladsch.flexmark.ext.admonition.AdmonitionExtension;
import com.vladsch.flexmark.ext.autolink.AutolinkExtension;
import com.vladsch.flexmark.ext.definition.DefinitionExtension;
import com.vladsch.flexmark.ext.tables.TablesExtension;
import com.vladsch.flexmark.ext.toc.TocExtension;
import com.vladsch.flexmark.ext.yaml.front.matter.AbstractYamlFrontMatterVisitor;
import com.vladsch.flexmark.ext.yaml.front.matter.YamlFrontMatterExtension;
import com.vladsch.flexmark.html.HtmlRenderer;
import com.vladsch.flexmark.parser.Parser;
import com.vladsch.flexmark.util.ast.*;
import com.vladsch.flexmark.util.data.DataKey;
import com.vladsch.flexmark.util.data.MutableDataSet;

import java.io.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.*;

import static java.nio.charset.StandardCharsets.UTF_8;
import static java.util.Arrays.asList;
import static java.util.stream.Collectors.toList;
import static java.util.stream.Collectors.toMap;


public final class Markdown {

	public static final DataKey SmartLinks=new DataKey<>("markdown-smart-links", false);
	public static final DataKey ExternalLinks=new DataKey<>("markdown-external-links", false);


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

	private final Parser.Builder parsers;
	private final HtmlRenderer.Builder renderers;


	public Markdown(final Mark mark) {

		if ( mark == null ) {
			throw new NullPointerException("null mark");
		}

		final MutableDataSet options=new MutableDataSet()

				.set(Parser.EXTENSIONS, asList(
						YamlFrontMatterExtension.create(),
						TocExtension.create(),
						TablesExtension.create(),
						DefinitionExtension.create(),
						AdmonitionExtension.create(),
						AutolinkExtension.create(),
						LinkRewriterExtension.create()
				))

				.set(HtmlRenderer.RENDER_HEADER_ID, true)
				.set(HtmlRenderer.GENERATE_HEADER_ID, true)
				.set(HtmlRenderer.HEADER_ID_GENERATOR_NO_DUPED_DASHES, true)
				.set(HtmlRenderer.HEADER_ID_GENERATOR_RESOLVE_DUPES, true)

				.set(SmartLinks, mark.get(SmartLinks.getName(), Boolean::parseBoolean))
				.set(ExternalLinks, mark.get(ExternalLinks.getName(), Boolean::parseBoolean));

		this.parsers=Parser.builder(options);
		this.renderers=HtmlRenderer.builder(options);

	}


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

	public Map read(final Path source) {

		if ( source == null ) {
			throw new NullPointerException("null source");
		}

		try ( final BufferedReader reader=Files.newBufferedReader(source, UTF_8) ) {

			final Node document=parsers.build().parseReader(reader);

			final Map model=metadata(document);

			model.put("headings", headings(document));
			model.put("body", body(document));

			return model;

		} catch ( final IOException e ) {
			throw new UncheckedIOException(e);
		}
	}


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

	private Map metadata(final Node document) {

		final AbstractYamlFrontMatterVisitor visitor=new AbstractYamlFrontMatterVisitor();

		visitor.visit(document);

		return visitor.getData().entrySet().stream().collect(toMap(

				field -> field.getKey().trim(),

				field -> new JoiningList(field.getValue().stream().map(String::trim).collect(toList()))

		));
	}

	private List headings(final Node document) {

		final List headings=new ArrayList<>();

		new NodeVisitor(new VisitHandler<>(Heading.class, headings::add)).visit(document);

		return headings;
	}

	private String body(final Node document) {
		return renderers.build().render(document);
	}


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

	private static final class JoiningList extends AbstractList {

		private final List values;

		private JoiningList(final List values) { this.values=values; }


		@Override public int size() { return values.size(); }

		@Override public String get(final int index) { return values.get(index); }

		@Override public String toString() { return String.join(", ", values); }

	}

}