com.g2forge.enigma.document.convert.md.MDRenderer Maven / Gradle / Ivy

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Models, parsers and renderers for common documentation formats. This library is helpful for generating documentation and translating formats like MD, wikitext and office documents.
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package com.g2forge.enigma.document.convert.md;

import java.lang.reflect.Type;
import java.util.Stack;

import com.g2forge.alexandria.java.close.ICloseable;
import com.g2forge.alexandria.java.core.error.NotYetImplementedError;
import com.g2forge.alexandria.java.enums.EnumException;
import com.g2forge.alexandria.java.function.IFunction1;
import com.g2forge.alexandria.java.typeswitch.TypeSwitch1;
import com.g2forge.enigma.document.Block;
import com.g2forge.enigma.document.Definition;
import com.g2forge.enigma.document.DocList;
import com.g2forge.enigma.document.Emphasis;
import com.g2forge.enigma.document.IBlock;
import com.g2forge.enigma.document.IDocListItem;
import com.g2forge.enigma.document.ISpan;
import com.g2forge.enigma.document.Image;
import com.g2forge.enigma.document.Link;
import com.g2forge.enigma.document.Section;
import com.g2forge.enigma.document.Span;
import com.g2forge.enigma.document.Text;

import lombok.Data;

public class MDRenderer {
	protected enum LineBreakStrategy {
		None,
		Item {
			@Override
			public void beforeItem(IMDRenderContext context, boolean first) {
				if (!first) {
					final String newline = context.getNewline();
					context.getBuilder().append(newline).append(newline);
				}
			}
		},
		Period {
			@Override
			public void text(IMDRenderContext context, String text) {
				final String broken = text.replaceAll("\\.\\s+", "." + context.getNewline());
				context.getBuilder().append(broken);
			}
		};

		public static LineBreakStrategy fromBlockType(Block.Type type) {
			switch (type) {
				case Document:
				case Block:
					return Item;
				case Paragraph:
				case ListItem:
					return Period;
				default:
					throw new EnumException(Block.Type.class, type);
			}
		}

		public void beforeItem(IMDRenderContext context, boolean first) {}

		public void text(IMDRenderContext context, String text) {
			context.getBuilder().append(text);
		}
	}

	@Data
	protected static class MDRenderContext implements IMDRenderContext {
		protected static final IFunction1 toExplicit = new TypeSwitch1.FunctionBuilder().with(builder -> {
			builder.add(IExplicitMDElement.class, IFunction1.identity());
			builder.add(Text.class, md -> c -> c.getLineBreakStrategy().text(c, md.getText()));
			builder.add(Span.class, md -> c -> {
				for (IBlock content : md.getContents()) {
					c.toExplicit(content, IBlock.class).render(c);
				}
			});
			builder.add(Link.class, md -> c -> {
				final String target = md.getTarget();
				final StringBuilder b = c.getBuilder();
				if (target != null) b.append('[');
				c.toExplicit(md.getBody(), ISpan.class).render(c);
				if (target != null) b.append("](").append(target).append(')');
			});
			builder.add(Emphasis.class, md -> c -> {
				final String delimiter;
				switch (md.getType()) {
					case Code:
						delimiter = "`";
						break;
					case Emphasis:
						delimiter = "*";
						break;
					case Strong:
						delimiter = "**";
						break;
					case Strikethrough:
						delimiter = "~~";
						break;
					default:
						throw new EnumException(Emphasis.Type.class, md.getType());
				}
				final StringBuilder b = c.getBuilder();
				b.append(delimiter);
				c.toExplicit(md.getSpan(), ISpan.class).render(c);
				b.append(delimiter);
			});

			builder.add(Block.class, md -> c -> {
				try (final ICloseable strategy = c.openLineBreakStrategy(LineBreakStrategy.fromBlockType(md.getType()))) {
					boolean first = true;
					for (IBlock content : md.getContents()) {
						if (first) first = false;
						else c.getLineBreakStrategy().beforeItem(c, first);
						c.toExplicit(content, IBlock.class).render(c);
					}
				}
			});
			builder.add(DocList.class, md -> c -> {
				final StringBuilder b = c.getBuilder();
				final String newline = c.getNewline();
				final java.util.List items = md.getItems();
				for (int i = 0; i < items.size(); i++) {
					switch (md.getMarker()) {
						case Ordered:
							b.append("* ");
							break;
						case Numbered:
							b.append(String.format("%1$d. ", i + 1));
							break;
					}
					c.toExplicit(items.get(i), IBlock.class).render(c);
					if (i < (items.size() - 1)) b.append(newline);
				}
			});
			builder.add(Definition.class, md -> c -> {
				c.toExplicit(md.getTerm(), ISpan.class).render(c);
				c.getBuilder().append(": ");
				c.toExplicit(md.getBody(), ISpan.class).render(c);
			});
			builder.add(Section.class, md -> c -> {
				final String newline = c.getNewline();
				final StringBuilder b = c.getBuilder();
				for (int i = 0; i < c.getSectionLevel(); i++) {
					b.append('#');
				}
				b.append(" ");
				c.toExplicit(md.getTitle(), ISpan.class).render(c);
				b.append(newline).append(newline);
				try (final ICloseable section = c.openSection()) {
					c.toExplicit(md.getBody(), IBlock.class).render(c);
				}
			});
			builder.add(Image.class, md -> c -> {
				c.getBuilder().append("![").append(md.getAlt()).append("](").append(md.getUrl()).append(')');
			});
			builder.fallback(md -> {
				throw new NotYetImplementedError(String.format("Renderer does not yet support elements of type %1$s", md.getClass().getSimpleName()));
			});
		}).build();

		protected final Stack lineBreakStrategies = new Stack<>();

		protected final StringBuilder builder;

		protected final String newline;

		protected final Stack stack = new Stack<>();

		@Override
		public LineBreakStrategy getLineBreakStrategy() {
			if (lineBreakStrategies.isEmpty()) return LineBreakStrategy.None;
			return lineBreakStrategies.peek();
		}

		@Override
		public int getSectionLevel() {
			return stack.size() + 1;
		}

		@Override
		public ICloseable openLineBreakStrategy(LineBreakStrategy strategy) {
			lineBreakStrategies.push(strategy);
			final int size = lineBreakStrategies.size();
			return () -> {
				if (lineBreakStrategies.size() != size) throw new IllegalStateException();
				lineBreakStrategies.pop();
			};
		}

		@Override
		public ICloseable openSection() {
			final ICloseable retVal = new ICloseable() {
				@Override
				public void close() {
					if (stack.peek() != this) throw new IllegalArgumentException();
					stack.pop();
				}
			};
			stack.push(retVal);
			return retVal;
		}

		@Override
		public IExplicitMDElement toExplicit(final Object element, Type type) {
			return toExplicit.apply(element);
		}
	}

	public String render(Object element) {
		final StringBuilder retVal = new StringBuilder();
		final MDRenderContext context = new MDRenderContext(retVal, "\n");
		context.toExplicit(element, null).render(context);
		return retVal.toString();
	}
}