EXTENSIONS = Collections.singleton(StrikethroughExtension.create());
+ private static final Parser PARSER = Parser.builder().extensions(EXTENSIONS).build();
+ private static final MarkdownRenderer RENDERER = MarkdownRenderer.builder().extensions(EXTENSIONS).build();
+
+ @Test
+ public void testStrikethrough() {
+ assertRoundTrip("~foo~ ~bar~\n");
+ assertRoundTrip("~~foo~~ ~~bar~~\n");
+ assertRoundTrip("~~f\\~oo~~ ~~bar~~\n");
+
+ assertRoundTrip("\\~foo\\~\n");
+ }
+
+ protected String render(String source) {
+ return RENDERER.render(PARSER.parse(source));
+ }
+
+ private void assertRoundTrip(String input) {
+ String rendered = render(input);
+ assertEquals(input, rendered);
+ }
+}
diff --git a/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/TableCell.java b/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/TableCell.java
index 61880c6c3..bd7b40e02 100644
--- a/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/TableCell.java
+++ b/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/TableCell.java
@@ -22,7 +22,7 @@ public void setHeader(boolean header) {
}
/**
- * @return the cell alignment
+ * @return the cell alignment or {@code null} if no specific alignment
*/
public Alignment getAlignment() {
return alignment;
diff --git a/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/TablesExtension.java b/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/TablesExtension.java
index 5707b0f14..d18c38283 100644
--- a/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/TablesExtension.java
+++ b/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/TablesExtension.java
@@ -3,16 +3,23 @@
import org.commonmark.Extension;
import org.commonmark.ext.gfm.tables.internal.TableBlockParser;
import org.commonmark.ext.gfm.tables.internal.TableHtmlNodeRenderer;
+import org.commonmark.ext.gfm.tables.internal.TableMarkdownNodeRenderer;
import org.commonmark.ext.gfm.tables.internal.TableTextContentNodeRenderer;
import org.commonmark.parser.Parser;
import org.commonmark.renderer.NodeRenderer;
import org.commonmark.renderer.html.HtmlNodeRendererContext;
import org.commonmark.renderer.html.HtmlNodeRendererFactory;
import org.commonmark.renderer.html.HtmlRenderer;
+import org.commonmark.renderer.markdown.MarkdownNodeRendererContext;
+import org.commonmark.renderer.markdown.MarkdownNodeRendererFactory;
+import org.commonmark.renderer.markdown.MarkdownRenderer;
import org.commonmark.renderer.text.TextContentNodeRendererContext;
import org.commonmark.renderer.text.TextContentNodeRendererFactory;
import org.commonmark.renderer.text.TextContentRenderer;
+import java.util.Collections;
+import java.util.Set;
+
/**
* Extension for GFM tables using "|" pipes (GitHub Flavored Markdown).
*
@@ -27,7 +34,7 @@
* @see Tables (extension) in GitHub Flavored Markdown Spec
*/
public class TablesExtension implements Parser.ParserExtension, HtmlRenderer.HtmlRendererExtension,
- TextContentRenderer.TextContentRendererExtension {
+ TextContentRenderer.TextContentRendererExtension, MarkdownRenderer.MarkdownRendererExtension {
private TablesExtension() {
}
@@ -60,4 +67,19 @@ public NodeRenderer create(TextContentNodeRendererContext context) {
}
});
}
+
+ @Override
+ public void extend(MarkdownRenderer.Builder rendererBuilder) {
+ rendererBuilder.nodeRendererFactory(new MarkdownNodeRendererFactory() {
+ @Override
+ public NodeRenderer create(MarkdownNodeRendererContext context) {
+ return new TableMarkdownNodeRenderer(context);
+ }
+
+ @Override
+ public Set getSpecialCharacters() {
+ return Collections.singleton('|');
+ }
+ });
+ }
}
diff --git a/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/internal/TableMarkdownNodeRenderer.java b/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/internal/TableMarkdownNodeRenderer.java
new file mode 100644
index 000000000..487147164
--- /dev/null
+++ b/commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/internal/TableMarkdownNodeRenderer.java
@@ -0,0 +1,90 @@
+package org.commonmark.ext.gfm.tables.internal;
+
+import org.commonmark.ext.gfm.tables.*;
+import org.commonmark.internal.util.AsciiMatcher;
+import org.commonmark.internal.util.CharMatcher;
+import org.commonmark.node.Node;
+import org.commonmark.renderer.NodeRenderer;
+import org.commonmark.renderer.markdown.MarkdownNodeRendererContext;
+import org.commonmark.renderer.markdown.MarkdownWriter;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * The Table node renderer that is needed for rendering GFM tables (GitHub Flavored Markdown) to text content.
+ */
+public class TableMarkdownNodeRenderer extends TableNodeRenderer implements NodeRenderer {
+ private final MarkdownWriter writer;
+ private final MarkdownNodeRendererContext context;
+
+ private final CharMatcher pipe = AsciiMatcher.builder().c('|').build();
+
+ private final List columns = new ArrayList<>();
+
+ public TableMarkdownNodeRenderer(MarkdownNodeRendererContext context) {
+ this.writer = context.getWriter();
+ this.context = context;
+ }
+
+ @Override
+ protected void renderBlock(TableBlock node) {
+ columns.clear();
+ writer.pushTight(true);
+ renderChildren(node);
+ writer.popTight();
+ writer.block();
+ }
+
+ @Override
+ protected void renderHead(TableHead node) {
+ renderChildren(node);
+ for (TableCell.Alignment columnAlignment : columns) {
+ writer.raw('|');
+ if (columnAlignment == TableCell.Alignment.LEFT) {
+ writer.raw(":---");
+ } else if (columnAlignment == TableCell.Alignment.RIGHT) {
+ writer.raw("---:");
+ } else if (columnAlignment == TableCell.Alignment.CENTER) {
+ writer.raw(":---:");
+ } else {
+ writer.raw("---");
+ }
+ }
+ writer.raw("|");
+ writer.block();
+ }
+
+ @Override
+ protected void renderBody(TableBody node) {
+ renderChildren(node);
+ }
+
+ @Override
+ protected void renderRow(TableRow node) {
+ renderChildren(node);
+ // Trailing | at the end of the line
+ writer.raw("|");
+ writer.block();
+ }
+
+ @Override
+ protected void renderCell(TableCell node) {
+ if (node.getParent() != null && node.getParent().getParent() instanceof TableHead) {
+ columns.add(node.getAlignment());
+ }
+ writer.raw("|");
+ writer.pushRawEscape(pipe);
+ renderChildren(node);
+ writer.popRawEscape();
+ }
+
+ private void renderChildren(Node parent) {
+ Node node = parent.getFirstChild();
+ while (node != null) {
+ Node next = node.getNext();
+ context.render(node);
+ node = next;
+ }
+ }
+}
diff --git a/commonmark-ext-gfm-tables/src/test/java/org/commonmark/ext/gfm/tables/TableMarkdownRendererTest.java b/commonmark-ext-gfm-tables/src/test/java/org/commonmark/ext/gfm/tables/TableMarkdownRendererTest.java
new file mode 100644
index 000000000..1db917d08
--- /dev/null
+++ b/commonmark-ext-gfm-tables/src/test/java/org/commonmark/ext/gfm/tables/TableMarkdownRendererTest.java
@@ -0,0 +1,76 @@
+package org.commonmark.ext.gfm.tables;
+
+import org.commonmark.Extension;
+import org.commonmark.parser.Parser;
+import org.commonmark.renderer.markdown.MarkdownRenderer;
+import org.junit.Test;
+
+import java.util.Collections;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+
+public class TableMarkdownRendererTest {
+
+ private static final Set EXTENSIONS = Collections.singleton(TablesExtension.create());
+ private static final Parser PARSER = Parser.builder().extensions(EXTENSIONS).build();
+ private static final MarkdownRenderer RENDERER = MarkdownRenderer.builder().extensions(EXTENSIONS).build();
+
+ @Test
+ public void testHeadNoBody() {
+ assertRoundTrip("|Abc|\n|---|\n");
+ assertRoundTrip("|Abc|Def|\n|---|---|\n");
+ assertRoundTrip("|Abc||\n|---|---|\n");
+ }
+
+ @Test
+ public void testHeadAndBody() {
+ assertRoundTrip("|Abc|\n|---|\n|1|\n");
+ assertRoundTrip("|Abc|Def|\n|---|---|\n|1|2|\n");
+ }
+
+ @Test
+ public void testBodyHasFewerColumns() {
+ // Could try not to write empty trailing cells but this is fine too
+ assertRoundTrip("|Abc|Def|\n|---|---|\n|1||\n");
+ }
+
+ @Test
+ public void testAlignment() {
+ assertRoundTrip("|Abc|Def|\n|:---|---|\n|1|2|\n");
+ assertRoundTrip("|Abc|Def|\n|---|---:|\n|1|2|\n");
+ assertRoundTrip("|Abc|Def|\n|:---:|:---:|\n|1|2|\n");
+ }
+
+ @Test
+ public void testInsideBlockQuote() {
+ assertRoundTrip("> |Abc|Def|\n> |---|---|\n> |1|2|\n");
+ }
+
+ @Test
+ public void testMultipleTables() {
+ assertRoundTrip("|Abc|Def|\n|---|---|\n\n|One|\n|---|\n|Only|\n");
+ }
+
+ @Test
+ public void testEscaping() {
+ assertRoundTrip("|Abc|Def|\n|---|---|\n|Pipe in|text \\||\n");
+ assertRoundTrip("|Abc|Def|\n|---|---|\n|Pipe in|code `\\|`|\n");
+ assertRoundTrip("|Abc|Def|\n|---|---|\n|Inline HTML|Foo\\|bar|\n");
+ }
+
+ @Test
+ public void testEscaped() {
+ // `|` in Text nodes needs to be escaped, otherwise the generated Markdown does not get parsed back as a table
+ assertRoundTrip("\\|Abc\\|\n\\|---\\|\n");
+ }
+
+ protected String render(String source) {
+ return RENDERER.render(PARSER.parse(source));
+ }
+
+ private void assertRoundTrip(String input) {
+ String rendered = render(input);
+ assertEquals(input, rendered);
+ }
+}
diff --git a/commonmark-ext-ins/src/main/java/org/commonmark/ext/ins/InsExtension.java b/commonmark-ext-ins/src/main/java/org/commonmark/ext/ins/InsExtension.java
index 2f980d93b..065719558 100644
--- a/commonmark-ext-ins/src/main/java/org/commonmark/ext/ins/InsExtension.java
+++ b/commonmark-ext-ins/src/main/java/org/commonmark/ext/ins/InsExtension.java
@@ -3,16 +3,23 @@
import org.commonmark.Extension;
import org.commonmark.ext.ins.internal.InsDelimiterProcessor;
import org.commonmark.ext.ins.internal.InsHtmlNodeRenderer;
+import org.commonmark.ext.ins.internal.InsMarkdownNodeRenderer;
import org.commonmark.ext.ins.internal.InsTextContentNodeRenderer;
import org.commonmark.parser.Parser;
import org.commonmark.renderer.NodeRenderer;
import org.commonmark.renderer.html.HtmlNodeRendererContext;
import org.commonmark.renderer.html.HtmlNodeRendererFactory;
import org.commonmark.renderer.html.HtmlRenderer;
+import org.commonmark.renderer.markdown.MarkdownNodeRendererContext;
+import org.commonmark.renderer.markdown.MarkdownNodeRendererFactory;
+import org.commonmark.renderer.markdown.MarkdownRenderer;
import org.commonmark.renderer.text.TextContentNodeRendererContext;
import org.commonmark.renderer.text.TextContentNodeRendererFactory;
import org.commonmark.renderer.text.TextContentRenderer;
+import java.util.Collections;
+import java.util.Set;
+
/**
* Extension for ins using ++
*
@@ -24,9 +31,7 @@
* The parsed ins text regions are turned into {@link Ins} nodes.
*
*/
-public class InsExtension implements Parser.ParserExtension,
- HtmlRenderer.HtmlRendererExtension,
- TextContentRenderer.TextContentRendererExtension {
+public class InsExtension implements Parser.ParserExtension, HtmlRenderer.HtmlRendererExtension, TextContentRenderer.TextContentRendererExtension, MarkdownRenderer.MarkdownRendererExtension {
private InsExtension() {
}
@@ -59,4 +64,21 @@ public NodeRenderer create(TextContentNodeRendererContext context) {
}
});
}
+
+ @Override
+ public void extend(MarkdownRenderer.Builder rendererBuilder) {
+ rendererBuilder.nodeRendererFactory(new MarkdownNodeRendererFactory() {
+ @Override
+ public NodeRenderer create(MarkdownNodeRendererContext context) {
+ return new InsMarkdownNodeRenderer(context);
+ }
+
+ @Override
+ public Set getSpecialCharacters() {
+ // We technically don't need to escape single occurrences of +, but that's all the extension API
+ // exposes currently.
+ return Collections.singleton('+');
+ }
+ });
+ }
}
diff --git a/commonmark-ext-ins/src/main/java/org/commonmark/ext/ins/internal/InsMarkdownNodeRenderer.java b/commonmark-ext-ins/src/main/java/org/commonmark/ext/ins/internal/InsMarkdownNodeRenderer.java
new file mode 100644
index 000000000..851d47282
--- /dev/null
+++ b/commonmark-ext-ins/src/main/java/org/commonmark/ext/ins/internal/InsMarkdownNodeRenderer.java
@@ -0,0 +1,32 @@
+package org.commonmark.ext.ins.internal;
+
+import org.commonmark.node.Node;
+import org.commonmark.renderer.markdown.MarkdownNodeRendererContext;
+import org.commonmark.renderer.markdown.MarkdownWriter;
+
+public class InsMarkdownNodeRenderer extends InsNodeRenderer {
+
+ private final MarkdownNodeRendererContext context;
+ private final MarkdownWriter writer;
+
+ public InsMarkdownNodeRenderer(MarkdownNodeRendererContext context) {
+ this.context = context;
+ this.writer = context.getWriter();
+ }
+
+ @Override
+ public void render(Node node) {
+ writer.raw("++");
+ renderChildren(node);
+ writer.raw("++");
+ }
+
+ private void renderChildren(Node parent) {
+ Node node = parent.getFirstChild();
+ while (node != null) {
+ Node next = node.getNext();
+ context.render(node);
+ node = next;
+ }
+ }
+}
diff --git a/commonmark-ext-ins/src/test/java/org/commonmark/ext/ins/InsMarkdownRendererTest.java b/commonmark-ext-ins/src/test/java/org/commonmark/ext/ins/InsMarkdownRendererTest.java
new file mode 100644
index 000000000..16cefc7f1
--- /dev/null
+++ b/commonmark-ext-ins/src/test/java/org/commonmark/ext/ins/InsMarkdownRendererTest.java
@@ -0,0 +1,34 @@
+package org.commonmark.ext.ins;
+
+import org.commonmark.Extension;
+import org.commonmark.parser.Parser;
+import org.commonmark.renderer.markdown.MarkdownRenderer;
+import org.junit.Test;
+
+import java.util.Collections;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+
+public class InsMarkdownRendererTest {
+
+ private static final Set EXTENSIONS = Collections.singleton(InsExtension.create());
+ private static final Parser PARSER = Parser.builder().extensions(EXTENSIONS).build();
+ private static final MarkdownRenderer RENDERER = MarkdownRenderer.builder().extensions(EXTENSIONS).build();
+
+ @Test
+ public void testStrikethrough() {
+ assertRoundTrip("++foo++\n");
+
+ assertRoundTrip("\\+\\+foo\\+\\+\n");
+ }
+
+ protected String render(String source) {
+ return RENDERER.render(PARSER.parse(source));
+ }
+
+ private void assertRoundTrip(String input) {
+ String rendered = render(input);
+ assertEquals(input, rendered);
+ }
+}
diff --git a/commonmark-integration-test/src/test/java/org/commonmark/integration/MarkdownRendererIntegrationTest.java b/commonmark-integration-test/src/test/java/org/commonmark/integration/MarkdownRendererIntegrationTest.java
new file mode 100644
index 000000000..51f761cfd
--- /dev/null
+++ b/commonmark-integration-test/src/test/java/org/commonmark/integration/MarkdownRendererIntegrationTest.java
@@ -0,0 +1,46 @@
+package org.commonmark.integration;
+
+import org.commonmark.Extension;
+import org.commonmark.ext.autolink.AutolinkExtension;
+import org.commonmark.ext.front.matter.YamlFrontMatterExtension;
+import org.commonmark.ext.gfm.strikethrough.StrikethroughExtension;
+import org.commonmark.ext.gfm.tables.TablesExtension;
+import org.commonmark.ext.image.attributes.ImageAttributesExtension;
+import org.commonmark.ext.ins.InsExtension;
+import org.commonmark.ext.task.list.items.TaskListItemsExtension;
+import org.commonmark.parser.Parser;
+import org.commonmark.renderer.markdown.MarkdownRenderer;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class MarkdownRendererIntegrationTest {
+
+ private static final List EXTENSIONS = Arrays.asList(
+ AutolinkExtension.create(),
+ ImageAttributesExtension.create(),
+ InsExtension.create(),
+ StrikethroughExtension.create(),
+ TablesExtension.create(),
+ TaskListItemsExtension.create(),
+ YamlFrontMatterExtension.create());
+ private static final Parser PARSER = Parser.builder().extensions(EXTENSIONS).build();
+ private static final MarkdownRenderer RENDERER = MarkdownRenderer.builder().extensions(EXTENSIONS).build();
+
+ @Test
+ public void testStrikethroughInTable() {
+ assertRoundTrip("|Abc|\n|---|\n|~strikethrough~|\n|\\~escaped\\~|\n");
+ }
+
+ private String render(String source) {
+ return RENDERER.render(PARSER.parse(source));
+ }
+
+ private void assertRoundTrip(String input) {
+ String rendered = render(input);
+ assertEquals(input, rendered);
+ }
+}
diff --git a/commonmark-test-util/src/main/java/org/commonmark/testutil/example/Example.java b/commonmark-test-util/src/main/java/org/commonmark/testutil/example/Example.java
index 417a66097..11e87d0aa 100644
--- a/commonmark-test-util/src/main/java/org/commonmark/testutil/example/Example.java
+++ b/commonmark-test-util/src/main/java/org/commonmark/testutil/example/Example.java
@@ -30,6 +30,10 @@ public String getHtml() {
return html;
}
+ public String getSection() {
+ return section;
+ }
+
@Override
public String toString() {
return "File \"" + filename + "\" section \"" + section + "\" example " + exampleNumber;
diff --git a/commonmark/pom.xml b/commonmark/pom.xml
index 64c456192..9988370a8 100644
--- a/commonmark/pom.xml
+++ b/commonmark/pom.xml
@@ -9,7 +9,7 @@
commonmark
commonmark-java core
- Core of commonmark-java (implementation of CommonMark for parsing markdown and rendering to HTML)
+ Core of commonmark-java (a library for parsing Markdown to an AST, modifying the AST and rendering it to HTML or Markdown)
diff --git a/commonmark/src/main/java/org/commonmark/internal/util/AsciiMatcher.java b/commonmark/src/main/java/org/commonmark/internal/util/AsciiMatcher.java
index 82d83ca46..dd7e8d5eb 100644
--- a/commonmark/src/main/java/org/commonmark/internal/util/AsciiMatcher.java
+++ b/commonmark/src/main/java/org/commonmark/internal/util/AsciiMatcher.java
@@ -1,6 +1,7 @@
package org.commonmark.internal.util;
import java.util.BitSet;
+import java.util.Set;
public class AsciiMatcher implements CharMatcher {
private final BitSet set;
@@ -22,6 +23,10 @@ public static Builder builder() {
return new Builder(new BitSet());
}
+ public static Builder builder(AsciiMatcher matcher) {
+ return new Builder((BitSet) matcher.set.clone());
+ }
+
public static class Builder {
private final BitSet set;
@@ -37,6 +42,20 @@ public Builder c(char c) {
return this;
}
+ public Builder anyOf(String s) {
+ for (int i = 0; i < s.length(); i++) {
+ c(s.charAt(i));
+ }
+ return this;
+ }
+
+ public Builder anyOf(Set characters) {
+ for (Character c : characters) {
+ c(c);
+ }
+ return this;
+ }
+
public Builder range(char from, char toInclusive) {
for (char c = from; c <= toInclusive; c++) {
c(c);
diff --git a/commonmark/src/main/java/org/commonmark/package-info.java b/commonmark/src/main/java/org/commonmark/package-info.java
index e784703e9..b683017f6 100644
--- a/commonmark/src/main/java/org/commonmark/package-info.java
+++ b/commonmark/src/main/java/org/commonmark/package-info.java
@@ -4,6 +4,7 @@
* {@link org.commonmark.parser} for parsing input text to AST nodes
* {@link org.commonmark.node} for AST node types and visitors
* {@link org.commonmark.renderer.html} for HTML rendering
+ * {@link org.commonmark.renderer.markdown} for Markdown rendering
*
*/
package org.commonmark;
diff --git a/commonmark/src/main/java/org/commonmark/renderer/markdown/CoreMarkdownNodeRenderer.java b/commonmark/src/main/java/org/commonmark/renderer/markdown/CoreMarkdownNodeRenderer.java
new file mode 100644
index 000000000..30d6d1a5c
--- /dev/null
+++ b/commonmark/src/main/java/org/commonmark/renderer/markdown/CoreMarkdownNodeRenderer.java
@@ -0,0 +1,532 @@
+package org.commonmark.renderer.markdown;
+
+import org.commonmark.internal.util.AsciiMatcher;
+import org.commonmark.internal.util.CharMatcher;
+import org.commonmark.internal.util.Parsing;
+import org.commonmark.node.*;
+import org.commonmark.renderer.NodeRenderer;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * The node renderer that renders all the core nodes (comes last in the order of node renderers).
+ *
+ * Note that while sometimes it would be easier to record what kind of syntax was used on parsing (e.g. ATX vs Setext
+ * heading), this renderer is intended to also work for documents that were created by directly creating
+ * {@link Node Nodes} instead. So in order to support that, it sometimes needs to do a bit more work.
+ */
+public class CoreMarkdownNodeRenderer extends AbstractVisitor implements NodeRenderer {
+
+ private final AsciiMatcher textEscape;
+ private final CharMatcher textEscapeInHeading;
+ private final CharMatcher linkDestinationNeedsAngleBrackets =
+ AsciiMatcher.builder().c(' ').c('(').c(')').c('<').c('>').c('\n').c('\\').build();
+ private final CharMatcher linkDestinationEscapeInAngleBrackets =
+ AsciiMatcher.builder().c('<').c('>').c('\n').c('\\').build();
+ private final CharMatcher linkTitleEscapeInQuotes =
+ AsciiMatcher.builder().c('"').c('\n').c('\\').build();
+
+ private final Pattern orderedListMarkerPattern = Pattern.compile("^([0-9]{1,9})([.)])");
+
+ protected final MarkdownNodeRendererContext context;
+ private final MarkdownWriter writer;
+ /**
+ * If we're currently within a {@link BulletList} or {@link OrderedList}, this keeps the context of that list.
+ * It has a parent field so that it can represent a stack (for nested lists).
+ */
+ private ListHolder listHolder;
+
+ public CoreMarkdownNodeRenderer(MarkdownNodeRendererContext context) {
+ this.context = context;
+ this.writer = context.getWriter();
+
+ textEscape = AsciiMatcher.builder().anyOf("[]<>`*_&\n\\").anyOf(context.getSpecialCharacters()).build();
+ textEscapeInHeading = AsciiMatcher.builder(textEscape).anyOf("#").build();
+ }
+
+ @Override
+ public Set> getNodeTypes() {
+ return new HashSet<>(Arrays.asList(
+ BlockQuote.class,
+ BulletList.class,
+ Code.class,
+ Document.class,
+ Emphasis.class,
+ FencedCodeBlock.class,
+ HardLineBreak.class,
+ Heading.class,
+ HtmlBlock.class,
+ HtmlInline.class,
+ Image.class,
+ IndentedCodeBlock.class,
+ Link.class,
+ ListItem.class,
+ OrderedList.class,
+ Paragraph.class,
+ SoftLineBreak.class,
+ StrongEmphasis.class,
+ Text.class,
+ ThematicBreak.class
+ ));
+ }
+
+ @Override
+ public void render(Node node) {
+ node.accept(this);
+ }
+
+ @Override
+ public void visit(Document document) {
+ // No rendering itself
+ visitChildren(document);
+ writer.line();
+ }
+
+ @Override
+ public void visit(ThematicBreak thematicBreak) {
+ // Let's use ___ as it doesn't introduce ambiguity with * or - list item markers
+ writer.raw("___");
+ writer.block();
+ }
+
+ @Override
+ public void visit(Heading heading) {
+ if (heading.getLevel() <= 2) {
+ LineBreakVisitor lineBreakVisitor = new LineBreakVisitor();
+ heading.accept(lineBreakVisitor);
+ boolean isMultipleLines = lineBreakVisitor.hasLineBreak();
+
+ if (isMultipleLines) {
+ // Setext headings: Can have multiple lines, but only level 1 or 2
+ visitChildren(heading);
+ writer.line();
+ if (heading.getLevel() == 1) {
+ // Note that it would be nice to match the length of the contents instead of just using 3, but that's
+ // not easy.
+ writer.raw("===");
+ } else {
+ writer.raw("---");
+ }
+ writer.block();
+ return;
+ }
+ }
+
+ // ATX headings: Can't have multiple lines, but up to level 6.
+ for (int i = 0; i < heading.getLevel(); i++) {
+ writer.raw('#');
+ }
+ writer.raw(' ');
+ visitChildren(heading);
+
+ writer.block();
+ }
+
+ @Override
+ public void visit(IndentedCodeBlock indentedCodeBlock) {
+ String literal = indentedCodeBlock.getLiteral();
+ // We need to respect line prefixes which is why we need to write it line by line (e.g. an indented code block
+ // within a block quote)
+ writer.writePrefix(" ");
+ writer.pushPrefix(" ");
+ List lines = getLines(literal);
+ for (int i = 0; i < lines.size(); i++) {
+ String line = lines.get(i);
+ writer.raw(line);
+ if (i != lines.size() - 1) {
+ writer.line();
+ }
+ }
+ writer.popPrefix();
+ writer.block();
+ }
+
+ @Override
+ public void visit(FencedCodeBlock fencedCodeBlock) {
+ String literal = fencedCodeBlock.getLiteral();
+ String fence = repeat(String.valueOf(fencedCodeBlock.getFenceChar()), fencedCodeBlock.getFenceLength());
+ int indent = fencedCodeBlock.getFenceIndent();
+
+ if (indent > 0) {
+ String indentPrefix = repeat(" ", indent);
+ writer.writePrefix(indentPrefix);
+ writer.pushPrefix(indentPrefix);
+ }
+
+ writer.raw(fence);
+ if (fencedCodeBlock.getInfo() != null) {
+ writer.raw(fencedCodeBlock.getInfo());
+ }
+ writer.line();
+ if (!literal.isEmpty()) {
+ List lines = getLines(literal);
+ for (String line : lines) {
+ writer.raw(line);
+ writer.line();
+ }
+ }
+ writer.raw(fence);
+ if (indent > 0) {
+ writer.popPrefix();
+ }
+ writer.block();
+ }
+
+ @Override
+ public void visit(HtmlBlock htmlBlock) {
+ List lines = getLines(htmlBlock.getLiteral());
+ for (int i = 0; i < lines.size(); i++) {
+ String line = lines.get(i);
+ writer.raw(line);
+ if (i != lines.size() - 1) {
+ writer.line();
+ }
+ }
+ writer.block();
+ }
+
+ @Override
+ public void visit(Paragraph paragraph) {
+ visitChildren(paragraph);
+ writer.block();
+ }
+
+ @Override
+ public void visit(BlockQuote blockQuote) {
+ writer.writePrefix("> ");
+ writer.pushPrefix("> ");
+ visitChildren(blockQuote);
+ writer.popPrefix();
+ writer.block();
+ }
+
+ @Override
+ public void visit(BulletList bulletList) {
+ writer.pushTight(bulletList.isTight());
+ listHolder = new BulletListHolder(listHolder, bulletList);
+ visitChildren(bulletList);
+ listHolder = listHolder.parent;
+ writer.popTight();
+ writer.block();
+ }
+
+ @Override
+ public void visit(OrderedList orderedList) {
+ writer.pushTight(orderedList.isTight());
+ listHolder = new OrderedListHolder(listHolder, orderedList);
+ visitChildren(orderedList);
+ listHolder = listHolder.parent;
+ writer.popTight();
+ writer.block();
+ }
+
+ @Override
+ public void visit(ListItem listItem) {
+ int contentIndent = listItem.getContentIndent();
+ boolean pushedPrefix = false;
+ if (listHolder instanceof BulletListHolder) {
+ BulletListHolder bulletListHolder = (BulletListHolder) listHolder;
+ String marker = repeat(" ", listItem.getMarkerIndent()) + bulletListHolder.bulletMarker;
+ writer.writePrefix(marker);
+ writer.writePrefix(repeat(" ", contentIndent - marker.length()));
+ writer.pushPrefix(repeat(" ", contentIndent));
+ pushedPrefix = true;
+ } else if (listHolder instanceof OrderedListHolder) {
+ OrderedListHolder orderedListHolder = (OrderedListHolder) listHolder;
+ String marker = repeat(" ", listItem.getMarkerIndent()) + orderedListHolder.number + orderedListHolder.delimiter;
+ orderedListHolder.number++;
+ writer.writePrefix(marker);
+ writer.writePrefix(repeat(" ", contentIndent - marker.length()));
+ writer.pushPrefix(repeat(" ", contentIndent));
+ pushedPrefix = true;
+ }
+ if (listItem.getFirstChild() == null) {
+ // Empty list item
+ writer.block();
+ } else {
+ visitChildren(listItem);
+ }
+ if (pushedPrefix) {
+ writer.popPrefix();
+ }
+ }
+
+ @Override
+ public void visit(Code code) {
+ String literal = code.getLiteral();
+ // If the literal includes backticks, we can surround them by using one more backtick.
+ int backticks = findMaxRunLength('`', literal);
+ for (int i = 0; i < backticks + 1; i++) {
+ writer.raw('`');
+ }
+ // If the literal starts or ends with a backtick, surround it with a single space.
+ // If it starts and ends with a space (but is not only spaces), add an additional space (otherwise they would
+ // get removed on parsing).
+ boolean addSpace = literal.startsWith("`") || literal.endsWith("`") ||
+ (literal.startsWith(" ") && literal.endsWith(" ") && Parsing.hasNonSpace(literal));
+ if (addSpace) {
+ writer.raw(' ');
+ }
+ writer.raw(literal);
+ if (addSpace) {
+ writer.raw(' ');
+ }
+ for (int i = 0; i < backticks + 1; i++) {
+ writer.raw('`');
+ }
+ }
+
+ @Override
+ public void visit(Emphasis emphasis) {
+ String delimiter = emphasis.getOpeningDelimiter();
+ // Use delimiter that was parsed if available
+ if (delimiter == null) {
+ // When emphasis is nested, a different delimiter needs to be used
+ delimiter = writer.getLastChar() == '*' ? "_" : "*";
+ }
+ writer.raw(delimiter);
+ super.visit(emphasis);
+ writer.raw(delimiter);
+ }
+
+ @Override
+ public void visit(StrongEmphasis strongEmphasis) {
+ writer.raw("**");
+ super.visit(strongEmphasis);
+ writer.raw("**");
+ }
+
+ @Override
+ public void visit(Link link) {
+ writeLinkLike(link.getTitle(), link.getDestination(), link, "[");
+ }
+
+ @Override
+ public void visit(Image image) {
+ writeLinkLike(image.getTitle(), image.getDestination(), image, "![");
+ }
+
+ @Override
+ public void visit(HtmlInline htmlInline) {
+ writer.raw(htmlInline.getLiteral());
+ }
+
+ @Override
+ public void visit(HardLineBreak hardLineBreak) {
+ writer.raw(" ");
+ writer.line();
+ }
+
+ @Override
+ public void visit(SoftLineBreak softLineBreak) {
+ writer.line();
+ }
+
+ @Override
+ public void visit(Text text) {
+ // Text is tricky. In Markdown special characters (`-`, `#` etc.) can be escaped (`\-`, `\#` etc.) so that
+ // they're parsed as plain text. Currently, whether a character was escaped or not is not recorded in the Node,
+ // so here we don't know. If we just wrote out those characters unescaped, the resulting Markdown would change
+ // meaning (turn into a list item, heading, etc.).
+ // You might say "Why not store that in the Node when parsing", but that wouldn't work for the use case where
+ // nodes are constructed directly instead of via parsing. This renderer needs to work for that too.
+ // So currently, when in doubt, we escape. For special characters only occurring at the beginning of a line,
+ // we only escape them then (we wouldn't want to escape every `.` for example).
+ String literal = text.getLiteral();
+ if (writer.isAtLineStart() && !literal.isEmpty()) {
+ char c = literal.charAt(0);
+ switch (c) {
+ case '-': {
+ // Would be ambiguous with a bullet list marker, escape
+ writer.raw("\\-");
+ literal = literal.substring(1);
+ break;
+ }
+ case '#': {
+ // Would be ambiguous with an ATX heading, escape
+ writer.raw("\\#");
+ literal = literal.substring(1);
+ break;
+ }
+ case '=': {
+ // Would be ambiguous with a Setext heading, escape
+ writer.raw("\\=");
+ literal = literal.substring(1);
+ break;
+ }
+ case '0':
+ case '1':
+ case '2':
+ case '3':
+ case '4':
+ case '5':
+ case '6':
+ case '7':
+ case '8':
+ case '9': {
+ // Check for ordered list marker
+ Matcher m = orderedListMarkerPattern.matcher(literal);
+ if (m.find()) {
+ writer.raw(m.group(1));
+ writer.raw("\\" + m.group(2));
+ literal = literal.substring(m.end());
+ }
+ break;
+ }
+ case '\t': {
+ writer.raw(" ");
+ literal = literal.substring(1);
+ break;
+ }
+ case ' ': {
+ writer.raw(" ");
+ literal = literal.substring(1);
+ break;
+ }
+ }
+ }
+
+ CharMatcher escape = text.getParent() instanceof Heading ? textEscapeInHeading : textEscape;
+
+ if (literal.endsWith("!") && text.getNext() instanceof Link) {
+ // If we wrote the `!` unescaped, it would turn the link into an image instead.
+ writer.text(literal.substring(0, literal.length() - 1), escape);
+ writer.raw("\\!");
+ } else {
+ writer.text(literal, escape);
+ }
+ }
+
+ @Override
+ protected void visitChildren(Node parent) {
+ Node node = parent.getFirstChild();
+ while (node != null) {
+ Node next = node.getNext();
+ context.render(node);
+ node = next;
+ }
+ }
+
+ private static int findMaxRunLength(char c, CharSequence s) {
+ int backticks = 0;
+ int start = 0;
+ while (start < s.length()) {
+ int index = Parsing.find(c, s, start);
+ if (index != -1) {
+ start = Parsing.skip(c, s, index + 1, s.length());
+ backticks = Math.max(backticks, start - index);
+ } else {
+ break;
+ }
+ }
+ return backticks;
+ }
+
+ private static boolean contains(String s, CharMatcher charMatcher) {
+ for (int i = 0; i < s.length(); i++) {
+ if (charMatcher.matches(s.charAt(i))) {
+ return true;
+ }
+ }
+ return false;
+ }
+
+ private static String repeat(String s, int count) {
+ StringBuilder sb = new StringBuilder(s.length() * count);
+ for (int i = 0; i < count; i++) {
+ sb.append(s);
+ }
+ return sb.toString();
+ }
+
+ private static List getLines(String literal) {
+ // Without -1, split would discard all trailing empty strings, which is not what we want, e.g. it would
+ // return the same result for "abc", "abc\n" and "abc\n\n".
+ // With -1, it returns ["abc"], ["abc", ""] and ["abc", "", ""].
+ String[] parts = literal.split("\n", -1);
+ if (parts[parts.length - 1].isEmpty()) {
+ // But we don't want the last empty string, as "\n" is used as a line terminator (not a separator),
+ // so return without the last element.
+ return Arrays.asList(parts).subList(0, parts.length - 1);
+ } else {
+ return Arrays.asList(parts);
+ }
+ }
+
+ private void writeLinkLike(String title, String destination, Node node, String opener) {
+ writer.raw(opener);
+ visitChildren(node);
+ writer.raw(']');
+ writer.raw('(');
+ if (contains(destination, linkDestinationNeedsAngleBrackets)) {
+ writer.raw('<');
+ writer.text(destination, linkDestinationEscapeInAngleBrackets);
+ writer.raw('>');
+ } else {
+ writer.raw(destination);
+ }
+ if (title != null) {
+ writer.raw(' ');
+ writer.raw('"');
+ writer.text(title, linkTitleEscapeInQuotes);
+ writer.raw('"');
+ }
+ writer.raw(')');
+ }
+
+ private static class ListHolder {
+ final ListHolder parent;
+
+ protected ListHolder(ListHolder parent) {
+ this.parent = parent;
+ }
+ }
+
+ private static class BulletListHolder extends ListHolder {
+ final char bulletMarker;
+
+ public BulletListHolder(ListHolder parent, BulletList bulletList) {
+ super(parent);
+ this.bulletMarker = bulletList.getBulletMarker();
+ }
+ }
+
+ private static class OrderedListHolder extends ListHolder {
+ final char delimiter;
+ private int number;
+
+ protected OrderedListHolder(ListHolder parent, OrderedList orderedList) {
+ super(parent);
+ delimiter = orderedList.getDelimiter();
+ number = orderedList.getStartNumber();
+ }
+ }
+
+ /**
+ * Visits nodes to check if there are any soft or hard line breaks.
+ */
+ private static class LineBreakVisitor extends AbstractVisitor {
+ private boolean lineBreak = false;
+
+ public boolean hasLineBreak() {
+ return lineBreak;
+ }
+
+ @Override
+ public void visit(SoftLineBreak softLineBreak) {
+ super.visit(softLineBreak);
+ lineBreak = true;
+ }
+
+ @Override
+ public void visit(HardLineBreak hardLineBreak) {
+ super.visit(hardLineBreak);
+ lineBreak = true;
+ }
+ }
+}
diff --git a/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownNodeRendererContext.java b/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownNodeRendererContext.java
new file mode 100644
index 000000000..40640d1b4
--- /dev/null
+++ b/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownNodeRendererContext.java
@@ -0,0 +1,30 @@
+package org.commonmark.renderer.markdown;
+
+import org.commonmark.node.Node;
+
+import java.util.Set;
+
+/**
+ * Context that is passed to custom node renderers, see {@link MarkdownNodeRendererFactory#create}.
+ */
+public interface MarkdownNodeRendererContext {
+
+ /**
+ * @return the writer to use
+ */
+ MarkdownWriter getWriter();
+
+ /**
+ * Render the specified node and its children using the configured renderers. This should be used to render child
+ * nodes; be careful not to pass the node that is being rendered, that would result in an endless loop.
+ *
+ * @param node the node to render
+ */
+ void render(Node node);
+
+ /**
+ * @return additional special characters that need to be escaped if they occur in normal text; currently only ASCII
+ * characters are allowed
+ */
+ Set getSpecialCharacters();
+}
diff --git a/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownNodeRendererFactory.java b/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownNodeRendererFactory.java
new file mode 100644
index 000000000..14221ea56
--- /dev/null
+++ b/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownNodeRendererFactory.java
@@ -0,0 +1,25 @@
+package org.commonmark.renderer.markdown;
+
+import org.commonmark.renderer.NodeRenderer;
+
+import java.util.Set;
+
+/**
+ * Factory for instantiating new node renderers for rendering custom nodes.
+ */
+public interface MarkdownNodeRendererFactory {
+
+ /**
+ * Create a new node renderer for the specified rendering context.
+ *
+ * @param context the context for rendering (normally passed on to the node renderer)
+ * @return a node renderer
+ */
+ NodeRenderer create(MarkdownNodeRendererContext context);
+
+ /**
+ * @return the additional special characters that this factory would like to have escaped in normal text; currently
+ * only ASCII characters are allowed
+ */
+ Set getSpecialCharacters();
+}
diff --git a/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownRenderer.java b/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownRenderer.java
new file mode 100644
index 000000000..25fa9a142
--- /dev/null
+++ b/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownRenderer.java
@@ -0,0 +1,162 @@
+package org.commonmark.renderer.markdown;
+
+import org.commonmark.Extension;
+import org.commonmark.internal.renderer.NodeRendererMap;
+import org.commonmark.node.Node;
+import org.commonmark.renderer.NodeRenderer;
+import org.commonmark.renderer.Renderer;
+
+import java.util.*;
+
+/**
+ * Renders nodes to Markdown (CommonMark syntax); use {@link #builder()} to create a renderer.
+ *
+ * Note that it doesn't currently preserve the exact syntax of the original input Markdown (if any):
+ *
+ * - Headings are output as ATX headings if possible (multi-line headings need Setext headings)
+ * - Escaping might be over-eager, e.g. a plain {@code *} might be escaped
+ * even though it doesn't need to be in that particular context
+ * - Leading whitespace in paragraphs is not preserved
+ *
+ * However, it should produce Markdown that is semantically equivalent to the input, i.e. if the Markdown was parsed
+ * again and compared against the original AST, it should be the same (minus bugs).
+ */
+public class MarkdownRenderer implements Renderer {
+
+ private final List nodeRendererFactories;
+
+ private MarkdownRenderer(Builder builder) {
+ this.nodeRendererFactories = new ArrayList<>(builder.nodeRendererFactories.size() + 1);
+ this.nodeRendererFactories.addAll(builder.nodeRendererFactories);
+ // Add as last. This means clients can override the rendering of core nodes if they want.
+ this.nodeRendererFactories.add(new MarkdownNodeRendererFactory() {
+ @Override
+ public NodeRenderer create(MarkdownNodeRendererContext context) {
+ return new CoreMarkdownNodeRenderer(context);
+ }
+
+ @Override
+ public Set getSpecialCharacters() {
+ return Collections.emptySet();
+ }
+ });
+ }
+
+ /**
+ * Create a new builder for configuring a {@link MarkdownRenderer}.
+ *
+ * @return a builder
+ */
+ public static Builder builder() {
+ return new Builder();
+ }
+
+ @Override
+ public void render(Node node, Appendable output) {
+ RendererContext context = new RendererContext(new MarkdownWriter(output));
+ context.render(node);
+ }
+
+ @Override
+ public String render(Node node) {
+ StringBuilder sb = new StringBuilder();
+ render(node, sb);
+ return sb.toString();
+ }
+
+ /**
+ * Builder for configuring a {@link MarkdownRenderer}. See methods for default configuration.
+ */
+ public static class Builder {
+
+ private final List nodeRendererFactories = new ArrayList<>();
+
+ /**
+ * @return the configured {@link MarkdownRenderer}
+ */
+ public MarkdownRenderer build() {
+ return new MarkdownRenderer(this);
+ }
+
+ /**
+ * Add a factory for instantiating a node renderer (done when rendering). This allows to override the rendering
+ * of node types or define rendering for custom node types.
+ *
+ * If multiple node renderers for the same node type are created, the one from the factory that was added first
+ * "wins". (This is how the rendering for core node types can be overridden; the default rendering comes last.)
+ *
+ * @param nodeRendererFactory the factory for creating a node renderer
+ * @return {@code this}
+ */
+ public Builder nodeRendererFactory(MarkdownNodeRendererFactory nodeRendererFactory) {
+ this.nodeRendererFactories.add(nodeRendererFactory);
+ return this;
+ }
+
+ /**
+ * @param extensions extensions to use on this renderer
+ * @return {@code this}
+ */
+ public Builder extensions(Iterable extensions) {
+ for (Extension extension : extensions) {
+ if (extension instanceof MarkdownRendererExtension) {
+ MarkdownRendererExtension markdownRendererExtension = (MarkdownRendererExtension) extension;
+ markdownRendererExtension.extend(this);
+ }
+ }
+ return this;
+ }
+ }
+
+ /**
+ * Extension for {@link MarkdownRenderer} for rendering custom nodes.
+ */
+ public interface MarkdownRendererExtension extends Extension {
+
+ /**
+ * Extend Markdown rendering, usually by registering custom node renderers using {@link Builder#nodeRendererFactory}.
+ *
+ * @param rendererBuilder the renderer builder to extend
+ */
+ void extend(Builder rendererBuilder);
+ }
+
+ private class RendererContext implements MarkdownNodeRendererContext {
+ private final MarkdownWriter writer;
+ private final NodeRendererMap nodeRendererMap = new NodeRendererMap();
+ private final Set additionalTextEscapes;
+
+ private RendererContext(MarkdownWriter writer) {
+ // Set fields that are used by interface
+ this.writer = writer;
+ Set escapes = new HashSet();
+ for (MarkdownNodeRendererFactory factory : nodeRendererFactories) {
+ escapes.addAll(factory.getSpecialCharacters());
+ }
+ additionalTextEscapes = Collections.unmodifiableSet(escapes);
+
+ // The first node renderer for a node type "wins".
+ for (int i = nodeRendererFactories.size() - 1; i >= 0; i--) {
+ MarkdownNodeRendererFactory nodeRendererFactory = nodeRendererFactories.get(i);
+ // Pass in this as context here, which uses the fields set above
+ NodeRenderer nodeRenderer = nodeRendererFactory.create(this);
+ nodeRendererMap.add(nodeRenderer);
+ }
+ }
+
+ @Override
+ public MarkdownWriter getWriter() {
+ return writer;
+ }
+
+ @Override
+ public void render(Node node) {
+ nodeRendererMap.render(node);
+ }
+
+ @Override
+ public Set getSpecialCharacters() {
+ return additionalTextEscapes;
+ }
+ }
+}
diff --git a/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownWriter.java b/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownWriter.java
new file mode 100644
index 000000000..1231a4a73
--- /dev/null
+++ b/commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownWriter.java
@@ -0,0 +1,246 @@
+package org.commonmark.renderer.markdown;
+
+import org.commonmark.internal.util.CharMatcher;
+
+import java.io.IOException;
+import java.util.LinkedList;
+
+/**
+ * Writer for Markdown (CommonMark) text.
+ */
+public class MarkdownWriter {
+
+ private final Appendable buffer;
+
+ private int blockSeparator = 0;
+ private char lastChar;
+ private boolean atLineStart = true;
+
+ // Stacks of settings that affect various rendering behaviors. The common pattern here is that callers use "push" to
+ // change a setting, render some nodes, and then "pop" the setting off the stack again to restore previous state.
+ private final LinkedList prefixes = new LinkedList<>();
+ private final LinkedList tight = new LinkedList<>();
+ private final LinkedList rawEscapes = new LinkedList<>();
+
+ public MarkdownWriter(Appendable out) {
+ buffer = out;
+ }
+
+ /**
+ * Write the supplied string (raw/unescaped except if {@link #pushRawEscape} was used).
+ */
+ public void raw(String s) {
+ flushBlockSeparator();
+ write(s, null);
+ }
+
+ /**
+ * Write the supplied character (raw/unescaped except if {@link #pushRawEscape} was used).
+ */
+ public void raw(char c) {
+ flushBlockSeparator();
+ write(c);
+ }
+
+ /**
+ * Write the supplied string with escaping.
+ *
+ * @param s the string to write
+ * @param escape which characters to escape
+ */
+ public void text(String s, CharMatcher escape) {
+ if (s.isEmpty()) {
+ return;
+ }
+ flushBlockSeparator();
+ write(s, escape);
+
+ lastChar = s.charAt(s.length() - 1);
+ atLineStart = false;
+ }
+
+ /**
+ * Write a newline (line terminator).
+ */
+ public void line() {
+ write('\n');
+ writePrefixes();
+ atLineStart = true;
+ }
+
+ /**
+ * Enqueue a block separator to be written before the next text is written. Block separators are not written
+ * straight away because if there are no more blocks to write we don't want a separator (at the end of the document).
+ */
+ public void block() {
+ // Remember whether this should be a tight or loose separator now because tight could get changed in between
+ // this and the next flush.
+ blockSeparator = isTight() ? 1 : 2;
+ atLineStart = true;
+ }
+
+ /**
+ * Push a prefix onto the top of the stack. All prefixes are written at the beginning of each line, until the
+ * prefix is popped again.
+ *
+ * @param prefix the raw prefix string
+ */
+ public void pushPrefix(String prefix) {
+ prefixes.addLast(prefix);
+ }
+
+ /**
+ * Write a prefix.
+ *
+ * @param prefix the raw prefix string to write
+ */
+ public void writePrefix(String prefix) {
+ boolean tmp = atLineStart;
+ raw(prefix);
+ atLineStart = tmp;
+ }
+
+ /**
+ * Remove the last prefix from the top of the stack.
+ */
+ public void popPrefix() {
+ prefixes.removeLast();
+ }
+
+ /**
+ * Change whether blocks are tight or loose. Loose is the default where blocks are separated by a blank line. Tight
+ * is where blocks are not separated by a blank line. Tight blocks are used in lists, if there are no blank lines
+ * within the list.
+ *
+ * Note that changing this does not affect block separators that have already been enqueued with {@link #block()},
+ * only future ones.
+ */
+ public void pushTight(boolean tight) {
+ this.tight.addLast(tight);
+ }
+
+ /**
+ * Remove the last "tight" setting from the top of the stack.
+ */
+ public void popTight() {
+ this.tight.removeLast();
+ }
+
+ /**
+ * Escape the characters matching the supplied matcher, in all text (text and raw). This might be useful to
+ * extensions that add another layer of syntax, e.g. the tables extension that uses `|` to separate cells and needs
+ * all `|` characters to be escaped (even in code spans).
+ *
+ * @param rawEscape the characters to escape in raw text
+ */
+ public void pushRawEscape(CharMatcher rawEscape) {
+ rawEscapes.add(rawEscape);
+ }
+
+ /**
+ * Remove the last raw escape from the top of the stack.
+ */
+ public void popRawEscape() {
+ rawEscapes.removeLast();
+ }
+
+ /**
+ * @return the last character that was written
+ */
+ public char getLastChar() {
+ return lastChar;
+ }
+
+ /**
+ * @return whether we're at the line start (not counting any prefixes), i.e. after a {@link #line} or {@link #block}.
+ */
+ public boolean isAtLineStart() {
+ return atLineStart;
+ }
+
+ private void write(String s, CharMatcher escape) {
+ try {
+ if (rawEscapes.isEmpty() && escape == null) {
+ // Normal fast path
+ buffer.append(s);
+ } else {
+ for (int i = 0; i < s.length(); i++) {
+ append(s.charAt(i), escape);
+ }
+ }
+ } catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+
+ int length = s.length();
+ if (length != 0) {
+ lastChar = s.charAt(length - 1);
+ }
+ atLineStart = false;
+ }
+
+ private void write(char c) {
+ try {
+ append(c, null);
+ } catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+
+ lastChar = c;
+ atLineStart = false;
+ }
+
+ private void writePrefixes() {
+ if (!prefixes.isEmpty()) {
+ for (String prefix : prefixes) {
+ write(prefix, null);
+ }
+ }
+ }
+
+ /**
+ * If a block separator has been enqueued with {@link #block()} but not yet written, write it now.
+ */
+ private void flushBlockSeparator() {
+ if (blockSeparator != 0) {
+ write('\n');
+ writePrefixes();
+ if (blockSeparator > 1) {
+ write('\n');
+ writePrefixes();
+ }
+ blockSeparator = 0;
+ }
+ }
+
+ private void append(char c, CharMatcher escape) throws IOException {
+ if (needsEscaping(c, escape)) {
+ if (c == '\n') {
+ // Can't escape this with \, use numeric character reference
+ buffer.append("
");
+ } else {
+ buffer.append('\\');
+ buffer.append(c);
+ }
+ } else {
+ buffer.append(c);
+ }
+ }
+
+ private boolean isTight() {
+ return !tight.isEmpty() && tight.getLast();
+ }
+
+ private boolean needsEscaping(char c, CharMatcher escape) {
+ return (escape != null && escape.matches(c)) || rawNeedsEscaping(c);
+ }
+
+ private boolean rawNeedsEscaping(char c) {
+ for (CharMatcher rawEscape : rawEscapes) {
+ if (rawEscape.matches(c)) {
+ return true;
+ }
+ }
+ return false;
+ }
+}
diff --git a/commonmark/src/main/java/org/commonmark/renderer/markdown/package-info.java b/commonmark/src/main/java/org/commonmark/renderer/markdown/package-info.java
new file mode 100644
index 000000000..f707671d5
--- /dev/null
+++ b/commonmark/src/main/java/org/commonmark/renderer/markdown/package-info.java
@@ -0,0 +1,4 @@
+/**
+ * Markdown rendering (see {@link org.commonmark.renderer.markdown.MarkdownRenderer})
+ */
+package org.commonmark.renderer.markdown;
diff --git a/commonmark/src/main/java/org/commonmark/renderer/text/package-info.java b/commonmark/src/main/java/org/commonmark/renderer/text/package-info.java
index 07a558091..8309f4bd6 100644
--- a/commonmark/src/main/java/org/commonmark/renderer/text/package-info.java
+++ b/commonmark/src/main/java/org/commonmark/renderer/text/package-info.java
@@ -1,4 +1,4 @@
/**
- * Text content rendering (see {@link org.commonmark.renderer.text.TextContentRenderer})
+ * Plain text rendering with minimal markup (see {@link org.commonmark.renderer.text.TextContentRenderer})
*/
package org.commonmark.renderer.text;
diff --git a/commonmark/src/test/java/org/commonmark/renderer/markdown/MarkdownRendererTest.java b/commonmark/src/test/java/org/commonmark/renderer/markdown/MarkdownRendererTest.java
new file mode 100644
index 000000000..9bab92bcc
--- /dev/null
+++ b/commonmark/src/test/java/org/commonmark/renderer/markdown/MarkdownRendererTest.java
@@ -0,0 +1,260 @@
+package org.commonmark.renderer.markdown;
+
+import org.commonmark.node.*;
+import org.commonmark.parser.Parser;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class MarkdownRendererTest {
+
+ // Leaf blocks
+
+ @Test
+ public void testThematicBreaks() {
+ assertRoundTrip("___\n");
+ assertRoundTrip("___\n\nfoo\n");
+ // List item with hr -> hr needs to not use the same as the marker
+ assertRoundTrip("* ___\n");
+ assertRoundTrip("- ___\n");
+ }
+
+ @Test
+ public void testHeadings() {
+ // Type of heading is currently not preserved
+ assertRoundTrip("# foo\n");
+ assertRoundTrip("## foo\n");
+ assertRoundTrip("### foo\n");
+ assertRoundTrip("#### foo\n");
+ assertRoundTrip("##### foo\n");
+ assertRoundTrip("###### foo\n");
+
+ assertRoundTrip("Foo\nbar\n===\n");
+ assertRoundTrip("Foo \nbar\n===\n");
+ assertRoundTrip("[foo\nbar](/url)\n===\n");
+
+ assertRoundTrip("# foo\n\nbar\n");
+ }
+
+ @Test
+ public void testIndentedCodeBlocks() {
+ assertRoundTrip(" hi\n");
+ assertRoundTrip(" hi\n code\n");
+ assertRoundTrip("> hi\n> code\n");
+ }
+
+ @Test
+ public void testFencedCodeBlocks() {
+ assertRoundTrip("```\ntest\n```\n");
+ assertRoundTrip("~~~~\ntest\n~~~~\n");
+ assertRoundTrip("```info\ntest\n```\n");
+ assertRoundTrip(" ```\n test\n ```\n");
+ assertRoundTrip("```\n```\n");
+ }
+
+ @Test
+ public void testHtmlBlocks() {
+ assertRoundTrip("
test
\n");
+ assertRoundTrip("> \n> test\n>
\n");
+ }
+
+ @Test
+ public void testParagraphs() {
+ assertRoundTrip("foo\n");
+ assertRoundTrip("foo\n\nbar\n");
+ }
+
+ // Container blocks
+
+ @Test
+ public void testBlockQuotes() {
+ assertRoundTrip("> test\n");
+ assertRoundTrip("> foo\n> bar\n");
+ assertRoundTrip("> > foo\n> > bar\n");
+ assertRoundTrip("> # Foo\n> \n> bar\n> baz\n");
+ }
+
+ @Test
+ public void testBulletListItems() {
+ assertRoundTrip("* foo\n");
+ assertRoundTrip("- foo\n");
+ assertRoundTrip("+ foo\n");
+ assertRoundTrip("* foo\n bar\n");
+ assertRoundTrip("* ```\n code\n ```\n");
+ assertRoundTrip("* foo\n\n* bar\n");
+ // Note that the " " in the second line is not necessary, but it's not wrong either.
+ // We could try to avoid it in a future change, but not sure if necessary.
+ assertRoundTrip("* foo\n \n bar\n");
+
+ // Tight list
+ assertRoundTrip("* foo\n* bar\n");
+ // Tight list where the second item contains a loose list
+ assertRoundTrip("- Foo\n - Bar\n \n - Baz\n");
+
+ // List item indent. This is a tricky one, but here the amount of space between the list marker and "one"
+ // determines whether "two" is part of the list item or an indented code block.
+ // In this case, it's an indented code block because it's not indented enough to be part of the list item.
+ // If the renderer would just use "- one", then "two" would change from being an indented code block to being
+ // a paragraph in the list item! So it is important for the renderer to preserve the content indent of the list
+ // item.
+ assertRoundTrip(" - one\n\n two\n");
+
+ // Empty list
+ assertRoundTrip("- \n\nFoo\n");
+ }
+
+ @Test
+ public void testOrderedListItems() {
+ assertRoundTrip("1. foo\n");
+ assertRoundTrip("2. foo\n\n3. bar\n");
+
+ // Tight list
+ assertRoundTrip("1. foo\n2. bar\n");
+ // Tight list where the second item contains a loose list
+ assertRoundTrip("1. Foo\n 1. Bar\n \n 2. Baz\n");
+
+ assertRoundTrip(" 1. one\n\n two\n");
+ }
+
+ // Inlines
+
+ @Test
+ public void testTabs() {
+ assertRoundTrip("a\tb\n");
+ }
+
+ @Test
+ public void testEscaping() {
+ // These are a bit tricky. We always escape some characters, even though they only need escaping if they would
+ // otherwise result in a different parse result (e.g. a link):
+ assertRoundTrip("\\[a\\](/uri)\n");
+ assertRoundTrip("\\`abc\\`\n");
+
+ // Some characters only need to be escaped at the beginning of the line
+ assertRoundTrip("\\- Test\n");
+ assertRoundTrip("\\-\n");
+ assertRoundTrip("Test -\n");
+ assertRoundTrip("Abc\n\n\\- Test\n");
+ assertRoundTrip("\\# Test\n");
+ assertRoundTrip("\\## Test\n");
+ assertRoundTrip("\\#\n");
+ assertRoundTrip("Foo\n\\===\n");
+ // The beginning of the line within the block, so disregarding prefixes
+ assertRoundTrip("> \\- Test\n");
+ assertRoundTrip("- \\- Test\n");
+ // That's not the beginning of the line
+ assertRoundTrip("`a`- foo\n");
+
+ // This is a bit more tricky as we need to check for a list start
+ assertRoundTrip("1\\. Foo\n");
+ assertRoundTrip("999\\. Foo\n");
+ assertRoundTrip("1\\.\n");
+ assertRoundTrip("1\\) Foo\n");
+
+ // Escaped whitespace, wow
+ assertRoundTrip(" foo\n");
+ assertRoundTrip(" foo\n");
+ assertRoundTrip("foo
bar\n");
+ }
+
+ @Test
+ public void testCodeSpans() {
+ assertRoundTrip("`foo`\n");
+ assertRoundTrip("``foo ` bar``\n");
+ assertRoundTrip("```foo `` ` bar```\n");
+
+ assertRoundTrip("`` `foo ``\n");
+ assertRoundTrip("`` ` ``\n");
+ assertRoundTrip("` `\n");
+ }
+
+ @Test
+ public void testEmphasis() {
+ assertRoundTrip("*foo*\n");
+ assertRoundTrip("foo*bar*\n");
+ // When nesting, a different delimiter needs to be used
+ assertRoundTrip("*_foo_*\n");
+ assertRoundTrip("*_*foo*_*\n");
+ assertRoundTrip("_*foo*_\n");
+
+ // Not emphasis (needs * inside words)
+ assertRoundTrip("foo\\_bar\\_\n");
+
+ // Even when rendering a manually constructed tree, the emphasis delimiter needs to be chosen correctly.
+ Document doc = new Document();
+ Paragraph p = new Paragraph();
+ doc.appendChild(p);
+ Emphasis e1 = new Emphasis();
+ p.appendChild(e1);
+ Emphasis e2 = new Emphasis();
+ e1.appendChild(e2);
+ e2.appendChild(new Text("hi"));
+ assertEquals("*_hi_*\n", render(doc));
+ }
+
+ @Test
+ public void testStrongEmphasis() {
+ assertRoundTrip("**foo**\n");
+ assertRoundTrip("foo**bar**\n");
+ }
+
+ @Test
+ public void testLinks() {
+ assertRoundTrip("[link](/uri)\n");
+ assertRoundTrip("[link](/uri \"title\")\n");
+ assertRoundTrip("[link]()\n");
+ assertRoundTrip("[a]()\n");
+ assertRoundTrip("[a]()\n");
+ assertRoundTrip("[a](c>)\n");
+ assertRoundTrip("[a](c>)\n");
+ assertRoundTrip("[a](/uri \"foo \\\" bar\")\n");
+ assertRoundTrip("[link](/uri \"tes\\\\\")\n");
+ assertRoundTrip("[link](/url \"test
\")\n");
+ assertRoundTrip("[link]()\n");
+ }
+
+ @Test
+ public void testImages() {
+ assertRoundTrip("\n");
+ assertRoundTrip("![link](/uri \"title\")\n");
+ assertRoundTrip("![link]()\n");
+ assertRoundTrip("![a]()\n");
+ assertRoundTrip("![a]()\n");
+ assertRoundTrip("\n");
+ assertRoundTrip("\n");
+ assertRoundTrip("![a](/uri \"foo \\\" bar\")\n");
+ }
+
+ @Test
+ public void testHtmlInline() {
+ assertRoundTrip("*foo*\n");
+ }
+
+ @Test
+ public void testHardLineBreaks() {
+ assertRoundTrip("foo \nbar\n");
+ }
+
+ @Test
+ public void testSoftLineBreaks() {
+ assertRoundTrip("foo\nbar\n");
+ }
+
+ private void assertRoundTrip(String input) {
+ String rendered = parseAndRender(input);
+ assertEquals(input, rendered);
+ }
+
+ private String parseAndRender(String source) {
+ Node parsed = parse(source);
+ return render(parsed);
+ }
+
+ private Node parse(String source) {
+ return Parser.builder().build().parse(source);
+ }
+
+ private String render(Node node) {
+ return MarkdownRenderer.builder().build().render(node);
+ }
+}
diff --git a/commonmark/src/test/java/org/commonmark/renderer/markdown/SpecMarkdownRendererTest.java b/commonmark/src/test/java/org/commonmark/renderer/markdown/SpecMarkdownRendererTest.java
new file mode 100644
index 000000000..5df2e5c80
--- /dev/null
+++ b/commonmark/src/test/java/org/commonmark/renderer/markdown/SpecMarkdownRendererTest.java
@@ -0,0 +1,97 @@
+package org.commonmark.renderer.markdown;
+
+import org.commonmark.node.Node;
+import org.commonmark.parser.Parser;
+import org.commonmark.renderer.html.HtmlRenderer;
+import org.commonmark.testutil.TestResources;
+import org.commonmark.testutil.example.Example;
+import org.commonmark.testutil.example.ExampleReader;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Tests Markdown rendering using the examples in the spec like this:
+ *
+ * - Parses the source to an AST and then renders it back to Markdown
+ * - Parses that to an AST and then renders it to HTML
+ * - Compares that HTML to the expected HTML of the example:
+ * If it's the same, then the expected elements were preserved in the Markdown rendering
+ *
+ */
+public class SpecMarkdownRendererTest {
+
+ public static final MarkdownRenderer MARKDOWN_RENDERER = MarkdownRenderer.builder().build();
+ // The spec says URL-escaping is optional, but the examples assume that it's enabled.
+ public static final HtmlRenderer HTML_RENDERER = HtmlRenderer.builder().percentEncodeUrls(true).build();
+
+ @Test
+ public void testCoverage() {
+ List examples = ExampleReader.readExamples(TestResources.getSpec());
+ List passes = new ArrayList<>();
+ List fails = new ArrayList<>();
+ for (Example example : examples) {
+ String markdown = renderMarkdown(example.getSource());
+ String rendered = renderHtml(markdown);
+ if (rendered.equals(example.getHtml())) {
+ passes.add(example);
+ } else {
+ fails.add(example);
+ }
+ }
+
+ System.out.println("Passed examples by section (total " + passes.size() + "):");
+ printCountsBySection(passes);
+ System.out.println();
+
+ System.out.println("Failed examples by section (total " + fails.size() + "):");
+ printCountsBySection(fails);
+ System.out.println();
+
+ System.out.println("Failed examples:");
+ for (Example fail : fails) {
+ System.out.println("Failed: " + fail);
+ System.out.println("````````````````````````````````");
+ System.out.print(fail.getSource());
+ System.out.println("````````````````````````````````");
+ System.out.println();
+ }
+
+ int expectedPassed = 652;
+ assertTrue("Expected at least " + expectedPassed + " examples to pass but was " + passes.size(), passes.size() >= expectedPassed);
+ assertEquals(0, fails.size());
+ }
+
+ private static void printCountsBySection(List examples) {
+ Map bySection = new LinkedHashMap<>();
+ for (Example example : examples) {
+ Integer count = bySection.get(example.getSection());
+ if (count == null) {
+ count = 0;
+ }
+ bySection.put(example.getSection(), count + 1);
+ }
+ for (Map.Entry entry : bySection.entrySet()) {
+ System.out.println(entry.getValue() + ": " + entry.getKey());
+ }
+ }
+
+ private Node parse(String source) {
+ return Parser.builder().build().parse(source);
+ }
+
+ private String renderMarkdown(String source) {
+ return MARKDOWN_RENDERER.render(parse(source));
+ }
+
+ private String renderHtml(String source) {
+ // The spec uses "rightwards arrow" to show tabs
+ return HTML_RENDERER.render(parse(source)).replace("\t", "\u2192");
+ }
+}
diff --git a/commonmark/src/test/java/org/commonmark/test/UsageExampleTest.java b/commonmark/src/test/java/org/commonmark/test/UsageExampleTest.java
index 9ff646630..08235965a 100644
--- a/commonmark/src/test/java/org/commonmark/test/UsageExampleTest.java
+++ b/commonmark/src/test/java/org/commonmark/test/UsageExampleTest.java
@@ -4,6 +4,7 @@
import org.commonmark.parser.Parser;
import org.commonmark.renderer.NodeRenderer;
import org.commonmark.renderer.html.*;
+import org.commonmark.renderer.markdown.MarkdownRenderer;
import org.junit.Ignore;
import org.junit.Test;
@@ -22,9 +23,21 @@ public class UsageExampleTest {
@Test
public void parseAndRender() {
Parser parser = Parser.builder().build();
- Node document = parser.parse("This is *Sparta*");
+ Node document = parser.parse("This is *Markdown*");
HtmlRenderer renderer = HtmlRenderer.builder().escapeHtml(true).build();
- assertEquals("This is Sparta
\n", renderer.render(document));
+ assertEquals("This is Markdown
\n", renderer.render(document));
+ }
+
+ @Test
+ public void renderToMarkdown() {
+ MarkdownRenderer renderer = MarkdownRenderer.builder().build();
+ Node document = new Document();
+ Heading heading = new Heading();
+ heading.setLevel(2);
+ heading.appendChild(new Text("My title"));
+ document.appendChild(heading);
+
+ assertEquals("## My title\n", renderer.render(document));
}
@Test