Ins extensions markdown renderer

commonmark-ext-ins/src/main/java/org/commonmark/ext/ins/InsExtension.java

@@ -3,16 +3,23 @@ package org.commonmark.ext.ins;
 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 ++
  * <p>
@@ -24,9 +31,7 @@ import org.commonmark.renderer.text.TextContentRenderer;
  * The parsed ins text regions are turned into {@link Ins} nodes.
  * </p>
  */
-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 class InsExtension implements Parser.ParserExtension,
             }
         });
     }
+
+    @Override
+    public void extend(MarkdownRenderer.Builder rendererBuilder) {
+        rendererBuilder.nodeRendererFactory(new MarkdownNodeRendererFactory() {
+            @Override
+            public NodeRenderer create(MarkdownNodeRendererContext context) {
+                return new InsMarkdownNodeRenderer(context);
+            }
+
+            @Override
+            public Set<Character> getSpecialCharacters() {
+                // We technically don't need to escape single occurrences of +, but that's all the extension API
+                // exposes currently.
+                return Collections.singleton('+');
+            }
+        });
+    }
 }

commonmark-ext-ins/src/main/java/org/commonmark/ext/ins/internal/InsMarkdownNodeRenderer.java

+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;
+        }
+    }
+}

commonmark-ext-ins/src/test/java/org/commonmark/ext/ins/InsMarkdownRendererTest.java

+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<Extension> 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);
+    }
+}