Make HTML rendering for nodes extensible (#35)

We had `CustomHtmlRenderer` for custom nodes before. That was ok for
that, but didn't allow clients to override rendering for core nodes.

This introduces a new concept `NodeRenderer` (including factories, who
doesn't like those?) that is also used for the core nodes. That allows
overriding the rendering and allows to define the rendering for custom
nodes at the same time.

NodeRenderers have access to rendering configuration and functionality,
such as extending attributes. That fixes the problem that the renderer
for table nodes wasn't extensible via `AttributeProvider` (#31).

Author: robinst

commonmark-ext-gfm-strikethrough/src/main/java/org/commonmark/ext/gfm/strikethrough/StrikethroughExtension.java

@@ -2,7 +2,10 @@
 
 import org.commonmark.Extension;
 import org.commonmark.ext.gfm.strikethrough.internal.StrikethroughDelimiterProcessor;
-import org.commonmark.ext.gfm.strikethrough.internal.StrikethroughHtmlRenderer;
+import org.commonmark.ext.gfm.strikethrough.internal.StrikethroughNodeRenderer;
+import org.commonmark.html.renderer.NodeRenderer;
+import org.commonmark.html.renderer.NodeRendererContext;
+import org.commonmark.html.renderer.NodeRendererFactory;
 import org.commonmark.parser.Parser;
 import org.commonmark.html.HtmlRenderer;
 
@@ -33,7 +36,11 @@ public void extend(Parser.Builder parserBuilder) {
 
     @Override
     public void extend(HtmlRenderer.Builder rendererBuilder) {
-        rendererBuilder.customHtmlRenderer(new StrikethroughHtmlRenderer());
+        rendererBuilder.nodeRendererFactory(new NodeRendererFactory() {
+            @Override
+            public NodeRenderer create(NodeRendererContext context) {
+                return new StrikethroughNodeRenderer(context);
+            }
+        });
     }
-
 }

commonmark-ext-gfm-strikethrough/src/main/java/org/commonmark/ext/gfm/strikethrough/internal/StrikethroughHtmlRenderer.java

@@ -0,0 +1,44 @@
+package org.commonmark.ext.gfm.strikethrough.internal;
+
+import org.commonmark.ext.gfm.strikethrough.Strikethrough;
+import org.commonmark.html.HtmlWriter;
+import org.commonmark.html.renderer.NodeRenderer;
+import org.commonmark.html.renderer.NodeRendererContext;
+import org.commonmark.node.Node;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+
+public class StrikethroughNodeRenderer implements NodeRenderer {
+
+    private final NodeRendererContext context;
+    private final HtmlWriter html;
+
+    public StrikethroughNodeRenderer(NodeRendererContext context) {
+        this.context = context;
+        this.html = context.getHtmlWriter();
+    }
+
+    @Override
+    public Set<Class<? extends Node>> getNodeTypes() {
+        return Collections.<Class<? extends Node>>singleton(Strikethrough.class);
+    }
+
+    @Override
+    public void render(Node node) {
+        Map<String, String> attributes = context.extendAttributes(node, Collections.<String, String>emptyMap());
+        html.tag("del", attributes);
+        renderChildren(node);
+        html.tag("/del");
+    }
+
+    private void renderChildren(Node parent) {
+        Node node = parent.getFirstChild();
+        while (node != null) {
+            Node next = node.getNext();
+            context.render(node);
+            node = next;
+        }
+    }
+}

commonmark-ext-gfm-strikethrough/src/main/java/org/commonmark/ext/gfm/strikethrough/internal/StrikethroughNodeRenderer.java

@@ -2,7 +2,10 @@
 
 import org.commonmark.Extension;
 import org.commonmark.ext.gfm.tables.internal.TableBlockParser;
-import org.commonmark.ext.gfm.tables.internal.TableHtmlRenderer;
+import org.commonmark.ext.gfm.tables.internal.TableNodeRenderer;
+import org.commonmark.html.renderer.NodeRenderer;
+import org.commonmark.html.renderer.NodeRendererContext;
+import org.commonmark.html.renderer.NodeRendererFactory;
 import org.commonmark.parser.Parser;
 import org.commonmark.html.HtmlRenderer;
 
@@ -33,7 +36,11 @@ public void extend(Parser.Builder parserBuilder) {
 
     @Override
     public void extend(HtmlRenderer.Builder rendererBuilder) {
-        rendererBuilder.customHtmlRenderer(new TableHtmlRenderer());
+        rendererBuilder.nodeRendererFactory(new NodeRendererFactory() {
+            @Override
+            public NodeRenderer create(NodeRendererContext context) {
+                return new TableNodeRenderer(context);
+            }
+        });
     }
-
 }

commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/TablesExtension.java

@@ -0,0 +1,118 @@
+package org.commonmark.ext.gfm.tables.internal;
+
+import org.commonmark.ext.gfm.tables.*;
+import org.commonmark.html.HtmlWriter;
+import org.commonmark.html.renderer.NodeRenderer;
+import org.commonmark.html.renderer.NodeRendererContext;
+import org.commonmark.node.Node;
+
+import java.util.*;
+
+public class TableNodeRenderer implements NodeRenderer {
+
+    private final HtmlWriter htmlWriter;
+    private final NodeRendererContext context;
+
+    public TableNodeRenderer(NodeRendererContext context) {
+        this.htmlWriter = context.getHtmlWriter();
+        this.context = context;
+    }
+
+    @Override
+    public Set<Class<? extends Node>> getNodeTypes() {
+        return new HashSet<>(Arrays.asList(
+                TableBlock.class,
+                TableHead.class,
+                TableBody.class,
+                TableRow.class,
+                TableCell.class
+        ));
+    }
+
+    @Override
+    public void render(Node node) {
+        if (node instanceof TableBlock) {
+            renderBlock((TableBlock) node);
+        } else if (node instanceof TableHead) {
+            renderHead((TableHead) node);
+        } else if (node instanceof TableBody) {
+            renderBody((TableBody) node);
+        } else if (node instanceof TableRow) {
+            renderRow((TableRow) node);
+        } else if (node instanceof TableCell) {
+            renderCell((TableCell) node);
+        }
+    }
+
+    private void renderBlock(TableBlock tableBlock) {
+        htmlWriter.line();
+        htmlWriter.tag("table", getAttributes(tableBlock));
+        renderChildren(tableBlock);
+        htmlWriter.tag("/table");
+        htmlWriter.line();
+    }
+
+    private void renderHead(TableHead tableHead) {
+        htmlWriter.line();
+        htmlWriter.tag("thead", getAttributes(tableHead));
+        renderChildren(tableHead);
+        htmlWriter.tag("/thead");
+        htmlWriter.line();
+    }
+
+    private void renderBody(TableBody tableBody) {
+        htmlWriter.line();
+        htmlWriter.tag("tbody", getAttributes(tableBody));
+        renderChildren(tableBody);
+        htmlWriter.tag("/tbody");
+        htmlWriter.line();
+    }
+
+    private void renderRow(TableRow tableRow) {
+        htmlWriter.line();
+        htmlWriter.tag("tr", getAttributes(tableRow));
+        renderChildren(tableRow);
+        htmlWriter.tag("/tr");
+        htmlWriter.line();
+    }
+
+    private void renderCell(TableCell tableCell) {
+        String tag = tableCell.isHeader() ? "th" : "td";
+        htmlWriter.tag(tag, getCellAttributes(tableCell));
+        renderChildren(tableCell);
+        htmlWriter.tag("/" + tag);
+    }
+
+    private Map<String, String> getAttributes(Node node) {
+        return context.extendAttributes(node, Collections.<String, String>emptyMap());
+    }
+
+    private Map<String, String> getCellAttributes(TableCell tableCell) {
+        if (tableCell.getAlignment() != null) {
+            return context.extendAttributes(tableCell, Collections.singletonMap("align", getAlignValue(tableCell.getAlignment())));
+        } else {
+            return context.extendAttributes(tableCell, Collections.<String, String>emptyMap());
+        }
+    }
+
+    private static String getAlignValue(TableCell.Alignment alignment) {
+        switch (alignment) {
+            case LEFT:
+                return "left";
+            case CENTER:
+                return "center";
+            case RIGHT:
+                return "right";
+        }
+        throw new IllegalStateException("Unknown alignment: " + alignment);
+    }
+
+    private void renderChildren(Node parent) {
+        Node node = parent.getFirstChild();
+        while (node != null) {
+            Node next = node.getNext();
+            context.render(node);
+            node = next;
+        }
+    }
+}