Strip empty nodes from output

9 files changed, 82 insertions, 5 deletions

diff --git a/src/main/java/org/zwobble/mammoth/DocumentConverter.java b/src/main/java/org/zwobble/mammoth/DocumentConverter.java
index 38455e3..a6029e0 100644
--- a/src/main/java/org/zwobble/mammoth/DocumentConverter.java
+++ b/src/main/java/org/zwobble/mammoth/DocumentConverter.java
@@ -81,11 +81,7 @@ public class DocumentConverter {
             @Override
             public List<HtmlNode> visit(Paragraph paragraph) {
                 List<HtmlNode> content = convertChildrenToHtml(paragraph);
-                if (content.isEmpty()) {
-                    return list();
-                } else {
-                    return list(Html.element("p", content));
-                }
+                return list(Html.element("p", content));
             }
 
             @Override
diff --git a/src/main/java/org/zwobble/mammoth/Mammoth.java b/src/main/java/org/zwobble/mammoth/Mammoth.java
index 79e15f7..3f9eddb 100644
--- a/src/main/java/org/zwobble/mammoth/Mammoth.java
+++ b/src/main/java/org/zwobble/mammoth/Mammoth.java
@@ -34,6 +34,7 @@ public class Mammoth {
             String idPrefix = "document";
             return reader.readElement(documentXml)
                 .map(nodes -> DocumentConverter.convertToHtml(idPrefix, nodes))
+                .map(Html::stripEmpty)
                 .map(Html::write);
         } catch (IOException e) {
             throw new UnsupportedOperationException("Should return a result of failure");   
diff --git a/src/main/java/org/zwobble/mammoth/html/Html.java b/src/main/java/org/zwobble/mammoth/html/Html.java
index 0a32e58..7e2a82e 100644
--- a/src/main/java/org/zwobble/mammoth/html/Html.java
+++ b/src/main/java/org/zwobble/mammoth/html/Html.java
@@ -1,5 +1,7 @@
 package org.zwobble.mammoth.html;
 
+import org.zwobble.mammoth.util.MammothLists;
+
 import java.util.List;
 import java.util.Map;
 
@@ -50,4 +52,45 @@ public class Html {
     public static HtmlNode selfClosingElement(String tagName, Map<String, String> attributes) {
         return new HtmlSelfClosingElement(tagName, attributes);
     }
+
+    public static List<HtmlNode> stripEmpty(List<HtmlNode> nodes) {
+        return MammothLists.eagerFlatMap(nodes, node -> stripEmpty(node));
+    }
+
+    private static List<HtmlNode> stripEmpty(HtmlNode node) {
+        return node.accept(new HtmlNode.Mapper<List<HtmlNode>>() {
+            @Override
+            public List<HtmlNode> visit(HtmlElement element) {
+                List<HtmlNode> children = stripEmpty(element.getChildren());
+                if (children.isEmpty()) {
+                    return list();
+                } else {
+                    return list(new HtmlElement(
+                        element.getTagName(),
+                        element.getAttributes(),
+                        children,
+                        element.isCollapsible()));
+                }
+            }
+
+            @Override
+            public List<HtmlNode> visit(HtmlSelfClosingElement element) {
+                return list(element);
+            }
+
+            @Override
+            public List<HtmlNode> visit(HtmlTextNode node) {
+                if (node.getValue().isEmpty()) {
+                    return list();
+                } else {
+                    return list(node);
+                }
+            }
+
+            @Override
+            public List<HtmlNode> visit(HtmlForceWrite forceWrite) {
+                return list(forceWrite);
+            }
+        });
+    }
 }
diff --git a/src/main/java/org/zwobble/mammoth/html/HtmlElement.java b/src/main/java/org/zwobble/mammoth/html/HtmlElement.java
index 59683ba..cc81aa2 100644
--- a/src/main/java/org/zwobble/mammoth/html/HtmlElement.java
+++ b/src/main/java/org/zwobble/mammoth/html/HtmlElement.java
@@ -28,8 +28,17 @@ public class HtmlElement implements HtmlNode {
         return children;
     }
 
+    public boolean isCollapsible() {
+        return collapsible;
+    }
+
     @Override
     public void visit(Visitor visitor) {
         visitor.visit(this);
     }
+
+    @Override
+    public <T> T accept(Mapper<T> visitor) {
+        return visitor.visit(this);
+    }
 }
diff --git a/src/main/java/org/zwobble/mammoth/html/HtmlForceWrite.java b/src/main/java/org/zwobble/mammoth/html/HtmlForceWrite.java
index 484be34..f704fd9 100644
--- a/src/main/java/org/zwobble/mammoth/html/HtmlForceWrite.java
+++ b/src/main/java/org/zwobble/mammoth/html/HtmlForceWrite.java
@@ -10,4 +10,9 @@ public class HtmlForceWrite implements HtmlNode {
     public void visit(Visitor visitor) {
         visitor.visit(this);
     }
+
+    @Override
+    public <T> T accept(Mapper<T> visitor) {
+        return visitor.visit(this);
+    }
 }
diff --git a/src/main/java/org/zwobble/mammoth/html/HtmlNode.java b/src/main/java/org/zwobble/mammoth/html/HtmlNode.java
index 823e362..6099519 100644
--- a/src/main/java/org/zwobble/mammoth/html/HtmlNode.java
+++ b/src/main/java/org/zwobble/mammoth/html/HtmlNode.java
@@ -1,7 +1,9 @@
 package org.zwobble.mammoth.html;
 
 public interface HtmlNode {
+    // TODO: rename visit to accept
     void visit(Visitor visitor);
+    <T> T accept(Mapper<T> visitor);
 
     interface Visitor {
         void visit(HtmlElement element);
@@ -9,4 +11,11 @@ public interface HtmlNode {
         void visit(HtmlTextNode node);
         void visit(HtmlForceWrite forceWrite);
     }
+
+    interface Mapper<T> {
+        T visit(HtmlElement element);
+        T visit(HtmlSelfClosingElement element);
+        T visit(HtmlTextNode node);
+        T visit(HtmlForceWrite forceWrite);
+    }
 }
diff --git a/src/main/java/org/zwobble/mammoth/html/HtmlSelfClosingElement.java b/src/main/java/org/zwobble/mammoth/html/HtmlSelfClosingElement.java
index a1ddf2b..62bfd73 100644
--- a/src/main/java/org/zwobble/mammoth/html/HtmlSelfClosingElement.java
+++ b/src/main/java/org/zwobble/mammoth/html/HtmlSelfClosingElement.java
@@ -23,4 +23,9 @@ public class HtmlSelfClosingElement implements HtmlNode {
     public void visit(Visitor visitor) {
         visitor.visit(this);
     }
+
+    @Override
+    public <T> T accept(Mapper<T> visitor) {
+        return visitor.visit(this);
+    }
 }
diff --git a/src/main/java/org/zwobble/mammoth/html/HtmlTextNode.java b/src/main/java/org/zwobble/mammoth/html/HtmlTextNode.java
index 37dceec..a9f9fd5 100644
--- a/src/main/java/org/zwobble/mammoth/html/HtmlTextNode.java
+++ b/src/main/java/org/zwobble/mammoth/html/HtmlTextNode.java
@@ -15,4 +15,9 @@ public class HtmlTextNode implements HtmlNode {
     public void visit(Visitor visitor) {
         visitor.visit(this);
     }
+
+    @Override
+    public <T> T accept(Mapper<T> visitor) {
+        return visitor.visit(this);
+    }
 }
diff --git a/src/main/java/org/zwobble/mammoth/util/MammothLists.java b/src/main/java/org/zwobble/mammoth/util/MammothLists.java
index 5a2e06b..bed3aa8 100644
--- a/src/main/java/org/zwobble/mammoth/util/MammothLists.java
+++ b/src/main/java/org/zwobble/mammoth/util/MammothLists.java
@@ -28,6 +28,10 @@ public class MammothLists {
         return ImmutableList.copyOf(Iterables.concat(first, second));
     }
 
+    public static <T, R> List<R> eagerMap(Iterable<T> iterable, Function<T, R> function) {
+        return ImmutableList.copyOf(Iterables.transform(iterable, function));
+    }
+
     public static <T, R> List<R> eagerFlatMap(Iterable<T> iterable, Function<T, Iterable<R>> function) {
         return ImmutableList.copyOf(Iterables.concat(Iterables.transform(iterable, function)));
     }