add a single-level list traversal of the tree

core/src/main/groovy/com/muwire/core/files/FileListCallback.java

@@ -0,0 +1,10 @@
+package com.muwire.core.files;
+
+import java.io.File;
+
+public interface FileListCallback<T> {
+
+    public void onFile(File f, T value);
+    
+    public void onDirectory(File f);
+}

core/src/main/groovy/com/muwire/core/files/FileTree.groovy

@@ -71,6 +71,21 @@ class FileTree<T> {
             callback.onDirectoryLeave()
     }
     
+    synchronized void list(File parent, FileListCallback<T> callback) {
+        TreeNode<T> node
+        if (parent == null)
+            node = root
+        else 
+            node = fileToNode.get(parent)
+            
+        node.children.each { 
+            if (it.file.isFile())
+                callback.onFile(it.file, it.value)
+            else
+                callback.onDirectory(it.file)
+        }
+    }
+    
     public static class TreeNode<T> {
         TreeNode parent
         File file

core/src/test/groovy/com/muwire/core/files/FileTreeTest.groovy

@@ -89,4 +89,49 @@ class FileTreeTest {
         assert values.contains("c")
         assert values.contains("e")
     }
+    
+    @Test
+    public void testList() {
+        Set<File> directories = new HashSet<>()
+        Set<String> values = new HashSet<>()
+        def cb = new FileListCallback<String>() {
+
+            @Override
+            public void onDirectory(File file) {
+                directories.add(file)
+            }
+
+            @Override
+            public void onFile(File file, String value) {
+                values.add(value)
+            }
+        }
+        
+        File a = new File("a")
+        a.createNewFile()
+        File b = new File("b")
+        b.mkdir()
+        File c = new File(b, "c")
+        c.createNewFile()
+        
+        FileTree<String> tree = new FileTree<>()
+        
+        tree.add(a, "a")
+        tree.add(b, "b")
+        tree.add(c, "c")
+        
+        tree.list(null, cb)
+        
+        assert directories.size() == 1
+        assert directories.contains(b)
+        assert values.size() == 1
+        assert values.contains("a")
+        
+        directories.clear()
+        values.clear()
+        tree.list(b, cb)
+        assert directories.isEmpty()
+        assert values.size() == 1
+        assert values.contains("c")
+    }
 }