transform with multimethod (transform')

src/instaparse/transform.cljc

@@ -20,34 +20,59 @@ something that can have a metamap attached."
   (let [transform (transform-map (:tag parse-tree))]
     (cond
       transform
-      (merge-meta 
-        (apply transform (map (partial enlive-transform transform-map)
-                              (:content parse-tree)))
-        (meta parse-tree))
+      (merge-meta
+       (apply transform (map (partial enlive-transform transform-map)
+                             (:content parse-tree)))
+       (meta parse-tree))
       (:tag parse-tree)
       (assoc parse-tree :content (map (partial enlive-transform transform-map)
                                       (:content parse-tree)))
       :else
       parse-tree)))
 
+(defn- enlive-transform'
+  [transform parse-tree]
+  (cond
+    transform
+    (merge-meta
+     (apply transform (map (partial enlive-transform transform)
+                           (:content parse-tree)))
+     (meta parse-tree))
+    (:tag parse-tree)
+    (assoc parse-tree :content (map (partial enlive-transform transform)
+                                    (:content parse-tree)))
+    :else
+    parse-tree))
+
 (defn- hiccup-transform
   [transform-map parse-tree]
   (if (and (sequential? parse-tree) (seq parse-tree))
     (if-let [transform (transform-map (first parse-tree))]
       (merge-meta
-        (apply transform (map (partial hiccup-transform transform-map)
-                              (next parse-tree)))
-        (meta parse-tree))
-      (with-meta 
-        (into [(first parse-tree)]
-              (map (partial hiccup-transform transform-map) 
-                   (next parse-tree)))
-        (meta parse-tree)))
+       (apply transform (map (partial hiccup-transform transform-map)
+                             (next parse-tree)))
+       (meta parse-tree))
+      (with-meta
+       (into [(first parse-tree)]
+             (map (partial hiccup-transform transform-map)
+                  (next parse-tree)))
+       (meta parse-tree)))
+    parse-tree))
+
+(defn- hiccup-transform'
+  [transform parse-tree]
+  (if (and (sequential? parse-tree) (seq parse-tree))
+    (merge-meta
+     (apply transform
+            (first parse-tree)
+            (map (partial hiccup-transform' transform)
+                 (next parse-tree)))
+     (meta parse-tree))
     parse-tree))
 
 (defn transform
   "Takes a transform map and a parse tree (or seq of parse-trees).
-   A transform map is a mapping from tags to 
+   A transform map is a mapping from tags to
    functions that take a node's contents and return
    a replacement for the node, i.e.,
    {:node-tag (fn [child1 child2 ...] node-replacement),
@@ -62,20 +87,51 @@ something that can have a metamap attached."
     (and (map? parse-tree) (:tag parse-tree))
     ; This is an enlive tree-seq
     (enlive-transform transform-map parse-tree)
-    
+
     (and (vector? parse-tree) (keyword? (first parse-tree)))
     ; This is a hiccup tree-seq
     (hiccup-transform transform-map parse-tree)
-    
+
     (sequential? parse-tree)
     ; This is either a sequence of parse results, or a tree
     ; with a hidden root tag.
     (map-preserving-meta (partial transform transform-map) parse-tree)
-    
+
     (instance? instaparse.gll.Failure parse-tree)
     ; pass failures through unchanged
     parse-tree
-
+
+    :else
+    (throw-illegal-argument-exception
+     "Invalid parse-tree, not recognized as either enlive or hiccup format.")))
+
+(defn transform'
+  "Takes a transform fn and a parse tree (or seq of parse-trees).
+   For hiccup format, transform fn is like (fn [tag & children] ...)"
+  [transform-fn parse-tree]
+  (cond
+    (string? parse-tree)
+    ; This is a leaf of the tree that should pass through unchanged
+    parse-tree
+
+    ;; TODO: how to handle enlive
+    #_(and (map? parse-tree) (:tag parse-tree))
+    ; This is an enlive tree-seq
+    #_(enlive-transform' transform-fn parse-tree)
+
+    (and (vector? parse-tree) (keyword? (first parse-tree)))
+    ; This is a hiccup tree-seq
+    (hiccup-transform' transform-fn parse-tree)
+
+    (sequential? parse-tree)
+    ; This is either a sequence of parse results, or a tree
+    ; with a hidden root tag.
+    (map-preserving-meta transform-fn parse-tree)
+
+    (instance? instaparse.gll.Failure parse-tree)
+    ; pass failures through unchanged
+    parse-tree
+
     :else
     (throw-illegal-argument-exception
-      "Invalid parse-tree, not recognized as either enlive or hiccup format.")))
+     "Invalid parse-tree, not recognized as either enlive or hiccup format.")))