traversing a vector tree - clojure

Question

I want to traverse a vector tree that represents hiccup data structures:
[:div {:class "special"} [:btn-grp '("Hello" "Hi")]]
Then I want to dispatch on the keyword of the vector, if a multimethod has been defined for the keyword, then it would return another set of vectors, which will replace the original tag.
For example, the above structure will be transformed to:
[:div {:class "special"} [:div [:button "Hello"] [:button "Hi"]]]
The custom multimethod will receive the list ("hello" "hi") as parameters. It will then return the div containing the buttons.
How do I write a function that traverses the vector and dispatches on the keyword with everything else in the form as parameter, and then replaces the current form with the returned form ?

Answer 1

(ns customtags
(:require [clojure.walk :as walk]))
(def customtags (atom {}))
(defn add-custom-tag [tag f]
(swap! customtags assoc tag f))
(defn try-transform [[tag & params :as coll]]
(if-let [f (get #customtags tag)]
(apply f params)
coll))
(defmacro defcustomtag [tag params & body]
`(add-custom-tag ~tag (fn ~params ~#body)))
(defn apply-custom-tags [coll]
(walk/prewalk
(fn [x]
(if (vector? x)
(try-transform x)
x)) coll))
Using it:
(require '[customtags :as ct])
(ct/defcustomtag :btn-grp [& coll] (into [:div] (map (fn [x] [:button x]) coll)))
(ct/defcustomtag :button [name] [:input {:type "button" :id name}])
(def data [:div {:class "special"} [:btn-grp "Hello" "Hi"]])
(ct/apply-custom-tags data)
[:div {:class "special"} [:div [:input {:type "button", :id "Hello"}] [:input {:type "button", :id "Hi"}]]]