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(ns defalt
(require [clojure.string :as string]))
;; ns -> symbol key -> :selected
;; ns -> symbol key -> :alternatives -> alternative key -> alternative function
(def registry (atom {}))
(defn parse-alt-name [alt-name]
(let [index (.lastIndexOf alt-name ":")]
(if (= index -1)
(throw (Exception. (str "defalt name \"" alt-name "\" does not contain a ':'"))))
(map #(symbol (apply str %))
[(take index alt-name)
(drop (inc index) alt-name)])))
(defmacro defalt
[combo-name params & impl]
(let [[master-name alt-name] (parse-alt-name (name combo-name))
fun `(fn ~(vec params) ~@impl)]
(if-not (get registry master-name)
(do
(swap! registry assoc-in
[*ns* master-name :selected] ::master)
(swap! registry assoc-in
[*ns* master-name :alternatives ::master] @(resolve master-name))))
(swap! registry assoc-in
[*ns* master-name :alternatives alt-name]
(with-meta
(eval fun)
{:source `'(~'defalt ~combo-name ~params ~@impl)}))
nil))
(defmacro switch [original alternative]
(let [alt (get-in @registry [*ns* original :alternatives alternative])]
(if-not alt
(throw
(Exception.
(str "No alternative \"" alternative "\" for function " original))))
(swap! registry assoc-in
[original :selected] alternative)
(alter-var-root
(resolve original)
(fn [_] alt)))
nil)
(defmacro reset [original]
`(switch ~original ::master))
(defmacro source [original alternative]
(:source
(meta
(get-in @registry [original :alternatives alternative]))))
(defn show*
([original] (show* *ns* original))
([ns original]
(let [enabled (get-in @registry
[ns original :selected])
names (remove #{::master}
(keys (get-in @registry
[ns original :alternatives])))
names (map (fn [x index] {:name x :index index :enabled? (= x enabled)})
names (iterate inc 1))]
(println (str "Alternatives for " original ":"))
(println (str (if (= enabled ::master) "* " " ") "0. <<master>>"))
(doseq [alt names]
(println (str (if (alt :enabled?) "* " " ")
(alt :index) ". "
(alt :name)))))))
(defmacro show [ns & [original]]
(if original
(show* ns original)
(show* ns)))
(defn show-ns* [& [ns]]
(let [ns (or ns *ns*)]
(println "Showing defalt info for namespace" (.getName ns))
(doseq [fun (sort-by name (keys (@registry ns)))]
(show* ns fun))))
(defmacro show-ns [& [ns]]
(if ns
(show-ns* ns)
(show-ns*)))
(defmacro show-global []
`(doseq [ns# (sort-by #(.getName %) (keys @registry))]
(show-ns* ns#)
(println)))
;;(defn add-numbers [a b] (+ a b))
;;(defalt add-numbers:memo [a b] 6)
;;(defalt add-numbers:mock [a b] 0)
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