tag.cljc

;   Copyright (c) Alan Thompson. All rights reserved.
;   The use and distribution terms for this software are covered by the Eclipse Public License 1.0
;   (http://opensource.org/licenses/eclipse-1.0.php) which can be found in the file epl-v10.html at
;   the root of this distribution.  By using this software in any fashion, you are agreeing to be
;   bound by the terms of this license.  You must not remove this notice, or any other, from this
;   software.
(ns tupelo.tag
  "Tupelo - Making Clojure even sweeter"
  (:require
    [schema.core :as s]
    [tupelo.core :as t]
    ))

(defprotocol IVal (<val [this]))
(defprotocol ITag (<tag [this]))
(defprotocol ITagMap (->tagmap [this]))

(defrecord TagVal
  [tag val]
  ITag (<tag [this] tag)
  IVal (<val [this] val))

; ***** fails strangely under lein-test-refresh after 1st file save if define this using Plumatic schema *****
(defn tagval? ; :- s/Bool
  [arg] (= TagVal (type arg)))

#?(:clj
   (defmethod print-method TagVal
     [tv ^java.io.Writer writer]
     (.write writer
       (format "<%s %s>" (<tag tv) (<val tv)))))
#?(:cljs
   ; https://stackoverflow.com/questions/42916447/adding-a-custom-print-method-for-clojurescript
     (extend-protocol IPrintWithWriter TagVal
       (-pr-writer [arg writer -opts-]
         (write-all writer "<TagVal" (<val arg) ">"))) )

(s/defn tagval-map? :- s/Bool
  "Returns true iff arg is a map that looks like a TagVal record:  {:tag :something :val 42}"
  [item]
  (and (t/map-plain? item)
    (= #{:tag :val} (set (keys item)))))

(s/defn tagval-with?
  [tag :- s/Keyword
   arg :- TagVal]
  (= tag (<tag arg)))

(defn tagged-param?
  [arg]
  (and (= TagVal (type arg))
                          (tagval-with? :param arg)))

(s/defn untagged :- s/Any
  [arg :- s/Any]
  (t/cond-it-> arg
    (satisfies? IVal it) (<val it)))