(ns user
  (:require [clojure.spec.alpha :as s]
            [reitit.ring :as ring]
            [reitit.coercion.spec]
            [muuntaja.core]
            [reitit.ring.middleware.exception]
            [reitit.ring.middleware.parameters]
            [reitit.ring.middleware.muuntaja]
            [reitit.ring.coercion]
            [spec-tools.core :as st]))

;; a spec-tools transformer
(defn- decode-local-date [_ value]
  (try
    (if (string? value)
      (java.time.LocalDate/parse value))
    (catch Exception _
      value)))

;; a local-date spec
(s/def ::local-date
  (st/spec
    {:spec (partial instance? java.time.LocalDate)
     :json-schema/type {:type "string", :format "date"}
     :decode/string decode-local-date
     :decode/json decode-local-date}))

;; application specs
(s/def ::date-str ::local-date)
(s/def ::string-to-date-body (s/keys :req-un [::date-str]))

;; swagger?
(spec-tools.swagger.core/transform ::local-date)
; {:title "user/local-date", :type {:type "string", :format "date"}}

;; from json
(st/decode (s/keys :req-un [::date-str]) {:date-str "2016-01-01"} st/json-transformer)
; {:date-str #object[java.time.LocalDate 0x29d996ae "2016-01-01"]}

;; from strings
(st/coerce (s/keys :req-un [::date-str]) {:date-str "2016-01-01"} st/string-transformer)
; {:date-str #object[java.time.LocalDate 0x29d996ae "2016-01-01"]}

;; the app
(def app
  (ring/ring-handler
    (ring/router
      [["/string-to-date"
        {:post {:parameters {:body (s/keys :req-un [::date-str])}
                :handler (fn [{{body :body} :parameters}]
                           (let [coerced-date (:date-str body)]
                             (if (instance? java.time.LocalDate coerced-date)
                               {:status 200, :body "its a LocalDate"}
                               {:status 500, :body (format "coerced type is %s" (type coerced-date))})))}}]]

      {:data {:coercion reitit.coercion.spec/coercion
              :muuntaja muuntaja.core/instance
              :middleware [reitit.ring.middleware.exception/exception-middleware
                           reitit.ring.middleware.parameters/parameters-middleware
                           reitit.ring.middleware.muuntaja/format-negotiate-middleware
                           reitit.ring.middleware.muuntaja/format-response-middleware
                           reitit.ring.middleware.muuntaja/format-request-middleware
                           reitit.ring.coercion/coerce-response-middleware
                           reitit.ring.coercion/coerce-request-middleware]}})))

;; testing
(app {:request-method :post,
      :headers {"content-type" "application/json"}
      :uri "/string-to-date",
      :body (muuntaja.core/encode "application/json" {:date-str "2016-01-01"})})
;; {:status 200, :body "its a LocalDate"}