(ns spec-tools.impl
  (:refer-clojure :exclude [resolve])
  #?(:cljs (:require-macros [spec-tools.impl :refer [resolve]]))
  (:require
    #?(:cljs [cljs.analyzer.api])
    [clojure.spec.alpha :as s]
    [clojure.walk :as walk])
  (:import
    #?@(:clj
        [(clojure.lang Var)])))

(defn in-cljs? [env]
  (:ns env))

;; ClojureScript 1.9.655 and later have a resolve macro - maybe this can be
;; eventually converted to use it.
(defmacro resolve
  [env sym]
  `(if (in-cljs? ~env)
     ((clojure.core/resolve 'cljs.analyzer.api/resolve) ~env ~sym)
     (clojure.core/resolve ~env ~sym)))

(defn- cljs-sym [x]
  (if (map? x)
    (:name x)
    x))

(defn- clj-sym [x]
  (if (var? x)
    (let [^Var v x]
      (symbol (str (.name (.ns v)))
              (str (.sym v))))
    x))

(defn ->sym [x]
  #?(:clj  (clj-sym x)
     :cljs (cljs-sym x)))

(defn- unfn [cljs? expr]
  (if (clojure.core/and (seq? expr)
                        (symbol? (first expr))
                        (= "fn*" (name (first expr))))
    (let [[[s] & form] (rest expr)]
      (conj (walk/postwalk-replace {s '%} form) '[%] (if cljs? 'cljs.core/fn 'clojure.core/fn)))
    expr))

#?(:clj
   (defn cljs-resolve [env symbol]
     (clojure.core/or (->> symbol (resolve env) cljs-sym) symbol)))

(defn polish [x]
  (cond
    (seq? x) (flatten (keep polish x))
    (symbol? x) nil
    :else x))

(defn polish-un [x]
  (some-> x polish name keyword))

(defn parse-keys [form]
  (let [m (some->> form (rest) (apply hash-map))]
    (cond-> m
            (:req m) (update :req #(->> % flatten (keep polish) (into [])))
            (:req-un m) (update :req-un #(->> % flatten (keep polish-un) (into [])))
            (:opt-un m) (update :opt-un #(->> % (keep polish-un) (into []))))))

(defn extract-keys [form]
  (let [{:keys [req opt req-un opt-un]} (some->> form (rest) (apply hash-map))]
    (flatten (map polish (concat req opt req-un opt-un)))))

#?(:clj
   (defn resolve-form [env pred]
     (let [cljs? (in-cljs? env)
           res (if cljs? (partial cljs-resolve env) clojure.core/resolve)]
       (->> pred
            (walk/postwalk
             (fn [x]
               (if (symbol? x)
                 (or (some->> x res ->sym) x)
                 x)))
            (unfn cljs?)))))

(defn extract-pred-and-info [x]
  (if (map? x)
    [(:spec x) (dissoc x :spec)]
    [x {}]))

(defn strip-fn-if-needed [form]
  (let [head (first form)]
    ;; Deal with the form (clojure.core/fn [%] (foo ... %))
    ;; We should just use core.match...
    (if (and (= (count form) 3) (= head #?(:clj 'clojure.core/fn :cljs 'cljs.core/fn)))
      (nth form 2)
      form)))

(defn normalize-symbol [kw]
  (case (and (symbol? kw) (namespace kw))
    "spec-tools.spec" (symbol "clojure.core" (name kw))
    "cljs.core" (symbol "clojure.core" (name kw))
    "cljs.spec.alpha" (symbol "clojure.spec.alpha" (name kw))
    kw))

(defn extract-form [spec]
  (if (seq? spec) spec (s/form spec)))

(defn qualified-name [key]
  (if key
    (if-let [nn (namespace key)]
      (str nn "/" (name key))
      (name key))))

(defn nilable-spec? [spec]
  (let [form (and spec (s/form spec))]
    (boolean
      (if-not (= form ::s/unknown)
        (some-> form
                seq
                first
                #{'clojure.spec.alpha/nilable
                  'cljs.spec.alpha/nilable})))))

(defn unwrap
  "Unwrap [x] to x. Asserts that coll has exactly one element."
  [coll]
  {:pre [(= 1 (count coll))]}
  (first coll))

(defn deep-merge [& values]
  (cond
    (every? map? values)
    (apply merge-with deep-merge values)

    (every? coll? values)
    (reduce into values)

    :else
    (last values)))

;;
;; FIXME: using ^:skip-wiki functions from clojure.spec. might break.
;;

(defn register-spec! [k s]
  (s/def-impl k (s/form s) s))