(ns pocketbook.hiccup
  "Minimal hiccup → HTML string renderer."
  (:require [clojure.string :as str]))

(def ^:private void-tags
  #{"area" "base" "br" "col" "embed" "hr" "img" "input"
    "link" "meta" "param" "source" "track" "wbr"})

(defn- esc [s]
  (-> (str s)
      (str/replace "&" "&")
      (str/replace "<" "&lt;")
      (str/replace ">" "&gt;")
      (str/replace "\"" "&quot;")))

(defn- render-attrs [m]
  (let [sb (js/Array.)]
    (doseq [[k v] m]
      (when (and (some? v) (not (false? v)))
        (.push sb " ")
        (.push sb (name k))
        (when-not (true? v)
          (.push sb "=\"")
          (.push sb (esc (str v)))
          (.push sb "\""))))
    (.join sb "")))

(defn- parse-tag
  "Parse :div.foo.bar#baz → [\"div\" \"foo bar\" \"baz\"]."
  [tag]
  (let [full     (name tag)
        id       (second (re-find #"#([^.#]+)" full))
        no-id    (str/replace full #"#[^.#]+" "")
        parts    (str/split no-id #"\.")
        tag-name (if (seq (first parts)) (first parts) "div")
        classes  (str/join " " (rest parts))]
    [tag-name (when (seq classes) classes) id]))

(deftype RawHTML [s])

(defn raw
  "Wrap a string to be emitted without HTML escaping."
  [s]
  (RawHTML. s))

(defn html
  "Convert a hiccup form to an HTML string."
  [form]
  (cond
    (nil? form)              ""
    (instance? RawHTML form) (.-s form)
    (string? form)           (esc form)
    (number? form)           (str form)
    (seq? form)              (apply str (map html form))
    (vector? form)
    (let [[tag & rest] form
          [tag-name tag-classes tag-id] (parse-tag tag)
          [attrs children] (if (map? (first rest))
                             [(first rest) (next rest)]
                             [nil rest])
          attrs (cond-> (or attrs {})
                  tag-id      (assoc :id tag-id)
                  tag-classes (update :class #(str tag-classes (when % (str " " %)))))
          inner (apply str (map html children))]
      (if (contains? void-tags tag-name)
        (str "<" tag-name (render-attrs attrs) " />")
        (str "<" tag-name (render-attrs attrs) ">" inner "</" tag-name ">")))
    :else (esc (str form))))