(ns ideal.tools.graph)

(defn add-edge
  [graph v w]
  (update graph v (fnil conj #{}) w))

(defn all-children
  [graph key]
  (if-let [first-children (get graph key)]
    (into #{}
          (concat first-children
                  (mapcat #(all-children graph %) first-children)))
    #{}))

(defn all-vertices
  [graph]
  (into #{}
        (concat (keys graph)
                (apply concat (vals graph)))))

(defn all-edges
  [graph]
  (into #{}
        (reduce-kv (fn [acc k vs]
                     (concat acc (map #(vector k %) vs)))
                   #{}
                   graph)))

(defn invert
  [graph]
  (into {}
        (reduce-kv (fn [acc k vs]
                     (reduce #(add-edge %1 %2 k) acc vs))
                   {}
                   graph)))