(ns outliner.model.history)

(def history-keys [:doc :view])

(defn record-history [doc view sys]
  (let [snapshot {:doc doc :view view}]
    (-> sys
        (update :undo-stack conj snapshot)
        (assoc :redo-stack []))))

(defn undo [doc view sys]
  (if-let [snapshot (peek (:undo-stack sys))]
    (let [current-snapshot {:doc doc :view view}]
      {:doc (:doc snapshot)
       :view (:view snapshot)
       :sys (-> sys
                (update :undo-stack pop)
                (update :redo-stack conj current-snapshot))})
    {:doc doc :view view :sys sys}))

(defn redo [doc view sys]
  (if-let [snapshot (peek (:redo-stack sys))]
    (let [current-snapshot {:doc doc :view view}]
      {:doc (:doc snapshot)
       :view (:view snapshot)
       :sys (-> sys
                (update :redo-stack pop)
                (update :undo-stack conj current-snapshot))})
    {:doc doc :view view :sys sys}))

(defn mark-edit [sys id]
  (assoc sys :last-edit-id id))

(defn clear-edit-marker [sys]
  (dissoc sys :last-edit-id))