(ns ^{:doc "Utilities used in more than one namespace within the parser."
      :author "Simon Brooke"}
  mw-parser.utils)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; This program is free software; you can redistribute it and/or
;; modify it under the terms of the GNU General Public License
;; as published by the Free Software Foundation; either version 2
;; of the License, or (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program; if not, write to the Free Software
;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
;; USA.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


(defn rule?
  "Return true if the argument appears to be a parsed rule tree, else false."
  [maybe-rule]
  (and (coll? maybe-rule) (= (first maybe-rule) :RULE)))


(defn TODO
  "Marker to indicate I'm not yet finished!"
  [message]
  message)


(defn suitable-fragment?
  "Return `true` if `tree-fragment` appears to be a tree fragment of the expected `type`."
  [tree-fragment type]
  (and (coll? tree-fragment)
       (= (first tree-fragment) type)))


(defn assert-type
  "If `tree-fragment` is not a tree fragment of the expected `type`, throw an exception."
  [tree-fragment type]
  (assert (suitable-fragment? tree-fragment type)
          (throw (Exception. (format "Expected a %s fragment" type)))))


(defn search-tree
  "Return the first element of this tree which has this tag in a depth-first, left-to-right search"
  [tree tag]
  (cond
    (= (first tree) tag) tree
    :else (first
            (remove nil?
                    (map
                      #(search-tree % tag)
                      (rest tree))))))