;;; shm-overlays.el --- Overlays

;; Copyright (c) 2014 Chris Done. All rights reserved.

;; This file 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 3, or (at your option)
;; any later version.

;; This file 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, see <http://www.gnu.org/licenses/>.

;;; Code:

(require 'cl)
(require 'shm-node)

(defvar shm-current-node-overlay nil
  "Overlay to highlight the current node.")

(defvar shm-last-point 0
  "When moving around, the current node overlay will update
  according to where you are. But often you can shrink/expand the
  scope of the current node. This variable lets us avoid the node
  being reset by realising we haven't actually moved the point.")

(defun shm-delete-overlays (start end type)
  "Delete overlays of the given type. This is used for both
current overlay and quarantines."
  (mapc (lambda (o)
          (when (overlay-get o type)
            (delete-overlay o)))
        (overlays-in start end)))

(defun shm-current-overlay (start end node-pair)
  "Make the overlay for current node at START to END, setting the
NODE-PAIR in the overlay."
  (let ((o (make-overlay start end nil nil t)))
    (overlay-put o 'shm-current-overlay t)
    (overlay-put o 'face 'shm-current-face)
    (overlay-put o 'node-pair node-pair)
    (overlay-put o 'priority 1)
    o))

(defun shm-quarantine-overlay (start end)
  "Make a quarantine from START to END."
  (let ((o (make-overlay start end nil nil t)))
    (overlay-put o 'shm-quarantine t)
    (overlay-put o 'face 'shm-quarantine-face)
    (overlay-put o 'priority 0)
    o))

(defun shm-find-overlay (type)
  "Find overlays at point."
  (remove-if-not (lambda (o) (overlay-get o type))
                 (overlays-in (point-min) (point-max))))

(provide 'shm-overlays)