Implement basic add/remove diff

origami.el

@@ -0,0 +1,148 @@
+;;; origami.el --- Flexible text folding  -*- lexical-binding: t -*-
+
+;; Author: Greg Sexton <gregsexton@gmail.com>
+;; Version: 1.0
+;; Keywords: folding
+;; URL: https://github.com/gregsexton/
+;; Package-Requires: ((emacs "24"))
+
+;; The MIT License (MIT)
+
+;; Copyright (c) 2014 Greg Sexton
+
+;; Permission is hereby granted, free of charge, to any person obtaining a copy
+;; of this software and associated documentation files (the "Software"), to deal
+;; in the Software without restriction, including without limitation the rights
+;; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+;; copies of the Software, and to permit persons to whom the Software is
+;; furnished to do so, subject to the following conditions:
+
+;; The above copyright notice and this permission notice shall be included in
+;; all copies or substantial portions of the Software.
+
+;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+;; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+;; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+;; THE SOFTWARE.
+
+;;; Commentary:
+
+;;; Code:
+
+;;; customisation
+
+;;; fold structure
+
+(defun origami-fold-node (beg end open &optional children data)
+  ;; TODO: ensure invariant: sort children and ensure that none
+  ;; overlap
+  (vector beg end open children data))
+
+(defun origami-top-level-node (&optional children)
+  (origami-fold-node 0 0 t children))
+
+(defun origami-fold-beg (node) (aref node 0))
+(defun origami-fold-end (node) (aref node 1))
+(defun origami-fold-open-p (node) (aref node 2))
+(defun origami-fold-children (node) (aref node 3))
+(defun origami-fold-data (node &optional data)
+  "With optional param DATA, add or replace data. This cannot be
+used to nil out data. This mutates the node."
+  (if data
+      (aset node 4 data)
+    (aref node 4)))
+
+(defun origami-fold-open-set (node value)
+  (origami-fold-node (origami-fold-beg node)
+                     (origami-fold-end node)
+                     value
+                     (origami-fold-children node)
+                     (origami-fold-data node)))
+
+(defun origami-fold-open-toggle (node)
+  (origami-fold-open-set node (not (origami-fold-open-p node))))
+
+(defun origami-fold-shallow-equal (a b)
+  (and (equal (origami-fold-beg a) (origami-fold-beg b))
+       (equal (origami-fold-end a) (origami-fold-end b))
+       (equal (origami-fold-open-p a) (origami-fold-open-p b))))
+
+(defun origami-fold-diff (old new on-add on-remove)
+  "Diff the two structures calling ON-ADD for nodes that have
+been added and ON-REMOVE for nodes that have been removed."
+  (cl-labels ((pair-off (old-children new-children)
+                        (let ((old (car old-children))
+                              (new (car new-children)))
+                          (cond ((null old) (-map (lambda (n) (cons nil n)) new-children))
+                                ((null new) (-map (lambda (n) (cons n nil)) old-children))
+                                ((and (null old) (null new)) '())
+                                ((origami-fold-shallow-equal old new) (cons (cons old new)
+                                                                            (pair-off (cdr old-children)
+                                                                                      (cdr new-children))))
+                                ((<= (origami-fold-beg old)
+                                     (origami-fold-beg new)) (cons (cons old nil)
+                                                                   (pair-off (cdr old-children)
+                                                                             new-children)))
+                                (t (cons (cons nil new)
+                                         (pair-off old-children
+                                                   (cdr new-children)))))))
+              (handle-pair (pair)
+                           (let ((old (car pair))
+                                 (new (cdr pair)))
+                             (cond ((and old new) (origami-fold-diff old new on-add on-remove))
+                                   (old (funcall on-remove old))
+                                   (new (funcall on-add new))
+                                   t (error "Illegal pairing.")))))
+    (unless (origami-fold-shallow-equal old new)
+      (error "Precondition invalid: old must be shallow-equal to new."))
+    (-each (pair-off (origami-fold-children old)
+                     (origami-fold-children new))
+           (lambda (pair) (handle-pair pair)))))
+
+(defun origami-fold-postorder-each (node f)
+  (-each (origami-fold-children node) f)
+  (funcall f node))
+
+;;; overlay manipulation
+
+(defun origami-create-fold-overlay (beg end buffer text)
+  (let ((ov (make-overlay beg end buffer)))
+    (overlay-put ov 'invisible 'origami)
+    ;; TODO: make this customizable
+    (overlay-put ov 'display text)
+    (overlay-put ov 'face 'font-lock-comment-delimiter-face)
+    ov))
+
+(defun origami-create-overlay-from-fold-fn (buffer)
+  (lambda (node)
+    (origami-fold-postorder-each
+     node (lambda (n)
+            (let ((overlay (origami-create-fold-overlay (origami-fold-beg n)
+                                                        (origami-fold-end n) buffer "...")))
+              (origami-fold-data n overlay))))))
+
+(defun origami-delete-overlay-from-fold-fn (buffer)
+  (lambda (node)
+    (origami-fold-postorder-each
+     node (lambda (node)
+            (-when-let (ov (origami-fold-data node))
+              (delete-overlay ov))))))
+
+(defun origami-remove-all-overlays (buffer)
+  ;; TODO:
+  )
+
+;;; commands
+
+(defun origami-reset (buffer)
+  ;; TODO: provide this to the user in case we get screwed up, maybe
+  ;; use this when disabling the minor mode?
+  (interactive)
+  (origami-remove-all-overlays buffer)
+  ;; TODO: remove fold ds
+  )
+
+;;; origami.el ends here