From 1a957be171f50621031f93cee2b800fd3fcb6d2f Mon Sep 17 00:00:00 2001
From: Greg Sexton <gregsexton@gmail.com>
Date: Sat, 9 Jul 2016 17:50:23 +0100
Subject: [PATCH] Add more interactive movement commands

---
 README.md  | 17 ++++++++++++++-
 origami.el | 61 ++++++++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 71 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index aab2866..67d4fba 100644
--- a/README.md
+++ b/README.md
@@ -123,7 +123,22 @@ buffer - those in bold are particularly useful:
 
   <tr>
     <td>origami-next-fold</td>
-    <td>Move to the next fold.</td>
+    <td>Move to the end of the next fold.</td>
+  </tr>
+
+  <tr>
+    <td>origami-forward-fold</td>
+    <td>Move to the start of the next fold.</td>
+  </tr>
+
+  <tr>
+    <td>origami-forward-fold-same-level</td>
+    <td>Move to the start of the next fold that is a sibling of the current fold.</td>
+  </tr>
+
+  <tr>
+    <td>origami-backward-fold-same-level</td>
+    <td>Move to the start of the previous fold that is a sibling of the current fold.</td>
   </tr>
 
   <tr>
diff --git a/origami.el b/origami.el
index 9c27976..f08cd0a 100644
--- a/origami.el
+++ b/origami.el
@@ -379,13 +379,27 @@ with the current state and the current node at each iteration."
 (defun origami-fold-shallow-merge (tree1 tree2)
   "Shallow merge the children of TREE2 in to TREE1."
   (-reduce-from (lambda (tree node)
-                  (origami-fold-assoc (origami-fold-find-path-containing-range tree
+  (origami-fold-assoc (origami-fold-find-path-containing-range tree
                                                                                (origami-fold-beg node)
                                                                                (origami-fold-end node))
                                       (lambda (leaf)
-                                        (origami-fold-add-child leaf node))))
+  (origami-fold-add-child leaf node))))
                 tree1 (origami-fold-children tree2)))
 
+(defun origami-fold-parent (path)
+  (-last-item (-butlast path)))
+
+(defun origami-fold-prev-sibling (siblings node)
+  (->> siblings
+       (-partition-in-steps 2 1)
+       (-drop-while (lambda (pair) (not (equal (cadr pair) node))))
+       caar))
+
+(defun origami-fold-next-sibling (siblings node)
+  (->> siblings
+       (-drop-while (lambda (n) (not (equal n node))))
+       cadr))
+
 ;;; linear history structure
 
 (defun origami-h-new (present)
@@ -686,10 +700,45 @@ a fold, move to the end of the fold that POINT is in."
   (interactive (list (current-buffer) (point)))
   (-when-let (tree (origami-get-fold-tree buffer))
     (-> tree
-      (origami-fold-postorder-reduce (lambda (state n)
-                                       (cons (origami-fold-end n) state)) nil)
-      (->> (-last (lambda (pos) (> pos point))))
-      goto-char)))
+        (origami-fold-postorder-reduce (lambda (state n)
+                                         (cons (origami-fold-end n) state)) nil)
+        (->> (-last (lambda (pos) (> pos point))))
+        goto-char)))
+
+(defun origami-forward-fold (buffer point)
+  "Move point to the beginning of the first fold in the BUFFER
+after POINT."
+  (interactive (list (current-buffer) (point)))
+  (-when-let (tree (origami-get-fold-tree buffer))
+    (-> tree
+        (origami-fold-preorder-reduce (lambda (state n)
+  (cons (origami-fold-beg n) state)) nil)
+        (->> (-last (lambda (pos) (> pos point))))
+        goto-char)))
+
+(defun origami-forward-fold-same-level (buffer point)
+  "Move point to the beginning of the next fold in the buffer
+that is a sibling of the fold the point is currently in."
+  (interactive (list (current-buffer) (point)))
+  (-when-let (tree (origami-get-fold-tree buffer))
+    (-when-let (path (origami-fold-find-path-containing tree point))
+      (when-let (c (-> (origami-fold-next-sibling (origami-fold-children
+                                                   (origami-fold-parent path))
+                                                  (-last-item path))
+                       origami-fold-beg))
+        (goto-char c)))))
+
+(defun origami-backward-fold-same-level (buffer point)
+  "Move point to the beginning of the previous fold in the buffer
+that is a sibling of the fold the point is currently in."
+  (interactive (list (current-buffer) (point)))
+  (-when-let (tree (origami-get-fold-tree buffer))
+    (-when-let (path (origami-fold-find-path-containing tree point))
+      (-when-let (c (-> (origami-fold-prev-sibling (origami-fold-children
+                                                    (origami-fold-parent path))
+                                                   (-last-item path))
+                        origami-fold-beg))
+        (goto-char c)))))
 
 (defun origami-undo (buffer)
   "Undo the last folding operation applied to BUFFER. Undo