vis: implement selection rotation

In visual mode + and - will rotate the selection count times to the
right or left respectively. If there exists a line containing multiple
selections then the rotation happens within each line. Otherwise if each
line contains at most one selection the rotation is performed among all
existing selections.

3 files changed, 85 insertions, 2 deletions

diff --git a/README.md b/README.md
index da9ccf3..c8b0ddb 100644
--- a/README.md
+++ b/README.md
@@ -221,6 +221,8 @@ Operators can be forced to work line wise by specifying `V`.
     Ctrl-P       remove primary cursor
     Ctrl-U       make the count previous cursor primary
     Ctrl-D       make the count next cursor primary
+    +            rotates selections rightwards count times
+    -            rotates selections leftwards count times
     Esc          clear all selections, switch to normal mode
 
   In insert/replace mode
diff --git a/config.def.h b/config.def.h
index 0b91be8..67e4c73 100644
--- a/config.def.h
+++ b/config.def.h
@@ -280,8 +280,10 @@ static const KeyBinding bindings_visual[] = {
 	{ "o",                  ACTION(SELECTION_FLIP)                      },
 	{ ">",                  ALIAS("<vis-operator-shift-right>gv")       },
 	{ "<",                  ALIAS("<vis-operator-shift-left>gv")        },
-	{ "<Tab>"  ,            ACTION(CURSORS_ALIGN_INDENT_LEFT)           },
-	{ "<S-Tab>"  ,          ACTION(CURSORS_ALIGN_INDENT_RIGHT)          },
+	{ "<Tab>",              ACTION(CURSORS_ALIGN_INDENT_LEFT)           },
+	{ "<S-Tab>",            ACTION(CURSORS_ALIGN_INDENT_RIGHT)          },
+	{ "-",                  ACTION(SELECTIONS_ROTATE_LEFT)              },
+	{ "+",                  ACTION(SELECTIONS_ROTATE_RIGHT)             },
 	{ 0 /* empty last element, array terminator */                      },
 };
 
diff --git a/main.c b/main.c
index a5fc2d3..6e8e245 100644
--- a/main.c
+++ b/main.c
@@ -12,6 +12,7 @@
 #include "text-objects.h"
 #include "util.h"
 #include "libutf.h"
+#include "array.h"
 
 #define PAGE      INT_MAX
 #define PAGE_HALF (INT_MAX-1)
@@ -56,6 +57,8 @@ static const char *cursors_select(Vis*, const char *keys, const Arg *arg);
 static const char *cursors_select_next(Vis*, const char *keys, const Arg *arg);
 /* clear current selection but select next match */
 static const char *cursors_select_skip(Vis*, const char *keys, const Arg *arg);
+/* rotate selection content count times left (arg->i < 0) or right (arg->i > 0) */
+static const char *selections_rotate(Vis*, const char *keys, const Arg *arg);
 /* adjust current used count according to keys */
 static const char *count(Vis*, const char *keys, const Arg *arg);
 /* move to the count-th line or if not given either to the first (arg->i < 0)
@@ -251,6 +254,8 @@ enum {
 	VIS_ACTION_CURSORS_REMOVE_LAST,
 	VIS_ACTION_CURSORS_PREV,
 	VIS_ACTION_CURSORS_NEXT,
+	VIS_ACTION_SELECTIONS_ROTATE_LEFT,
+	VIS_ACTION_SELECTIONS_ROTATE_RIGHT,
 	VIS_ACTION_TEXT_OBJECT_WORD_OUTER,
 	VIS_ACTION_TEXT_OBJECT_WORD_INNER,
 	VIS_ACTION_TEXT_OBJECT_LONGWORD_OUTER,
@@ -961,6 +966,16 @@ static const KeyAction vis_action[] = {
 		"Move to the next cursor",
 		cursors_navigate, { .i = +PAGE_HALF }
 	},
+	[VIS_ACTION_SELECTIONS_ROTATE_LEFT] = {
+		"selections-rotate-left",
+		"Rotate selections left",
+		selections_rotate, { .i = -1 }
+	},
+	[VIS_ACTION_SELECTIONS_ROTATE_RIGHT] = {
+		"selections-rotate-right",
+		"Rotate selections right",
+		selections_rotate, { .i = +1 }
+	},
 	[VIS_ACTION_TEXT_OBJECT_WORD_OUTER] = {
 		"text-object-word-outer",
 		"A word leading and trailing whitespace included",
@@ -1405,6 +1420,70 @@ static const char *cursors_navigate(Vis *vis, const char *keys, const Arg *arg)
 	return keys;
 }
 
+static const char *selections_rotate(Vis *vis, const char *keys, const Arg *arg) {
+
+	typedef struct {
+		Cursor *cursor;
+		char *data;
+		size_t len;
+	} Rotate;
+
+	Array arr;
+	Text *txt = vis_text(vis);
+	View *view = vis_view(vis);
+	int columns = view_cursors_column_count(view);
+	int selections = columns == 1 ? view_cursors_count(view) : columns;
+	int count = vis_count_get_default(vis, 1);
+	array_init_sized(&arr, sizeof(Rotate));
+	if (!array_reserve(&arr, selections))
+		return keys;
+	size_t line_prev = 0;
+
+	for (Cursor *c = view_cursors(view), *next; c; c = next) {
+		next = view_cursors_next(c);
+
+		Filerange sel = view_cursors_selection_get(c);
+		Rotate rot;
+		rot.cursor = c;
+		rot.len = text_range_size(&sel);
+		if ((rot.data = malloc(rot.len)))
+			rot.len = text_bytes_get(txt, sel.start, rot.len, rot.data);
+		else
+			rot.len = 0;
+		array_add(&arr, &rot);
+
+		size_t pos = view_cursors_pos(c);
+		size_t line = text_lineno_by_pos(txt, pos);
+		if (!next || (columns > 1 && line_prev && line != line_prev)) {
+			size_t len = array_length(&arr);
+			size_t off = arg->i > 0 ? count % len : len - (count % len);
+			for (size_t i = 0; i < len; i++) {
+				size_t j = (i + off) % len;
+				Rotate *oldrot = array_get(&arr, i);
+				Rotate *newrot = array_get(&arr, j);
+				if (!oldrot || !newrot || oldrot == newrot)
+					continue;
+				Filerange newsel = view_cursors_selection_get(newrot->cursor);
+				if (!text_range_valid(&newsel))
+					continue;
+				if (!text_delete_range(txt, &newsel))
+					continue;
+				if (!text_insert(txt, newsel.start, oldrot->data, oldrot->len))
+					continue;
+				newsel.end = newsel.start + oldrot->len;
+				view_cursors_selection_set(newrot->cursor, &newsel);
+				view_cursors_selection_sync(newrot->cursor);
+				free(oldrot->data);
+			}
+			array_clear(&arr);
+		}
+		line_prev = line;
+	}
+
+	vis_count_set(vis, VIS_COUNT_UNKNOWN);
+	return keys;
+}
+
 static const char *replace(Vis *vis, const char *keys, const Arg *arg) {
 	if (!keys[0])
 		return NULL;