Make :earlier and :later accept arguments similar to vim

Currently the following arguments are accepted:

 {count} Go to older text state {count} times.
 {N}s    Go to older text state about {N} seconds before.
 {N}m    Go to older text state about {N} minutes before.
 {N}h    Go to older text state about {N} hours before.
 {N}d    Go to older text state about {N} days before

4 files changed, 90 insertions, 31 deletions

diff --git a/config.def.h b/config.def.h
index 09ba706..044c530 100644
--- a/config.def.h
+++ b/config.def.h
@@ -67,8 +67,8 @@ static Command cmds[] = {
 	{ { "wq",                      }, cmd_wq,         CMD_OPT_FORCE },
 	{ { "write", "w"               }, cmd_write,      CMD_OPT_FORCE },
 	{ { "xit",                     }, cmd_xit,        CMD_OPT_FORCE },
-	{ { "earlier"                  }, cmd_earlier,    CMD_OPT_NONE  },
-	{ { "later"                    }, cmd_later,      CMD_OPT_NONE  },
+	{ { "earlier"                  }, cmd_earlier_later, CMD_OPT_NONE },
+	{ { "later"                    }, cmd_earlier_later, CMD_OPT_NONE },
 	{ { "!",                       }, cmd_filter,     CMD_OPT_NONE  },
 	{ /* array terminator */                                        },
 };
diff --git a/text.c b/text.c
index cb7e1c7..f19d5cb 100644
--- a/text.c
+++ b/text.c
@@ -647,14 +647,36 @@ static size_t history_traverse_to(Text *txt, Action *a) {
 	return pos;
 }
 
-size_t text_earlier(Text *txt) {
-	Action *earlier = txt->history->earlier;
-	return history_traverse_to(txt, earlier);
-}
-
-size_t text_later(Text *txt) {
-	Action *later = txt->history->later;
-	return history_traverse_to(txt, later);
+size_t text_earlier(Text *txt, int count) {
+	Action *a = txt->history;
+	while (count-- > 0 && a->earlier)
+		a = a->earlier;
+	return history_traverse_to(txt, a);
+}
+
+size_t text_later(Text *txt, int count) {
+	Action *a = txt->history;
+	while (count-- > 0 && a->later)
+		a = a->later;
+	return history_traverse_to(txt, a);
+}
+
+size_t text_restore(Text *txt, time_t time) {
+	Action *a = txt->history;
+	while (time < a->time && a->earlier)
+		a = a->earlier;
+	while (time > a->time && a->later)
+		a = a->later;
+	time_t diff = labs(a->time - time);
+	if (a->earlier && a->earlier != txt->history && labs(a->earlier->time - time) < diff)
+		a = a->earlier;
+	if (a->later && a->later != txt->history && labs(a->later->time - time) < diff)
+		a = a->earlier;
+	return history_traverse_to(txt, a);
+}
+
+time_t text_state(Text *txt) {
+	return txt->history->time;
 }
 
 bool text_save(Text *txt, const char *filename) {
diff --git a/text.h b/text.h
index f5091c5..e015abb 100644
--- a/text.h
+++ b/text.h
@@ -2,6 +2,7 @@
 #define TEXT_H
 
 #include <stdbool.h>
+#include <time.h>
 #include <sys/types.h>
 
 #define EPOS ((size_t)-1)         /* invalid position */
@@ -49,8 +50,13 @@ void text_snapshot(Text*);
  * the change occured or EPOS if nothing could be undo/redo. */
 size_t text_undo(Text*);
 size_t text_redo(Text*);
-size_t text_earlier(Text*);
-size_t text_later(Text*);
+/* move chronlogically to the count earlier/later revision */
+size_t text_earlier(Text*, int count);
+size_t text_later(Text*, int count);
+/* restore the text to the state closest to the time given */
+size_t text_restore(Text*, time_t);
+/* get creation time of current state */
+time_t text_state(Text*);
 
 size_t text_pos_by_lineno(Text*, size_t lineno);
 size_t text_lineno_by_pos(Text*, size_t pos);
diff --git a/vis.c b/vis.c
index 2529f65..b85ae47 100644
--- a/vis.c
+++ b/vis.c
@@ -25,6 +25,7 @@
 #include <fcntl.h>
 #include <limits.h>
 #include <ctype.h>
+#include <time.h>
 #include <sys/select.h>
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -419,10 +420,8 @@ static bool cmd_write(Filerange*, enum CmdOpt, const char *argv[]);
 static bool cmd_saveas(Filerange*, enum CmdOpt, const char *argv[]);
 /* filter range through external program argv[1] */
 static bool cmd_filter(Filerange*, enum CmdOpt, const char *argv[]);
-/* switch to the previous saved state of the text, chronologically */
-static bool cmd_earlier(Filerange*, enum CmdOpt, const char *argv[]);
-/* switch to the next saved state of the text, chronologically */
-static bool cmd_later(Filerange*, enum CmdOpt, const char *argv[]);
+/* switch to the previous/next saved state of the text, chronologically */
+static bool cmd_earlier_later(Filerange*, enum CmdOpt, const char *argv[]);
 
 static void action_reset(Action *a);
 static void switchmode_to(Mode *new_mode);
@@ -955,7 +954,7 @@ static void redo(const Arg *arg) {
 }
 
 static void earlier(const Arg *arg) {
-	size_t pos = text_earlier(vis->win->file->text);
+	size_t pos = text_earlier(vis->win->file->text, MAX(vis->action.count, 1));
 	if (pos != EPOS) {
 		view_cursor_to(vis->win->view, pos);
 		/* redraw all windows in case some display the same file */
@@ -964,7 +963,7 @@ static void earlier(const Arg *arg) {
 }
 
 static void later(const Arg *arg) {
-	size_t pos = text_later(vis->win->file->text);
+	size_t pos = text_later(vis->win->file->text, MAX(vis->action.count, 1));
 	if (pos != EPOS) {
 		view_cursor_to(vis->win->view, pos);
 		/* redraw all windows in case some display the same file */
@@ -1879,20 +1878,52 @@ static bool cmd_filter(Filerange *range, enum CmdOpt opt, const char *argv[]) {
 	return status == 0;
 }
 
-static bool cmd_earlier(Filerange *range, enum CmdOpt opt, const char *argv[]) {
-	if (argv[1])
-		return false;
-	//TODO eventually support time arguments
-	text_earlier(vis->win->file->text);
-	return true;
-}
+static bool cmd_earlier_later(Filerange *range, enum CmdOpt opt, const char *argv[]) {
+	Text *txt = vis->win->file->text;
+	char *unit = "";
+	long count = 1;
+	size_t pos = EPOS;
+	if (argv[1]) {
+		errno = 0;
+		count = strtol(argv[1], &unit, 10);
+		if (errno || unit == argv[1] || count < 0) {
+			editor_info_show(vis, "Invalid number");
+			return false;
+		}
 
-static bool cmd_later(Filerange *range, enum CmdOpt opt, const char *argv[]) {
-	if (argv[1])
-		return false;
-	//TODO eventually support time arguments
-	text_later(vis->win->file->text);
-	return true;
+		if (*unit) {
+			while (*unit && isspace((unsigned char)*unit))
+				unit++;
+			switch (*unit) {
+			case 'd': count *= 24;
+			case 'h': count *= 60;
+			case 'm': count *= 60;
+			case 's': break;
+			default:
+				editor_info_show(vis, "Unknown time specifier (use: s,m,h or d)");
+				return false;
+			}
+
+			if (argv[0][0] == 'e')
+				count = -count; /* earlier, move back in time */
+
+			pos = text_restore(txt, text_state(txt) + count);
+		}
+	}
+
+	if (!*unit) {
+		if (argv[0][0] == 'e')
+			pos = text_earlier(txt, count);
+		else
+			pos = text_later(txt, count);
+	}
+
+	time_t state = text_state(txt);
+	char buf[32];
+	strftime(buf, sizeof buf, "State from %H:%M", localtime(&state));
+	editor_info_show(vis, "%s", buf);
+
+	return pos != EPOS;
 }
 
 static Filepos parse_pos(char **cmd) {