From 75a26404bd67d386cebd8014d90f576cc915948e Mon Sep 17 00:00:00 2001
From: Anthony Howe <achowe@snert.com>
Date: Tue, 22 Oct 2024 13:00:15 -0400
Subject: [PATCH] Add small history buffer to aline.c.

---
 README.md   |  3 ++-
 src/aline.c | 23 ++++++++++++++---------
 src/aline.h |  3 +++
 3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/README.md b/README.md
index 6b7328e..1b4490c 100755
--- a/README.md
+++ b/README.md
@@ -109,7 +109,8 @@ To leave Post4 either type the `EOF` terminal character, `BYE`, or `code BYE-COD
 
 Post4 implements simple TTY style line editing for the last interactive input line.  GNU `readline` or BSD `libedit` are not supported.  Essentially the `stty(1)` keys are supported, in addition to being able to edit the last input line.
 
-        up      ^K      Edit the previous input line.
+        up      ^K      Cycle to the previous input line to edit.
+        down    ^L      Cycle to the next input line to edit.
         left    right   Cursor left or right within line.
         ERASE   ^H  ^?  Erase character before the cursor.
         WERASE          Erase the previous white space delimited word.
diff --git a/src/aline.c b/src/aline.c
index 9dd16b7..3199aca 100644
--- a/src/aline.c
+++ b/src/aline.c
@@ -19,8 +19,9 @@ int is_tty;
 static int tty_fd = -1;
 static int tty_mode = 0;
 static struct termios tty_modes[3];
-static char lastline[256];
+static char history[ALINE_HISTORY][MAX_INPUT];
 static const char *ps2;
+static int lastline;
 
 #define tty_saved	tty_modes[ALINE_CANONICAL]
 #define tty_raw		tty_modes[ALINE_RAW]
@@ -136,7 +137,7 @@ int
 alineInput(FILE *fp, const char *prompt, char *buf, size_t size)
 {
 	unsigned i;
-	int ch, pcol, pos[2];
+	int ch, pcol, pos[2], prevline = lastline;
 
 	if (buf == NULL || size < 1) {
 		return EOF;
@@ -153,8 +154,8 @@ alineInput(FILE *fp, const char *prompt, char *buf, size_t size)
 		prompt = ps2;
 	}
 	pcol = strlen(prompt);
-	if (sizeof (lastline) < size) {
-		size = sizeof (lastline);
+	if (sizeof (*history) < size) {
+		size = sizeof (*history);
 	}
 	alineGetRowCol(pos);
 	(void) printf(ANSI_SAVE_CURSOR);
@@ -171,8 +172,10 @@ alineInput(FILE *fp, const char *prompt, char *buf, size_t size)
 		if (ch == '\e') {
 			if ((ch = fgetc(stdin)) == '[') {
 				ch = fgetc(stdin);
-				if (ch == 'A' || ch == 'B') {
+				if (ch == 'A') {
 					ch = '\v';
+				} else if (ch == 'B') {
+					ch = '\f';
 				} else if (ch == 'C') {
 					i += i < size && buf[i] != '\0';
 					continue;
@@ -182,10 +185,11 @@ alineInput(FILE *fp, const char *prompt, char *buf, size_t size)
 				}
 			}
 		}
-		if (ch == '\v') {
+		if (ch == '\v' || ch == '\f') {
 			/* Restore intput to last input line. */
-			(void) strncpy(buf, lastline, size-1);
-			i = strlen(lastline);
+			prevline = (prevline+(ch == '\v' ? -1 : 1)) & (ALINE_HISTORY-1);
+			(void) strncpy(buf, history[prevline], size-1);
+			i = strlen(history[prevline]);
 		} else if (ch == tty_saved.c_cc[VERASE] || ch == '\b' || ch == 127) {
 			if (0 < i) {
 				i--;
@@ -210,7 +214,8 @@ alineInput(FILE *fp, const char *prompt, char *buf, size_t size)
 		}
 	}
 	if (0 < i) {
-		(void) strncpy(lastline, buf, size-1);
+		(void) strncpy(history[lastline], buf, size-1);
+		lastline = (lastline+1) & (ALINE_HISTORY-1);
 	}
 	return (int) strlen(buf);
 }
diff --git a/src/aline.h b/src/aline.h
index b7974a5..f3169c2 100644
--- a/src/aline.h
+++ b/src/aline.h
@@ -31,6 +31,7 @@ extern "C" {
 #include "ansiterm.h"
 
 #include <stdio.h>
+#include <limits.h>
 
 #ifdef HAVE_TERMIOS_H
 # include <termios.h>
@@ -50,6 +51,8 @@ extern struct winsize window;
 #define ALINE_RAW		1
 #define ALINE_RAW_NB		2
 
+#define ALINE_HISTORY		4
+
 extern void alineInit(void);
 extern void alineFini(void);
 extern int alineReadByte(void);