From e81b7a5faa3c713ce4d4e0952d7640517f13ef69 Mon Sep 17 00:00:00 2001
From: Scott Worley <scottworley@scottworley.com>
Date: Wed, 13 Sep 2023 11:11:49 -0700
Subject: [PATCH] Interactive mode: Prompt, feedback, & screen clearing

---
 tl-append.c | 45 ++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 40 insertions(+), 5 deletions(-)

diff --git a/tl-append.c b/tl-append.c
index f8bacdd..c4a4ac6 100644
--- a/tl-append.c
+++ b/tl-append.c
@@ -1,11 +1,39 @@
+#define _POSIX_C_SOURCE 199309L
+
+#include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
 
 #include "common.h"
 
 const size_t BUF_SIZE = 1024;
 
-static void read_line(char *buf) {
+const char PROMPT[] = "\33[H" /* Move cursor 'home' */
+                      "\33[J" /* Clear screen */
+                      "> ";
+const char ACKNOWLEDGE[] = "[OK]";
+const struct timespec ACKNOWLEDGE_DELAY = {0, 300000000};
+
+typedef struct {
+  int interactive;
+} conf_t;
+
+conf_t parse_command_line(int argc, char *argv[]) {
+  conf_t conf = {0};
+
+  if (argc == 2 && strcmp(argv[1], "-i") == 0 && isatty(2))
+    conf.interactive = 1;
+
+  return conf;
+}
+
+static void read_line(conf_t conf, char *buf) {
+  if (conf.interactive)
+    if (fputs(PROMPT, stderr) == EOF)
+      die("I/O error writing prompt");
   if (fgets(buf, BUF_SIZE, stdin) == NULL) {
     if (ferror(stdin))
       die("I/O error reading line");
@@ -17,7 +45,7 @@ static void read_line(char *buf) {
   }
 }
 
-static void write_line(const char *line) {
+static void write_line(conf_t conf, const char *line) {
   const char *now = encode_time(time(NULL));
   FILE *f = fopen(FILENAME, "a");
   if (f == NULL)
@@ -30,12 +58,19 @@ static void write_line(const char *line) {
     die("Error writing to output file");
   if (fclose(f) != 0)
     die_err("Error closing output file");
+  if (conf.interactive) {
+    if (fputs(ACKNOWLEDGE, stderr) == EOF)
+      die("Error writing acknowledgment");
+    if (nanosleep(&ACKNOWLEDGE_DELAY, NULL) == -1 && errno != EINTR)
+      die_err("Error sleeping");
+  }
 }
 
-int main() {
+int main(int argc, char *argv[]) {
+  conf_t conf = parse_command_line(argc, argv);
   char buf[BUF_SIZE];
-  for (read_line(buf); buf[0]; read_line(buf)) {
-    write_line(buf);
+  for (read_line(conf, buf); buf[0]; read_line(conf, buf)) {
+    write_line(conf, buf);
   }
   return 0;
 }
-- 
2.44.1