From 3b38913aa1033e6d5ba70f9728ca4c86b0f1ad70 Mon Sep 17 00:00:00 2001
From: subrata05 <ss9sarkar@gmail.com>
Date: Fri, 3 Apr 2026 19:55:22 +0530
Subject: [PATCH] feat: pause/resume terminal output with 'P' key

Press 'p' or 'P' to toggle pause state. Display freezes but serial
data continues buffering in ring buffer to prevent data loss. Works
in both normal and command (Ctrl+A) modes.
---
 src/io/engine.c | 42 +++++++++++++++++++++++++++++++++---------
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/src/io/engine.c b/src/io/engine.c
index 1b05400..d3f5018 100644
--- a/src/io/engine.c
+++ b/src/io/engine.c
@@ -56,8 +56,16 @@ static uint8_t g_display_batch[DISPLAY_BATCH_SIZE];
 static int g_display_batch_len = 0;
 static struct timespec last_display_update = {0, 0};
 
+static int g_paused = 0;  // Pause state: 0 = running, 1 = paused
+
 #define CMD_ESCAPE 0x01  // Ctrl+A
 
+/* Toggle pause/resume state - can be called from main loop */
+static void toggle_pause(void)
+{
+    g_paused = !g_paused;
+}
+
 static inline long long timespec_diff_ms(struct timespec *a, struct timespec *b)
 {
     return (a->tv_sec - b->tv_sec) * 1000LL + (a->tv_nsec - b->tv_nsec) / 1000000LL;
@@ -132,7 +140,7 @@ static void process_serial_input(int serial_fd, int hex_mode)
             ring_buff_advance_write(&g_ring_buf, (size_t)n);
             total_read += (int)n;
             
-            if (logger_active() && !hex_mode) {
+            if (logger_active() && !hex_mode && !g_paused) {
                 logger_write((const char *)write_ptr, (int)n);
             }
         } else if (n == 0) {
@@ -148,6 +156,9 @@ static void process_serial_input(int serial_fd, int hex_mode)
 
 static void flush_display_batch(TermConfig *cfg, int hex_mode)
 {
+    // Skip flushing if paused - don't write to display or log
+    if (g_paused) return;
+
     if (g_display_batch_len > 0) {
         if (hex_mode) {
             // In hex mode, format the batch before display
@@ -175,6 +186,9 @@ static void flush_display_batch(TermConfig *cfg, int hex_mode)
 
 static void drain_ring_buffer(TermConfig *cfg, int hex_mode)
 {
+    // Skip draining if paused - data stays in ring buffer
+    if (g_paused) return;
+
     uint8_t *read_ptr;
     size_t contiguous;
     
@@ -202,7 +216,7 @@ static void handle_command_mode(TermConfig *cfg, int serial_fd)
     (void)serial_fd;
     
     tui_update_status(cfg, 1);
-    mvwprintw(status_win, 0, 1, "CMD: l=toggle log   q=quit   Esc=cancel");
+    mvwprintw(status_win, 0, 1, "CMD: l=toggle log   q=quit   p=pause/resume   Esc=cancel");
     wrefresh(status_win);
     
     tui_set_timeout(1000);
@@ -216,6 +230,9 @@ static void handle_command_mode(TermConfig *cfg, int serial_fd)
             logger_stop();
             cfg->log_enabled = 0;
         }
+    } else if (ch == 'p' || ch == 'P') {
+        // Toggle pause state
+        g_paused = !g_paused;
     } else if (ch == 'q' || ch == 'Q' || ch == 27) {
         ungetch('q');
     }
@@ -232,6 +249,7 @@ void run_engine(int serial_fd, TermConfig *cfg)
     
     g_serial_out_len = 0;
     g_display_batch_len = 0;
+    g_paused = 0;  // Start in running state
     clock_gettime(CLOCK_MONOTONIC, &last_display_update);
     
     tui_init(cfg);
@@ -280,11 +298,15 @@ void run_engine(int serial_fd, TermConfig *cfg)
             } else if (ch == 'h' || ch == 'H') {
                 // Toggle between raw and hex display modes
                 hex_mode = !hex_mode;
+            } else if (ch == 'p' || ch == 'P') {
+                // Toggle pause/resume
+                toggle_pause();
+                tui_update_status(cfg, 1);  // Update status to show PAUSED state
             } else if (ch > 0 && ch != ERR) {
                 if (isprint(ch) || ch == '\n' || ch == '\r' || ch == '\t' || ch == 0x08) {
                     queue_serial_output(serial_fd, (char)ch);
                 }
-            }
+            } 
         }
         
         // Serial output (non-blocking)
@@ -309,12 +331,14 @@ void run_engine(int serial_fd, TermConfig *cfg)
         // Drain ring buffer to display (throttled internally)
         drain_ring_buffer(cfg, hex_mode);
         
-        // Periodic display update
-        struct timespec now;
-        clock_gettime(CLOCK_MONOTONIC, &now);
-        if (timespec_diff_ms(&now, &last_display_update) > 16) {
-            tui_refresh();
-            last_display_update = now;
+        // Periodic display update - also respect pause state
+        if (!g_paused) {
+            struct timespec now;
+            clock_gettime(CLOCK_MONOTONIC, &now);
+            if (timespec_diff_ms(&now, &last_display_update) > 16) {
+                tui_refresh();
+                last_display_update = now;
+            }
         }
     }