feat: add @mention notifications, idle timeout, and online duration

- @mention: typing @username in a message sends bell char to that user
  and highlights the message content in bold yellow for them
- Idle timeout: disconnect inactive clients after TNT_IDLE_TIMEOUT
  seconds (default 1800 = 30min, 0 to disable)
- :list now shows connection duration per user (e.g. "alice (12m)")
- Document all three features in help text, manpage, and README

Closes #46

README.md

@@ -92,6 +92,7 @@ ESC                  - Return to NORMAL mode
 **Special messages (INSERT mode)**
 ```
 /me <action>         - Send action (e.g. /me waves)
+@username            - Mention user (bell + highlight)
 ```
 
 ### Security Configuration
@@ -127,6 +128,9 @@ TNT_MAX_CONN_RATE_PER_IP=30 tnt
 
 # Disable connection-rate and auth-failure blocking (testing only)
 TNT_RATE_LIMIT=0 tnt
+
+# Idle timeout in seconds (default 1800 = 30min, 0 to disable)
+TNT_IDLE_TIMEOUT=3600 tnt
 ```
 
 **SSH logging:**

include/common.h

@@ -25,6 +25,7 @@
 #define MAX_LOG_SIZE (10 * 1024 * 1024)  /* 10 MiB */
 #define HOST_KEY_FILE "host_key"
 #define TNT_DEFAULT_STATE_DIR "."
+#define DEFAULT_IDLE_TIMEOUT 1800  /* 30 minutes */
 
 /* ANSI color codes */
 #define ANSI_RESET "\033[0m"

include/ssh_server.h

@@ -27,6 +27,8 @@ typedef struct client {
     char command_output[2048];
     char exec_command[MAX_EXEC_COMMAND_LEN];
     char ssh_login[MAX_USERNAME_LEN];
+    time_t connect_time;
+    time_t last_active;
     atomic_bool redraw_pending;
     pthread_t thread;
     atomic_bool connected;

src/main.c

@@ -65,6 +65,7 @@ int main(int argc, char **argv) {
             printf("  TNT_ACCESS_TOKEN      Require this password for SSH auth\n");
             printf("  TNT_MAX_CONNECTIONS   Global connection limit (default: 64)\n");
             printf("  TNT_RATE_LIMIT        Set to 0 to disable rate limiting\n");
+            printf("  TNT_IDLE_TIMEOUT      Idle disconnect timeout in seconds (default: 1800)\n");
             return 0;
         } else {
             fprintf(stderr, "Unknown option: %s\n", argv[i]);

src/ssh_server.c

@@ -66,6 +66,7 @@ static int g_max_conn_per_ip = 5;
 static int g_max_conn_rate_per_ip = 10;
 static int g_rate_limit_enabled = 1;
 static char g_access_token[256] = "";
+static int g_idle_timeout = DEFAULT_IDLE_TIMEOUT;
 
 static void buffer_appendf(char *buffer, size_t buf_size, size_t *pos,
                            const char *fmt, ...) {
@@ -142,6 +143,8 @@ static void init_rate_limit_config(void) {
     g_max_conn_rate_per_ip = env_int("TNT_MAX_CONN_RATE_PER_IP", 10, 1, 1024);
     g_rate_limit_enabled = env_int("TNT_RATE_LIMIT", 1, 0, 1);
 
+    g_idle_timeout = env_int("TNT_IDLE_TIMEOUT", DEFAULT_IDLE_TIMEOUT, 0, 86400);
+
     if ((env = getenv("TNT_ACCESS_TOKEN")) != NULL) {
         strncpy(g_access_token, env, sizeof(g_access_token) - 1);
         g_access_token[sizeof(g_access_token) - 1] = '\0';
@@ -979,6 +982,31 @@ static int exec_command_tail(client_t *client, const char *args) {
     return rc;
 }
 
+static void notify_mentions(const char *content, const client_t *sender) {
+    pthread_rwlock_rdlock(&g_room->lock);
+    int count = g_room->client_count;
+    client_t *targets[MAX_CLIENTS];
+    int target_count = 0;
+
+    for (int i = 0; i < count; i++) {
+        client_t *c = g_room->clients[i];
+        if (c == sender) continue;
+        char mention[MAX_USERNAME_LEN + 2];
+        snprintf(mention, sizeof(mention), "@%s", c->username);
+        if (strstr(content, mention) != NULL) {
+            client_addref(c);
+            targets[target_count++] = c;
+        }
+    }
+    pthread_rwlock_unlock(&g_room->lock);
+
+    for (int i = 0; i < target_count; i++) {
+        client_send(targets[i], "\a", 1);
+        targets[i]->redraw_pending = true;
+        client_release(targets[i]);
+    }
+}
+
 static int exec_command_post(client_t *client, const char *args) {
     char content[MAX_MESSAGE_LEN];
     char username[MAX_USERNAME_LEN];
@@ -1022,6 +1050,7 @@ static int exec_command_post(client_t *client, const char *args) {
     }
 
     room_broadcast(g_room, &msg);
+    notify_mentions(msg.content, client);
     if (message_save(&msg) < 0) {
         client_printf(client, "post: failed to persist message\n");
         return 1;
@@ -1138,11 +1167,21 @@ static void execute_command(client_t *client) {
                        "----------------------------------------\n",
                        g_room->client_count);
 
+        time_t now = time(NULL);
         for (int i = 0; i < g_room->client_count; i++) {
             char marker = (g_room->clients[i] == client) ? '*' : ' ';
+            int dur = (int)(now - g_room->clients[i]->connect_time);
+            char dur_str[32];
+            if (dur < 60) {
+                snprintf(dur_str, sizeof(dur_str), "%ds", dur);
+            } else if (dur < 3600) {
+                snprintf(dur_str, sizeof(dur_str), "%dm", dur / 60);
+            } else {
+                snprintf(dur_str, sizeof(dur_str), "%dh%dm", dur / 3600, (dur % 3600) / 60);
+            }
             buffer_appendf(output, sizeof(output), &pos,
-                           "%c %d. %s\n", marker, i + 1,
-                           g_room->clients[i]->username);
+                           "%c %d. %s (%s)\n", marker, i + 1,
+                           g_room->clients[i]->username, dur_str);
         }
 
         pthread_rwlock_unlock(&g_room->lock);
@@ -1166,6 +1205,7 @@ static void execute_command(client_t *client) {
                        "========================================\n"
                        "In INSERT mode:\n"
                        "  /me <action>      - Send action message\n"
+                       "  @username         - Mention (bell notify)\n"
                        "========================================\n");
 
     } else if (strncmp(cmd, "msg ", 4) == 0 || strncmp(cmd, "w ", 2) == 0) {
@@ -1357,6 +1397,7 @@ static bool handle_key(client_t *client, unsigned char key, char *input) {
                         snprintf(msg.content, sizeof(msg.content), "%s", input);
                     }
                     room_broadcast(g_room, &msg);
+                    notify_mentions(msg.content, client);
                     message_save(&msg);
                     input[0] = '\0';
                 }
@@ -1534,6 +1575,8 @@ void* client_handle_session(void *arg) {
     client->connected = true;
     client->command_history_count = 0;
     client->command_history_pos = 0;
+    client->connect_time = time(NULL);
+    client->last_active = time(NULL);
 
     /* Check for exec command */
     if (client->exec_command[0] != '\0') {
@@ -1610,6 +1653,13 @@ void* client_handle_session(void *arg) {
                 }
                 last_keepalive = time(NULL);
             }
+
+            if (g_idle_timeout > 0 && joined_room &&
+                time(NULL) - client->last_active >= g_idle_timeout) {
+                client_printf(client, "\r\n\033[33mDisconnected: idle timeout (%d min)\033[0m\r\n",
+                              g_idle_timeout / 60);
+                break;
+            }
             continue;
         }
 
@@ -1621,6 +1671,7 @@ void* client_handle_session(void *arg) {
         }
 
         last_keepalive = time(NULL);
+        client->last_active = last_keepalive;
 
         unsigned char b = buf[0];
 

src/tui.c

@@ -17,12 +17,25 @@ static const char *username_color(const char *name) {
 }
 
 static void format_message_colored(const message_t *msg, char *buffer,
-                                   size_t buf_size, int width) {
+                                   size_t buf_size, int width,
+                                   const char *my_username) {
     struct tm tm_info;
     localtime_r(&msg->timestamp, &tm_info);
     char time_str[32];
     strftime(time_str, sizeof(time_str), "%H:%M", &tm_info);
 
+    bool mentioned = false;
+    if (my_username && my_username[0] != '\0' &&
+        strcmp(msg->username, "系统") != 0) {
+        char mention[MAX_USERNAME_LEN + 2];
+        snprintf(mention, sizeof(mention), "@%s", my_username);
+        if (strstr(msg->content, mention) != NULL) {
+            mentioned = true;
+        }
+    }
+    const char *hl_start = mentioned ? "\033[1;33m" : "";
+    const char *hl_end = mentioned ? "\033[0m" : "";
+
     if (strcmp(msg->username, "系统") == 0) {
         snprintf(buffer, buf_size,
                  "\033[90m--> %s\033[0m", msg->content);
@@ -32,9 +45,9 @@ static void format_message_colored(const message_t *msg, char *buffer,
                  time_str, msg->content);
     } else {
         snprintf(buffer, buf_size,
-                 "\033[90m%s\033[0m %s%s\033[0m: %s",
+                 "\033[90m%s\033[0m %s%s\033[0m: %s%s%s",
                  time_str, username_color(msg->username),
-                 msg->username, msg->content);
+                 msg->username, hl_start, msg->content, hl_end);
     }
 
     /* Plain-text version for width calculation */
@@ -85,9 +98,9 @@ static void format_message_colored(const message_t *msg, char *buffer,
                      time_str, truncated_content);
         } else {
             snprintf(buffer, buf_size,
-                     "\033[90m%s\033[0m %s%s\033[0m: %s",
+                     "\033[90m%s\033[0m %s%s\033[0m: %s%s%s",
                      time_str, username_color(msg->username),
-                     msg->username, truncated_content);
+                     msg->username, hl_start, truncated_content, hl_end);
         }
     }
 }
@@ -236,7 +249,8 @@ void tui_render_screen(client_t *client) {
     if (msg_snapshot) {
         for (int i = 0; i < snapshot_count; i++) {
             char msg_line[2048];
-            format_message_colored(&msg_snapshot[i], msg_line, sizeof(msg_line), render_width);
+            format_message_colored(&msg_snapshot[i], msg_line, sizeof(msg_line),
+                                   render_width, client->username);
             buffer_appendf(buffer, buf_size, &pos, "%s\033[K\r\n", msg_line);
         }
         free(msg_snapshot);
@@ -411,6 +425,7 @@ const char* tui_get_help_text(help_lang_t lang) {
                "\n"
                "SPECIAL MESSAGES:\n"
                "  /me <action>      - Send action (e.g. /me waves)\n"
+               "  @username         - Mention user (bell + highlight)\n"
                "\n"
                "HELP SCREEN KEYS:\n"
                "  q, ESC     - Close help\n"
@@ -454,6 +469,7 @@ const char* tui_get_help_text(help_lang_t lang) {
                "\n"
                "特殊消息:\n"
                "  /me <动作>        - 发送动作 (如 /me 挥手)\n"
+               "  @用户名           - 提及用户 (响铃+高亮)\n"
                "\n"
                "帮助界面按键:\n"
                "  q, ESC     - 关闭帮助\n"

tnt.1

@@ -85,6 +85,7 @@ Ctrl+W	Delete last word
 Ctrl+U	Clear input line
 Ctrl+C	Switch to NORMAL
 /me \fIaction\fR	Send action message (e.g. /me waves)
+@\fIusername\fR	Mention user (bell notification + highlight)
 .TE
 .SS NORMAL mode
 .TS
@@ -152,6 +153,10 @@ Max new connections per IP per 60\-second window (default: 10).
 .B TNT_RATE_LIMIT
 Set to 0 to disable rate\-based blocking and auth\-failure IP blocking.
 Explicit capacity limits still apply (default: 1).
+.TP
+.B TNT_IDLE_TIMEOUT
+Disconnect clients after this many seconds of inactivity.
+Set to 0 to disable (default: 1800, i.e. 30 minutes).
 .SH FILES
 .TP
 .I messages.log