feat: add rudimentary tab completion for executables to shell

programs/src/shell/main.cpp

@@ -39,8 +39,6 @@ void sync_cwd() {
 // ---- Session info (read once at startup) ----
 
 void read_session() {
-    // TODO Why is getuser treated as not defined in VSCode intellisense?
-
     montauk::getuser(
         (char *)&session_user, // Buffer
         32                     // Buffer max size
@@ -352,6 +350,10 @@ static constexpr uint8_t SC_DOWN  = 0x50;
 static constexpr uint8_t SC_LEFT  = 0x4B;
 static constexpr uint8_t SC_RIGHT = 0x4D;
 
+// ---- Tab key scancode ----
+
+static constexpr uint8_t SC_TAB   = 0x0F;
+
 static bool empty_key_event(const montauk::abi::KeyEvent& ev) {
     return ev.scancode == 0 && ev.ascii == 0 && !ev.pressed &&
            !ev.shift && !ev.ctrl && !ev.alt;
@@ -427,6 +429,26 @@ extern "C" void _start() {
                     line[0] = '\0';
                 }
             }
+
+            continue;
+        }
+
+        if (ev.scancode == SC_TAB) {
+            line[pos] = '\0';
+
+            char* table[128] = { };
+            int n = get_completions(line, table, 128);
+
+            montauk::print("\n");
+            for (int i = 0; i < n; i++) {
+                montauk::print("  ");
+                montauk::print(table[i]);
+                montauk::print("\n");
+            }
+
+            pos = 0;
+            prompt();
+
             continue;
         }