From 3b87ab5ec5d4fdaa15e2fc35294fa2795d0f956f Mon Sep 17 00:00:00 2001
From: Daniel Hammer <daniel@nexlink.cloud>
Date: Tue, 16 Jun 2026 14:02:46 +0200
Subject: [PATCH] feat: add rudimentary tab completion for executables to shell

---
 kernel/src/Api/BuildNo.hpp           |  2 +-
 programs/src/shell/Makefile          |  2 +-
 programs/src/shell/main.cpp          | 26 +++++++++-
 programs/src/shell/shell.h           |  4 ++
 programs/src/shell/tabcompletion.cpp | 74 ++++++++++++++++++++++++++++
 5 files changed, 104 insertions(+), 4 deletions(-)
 create mode 100644 programs/src/shell/tabcompletion.cpp

diff --git a/kernel/src/Api/BuildNo.hpp b/kernel/src/Api/BuildNo.hpp
index 39cdee0..5b60b68 100644
--- a/kernel/src/Api/BuildNo.hpp
+++ b/kernel/src/Api/BuildNo.hpp
@@ -12,4 +12,4 @@
 
 #pragma once
 
-#define MONTAUK_BUILD_NUMBER 25
+#define MONTAUK_BUILD_NUMBER 64
diff --git a/programs/src/shell/Makefile b/programs/src/shell/Makefile
index d52cb28..496861c 100644
--- a/programs/src/shell/Makefile
+++ b/programs/src/shell/Makefile
@@ -64,7 +64,7 @@ LDFLAGS := \
 
 # ---- Source files ----
 
-SRCS := main.cpp vars.cpp builtins.cpp exec.cpp
+SRCS := main.cpp vars.cpp builtins.cpp exec.cpp tabcompletion.cpp
 OBJS := $(addprefix $(OBJDIR)/,$(SRCS:.cpp=.o))
 
 # ---- Target ----
diff --git a/programs/src/shell/main.cpp b/programs/src/shell/main.cpp
index efa7b49..f27f346 100644
--- a/programs/src/shell/main.cpp
+++ b/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;
         }
 
diff --git a/programs/src/shell/shell.h b/programs/src/shell/shell.h
index 52c139a..e457e61 100644
--- a/programs/src/shell/shell.h
+++ b/programs/src/shell/shell.h
@@ -126,3 +126,7 @@ bool switch_drive(int drive);
 // ---- External execution (exec.cpp) ----
 
 int exec_external(const char* cmd, const char* args);
+
+// ---- Tab completion (tabcompletion.cpp) ----
+
+int get_completions(char* string, char** array, int arrayMax);
diff --git a/programs/src/shell/tabcompletion.cpp b/programs/src/shell/tabcompletion.cpp
new file mode 100644
index 0000000..e95e2c4
--- /dev/null
+++ b/programs/src/shell/tabcompletion.cpp
@@ -0,0 +1,74 @@
+/* 
+ * tabcompletion.cpp
+ * Tab completion module
+ * Copyright (c) 2026 Daniel Hammer
+ */ 
+
+#include <montauk/string.h>
+#include <montauk/syscall.h>
+
+#define RD_MAX 128
+
+/*
+	Does the file path end with .elf? 
+*/
+bool is_executable(const char* path) {
+	size_t len = montauk::slen(path);
+
+	if (path[len - 1] == 'f' &&
+		path[len - 2] == 'l' &&
+		path[len - 3] == 'e' && 
+		path[len - 4] == '.')
+	{
+		return true;
+	}
+
+	return false;
+}
+
+/*
+	i.e., "shell.elf" => "shell"
+*/
+const char* strip_elf_extension(const char* path) {
+	size_t len = montauk::slen(path);
+
+	char* p = (char* ) path;
+	p[len - 4] = '\0';
+
+	return (const char*)p;
+}
+
+int get_completions(		// returns no. of results 
+		char*	string, 	// String to match/complete
+		char**	array, 		// Array of strings containing completions
+		int	arrayMax
+	) {
+	
+	const char* names[RD_MAX] 	= { };
+
+	int n = montauk::readdir("0:/os", names, RD_MAX);
+	int r = 0;
+
+	for (int i = 0; i < n; i++) {
+		/*
+			Shift by 3 characters (names[i] + 3):
+				"os/shell.elf" => "shell.elf"
+
+			This is somewhat of a workaround. 
+		*/
+		if (montauk::starts_with(names[i] + 3, (const char*)string)) {
+			if (
+				r > arrayMax ||
+				!is_executable(names[i])
+			) break;
+
+			char* p = (char *)names[i] + 3;
+			strip_elf_extension(p);
+
+			array[r] = (char *)p;
+			r++;
+		} 
+	}
+
+	return r;
+}