nut_shell/shell/

mod.rs

//! Shell orchestration and command processing.
//!
//! Brings together I/O, command trees, authentication, and history into interactive CLI.
//! Follows unified architecture: single code path handles both auth-enabled and auth-disabled modes.
//! Lifecycle: `Inactive` → `activate()` → (`LoggedOut` →) `LoggedIn` → `deactivate()`.

use crate::auth::{AccessLevel, User};
use crate::config::ShellConfig;
use crate::error::CliError;
use crate::io::CharIo;
use crate::response::Response;
use crate::tree::{CommandKind, Directory, Node};
use core::marker::PhantomData;

#[cfg(feature = "completion")]
use crate::tree::completion::suggest_completions;

// Sub-modules
pub mod decoder;
pub mod handler;
pub mod history;

// Re-export key types
pub use decoder::{InputDecoder, InputEvent};
pub use handler::CommandHandler;
pub use history::CommandHistory;

/// History navigation direction.
///
/// Used by `Request::History` variant. Self-documenting alternative to bool.
#[repr(u8)]
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum HistoryDirection {
    /// Up arrow key (navigate to older command)
    Previous = 0,

    /// Down arrow key (navigate to newer command or restore original)
    Next = 1,
}

/// CLI state (authentication state).
///
/// Tracks whether the CLI is active and whether user is authenticated.
/// Used by unified architecture pattern to drive behavior.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum CliState {
    /// CLI not active
    Inactive,

    /// Awaiting authentication
    #[cfg(feature = "authentication")]
    LoggedOut,

    /// Authenticated or auth-disabled mode
    LoggedIn,
}

/// Request type representing parsed user input.
///
/// Generic over `C: ShellConfig` to use configured buffer sizes.
/// Variants are feature-gated based on available features.
#[derive(Debug, Clone)]
#[allow(clippy::large_enum_variant)]
pub enum Request<C: ShellConfig> {
    /// Valid authentication attempt
    #[cfg(feature = "authentication")]
    Login {
        /// Username
        username: heapless::String<32>,
        /// Password
        password: heapless::String<64>,
    },

    /// Invalid authentication attempt
    #[cfg(feature = "authentication")]
    InvalidLogin,

    /// Execute command
    Command {
        /// Command path
        path: heapless::String<128>, // TODO: Use C::MAX_INPUT when const generics stabilize
        /// Command arguments
        args: heapless::Vec<heapless::String<128>, 16>, // TODO: Use C::MAX_INPUT and C::MAX_ARGS
        /// Original command string for history
        #[cfg(feature = "history")]
        original: heapless::String<128>, // TODO: Use C::MAX_INPUT
        /// Phantom data for config type (will be used when const generics stabilize)
        _phantom: PhantomData<C>,
    },

    /// Request completions
    #[cfg(feature = "completion")]
    TabComplete {
        /// Partial path to complete
        path: heapless::String<128>, // TODO: Use C::MAX_INPUT
    },

    /// Navigate history
    #[cfg(feature = "history")]
    History {
        /// Navigation direction
        direction: HistoryDirection,
        /// Current buffer content
        buffer: heapless::String<128>, // TODO: Use C::MAX_INPUT
    },
}

/// Shell orchestration struct.
///
/// Brings together all components following the unified architecture pattern.
/// Uses single code path for both auth-enabled and auth-disabled modes.
pub struct Shell<'tree, L, IO, H, C>
where
    L: AccessLevel,
    IO: CharIo,
    H: CommandHandler<C>,
    C: ShellConfig,
{
    /// Command tree root
    tree: &'tree Directory<L>,

    /// Current user (None when logged out or auth disabled)
    current_user: Option<User<L>>,

    /// CLI state (auth state)
    state: CliState,

    /// Input buffer (using concrete size for now - TODO: use C::MAX_INPUT when const generics stabilize)
    input_buffer: heapless::String<128>,

    /// Current directory path (stack of child indices, using concrete size - TODO: use C::MAX_PATH_DEPTH when const generics stabilize)
    current_path: heapless::Vec<usize, 8>,

    /// Input decoder (escape sequence state machine)
    decoder: InputDecoder,

    /// Command history (using concrete sizes - TODO: use C::HISTORY_SIZE and C::MAX_INPUT when const generics stabilize)
    #[cfg_attr(not(feature = "history"), allow(dead_code))]
    history: CommandHistory<10, 128>,

    /// I/O interface
    io: IO,

    /// Command handler
    handler: H,

    /// Credential provider
    #[cfg(feature = "authentication")]
    credential_provider: &'tree (dyn crate::auth::CredentialProvider<L, Error = ()> + 'tree),

    /// Config type marker (zero-size)
    _config: PhantomData<C>,
}

// ============================================================================
// Debug implementation
// ============================================================================

impl<'tree, L, IO, H, C> core::fmt::Debug for Shell<'tree, L, IO, H, C>
where
    L: AccessLevel,
    IO: CharIo,
    H: CommandHandler<C>,
    C: ShellConfig,
{
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        let mut debug_struct = f.debug_struct("Shell");
        debug_struct
            .field("state", &self.state)
            .field("input_buffer", &self.input_buffer.as_str())
            .field("current_path", &self.current_path);

        if let Some(user) = &self.current_user {
            debug_struct.field("current_user", &user.username.as_str());
        } else {
            debug_struct.field("current_user", &"None");
        }

        #[cfg(feature = "authentication")]
        debug_struct.field("credential_provider", &"<dyn CredentialProvider>");

        debug_struct.finish_non_exhaustive()
    }
}

// ============================================================================
// Constructors (feature-conditional)
// ============================================================================

#[cfg(feature = "authentication")]
impl<'tree, L, IO, H, C> Shell<'tree, L, IO, H, C>
where
    L: AccessLevel,
    IO: CharIo,
    H: CommandHandler<C>,
    C: ShellConfig,
{
    /// Create shell with authentication enabled (starts `Inactive`).
    /// Call `activate()` to show welcome message and login prompt.
    pub fn new(
        tree: &'tree Directory<L>,
        handler: H,
        credential_provider: &'tree (dyn crate::auth::CredentialProvider<L, Error = ()> + 'tree),
        io: IO,
    ) -> Self {
        Self {
            tree,
            handler,
            current_user: None,
            state: CliState::Inactive,
            input_buffer: heapless::String::new(),
            current_path: heapless::Vec::new(),
            decoder: InputDecoder::new(),
            history: CommandHistory::new(),
            io,
            credential_provider,
            _config: PhantomData,
        }
    }
}

#[cfg(not(feature = "authentication"))]
impl<'tree, L, IO, H, C> Shell<'tree, L, IO, H, C>
where
    L: AccessLevel,
    IO: CharIo,
    H: CommandHandler<C>,
    C: ShellConfig,
{
    /// Create new Shell
    ///
    /// Starts in `Inactive` state. Call `activate()` to show welcome message and prompt.
    pub fn new(tree: &'tree Directory<L>, handler: H, io: IO) -> Self {
        Self {
            tree,
            handler,
            current_user: None,
            state: CliState::Inactive,
            input_buffer: heapless::String::new(),
            current_path: heapless::Vec::new(),
            decoder: InputDecoder::new(),
            history: CommandHistory::new(),
            io,
            _config: PhantomData,
        }
    }
}

// ============================================================================
// Core methods (unified implementation for both modes)
// ============================================================================

impl<'tree, L, IO, H, C> Shell<'tree, L, IO, H, C>
where
    L: AccessLevel,
    IO: CharIo,
    H: CommandHandler<C>,
    C: ShellConfig,
{
    /// Activate the shell (show welcome message and initial prompt).
    ///
    /// Transitions from `Inactive` to appropriate state (LoggedOut or LoggedIn).
    pub fn activate(&mut self) -> Result<(), IO::Error> {
        self.io.write_str(C::MSG_WELCOME)?;
        self.io.write_str("\r\n")?;

        #[cfg(feature = "authentication")]
        {
            self.state = CliState::LoggedOut;
            self.io.write_str(C::MSG_LOGIN_PROMPT)?;
        }

        #[cfg(not(feature = "authentication"))]
        {
            self.state = CliState::LoggedIn;
            self.generate_and_write_prompt()?;
        }

        Ok(())
    }

    /// Deactivate shell (transition to `Inactive`).
    /// Clears session and resets to root directory.
    pub fn deactivate(&mut self) {
        self.state = CliState::Inactive;
        self.current_user = None;
        self.input_buffer.clear();
        self.current_path.clear();
    }

    /// Process single character of input (main entry point for char-by-char processing).
    pub fn process_char(&mut self, c: char) -> Result<(), IO::Error> {
        // Decode character into logical event
        let event = self.decoder.decode_char(c);

        match event {
            InputEvent::None => Ok(()), // Still accumulating sequence

            InputEvent::Char(ch) => {
                // Try to add to buffer
                match self.input_buffer.push(ch) {
                    Ok(_) => {
                        // Successfully added - echo (with password masking if applicable)
                        let echo_char = self.get_echo_char(ch);
                        self.io.put_char(echo_char)?;
                        Ok(())
                    }
                    Err(_) => {
                        // Buffer full - beep and ignore
                        self.io.put_char('\x07')?; // Bell character
                        Ok(())
                    }
                }
            }

            InputEvent::Backspace => {
                // Remove from buffer if not empty
                if !self.input_buffer.is_empty() {
                    self.input_buffer.pop();
                    // Echo backspace sequence
                    self.io.write_str("\x08 \x08")?;
                }
                Ok(())
            }

            InputEvent::DoubleEsc => {
                // Clear buffer and redraw (Shell's interpretation of double-ESC)
                self.input_buffer.clear();
                self.clear_line_and_redraw()
            }

            InputEvent::Enter => self.handle_enter(),

            InputEvent::Tab => self.handle_tab(),

            InputEvent::UpArrow => self.handle_history(HistoryDirection::Previous),

            InputEvent::DownArrow => self.handle_history(HistoryDirection::Next),
        }
    }

    /// Process single character of input (async version).
    /// Can execute both sync and async commands.
    #[cfg(feature = "async")]
    pub async fn process_char_async(&mut self, c: char) -> Result<(), IO::Error> {
        // Decode character into logical event
        let event = self.decoder.decode_char(c);

        match event {
            InputEvent::None => Ok(()), // Still accumulating sequence

            InputEvent::Char(ch) => {
                // Try to add to buffer
                match self.input_buffer.push(ch) {
                    Ok(_) => {
                        // Successfully added - echo (with password masking if applicable)
                        let echo_char = self.get_echo_char(ch);
                        self.io.put_char(echo_char)?;
                        Ok(())
                    }
                    Err(_) => {
                        // Buffer full - beep and ignore
                        self.io.put_char('\x07')?; // Bell character
                        Ok(())
                    }
                }
            }

            InputEvent::Backspace => {
                // Remove from buffer if not empty
                if !self.input_buffer.is_empty() {
                    self.input_buffer.pop();
                    // Echo backspace sequence
                    self.io.write_str("\x08 \x08")?;
                }
                Ok(())
            }

            InputEvent::DoubleEsc => {
                // Clear buffer and redraw (Shell's interpretation of double-ESC)
                self.input_buffer.clear();
                self.clear_line_and_redraw()
            }

            InputEvent::Enter => self.handle_enter_async().await,

            InputEvent::Tab => self.handle_tab(),

            InputEvent::UpArrow => self.handle_history(HistoryDirection::Previous),

            InputEvent::DownArrow => self.handle_history(HistoryDirection::Next),
        }
    }

    /// Poll for incoming characters and process them.
    /// For interrupt-driven/DMA/async/RTOS use `process_char()` directly.
    pub fn poll(&mut self) -> Result<(), IO::Error> {
        if let Some(c) = self.io.get_char()? {
            self.process_char(c)?;
        }
        Ok(())
    }

    /// Determine what character to echo based on password masking rules.
    ///
    /// During login, masks characters after `:` delimiter with `*` for password privacy.
    fn get_echo_char(&self, ch: char) -> char {
        #[cfg(feature = "authentication")]
        {
            // Password masking only applies during login (LoggedOut state)
            if self.state == CliState::LoggedOut {
                // Count colons in buffer (parser has already added current char)
                let colon_count = self.input_buffer.matches(':').count();

                // Logic: Mask if buffer had at least one colon before this character
                // - colon_count == 0: No delimiter yet, echo normally
                // - colon_count == 1 && ch == ':': First colon (just added), echo normally
                // - Otherwise: We're in password territory, mask it
                if colon_count == 0 || (colon_count == 1 && ch == ':') {
                    return ch; // Username or delimiter
                } else {
                    return '*'; // Password
                }
            }
        }

        // Default: echo character as-is
        ch
    }

    /// Generate prompt string.
    ///
    /// Format: `username@path> ` (or `@path> ` when no user/auth disabled)
    // TODO: Use C::MAX_PROMPT when const generics stabilize
    fn generate_prompt(&self) -> heapless::String<128> {
        let mut prompt = heapless::String::new();

        // Username part
        if let Some(user) = &self.current_user {
            prompt.push_str(user.username.as_str()).ok();
        }
        prompt.push('@').ok();

        // Path part
        prompt.push('/').ok();
        if !self.current_path.is_empty()
            && let Ok(path_str) = self.get_current_path_string()
        {
            prompt.push_str(&path_str).ok();
        }

        prompt.push_str("> ").ok();
        prompt
    }

    /// Write prompt to I/O.
    fn generate_and_write_prompt(&mut self) -> Result<(), IO::Error> {
        let prompt = self.generate_prompt();
        self.io.write_str(prompt.as_str())
    }

    /// Write formatted response to I/O, applying Response formatting flags.
    ///
    /// Applies `prefix_newline`, `indent_message`, and `postfix_newline` flags.
    /// Note: `inline_message` and `show_prompt` are handled by callers.
    fn write_formatted_response(&mut self, response: &Response<C>) -> Result<(), IO::Error> {
        // Prefix newline (blank line before output)
        if response.prefix_newline {
            self.io.write_str("\r\n")?;
        }

        // Write message (with optional indentation)
        if response.indent_message {
            // Split by lines and indent each
            for (i, line) in response.message.split("\r\n").enumerate() {
                if i > 0 {
                    self.io.write_str("\r\n")?;
                }
                self.io.write_str("  ")?; // 2-space indent
                self.io.write_str(line)?;
            }
        } else {
            // Write message as-is
            self.io.write_str(&response.message)?;
        }

        // Postfix newline
        if response.postfix_newline {
            self.io.write_str("\r\n")?;
        }

        Ok(())
    }

    /// Format error message using Display trait.
    ///
    /// Converts CliError to a heapless string using its Display implementation.
    /// Returns a buffer containing the formatted error message.
    // TODO: Use C::MAX_RESPONSE when const generics stabilize
    fn format_error(error: &CliError) -> heapless::String<256> {
        use core::fmt::Write;
        let mut buffer = heapless::String::new();
        // Write using Display trait implementation
        // Ignore write errors (buffer full) - partial message is better than none
        let _ = write!(&mut buffer, "{}", error);
        buffer
    }

    /// Get current directory node.
    fn get_current_dir(&self) -> Result<&'tree Directory<L>, CliError> {
        let mut current: &Directory<L> = self.tree;

        for &index in self.current_path.iter() {
            match current.children.get(index) {
                Some(Node::Directory(dir)) => current = dir,
                Some(Node::Command(_)) | None => return Err(CliError::InvalidPath),
            }
        }

        Ok(current)
    }

    /// Get current path as string (for prompt).
    // TODO: Use C::MAX_INPUT when const generics stabilize
    fn get_current_path_string(&self) -> Result<heapless::String<128>, CliError> {
        let mut path_str = heapless::String::new();
        let mut current: &Directory<L> = self.tree;

        for (i, &index) in self.current_path.iter().enumerate() {
            match current.children.get(index) {
                Some(Node::Directory(dir)) => {
                    if i > 0 {
                        path_str.push('/').map_err(|_| CliError::BufferFull)?;
                    }
                    path_str
                        .push_str(dir.name)
                        .map_err(|_| CliError::BufferFull)?;
                    current = dir;
                }
                _ => return Err(CliError::InvalidPath),
            }
        }

        Ok(path_str)
    }

    /// Handle Enter key (submit command or login).
    fn handle_enter(&mut self) -> Result<(), IO::Error> {
        // Note: Newline after input is written by the handler
        // (conditionally based on Response.inline_message flag for commands)

        let input = self.input_buffer.clone();
        self.input_buffer.clear();

        match self.state {
            CliState::Inactive => Ok(()),

            #[cfg(feature = "authentication")]
            CliState::LoggedOut => self.handle_login_input(&input),

            CliState::LoggedIn => self.handle_input_line(&input),
        }
    }

    /// Handle Enter key press - async version.
    ///
    /// Dispatches to appropriate handler based on current state.
    #[cfg(feature = "async")]
    async fn handle_enter_async(&mut self) -> Result<(), IO::Error> {
        // Note: Newline after input is written by the handler
        // (conditionally based on Response.inline_message flag for commands)

        let input = self.input_buffer.clone();
        self.input_buffer.clear();

        match self.state {
            CliState::Inactive => Ok(()),

            #[cfg(feature = "authentication")]
            CliState::LoggedOut => self.handle_login_input(&input),

            CliState::LoggedIn => self.handle_input_line_async(&input).await,
        }
    }

    /// Handle a valid login attempt.
    #[cfg(feature = "authentication")]
    fn handle_login_input(&mut self, input: &str) -> Result<(), IO::Error> {
        // Login doesn't support inline mode - always add newline
        self.io.write_str("\r\n  ")?;

        if input.contains(':') {
            // Format: username:password
            let parts: heapless::Vec<&str, 2> = input.splitn(2, ':').collect();
            if parts.len() == 2 {
                let username = parts[0];
                let password = parts[1];

                // Attempt authentication
                match self.credential_provider.find_user(username) {
                    Ok(Some(user)) if self.credential_provider.verify_password(&user, password) => {
                        // Login successful
                        self.current_user = Some(user);
                        self.state = CliState::LoggedIn;
                        self.io.write_str(C::MSG_LOGIN_SUCCESS)?;
                        self.io.write_str("\r\n")?;
                        self.generate_and_write_prompt()?;
                    }
                    _ => {
                        // Login failed (user not found or wrong password)
                        self.io.write_str(C::MSG_LOGIN_FAILED)?;
                        self.io.write_str("\r\n")?;
                        self.io.write_str(C::MSG_LOGIN_PROMPT)?;
                    }
                }
            } else {
                self.io.write_str(C::MSG_INVALID_LOGIN_FORMAT)?;
                self.io.write_str("\r\n")?;
                self.io.write_str(C::MSG_LOGIN_PROMPT)?;
            }
        } else {
            // No colon - invalid format, show error
            self.io.write_str(C::MSG_INVALID_LOGIN_FORMAT)?;
            self.io.write_str("\r\n")?;
            self.io.write_str(C::MSG_LOGIN_PROMPT)?;
        }

        Ok(())
    }

    /// Process global commands (?, ls, clear, logout).
    ///
    /// Returns true if a global command was handled, false otherwise.
    fn handle_global_commands(&mut self, input: &str) -> Result<bool, IO::Error> {
        // Check for global commands first (non-tree operations)
        // Global commands don't support inline mode
        match input.trim() {
            "?" => {
                self.io.write_str("\r\n")?;
                self.show_help()?;
                self.generate_and_write_prompt()?;
                Ok(true)
            }
            "ls" => {
                self.io.write_str("\r\n")?;
                self.show_ls()?;
                self.generate_and_write_prompt()?;
                Ok(true)
            }
            "clear" => {
                // Clear screen - no newline needed before ANSI clear sequence
                self.io.write_str("\x1b[2J\x1b[H")?; // ANSI clear screen
                self.generate_and_write_prompt()?;
                Ok(true)
            }
            #[cfg(feature = "authentication")]
            "logout" => {
                self.io.write_str("\r\n  ")?;
                self.current_user = None;
                self.state = CliState::LoggedOut;
                self.current_path.clear();
                self.io.write_str(C::MSG_LOGOUT)?;
                self.io.write_str("\r\n")?;
                self.io.write_str(C::MSG_LOGIN_PROMPT)?;
                Ok(true)
            }
            _ => Ok(false),
        }
    }

    /// Write response and handle history/prompt based on Response flags.
    fn write_response_and_prompt(
        &mut self,
        response: Response<C>,
        #[cfg_attr(not(feature = "history"), allow(unused_variables))] input: &str,
    ) -> Result<(), IO::Error> {
        // Add newline after input UNLESS response wants inline mode
        if !response.inline_message {
            self.io.write_str("\r\n")?;
        }

        // Write formatted response (implements all Response flags!)
        self.write_formatted_response(&response)?;

        // Add to history if not excluded
        #[cfg(feature = "history")]
        if !response.exclude_from_history {
            self.history.add(input);
        }

        // Show prompt if requested by response
        if response.show_prompt {
            self.generate_and_write_prompt()?;
        }

        Ok(())
    }

    /// Write error message with formatting.
    fn write_error_and_prompt(&mut self, error: CliError) -> Result<(), IO::Error> {
        // Errors don't support inline mode - add newline
        self.io.write_str("\r\n  ")?;

        // Format and write error message using Display trait
        self.io.write_str("Error: ")?;
        let error_msg = Self::format_error(&error);
        self.io.write_str(error_msg.as_str())?;
        self.io.write_str("\r\n")?;
        self.generate_and_write_prompt()?;

        Ok(())
    }

    /// Handle user input line when in LoggedIn state.
    ///
    /// Processes three types of input:
    /// 1. Global commands (?, ls, clear, logout)
    /// 2. Tree navigation (paths resolving to directories)
    /// 3. Tree commands (paths resolving to Node::Command)
    fn handle_input_line(&mut self, input: &str) -> Result<(), IO::Error> {
        // Skip empty input
        if input.trim().is_empty() {
            self.io.write_str("\r\n")?;
            self.generate_and_write_prompt()?;
            return Ok(());
        }

        // Check for global commands first (non-tree operations)
        if self.handle_global_commands(input)? {
            return Ok(());
        }

        // Handle tree operations (navigation or command execution)
        match self.execute_tree_path(input) {
            Ok(response) => self.write_response_and_prompt(response, input),
            Err(e) => self.write_error_and_prompt(e),
        }
    }

    /// Handle user input line when in LoggedIn state - async version.
    ///
    /// Processes three types of input:
    /// 1. Global commands (?, ls, clear, logout)
    /// 2. Tree navigation (paths resolving to directories)
    /// 3. Tree commands (paths resolving to Node::Command - both sync and async)
    #[cfg(feature = "async")]
    async fn handle_input_line_async(&mut self, input: &str) -> Result<(), IO::Error> {
        // Skip empty input
        if input.trim().is_empty() {
            self.io.write_str("\r\n")?;
            self.generate_and_write_prompt()?;
            return Ok(());
        }

        // Check for global commands first (non-tree operations)
        if self.handle_global_commands(input)? {
            return Ok(());
        }

        // Handle tree operations (navigation or command execution) - async version
        match self.execute_tree_path_async(input).await {
            Ok(response) => self.write_response_and_prompt(response, input),
            Err(e) => self.write_error_and_prompt(e),
        }
    }

    /// Execute a tree path (navigation or command execution).
    ///
    /// Resolves the path and either:
    /// - Navigates to a directory (if path resolves to Node::Directory)
    /// - Executes a tree command (if path resolves to Node::Command)
    ///
    /// Note: "command" here refers specifically to Node::Command,
    /// not generic user input.
    fn execute_tree_path(&mut self, input: &str) -> Result<Response<C>, CliError> {
        // Parse path and arguments
        // TODO: Use C::MAX_ARGS + 1 when const generics stabilize (command + args)
        let parts: heapless::Vec<&str, 17> = input.split_whitespace().collect();
        if parts.is_empty() {
            return Err(CliError::CommandNotFound);
        }

        let path_str = parts[0];
        let args = &parts[1..];

        // Resolve path to node (None represents root directory)
        let (target_node, new_path) = self.resolve_path(path_str)?;

        // Case 1: Directory navigation
        match target_node {
            None | Some(Node::Directory(_)) => {
                if !args.is_empty() {
                    return Err(CliError::InvalidArgumentCount {
                        expected_min: 0,
                        expected_max: 0,
                        received: args.len(),
                    });
                }
                // Directory navigation - update path and return
                self.current_path = new_path;
                #[cfg(feature = "history")]
                return Ok(Response::success("")
                    .without_history()
                    .without_postfix_newline());
                #[cfg(not(feature = "history"))]
                return Ok(Response::success("").without_postfix_newline());
            }
            Some(Node::Command(cmd_meta)) => {
                // Case 2: Tree command execution
                // Check access control - use InvalidPath for security (don't reveal access denied)
                if let Some(user) = &self.current_user
                    && user.access_level < cmd_meta.access_level
                {
                    return Err(CliError::InvalidPath);
                }

                // Validate argument count
                if args.len() < cmd_meta.min_args || args.len() > cmd_meta.max_args {
                    return Err(CliError::InvalidArgumentCount {
                        expected_min: cmd_meta.min_args,
                        expected_max: cmd_meta.max_args,
                        received: args.len(),
                    });
                }

                // Dispatch to command handler
                match cmd_meta.kind {
                    CommandKind::Sync => {
                        // Execute synchronous tree command (dispatch by unique ID)
                        self.handler.execute_sync(cmd_meta.id, args)
                    }
                    #[cfg(feature = "async")]
                    CommandKind::Async => {
                        // Async tree command called from sync context
                        Err(CliError::AsyncInSyncContext)
                    }
                }
            }
        }
    }

    /// Execute a tree path (navigation or command execution) - async version.
    ///
    /// Resolves the path and either:
    /// - Navigates to a directory (if path resolves to Node::Directory)
    /// - Executes a tree command (if path resolves to Node::Command)
    ///
    /// This async version can execute both sync and async commands.
    /// Sync commands are called directly, async commands are awaited.
    ///
    /// Note: "command" here refers specifically to Node::Command,
    /// not generic user input.
    #[cfg(feature = "async")]
    async fn execute_tree_path_async(&mut self, input: &str) -> Result<Response<C>, CliError> {
        // Parse path and arguments
        // TODO: Use C::MAX_ARGS + 1 when const generics stabilize (command + args)
        let parts: heapless::Vec<&str, 17> = input.split_whitespace().collect();
        if parts.is_empty() {
            return Err(CliError::CommandNotFound);
        }

        let path_str = parts[0];
        let args = &parts[1..];

        // Resolve path to node (None represents root directory)
        let (target_node, new_path) = self.resolve_path(path_str)?;

        // Case 1: Directory navigation
        match target_node {
            None | Some(Node::Directory(_)) => {
                if !args.is_empty() {
                    return Err(CliError::InvalidArgumentCount {
                        expected_min: 0,
                        expected_max: 0,
                        received: args.len(),
                    });
                }
                // Directory navigation - update path and return
                self.current_path = new_path;
                #[cfg(feature = "history")]
                return Ok(Response::success("")
                    .without_history()
                    .without_postfix_newline());
                #[cfg(not(feature = "history"))]
                return Ok(Response::success("").without_postfix_newline());
            }
            Some(Node::Command(cmd_meta)) => {
                // Case 2: Tree command execution
                // Check access control - use InvalidPath for security (don't reveal access denied)
                if let Some(user) = &self.current_user
                    && user.access_level < cmd_meta.access_level
                {
                    return Err(CliError::InvalidPath);
                }

                // Validate argument count
                if args.len() < cmd_meta.min_args || args.len() > cmd_meta.max_args {
                    return Err(CliError::InvalidArgumentCount {
                        expected_min: cmd_meta.min_args,
                        expected_max: cmd_meta.max_args,
                        received: args.len(),
                    });
                }

                // Dispatch to command handler (handle both sync and async)
                match cmd_meta.kind {
                    CommandKind::Sync => {
                        // Sync command in async context - call directly
                        self.handler.execute_sync(cmd_meta.id, args)
                    }
                    CommandKind::Async => {
                        // Async command - await execution
                        self.handler.execute_async(cmd_meta.id, args).await
                    }
                }
            }
        }
    }

    /// Resolve a path string to a node.
    ///
    /// Returns (node, path_stack) where path_stack is the navigation path.
    /// Node is None when path resolves to root directory.
    // TODO: Use C::MAX_PATH_DEPTH when const generics stabilize
    fn resolve_path(
        &self,
        path_str: &str,
    ) -> Result<(Option<&'tree Node<L>>, heapless::Vec<usize, 8>), CliError> {
        // Start from current directory or root
        // TODO: Use C::MAX_PATH_DEPTH when const generics stabilize
        let mut working_path: heapless::Vec<usize, 8> = if path_str.starts_with('/') {
            heapless::Vec::new() // Absolute path starts from root
        } else {
            self.current_path.clone() // Relative path starts from current
        };

        // Parse path
        // TODO: Use C::MAX_PATH_DEPTH when const generics stabilize
        let segments: heapless::Vec<&str, 8> = path_str
            .trim_start_matches('/')
            .split('/')
            .filter(|s| !s.is_empty() && *s != ".")
            .collect();

        // Navigate through segments
        for (seg_idx, segment) in segments.iter().enumerate() {
            if *segment == ".." {
                // Parent directory
                working_path.pop();
                continue;
            }

            let is_last_segment = seg_idx == segments.len() - 1;

            // Find child with this name
            let current_dir = self.get_dir_at_path(&working_path)?;
            let mut found = false;

            for (index, child) in current_dir.children.iter().enumerate() {
                // Check access control
                let node_level = match child {
                    Node::Command(cmd) => cmd.access_level,
                    Node::Directory(dir) => dir.access_level,
                };

                if let Some(user) = &self.current_user
                    && user.access_level < node_level
                {
                    continue; // User lacks access, skip this node
                }

                if child.name() == *segment {
                    // Found it!
                    if child.is_directory() {
                        // Navigate into directory
                        working_path
                            .push(index)
                            .map_err(|_| CliError::PathTooDeep)?;
                    } else {
                        // It's a command - can only return if this is the last segment
                        if is_last_segment {
                            return Ok((Some(child), working_path));
                        } else {
                            // Trying to navigate through a command - invalid path structure
                            return Err(CliError::InvalidPath);
                        }
                    }
                    found = true;
                    break;
                }
            }

            if !found {
                return Err(CliError::CommandNotFound);
            }
        }

        // Path resolved to a directory
        // Handle root directory specially (when path is empty)
        if working_path.is_empty() {
            // Return None to represent root directory
            return Ok((None, working_path));
        }

        let dir_node = self.get_node_at_path(&working_path)?;
        Ok((Some(dir_node), working_path))
    }

    /// Get directory at specific path.
    // TODO: Use C::MAX_PATH_DEPTH when const generics stabilize
    fn get_dir_at_path(
        &self,
        path: &heapless::Vec<usize, 8>,
    ) -> Result<&'tree Directory<L>, CliError> {
        let mut current: &Directory<L> = self.tree;

        for &index in path.iter() {
            match current.children.get(index) {
                Some(Node::Directory(dir)) => current = dir,
                Some(Node::Command(_)) | None => return Err(CliError::InvalidPath),
            }
        }

        Ok(current)
    }

    /// Get node at specific path.
    // TODO: Use C::MAX_PATH_DEPTH when const generics stabilize
    fn get_node_at_path(&self, path: &heapless::Vec<usize, 8>) -> Result<&'tree Node<L>, CliError> {
        if path.is_empty() {
            // Root directory - need to find a way to return it as a Node
            // For now, return error since we can't construct Node::Directory here
            return Err(CliError::InvalidPath);
        }

        // TODO: Use C::MAX_PATH_DEPTH when const generics stabilize
        let parent_path: heapless::Vec<usize, 8> =
            path.iter().take(path.len() - 1).copied().collect();
        let parent_dir = self.get_dir_at_path(&parent_path)?;

        let last_index = *path.last().ok_or(CliError::InvalidPath)?;
        parent_dir
            .children
            .get(last_index)
            .ok_or(CliError::InvalidPath)
    }

    /// Handle Tab completion.
    fn handle_tab(&mut self) -> Result<(), IO::Error> {
        #[cfg(feature = "completion")]
        {
            // Get current directory
            let current_dir = match self.get_current_dir() {
                Ok(dir) => dir,
                Err(_) => return self.generate_and_write_prompt(), // Error, just redraw prompt
            };

            // Suggest completions
            let result = suggest_completions::<L, 16>(
                current_dir,
                self.input_buffer.as_str(),
                self.current_user.as_ref(),
            );

            match result {
                Ok(crate::tree::completion::CompletionResult::Single { completion, .. }) => {
                    // Single match - replace buffer and update display
                    self.input_buffer.clear();
                    match self.input_buffer.push_str(&completion) {
                        Ok(()) => {
                            // Redraw line
                            self.io.write_str("\r")?; // Carriage return
                            let prompt = self.generate_prompt();
                            self.io.write_str(prompt.as_str())?;
                            self.io.write_str(self.input_buffer.as_str())?;
                        }
                        Err(_) => {
                            // Completion too long for buffer - beep
                            self.io.put_char('\x07')?;
                        }
                    }
                }
                Ok(crate::tree::completion::CompletionResult::Multiple { all_matches, .. }) => {
                    // Multiple matches - show them
                    self.io.write_str("\r\n")?;
                    for m in all_matches.iter() {
                        self.io.write_str("  ")?; // 2-space indentation
                        self.io.write_str(m.as_str())?;
                        self.io.write_str("  ")?;
                    }
                    self.io.write_str("\r\n")?;
                    self.generate_and_write_prompt()?;
                    self.io.write_str(self.input_buffer.as_str())?;
                }
                _ => {
                    // No matches or error - just beep
                    self.io.put_char('\x07')?; // Bell character
                }
            }
        }

        #[cfg(not(feature = "completion"))]
        {
            // Completion disabled - just beep
            self.io.put_char('\x07')?; // Bell character
        }

        Ok(())
    }

    /// Handle history navigation.
    fn handle_history(&mut self, direction: HistoryDirection) -> Result<(), IO::Error> {
        #[cfg(feature = "history")]
        {
            let history_entry = match direction {
                HistoryDirection::Previous => self.history.previous_command(),
                HistoryDirection::Next => self.history.next_command(),
            };

            if let Some(entry) = history_entry {
                // Replace buffer with history entry
                self.input_buffer = entry;
                // Redraw line
                self.clear_line_and_redraw()?;
            }
        }

        #[cfg(not(feature = "history"))]
        {
            // History disabled - ignore
            let _ = direction; // Silence unused warning
        }

        Ok(())
    }

    /// Show help (? command).
    fn show_help(&mut self) -> Result<(), IO::Error> {
        self.io.write_str("  ?        - List global commands\r\n")?;
        self.io
            .write_str("  ls       - List directory contents\r\n")?;

        #[cfg(feature = "authentication")]
        self.io.write_str("  logout   - End session\r\n")?;

        self.io.write_str("  clear    - Clear screen\r\n")?;
        self.io.write_str("  ESC ESC  - Clear input buffer\r\n")?;

        Ok(())
    }

    /// Show directory listing (ls command).
    fn show_ls(&mut self) -> Result<(), IO::Error> {
        let current_dir = match self.get_current_dir() {
            Ok(dir) => dir,
            Err(_) => {
                self.io.write_str("Error accessing directory\r\n")?;
                return Ok(());
            }
        };

        for child in current_dir.children.iter() {
            // Check access control
            let node_level = match child {
                Node::Command(cmd) => cmd.access_level,
                Node::Directory(dir) => dir.access_level,
            };

            if let Some(user) = &self.current_user
                && user.access_level < node_level
            {
                continue; // User lacks access, skip this node
            }

            // Format output
            match child {
                Node::Command(cmd) => {
                    self.io.write_str("  ")?;
                    self.io.write_str(cmd.name)?;
                    self.io.write_str("  - ")?;
                    self.io.write_str(cmd.description)?;
                    self.io.write_str("\r\n")?;
                }
                Node::Directory(dir) => {
                    self.io.write_str("  ")?;
                    self.io.write_str(dir.name)?;
                    self.io.write_str("/  - Directory\r\n")?;
                }
            }
        }

        Ok(())
    }

    /// Clear current line and redraw with prompt and buffer.
    fn clear_line_and_redraw(&mut self) -> Result<(), IO::Error> {
        self.io.write_str("\r\x1b[K")?; // CR + clear to end of line
        self.generate_and_write_prompt()?;
        self.io.write_str(self.input_buffer.as_str())?;
        Ok(())
    }

    // ========================================
    // I/O Access
    // ========================================

    /// Get reference to I/O interface (for inspection or direct control).
    pub fn io(&self) -> &IO {
        &self.io
    }

    /// Get mutable reference to I/O interface (for manipulation or direct control).
    pub fn io_mut(&mut self) -> &mut IO {
        &mut self.io
    }
}

// ============================================================================
// Tests
// ============================================================================

#[cfg(test)]
mod tests {
    use super::*;
    use crate::auth::AccessLevel;
    use crate::config::DefaultConfig;
    use crate::io::CharIo;
    use crate::tree::{CommandKind, CommandMeta, Directory, Node};

    // Mock access level
    #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
    enum MockLevel {
        User = 0,
    }

    impl AccessLevel for MockLevel {
        fn from_str(s: &str) -> Option<Self> {
            match s {
                "User" => Some(Self::User),
                _ => None,
            }
        }

        fn as_str(&self) -> &'static str {
            "User"
        }
    }

    // Mock I/O that captures output
    struct MockIo {
        output: heapless::String<512>,
    }
    impl MockIo {
        fn new() -> Self {
            Self {
                output: heapless::String::new(),
            }
        }

        #[allow(dead_code)]
        fn get_output(&self) -> &str {
            &self.output
        }
    }
    impl CharIo for MockIo {
        type Error = ();
        fn get_char(&mut self) -> Result<Option<char>, ()> {
            Ok(None)
        }
        fn put_char(&mut self, c: char) -> Result<(), ()> {
            self.output.push(c).map_err(|_| ())
        }
        fn write_str(&mut self, s: &str) -> Result<(), ()> {
            self.output.push_str(s).map_err(|_| ())
        }
    }

    // Mock handler
    struct MockHandler;
    impl CommandHandler<DefaultConfig> for MockHandler {
        fn execute_sync(
            &self,
            _id: &str,
            _args: &[&str],
        ) -> Result<crate::response::Response<DefaultConfig>, crate::error::CliError> {
            Err(crate::error::CliError::CommandNotFound)
        }

        #[cfg(feature = "async")]
        async fn execute_async(
            &self,
            _id: &str,
            _args: &[&str],
        ) -> Result<crate::response::Response<DefaultConfig>, crate::error::CliError> {
            Err(crate::error::CliError::CommandNotFound)
        }
    }

    // Test commands
    const CMD_TEST: CommandMeta<MockLevel> = CommandMeta {
        id: "test-cmd",
        name: "test-cmd",
        description: "Test command",
        access_level: MockLevel::User,
        kind: CommandKind::Sync,
        min_args: 0,
        max_args: 0,
    };

    const CMD_REBOOT: CommandMeta<MockLevel> = CommandMeta {
        id: "reboot",
        name: "reboot",
        description: "Reboot the system",
        access_level: MockLevel::User,
        kind: CommandKind::Sync,
        min_args: 0,
        max_args: 0,
    };

    const CMD_STATUS: CommandMeta<MockLevel> = CommandMeta {
        id: "status",
        name: "status",
        description: "Show status",
        access_level: MockLevel::User,
        kind: CommandKind::Sync,
        min_args: 0,
        max_args: 0,
    };

    const CMD_LED: CommandMeta<MockLevel> = CommandMeta {
        id: "led",
        name: "led",
        description: "Control LED",
        access_level: MockLevel::User,
        kind: CommandKind::Sync,
        min_args: 1,
        max_args: 1,
    };

    const CMD_NETWORK_STATUS: CommandMeta<MockLevel> = CommandMeta {
        id: "network_status",
        name: "status",
        description: "Network status",
        access_level: MockLevel::User,
        kind: CommandKind::Sync,
        min_args: 0,
        max_args: 0,
    };

    // Test directories
    const DIR_HARDWARE: Directory<MockLevel> = Directory {
        name: "hardware",
        children: &[Node::Command(&CMD_LED)],
        access_level: MockLevel::User,
    };

    const DIR_NETWORK: Directory<MockLevel> = Directory {
        name: "network",
        children: &[Node::Command(&CMD_NETWORK_STATUS)],
        access_level: MockLevel::User,
    };

    const DIR_SYSTEM: Directory<MockLevel> = Directory {
        name: "system",
        children: &[
            Node::Command(&CMD_REBOOT),
            Node::Command(&CMD_STATUS),
            Node::Directory(&DIR_HARDWARE),
            Node::Directory(&DIR_NETWORK),
        ],
        access_level: MockLevel::User,
    };

    // Test tree
    const TEST_TREE: Directory<MockLevel> = Directory {
        name: "/",
        children: &[Node::Command(&CMD_TEST), Node::Directory(&DIR_SYSTEM)],
        access_level: MockLevel::User,
    };

    #[test]
    fn test_request_command_no_args() {
        let mut path = heapless::String::<128>::new();
        path.push_str("help").unwrap();
        let args = heapless::Vec::new();
        #[cfg(feature = "history")]
        let original = {
            let mut s = heapless::String::<128>::new();
            s.push_str("help").unwrap();
            s
        };

        let request = Request::<DefaultConfig>::Command {
            path,
            args,
            #[cfg(feature = "history")]
            original,
            _phantom: core::marker::PhantomData,
        };

        match request {
            Request::Command { path, args, .. } => {
                assert_eq!(path.as_str(), "help");
                assert_eq!(args.len(), 0);
            }
            #[allow(unreachable_patterns)]
            _ => panic!("Expected Command variant"),
        }
    }

    #[test]
    fn test_request_command_with_args() {
        let mut path = heapless::String::<128>::new();
        path.push_str("echo").unwrap();

        let mut args = heapless::Vec::new();
        let mut hello = heapless::String::<128>::new();
        hello.push_str("hello").unwrap();
        let mut world = heapless::String::<128>::new();
        world.push_str("world").unwrap();
        args.push(hello).unwrap();
        args.push(world).unwrap();

        #[cfg(feature = "history")]
        let original = {
            let mut s = heapless::String::<128>::new();
            s.push_str("echo hello world").unwrap();
            s
        };

        let request = Request::<DefaultConfig>::Command {
            path,
            args,
            #[cfg(feature = "history")]
            original,
            _phantom: core::marker::PhantomData,
        };

        match request {
            Request::Command { path, args, .. } => {
                assert_eq!(path.as_str(), "echo");
                assert_eq!(args.len(), 2);
                assert_eq!(args[0].as_str(), "hello");
                assert_eq!(args[1].as_str(), "world");
            }
            #[allow(unreachable_patterns)]
            _ => panic!("Expected Command variant"),
        }
    }

    #[test]
    #[cfg(feature = "history")]
    fn test_request_command_with_original() {
        let mut path = heapless::String::<128>::new();
        path.push_str("reboot").unwrap();
        let mut original = heapless::String::<128>::new();
        original.push_str("reboot").unwrap();

        let request = Request::<DefaultConfig>::Command {
            path,
            args: heapless::Vec::new(),
            original,
            _phantom: core::marker::PhantomData,
        };

        match request {
            Request::Command { path, original, .. } => {
                assert_eq!(path.as_str(), "reboot");
                assert_eq!(original.as_str(), "reboot");
            }
            #[allow(unreachable_patterns)]
            _ => panic!("Expected Command variant"),
        }
    }

    #[test]
    #[cfg(feature = "authentication")]
    fn test_request_login() {
        let mut username = heapless::String::<32>::new();
        username.push_str("admin").unwrap();
        let mut password = heapless::String::<64>::new();
        password.push_str("secret123").unwrap();

        let request = Request::<DefaultConfig>::Login { username, password };

        match request {
            Request::Login { username, password } => {
                assert_eq!(username.as_str(), "admin");
                assert_eq!(password.as_str(), "secret123");
            }
            #[allow(unreachable_patterns)]
            _ => panic!("Expected Login variant"),
        }
    }

    #[test]
    #[cfg(feature = "authentication")]
    fn test_request_invalid_login() {
        let request = Request::<DefaultConfig>::InvalidLogin;

        match request {
            Request::InvalidLogin => {}
            #[allow(unreachable_patterns)]
            _ => panic!("Expected InvalidLogin variant"),
        }
    }

    #[test]
    #[cfg(feature = "completion")]
    fn test_request_tab_complete() {
        let mut path = heapless::String::<128>::new();
        path.push_str("sys").unwrap();

        let request = Request::<DefaultConfig>::TabComplete { path };

        match request {
            Request::TabComplete { path } => {
                assert_eq!(path.as_str(), "sys");
            }
            #[allow(unreachable_patterns)]
            _ => panic!("Expected TabComplete variant"),
        }
    }

    #[test]
    #[cfg(feature = "completion")]
    fn test_request_tab_complete_empty() {
        let request = Request::<DefaultConfig>::TabComplete {
            path: heapless::String::new(),
        };

        match request {
            Request::TabComplete { path } => {
                assert_eq!(path.as_str(), "");
            }
            #[allow(unreachable_patterns)]
            _ => panic!("Expected TabComplete variant"),
        }
    }

    #[test]
    #[cfg(feature = "history")]
    fn test_request_history_previous() {
        let mut buffer = heapless::String::<128>::new();
        buffer.push_str("current input").unwrap();

        let request = Request::<DefaultConfig>::History {
            direction: HistoryDirection::Previous,
            buffer,
        };

        match request {
            Request::History { direction, buffer } => {
                assert_eq!(direction, HistoryDirection::Previous);
                assert_eq!(buffer.as_str(), "current input");
            }
            #[allow(unreachable_patterns)]
            _ => panic!("Expected History variant"),
        }
    }

    #[test]
    #[cfg(feature = "history")]
    fn test_request_history_next() {
        let request = Request::<DefaultConfig>::History {
            direction: HistoryDirection::Next,
            buffer: heapless::String::new(),
        };

        match request {
            Request::History { direction, buffer } => {
                assert_eq!(direction, HistoryDirection::Next);
                assert_eq!(buffer.as_str(), "");
            }
            #[allow(unreachable_patterns)]
            _ => panic!("Expected History variant"),
        }
    }

    #[test]
    fn test_request_variants_match_features() {
        let _cmd = Request::<DefaultConfig>::Command {
            path: heapless::String::new(),
            args: heapless::Vec::new(),
            #[cfg(feature = "history")]
            original: heapless::String::new(),
            _phantom: core::marker::PhantomData,
        };

        #[cfg(feature = "authentication")]
        let _login = Request::<DefaultConfig>::Login {
            username: heapless::String::new(),
            password: heapless::String::new(),
        };

        #[cfg(feature = "completion")]
        let _complete = Request::<DefaultConfig>::TabComplete {
            path: heapless::String::new(),
        };

        #[cfg(feature = "history")]
        let _history = Request::<DefaultConfig>::History {
            direction: HistoryDirection::Previous,
            buffer: heapless::String::new(),
        };
    }

    #[test]
    fn test_activate_deactivate_lifecycle() {
        let io = MockIo::new();
        let handler = MockHandler;

        // Create shell - should start in Inactive state
        #[cfg(feature = "authentication")]
        {
            use crate::auth::CredentialProvider;
            struct MockProvider;
            impl CredentialProvider<MockLevel> for MockProvider {
                type Error = ();
                fn find_user(
                    &self,
                    _username: &str,
                ) -> Result<Option<crate::auth::User<MockLevel>>, ()> {
                    Ok(None)
                }
                fn verify_password(
                    &self,
                    _user: &crate::auth::User<MockLevel>,
                    _password: &str,
                ) -> bool {
                    false
                }
            }
            let provider = MockProvider;
            let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
                Shell::new(&TEST_TREE, handler, &provider, io);

            // Should start in Inactive state
            assert_eq!(shell.state, CliState::Inactive);
            assert!(shell.current_user.is_none());

            // Activate should transition to LoggedOut (auth enabled)
            shell.activate().unwrap();
            assert_eq!(shell.state, CliState::LoggedOut);

            // Deactivate should return to Inactive
            shell.deactivate();
            assert_eq!(shell.state, CliState::Inactive);
            assert!(shell.current_user.is_none());
            assert!(shell.input_buffer.is_empty());
            assert!(shell.current_path.is_empty());
        }

        #[cfg(not(feature = "authentication"))]
        {
            let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
                Shell::new(&TEST_TREE, handler, io);

            // Should start in Inactive state
            assert_eq!(shell.state, CliState::Inactive);

            // Activate should transition to LoggedIn (auth disabled)
            shell.activate().unwrap();
            assert_eq!(shell.state, CliState::LoggedIn);

            // Deactivate should return to Inactive
            shell.deactivate();
            assert_eq!(shell.state, CliState::Inactive);
            assert!(shell.current_user.is_none());
            assert!(shell.input_buffer.is_empty());
            assert!(shell.current_path.is_empty());
        }
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_write_formatted_response_default() {
        // Test default formatting (no flags set)
        let io = MockIo::new();
        let handler = MockHandler;
        let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        let response = crate::response::Response::<DefaultConfig>::success("Test message");
        shell.write_formatted_response(&response).unwrap();

        // Default: message + postfix newline
        assert_eq!(shell.io.get_output(), "Test message\r\n");
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_write_formatted_response_with_prefix_newline() {
        let io = MockIo::new();
        let handler = MockHandler;
        let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        let response =
            crate::response::Response::<DefaultConfig>::success("Test").with_prefix_newline();
        shell.write_formatted_response(&response).unwrap();

        // prefix newline + message + postfix newline
        assert_eq!(shell.io.get_output(), "\r\nTest\r\n");
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_write_formatted_response_indented() {
        let io = MockIo::new();
        let handler = MockHandler;
        let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        let response =
            crate::response::Response::<DefaultConfig>::success("Line 1\r\nLine 2").indented();
        shell.write_formatted_response(&response).unwrap();

        // Each line indented with 2 spaces + postfix newline
        assert_eq!(shell.io.get_output(), "  Line 1\r\n  Line 2\r\n");
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_write_formatted_response_indented_single_line() {
        let io = MockIo::new();
        let handler = MockHandler;
        let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        let response =
            crate::response::Response::<DefaultConfig>::success("Single line").indented();
        shell.write_formatted_response(&response).unwrap();

        // Single line indented
        assert_eq!(shell.io.get_output(), "  Single line\r\n");
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_write_formatted_response_without_postfix_newline() {
        let io = MockIo::new();
        let handler = MockHandler;
        let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        let response = crate::response::Response::<DefaultConfig>::success("No newline")
            .without_postfix_newline();
        shell.write_formatted_response(&response).unwrap();

        // Message without trailing newline
        assert_eq!(shell.io.get_output(), "No newline");
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_write_formatted_response_combined_flags() {
        let io = MockIo::new();
        let handler = MockHandler;
        let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        let response = crate::response::Response::<DefaultConfig>::success("Multi\r\nLine")
            .with_prefix_newline()
            .indented();
        shell.write_formatted_response(&response).unwrap();

        // Prefix newline + indented lines + postfix newline
        assert_eq!(shell.io.get_output(), "\r\n  Multi\r\n  Line\r\n");
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_write_formatted_response_all_flags_off() {
        let io = MockIo::new();
        let handler = MockHandler;
        let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        let response =
            crate::response::Response::<DefaultConfig>::success("Raw").without_postfix_newline();
        shell.write_formatted_response(&response).unwrap();

        // No formatting at all
        assert_eq!(shell.io.get_output(), "Raw");
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_write_formatted_response_empty_message() {
        let io = MockIo::new();
        let handler = MockHandler;
        let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        let response = crate::response::Response::<DefaultConfig>::success("");
        shell.write_formatted_response(&response).unwrap();

        // Empty message still gets postfix newline
        assert_eq!(shell.io.get_output(), "\r\n");
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_write_formatted_response_indented_multiline() {
        let io = MockIo::new();
        let handler = MockHandler;
        let mut shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        let response = crate::response::Response::<DefaultConfig>::success("A\r\nB\r\nC\r\nD")
            .indented()
            .without_postfix_newline();
        shell.write_formatted_response(&response).unwrap();

        // All 4 lines indented, no trailing newline
        assert_eq!(shell.io.get_output(), "  A\r\n  B\r\n  C\r\n  D");
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_inline_message_flag() {
        // Test that inline_message flag is properly recognized
        let response =
            crate::response::Response::<DefaultConfig>::success("... processing").inline();

        assert!(
            response.inline_message,
            "inline() should set inline_message flag"
        );

        // Note: The actual inline behavior (no newline after input) is tested
        // via integration tests, as it requires simulating full command execution.
        // This test verifies the flag is set correctly.
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_resolve_path_cannot_navigate_through_command() {
        // Test that resolve_path returns InvalidPath when trying to navigate through a command
        let io = MockIo::new();
        let handler = MockHandler;
        let shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        // Valid: Command as last segment should succeed
        let result = shell.resolve_path("test-cmd");
        assert!(result.is_ok(), "Should resolve path to command");
        if let Ok((node, _)) = result {
            assert!(node.is_some());
            if let Some(Node::Command(cmd)) = node {
                assert_eq!(cmd.name, "test-cmd");
            } else {
                panic!("Expected Command node");
            }
        }

        // Invalid: Cannot navigate through command to another segment
        let result = shell.resolve_path("test-cmd/invalid");
        assert!(
            result.is_err(),
            "Should fail when navigating through command"
        );
        assert_eq!(
            result.unwrap_err(),
            CliError::InvalidPath,
            "Should return InvalidPath when trying to navigate through command"
        );

        // Invalid: Multiple segments after command
        let result = shell.resolve_path("test-cmd/extra/path");
        assert!(
            result.is_err(),
            "Should fail with multiple segments after command"
        );
        assert_eq!(
            result.unwrap_err(),
            CliError::InvalidPath,
            "Should return InvalidPath for multiple segments after command"
        );
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_resolve_path_comprehensive() {
        let io = MockIo::new();
        let handler = MockHandler;
        let shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        // Test 1: Root level command
        let result = shell.resolve_path("test-cmd");
        assert!(result.is_ok(), "Should resolve root-level command");
        if let Ok((node, _)) = result {
            assert!(node.is_some());
            if let Some(Node::Command(cmd)) = node {
                assert_eq!(cmd.name, "test-cmd");
            }
        }

        // Test 2: Verify command metadata properties
        let result = shell.resolve_path("system/reboot");
        assert!(result.is_ok(), "Should resolve system/reboot");
        if let Ok((node, _)) = result {
            assert!(node.is_some());
            if let Some(Node::Command(cmd)) = node {
                assert_eq!(cmd.name, "reboot");
                assert_eq!(cmd.description, "Reboot the system");
                assert_eq!(cmd.access_level, MockLevel::User);
                assert_eq!(cmd.kind, CommandKind::Sync);
            }
        }

        // Test 3: Verify unique command ID (critical for handler dispatch)
        let result = shell.resolve_path("system/status");
        assert!(result.is_ok(), "Should resolve system/status");
        if let Ok((node, _)) = result {
            assert!(node.is_some());
            if let Some(Node::Command(cmd)) = node {
                assert_eq!(cmd.name, "status");
                assert_eq!(cmd.id, "status");
                // Verify this is different from network/status which has id "network_status"
            }
        }

        // Test 4: Second-level nested command (system/network/status)
        let result = shell.resolve_path("system/network/status");
        assert!(result.is_ok(), "Should resolve system/network/status");
        if let Ok((node, _)) = result {
            assert!(node.is_some());
            if let Some(Node::Command(cmd)) = node {
                assert_eq!(cmd.name, "status");
            }
        }

        // Test 5: Second-level nested command (system/hardware/led)
        let result = shell.resolve_path("system/hardware/led");
        assert!(result.is_ok(), "Should resolve system/hardware/led");
        if let Ok((node, _)) = result {
            assert!(node.is_some());
            if let Some(Node::Command(cmd)) = node {
                assert_eq!(cmd.name, "led");
                assert_eq!(cmd.min_args, 1);
                assert_eq!(cmd.max_args, 1);
            }
        }

        // Test 6: Non-existent command at root
        let result = shell.resolve_path("nonexistent");
        assert!(result.is_err(), "Should fail for non-existent command");
        assert_eq!(
            result.unwrap_err(),
            CliError::CommandNotFound,
            "Should return CommandNotFound for non-existent command"
        );

        // Test 7: Invalid path (nonexistent directory)
        let result = shell.resolve_path("invalid/path/command");
        assert!(result.is_err(), "Should fail for nonexistent path");
        assert_eq!(
            result.unwrap_err(),
            CliError::CommandNotFound,
            "Should return CommandNotFound when first segment doesn't exist"
        );

        // Test 7b: Invalid path (attempting to navigate through a command)
        let result = shell.resolve_path("test-cmd/something");
        assert!(
            result.is_err(),
            "Should fail when navigating through command"
        );
        assert_eq!(
            result.unwrap_err(),
            CliError::InvalidPath,
            "Should return InvalidPath when trying to navigate through a command"
        );

        // Test 8: Resolve to directory (system)
        let result = shell.resolve_path("system");
        assert!(result.is_ok(), "Should resolve directory path");
        if let Ok((node, _)) = result {
            assert!(node.is_some());
            if let Some(Node::Directory(dir)) = node {
                assert_eq!(dir.name, "system");
            }
        }

        // Test 9: Resolve nested directory (system/network)
        let result = shell.resolve_path("system/network");
        assert!(result.is_ok(), "Should resolve nested directory");
        if let Ok((node, _)) = result {
            assert!(node.is_some());
            if let Some(Node::Directory(dir)) = node {
                assert_eq!(dir.name, "network");
            }
        }
    }

    #[test]
    #[cfg(not(feature = "authentication"))]
    fn test_resolve_path_parent_directory() {
        let io = MockIo::new();
        let handler = MockHandler;
        let shell: Shell<MockLevel, MockIo, MockHandler, DefaultConfig> =
            Shell::new(&TEST_TREE, handler, io);

        // Test 1: Navigate into directory then back up with ..
        // First navigate to system/network/status
        let result = shell.resolve_path("system/network/status");
        assert!(result.is_ok(), "Should resolve system/network/status");
        let (_, path) = result.unwrap();
        // Path should have indices for system (1), network (3)
        // [1] = system (index 1 in children of root: test-cmd, system)
        // [3] = network (index 3 in children of system: reboot, status, hardware, network)
        assert_eq!(
            path.len(),
            2,
            "Path should have 2 elements (system, network)"
        );
        assert_eq!(path[0], 1, "system should be at index 1 in root");
        assert_eq!(path[1], 3, "network should be at index 3 in system");

        // Test 2: Use .. to go back to system from system/network
        let result = shell.resolve_path("system/network/..");
        assert!(result.is_ok(), "Should resolve system/network/..");
        if let Ok((node, path)) = result {
            assert!(node.is_some());
            if let Some(Node::Directory(dir)) = node {
                assert_eq!(dir.name, "system", "Should be back at system directory");
            }
            assert_eq!(path.len(), 1, "Path should have 1 element");
            assert_eq!(path[0], 1, "system should be at index 1 in root");
        }

        // Test 3: Multiple .. to go back to root
        let result = shell.resolve_path("system/network/../..");
        assert!(result.is_ok(), "Should resolve system/network/../..");
        if let Ok((node, path)) = result {
            assert_eq!(path.len(), 0, "Path should be empty (at root)");
            assert!(node.is_none(), "Node should be None (representing root)");
        }

        // Test 4: Go beyond root with .. (should stay at root)
        let result = shell.resolve_path("..");
        assert!(result.is_ok(), "Should handle .. at root");
        if let Ok((node, path)) = result {
            assert_eq!(path.len(), 0, "Path should stay at root");
            assert!(node.is_none(), "Node should be None (representing root)");
        }
    }
}