Example Function

// Even though not a perfect example of the linear function principle (LFP) 
// this function from stygiansift illustrates many of the ideas talked about in the essay.
// Things like linear flow, fault isolation and local abstractions.

#[rustfmt::skip]
pub fn display_help_screen(
    stdout: &mut impl Write,
    config: &Config,
    app_state: &AppState,
    full_redraw: bool,
) -> io::Result<()> {
let mut current_page = 1;
    let total_pages = 2;
    
    let _ = full_redraw;
    let (width, height) = size()?;
    let nav_width = width / 2;
    let _preview_width = width - nav_width - 2;

    let _ = clear_nav();
    let _ = clear_preview();

    let title = "File Browser Help Menu\r";
    let separator = "=".repeat(title.len());
    execute!(stdout, MoveTo(nav_width / 3, 3))?;
    writeln!(stdout, "{}\r", title.bold().green())?;
    execute!(stdout, MoveTo(nav_width / 3, 4))?;
    writeln!(stdout, "{}\r", separator.green())?;

    let get_key_for_action = |action: &Action| -> String {
        config
            .keybindings
            .as_ref()
            .and_then(|kb| {
                kb.iter().find_map(|(k, v)| {
                    if v == action {
                        Some(key_event_to_string(k))
                    } else {
                        None
                    }
                })
            })
            .unwrap_or_else(|| "Unbound".to_string())
    };
    let page1_sections = [
        (
            "Navigation",
            vec![
                (format!("{} / {}", get_key_for_action(&Action::MoveUp).trim_matches('"'), "k"), "Move up in the file list"),
                (format!("{} / {}", get_key_for_action(&Action::MoveDown).trim_matches('"'), "j"), "Move down in the file list"),
                (format!("{} / {}", get_key_for_action(&Action::MoveLeft).trim_matches('"'), "h"), "Go to parent directory"),
                (format!("{} / {}", get_key_for_action(&Action::MoveRight).trim_matches('"'), "l"), "Enter selected directory"),
                (get_key_for_action(&Action::GoToTop).trim_matches('"').to_string(), "Go to top of list"),
                (get_key_for_action(&Action::GoToBottom).trim_matches('"').to_string(), "Go to bottom of list"),
                (get_key_for_action(&Action::SearchFiles).trim_matches('"').to_string(), "Search the file system"),
                ("0-9".to_string(), "Navigate to shortcut directory"),
            ],
        ),
        (
            "File Operations",
            vec![
                (get_key_for_action(&Action::ExecuteFile).trim_matches('"').to_string(), "Execute a file"),
                (get_key_for_action(&Action::GiveBirthDir).trim_matches('"').to_string(), "Create a directory"),
                (get_key_for_action(&Action::GiveBirthFile).trim_matches('"').to_string(), "Create a file"),
                (get_key_for_action(&Action::MoveItem).trim_matches('"').to_string(), "Move selected file or directory"),
                (get_key_for_action(&Action::Rename).trim_matches('"').to_string(), "Rename (keep extension)"),
                (get_key_for_action(&Action::RenameWithoutExtension).trim_matches('"').to_string(), "Rename (allow extension change)"),
                (get_key_for_action(&Action::Duplicate).trim_matches('"').to_string(), "Duplicate selected file/folder"),
                (get_key_for_action(&Action::Murder).trim_matches('"').to_string(), "Delete selected file(s)/folder(s)"),
                (get_key_for_action(&Action::Copy).trim_matches('"').to_string(), "Copy to clipboard"),
                (get_key_for_action(&Action::Paste).trim_matches('"').to_string(), "Paste from clipboard"),
                (get_key_for_action(&Action::OpenInEditor).trim_matches('"').to_string(), "Open in text editor"),
            ],
        ),
        (
            "View and Display",
            vec![
                (get_key_for_action(&Action::TogglePreview).trim_matches('"').to_string(), "Toggle preview pane"),
                (get_key_for_action(&Action::ToggleCount).trim_matches('"').to_string(), "Toggle item count display"),
                (get_key_for_action(&Action::SortCycleForward).trim_matches('"').to_string(), "Change sort order (forward)"),
                (get_key_for_action(&Action::SetLineAmount).trim_matches('"').to_string(), "Set number of lines in preview"),
                (get_key_for_action(&Action::CycleItemColor).trim_matches('"').to_string(), "Cycle item color"),
                (get_key_for_action(&Action::RemoveItemColor).trim_matches('"').to_string(), "Remove item color"),
                (get_key_for_action(&Action::SetColorRules).trim_matches('"').to_string(), "Set color rules"),
            ],
        ),
        (
            "Search and Filter",
            vec![
                (get_key_for_action(&Action::Search).trim_matches('"').to_string(), "Search the selected file"),
                (get_key_for_action(&Action::SearchFiles).trim_matches('"').to_string(), "Search for files"),
            ],
        ),
        (
            "Multi-Select",
            vec![
                (get_key_for_action(&Action::SelectAll).trim_matches('"').to_string(), "Select all files"),
                (get_key_for_action(&Action::ToggleSelect).trim_matches('"').to_string(), "Toggle select mode"),
                (get_key_for_action(&Action::MultiSelectUp).trim_matches('"').to_string(), "Select multiple files (moving up)"),
                (get_key_for_action(&Action::MultiSelectDown).trim_matches('"').to_string(), "Select multiple files (moving down)"),
            ],
        ),
        (
            "System and Tools",
            vec![
                (get_key_for_action(&Action::TerminalCommand).trim_matches('"').to_string(), "Open terminal"),
                (get_key_for_action(&Action::CastCommandLineSpell).trim_matches('"').to_string(), "Open terminal within in StygianSift"),
                (get_key_for_action(&Action::GitMenu).trim_matches('"').to_string(), "Open Git menu"),
                (get_key_for_action(&Action::Undo).trim_matches('"').to_string(), "Undo last operation"),
            ],
        ),
        (
            "Configuration and Help",
            vec![
                (get_key_for_action(&Action::EditConfig).trim_matches('"').to_string(), "Open configuration menu"),
                (get_key_for_action(&Action::Help).trim_matches('"').to_string(), "Show this help menu"),
                (get_key_for_action(&Action::ShowShortcuts).trim_matches('"').to_string(), "Show your stored shortcuts"),
            ],
        ),
    (
        "Shortcuts",
        vec![
            ("0-9".to_string(), "Use shortcut from current layer"),
            ("Shift + 0-9".to_string(), "Set shortcut in current layer"),
            ("F1-F10".to_string(), "Quick switch between layers"),
        ],
    ),
    ];
    let page2_sections: [(&str, Vec<(String, &str)>); 8] = [
            (
                "Layer Management",
                vec![
                    ("F1-F10".to_string(), "Switch to corresponding layer"),
                    (get_key_for_action(&Action::RenameLayer).trim_matches('"').to_string(), "Rename current layer"),
                    ("!-) (Shift+0-9)".to_string(), "Set shortcut in current layer"),
                    ("0-9".to_string(), "Use shortcut from current layer"),
                    ("F2".to_string(), "Show layer overview and shortcuts"),
                ],
            ),
            (
                "Visual Settings",
                vec![
                    (get_key_for_action(&Action::DecreaseDimDistance).trim_matches('"').to_string(), "Decrease dimming distance"),
                    (get_key_for_action(&Action::IncreaseDimDistance).trim_matches('"').to_string(), "Increase dimming distance"),
                    (get_key_for_action(&Action::DecreaseDimIntensity).trim_matches('"').to_string(), "Decrease dimming intensity"),
                    (get_key_for_action(&Action::IncreaseDimIntensity).trim_matches('"').to_string(), "Increase dimming intensity"),
                    (get_key_for_action(&Action::BorderStyle).trim_matches('"').to_string(), "Toggle border style"),
                ],
            ),
            (
        "",
                vec![(" ".to_string(), "")],
            ),
            (
        "",
                vec![(" ".to_string(), "")],
            ),
            (
        "",
                vec![(" ".to_string(), "")],
            ),
            (
        "",
                vec![(" ".to_string(), "")],
            ),
            (
        "",
                vec![(" ".to_string(), "")],
            ),
            (
        "",
                vec![(" ".to_string(), "")],
            ),
            
        ];

         loop {
        let _ = clear_nav();
        let _ = clear_preview();

        let title = "File Browser Help Menu\r";
        let separator = "=".repeat(title.len());
        execute!(stdout, MoveTo(nav_width / 3, 3))?;
        writeln!(stdout, "{}\r", title.bold().green())?;
        execute!(stdout, MoveTo(nav_width / 3, 4))?;
        writeln!(stdout, "{}\r", separator.green())?;

        let sections = if current_page == 1 { &page1_sections } else { &page2_sections };
        let mut current_column = 0;
        let mut current_row = height / 8;
        let column_width = (width / 2) - 4;

        for (i, (section_title, commands)) in sections.iter().enumerate() {
            if i > 0 && i % 4 == 0 {
                current_column += column_width;
                current_row = 6;
            }

            execute!(stdout, MoveTo(current_column + 8, current_row))?;
            writeln!(stdout, "{}\r", section_title.bold().green())?;
            current_row += 1;

            for (key, description) in commands {
                execute!(stdout, MoveTo(current_column + 8, current_row))?;
                writeln!(stdout, "{:<15}  {}\r", key.clone().red(), description.cyan())?;
                current_row += 1;
            }
            current_row += 1;
        }

        execute!(stdout, MoveTo((width / 2) + 4, height - 18))?;
        writeln!(stdout, "{}\r", "Search Depth:".bold().yellow())?;
        execute!(stdout, MoveTo((width / 2) + 4, height - 17))?;
        writeln!(stdout, "Current Depth: {}\r", app_state.search_depth_limit.to_string().red())?;

        execute!(stdout, MoveTo((width / 2) + 4, height - 15))?;
        writeln!(stdout, "{}\r", "Undo System Information:".bold().yellow())?;
        execute!(stdout, MoveTo((width / 2) + 4, height - 14))?;
        writeln!(stdout, "RAM Limit: {} MB\r", app_state.undo_manager.ram_limit / 1_048_576)?;
        execute!(stdout, MoveTo((width / 2) + 4, height - 13))?;
        writeln!(stdout, "Disk Limit: {} GB\r", app_state.undo_manager.disk_limit / 1_073_741_824)?;
        execute!(stdout, MoveTo((width / 2) + 4, height - 12))?;
        writeln!(stdout, "Disk Storage Allowed: {}\r",
            if app_state.undo_manager.allow_disk_storage { "Yes".green() } else { "No".red() }
        )?;

        execute!(stdout, MoveTo((width / 2) + 4, height - 10))?;
        writeln!(stdout, "{}\r", "Navigation:".bold().yellow())?;
        execute!(stdout, MoveTo((width / 2) + 4, height - 9))?;
        writeln!(stdout, "Page {} of {} (Use → and ← to navigate pages)\r", current_page, total_pages)?;
        execute!(stdout, MoveTo((width / 2) + 4, height - 8))?;
        writeln!(stdout, "Press ESC to return to the file browser...\r")?;
        execute!(stdout, MoveTo((width / 2) + 4, height - 7))?;
        writeln!(stdout, "{}: {}\r", "Tip: You can remap these keybindings by pressing".italic().blue(), "F3".italic().red())?;
        execute!(stdout, MoveTo((width / 2) + 4, height - 6))?;
        writeln!(stdout, "{}\r", "Tip: Experiment with different commands to become more proficient!".italic().blue())?;

        stdout.flush()?;

        if let Event::Key(key) = event::read()? {
            match key.code {
                KeyCode::Esc => break,
                KeyCode::Right | KeyCode::Char('l') if current_page < total_pages => {
                    current_page += 1;
                }
                KeyCode::Left | KeyCode::Char('h') if current_page > 1 => {
                    current_page -= 1;
                }
                _ => {}
            }
        }
    }
    Ok(())
}