neural

```python
# File: src/utils/string_utils.py
# Description: Utility functions for string manipulation
# Created: 2024-05-15
# Author: AI Assistant

from typing import Optional
import re


def sanitize_input(input_str: str, max_length: int = 100) -> Optional[str]:
    """
    Sanitizes user input by removing leading/trailing whitespace, 
    limiting length, and escaping HTML characters.
    
    Args:
        input_str: Raw user input string
        max_length: Maximum allowed string length (default: 100)
    
    Returns:
        Sanitized string or None if input is empty after sanitization
    
    Raises:
        ValueError: If input_str exceeds max_length
    """
    if not input_str:
        return None
    
    # Check length constraint
    if len(input_str) > max_length:
        raise ValueError(f"Input exceeds maximum length of {max_length} characters")
    
    # Remove leading/trailing whitespace
    sanitized = input_str.strip()
    
    # Escape HTML characters to prevent XSS
    sanitized = re.sub(r'[<>&"\']', lambda m: {
        '<': '&lt;',
        '>': '&gt;',
        '&': '&amp;',
        '"': '&quot;',
        "'": '&#39;'
    }[m.group(0)], sanitized)
    
    return sanitized if sanitized else None


# Unit test stubs using pytest
# File: tests/test_string_utils.py
# To run: pytest tests/test_string_utils.py -v

# def test_sanitize_input_empty_string():
#     assert sanitize_input("") is None

# def test_sanitize_input_normal_string():
#     assert sanitize_input("  Hello World  ") == "Hello World"

# def test_sanitize_input_html_escaping():
#     assert sanitize_input("<script>alert('xss')</script>") == "&lt;script&gt;alert(&#39;xss&#39;)&lt;/script&gt;"

# def test_sanitize_input_length_exceeded():
#     with pytest.raises(ValueError):
#         sanitize_input("a" * 101)
```

```lua
-- File: lua/plugins/config.lua
-- Description: Neovim plugin configuration
-- Created: 2024-05-15
-- Author: AI Assistant

local M = {}

--- Configure the Neural plugin with custom settings
---@param opts table Configuration options
function M.setup(opts)
  opts = opts or {}
  
  -- Enable code completion
  vim.g.neural_enable_completion = true
  
  -- Set default model (gpt-4o for balance of speed and quality)
  vim.g.neural_default_model = "gpt-4o"
  
  -- Configure context window size
  vim.g.neural_context_window = 4096
  
  -- Set custom prompt template for code generation
  vim.g.neural_prompt_template = [[
    You are an expert {language} developer. Write clean, efficient code following these guidelines:
    1. Use modern {language} features
    2. Include type hints where applicable
    3. Add JSDoc/Docstring comments
    4. Follow {style_guide} style guide
    5. Add error handling
    
    Task: {task_description}
    
    File context:
    {file_context}
  ]]
  
  -- Enable streaming responses for large outputs
  vim.g.neural_streaming = true
  
  -- Configure keybindings
  vim.keymap.set('n', '<leader>nc', '<cmd>NeuralCode<cr>', {desc = "Generate code with Neural"})
  vim.keymap.set('v', '<leader>nc', '<cmd>NeuralCode<cr>', {desc = "Generate code with Neural"})
end

return M
```