```python
def word_reverse(line: str) -> str:
    """
    Reverse the letters of each word in the input string, maintaining the order of words and spaces.
    """
    if not line:
        return ""
    
    # Split the line into words using whitespace as the delimiter
    words = line.split()
    
    # Reverse each word and join them back with a single space
    reversed_words = [word[::-1] for word in words]
    
    # Join the reversed words with a single space
    return " ".join(reversed_words)
```