Parameters:
-----------
df : pandas.DataFrame
    The DataFrame to search in
column_name : str
    The case-insensitive column name to search for
new_name : str, optional
    If provided, the column will be renamed to this value
inplace : bool, default False
    If True and new_name is provided, modifies the DataFrame in-place and returns None.
    If False and new_name is provided, returns a copy of the DataFrame with renamed column.
    If new_name is None, this parameter has no effect.

Returns:
--------
str or pandas.DataFrame or None
    - If new_name is None: returns the exact case-sensitive column name
    - If new_name is provided and inplace=False: returns the DataFrame with renamed column
    - If new_name is provided and inplace=True: returns None

Raises:
-------
ValueError
    If no matching column is found or if multiple matches are found
"""
# Check if the dataframe is empty or has no columns
if df.empty or len(df.columns) == 0:
    raise ValueError("DataFrame is empty or has no columns")
    
# Strip whitespace from column names for comparison
clean_columns = {col.lower().strip(): col for col in df.columns}

# Clean and lowercase the search term
search_term = column_name.lower().strip()

# Check if the lowercase version of the input exists
if search_term not in clean_columns:
    matches = []
    # Check for partial matches (e.g., "jack" might match "jackson")
    for col_lower, col_original in clean_columns.items():
        if search_term in col_lower or col_lower in search_term:
            matches.append(col_original)
    
    if matches:
        original_column_name = matches[0]  # Get the first partial match
    else:
        raise ValueError(f"No column matching '{column_name}' was found in the DataFrame")
else:
    # Check for multiple exact matches with the same spelling but different cases
    exact_matches = [col for col in df.columns if col.lower().strip() == search_term]
    if len(exact_matches) > 1:
        raise ValueError(f"Multiple columns with the same name but different cases found: {exact_matches}")
    
    # Get the exact case-sensitive column name
    original_column_name = clean_columns[search_term]

# If new_name is not provided, just return the original column name
if new_name is None:
    return original_column_name

# If new_name is provided, rename the column
if inplace:
    df.rename(columns={original_column_name: new_name}, inplace=True)
    return None
else:
    return df.rename(columns={original_column_name: new_name})