This function will process each line of the input file, where each line contains three names: the boy, his enemy, and his best friend. The data will be stored in a suitable structure (such as a dictionary or a list of tuples) for further processing.

Here's a Python function that reads the input file and stores the data in a dictionary where the keys are the boy's names and the values are dictionaries containing the enemy's name and the best friend's name.

```python
def process_file(file_path):
    """
    Process each line of the input file and store the data in a dictionary.

    Args:
        file_path (str): The path to the input file.

    Returns:
        dict: A dictionary where the keys are the boy's names and the values are dictionaries containing the enemy's name and the best friend's name.
    """
    data = {}
    try:
        with open(file_path, 'r') as file:
            for line in file:
                # Remove leading and trailing whitespaces
                line = line.strip()
                # Split the line into three names
                boy, enemy, best_friend = line.split(',')
                # Store the data in the dictionary
                data[boy] = {'enemy': enemy, 'best_friend': best_friend}
    except FileNotFoundError:
        print(f"File {file_path} not found.")
    except Exception as e:
        print(f"An error occurred: {e}")
    return data

# Example usage:
file_path = 'input.txt'  # Replace with your input file path
data = process_file(file_path)
print(data)
```

In this code:

1.  We define a function `process_file` that takes the file path as an argument.
2.  We open the file in read mode (`'r'`) using a `with` statement, which ensures the file is properly closed after we're done with it.
3.  We iterate over each line in the file, remove leading and trailing whitespaces, and split the line into three names using the `split` method with a comma as the separator.
4.  We store the data in a dictionary where the keys are the boy's names and the values are dictionaries containing the enemy's name and the best friend's name.
5.  We handle potential exceptions, such as a `FileNotFoundError` if the file does not exist, and print an error message if an exception occurs.
6.  Finally, we return the dictionary containing the processed data.

You can replace `'input.txt'` with the path to your input file and run the code to process the file and store the data in a dictionary.