import black
from pylint import lint
from io import StringIO
from typing import List, Dict, Optional

# --- Define custom exceptions for better error handling ---
class CodeRefinementError(Exception):
    """Raised when code refinement fails."""
    pass

class CodeTestingError(Exception):
    """Raised when code testing fails."""
    pass

class CodeIntegrationError(Exception):
    """Raised when code integration fails."""
    pass

# --- Implement code refinement functionality ---
def refine_code(file_path: str) -> str:
    """Refines the code in the specified file."""
    try:
        with open(file_path, 'r') as f:
            code = f.read()
        refined_code = black.format_str(code, mode=black.FileMode())
        return refined_code
    except black.InvalidInput:
        raise CodeRefinementError("Error: Invalid code input for black formatting.")
    except FileNotFoundError:
        raise CodeRefinementError(f"Error: File not found: {file_path}")
    except Exception as e:
        raise CodeRefinementError(f"Error during code refinement: {e}")

# --- Implement code testing functionality ---
def test_code(file_path: str) -> str:
    """Tests the code in the specified file."""
    try:
        with open(file_path, 'r') as f:
            code = f.read()
        output = StringIO()
        lint.run(code, output=output)
        return output.getvalue()
    except FileNotFoundError:
        raise CodeTestingError(f"Error: File not found: {file_path}")
    except Exception as e:
        raise CodeTestingError(f"Error during code testing: {e}")

# --- Implement code integration functionality ---
def integrate_code(file_path: str, code_snippet: str) -> str:
    """Integrates the code snippet into the specified file."""
    try:
        with open(file_path, 'a') as f:
            f.write(code_snippet)
        return "Code integrated successfully."
    except FileNotFoundError:
        raise CodeIntegrationError(f"Error: File not found: {file_path}")
    except Exception as e:
        raise CodeIntegrationError(f"Error during code integration: {e}")