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Exceptions

Custom exception classes for EncryptoCLI error handling.

Exception Hierarchy

Exception
├── EncryptoCLIException (base class)
│   ├── EncryptionError
│   ├── DecryptionError
│   ├── FileOperationError
│   └── InvalidInputError

Base Exception

EncryptoCLIException

Base exception for all EncryptoCLI errors.

from encryptocli.util.exceptions import EncryptoCLIException

try:
    # Some operation
    pass
except EncryptoCLIException as e:
    # Catches any EncryptoCLI error
    print(f"Error: {e}")

Specific Exceptions

EncryptionError

Raised when encryption operation fails.

Causes: - Invalid plaintext - Invalid password/key - Cipher initialization failure - Unsupported encryption method - File permission issues

Example: 

from encryptocli.encryption.aes import AESCipher
from encryptocli.util.exceptions import EncryptionError

cipher = AESCipher()

try:
    encrypted = cipher.encrypt(plaintext, password)
except EncryptionError as e:
    print(f"Encryption failed: {e}")

DecryptionError

Raised when decryption operation fails.

Causes: - Wrong password - Corrupted ciphertext - Invalid cipher format - Unsupported decryption method - Key not found (PGP)

Example: 

from encryptocli.encryption.aes import AESCipher
from encryptocli.util.exceptions import DecryptionError

cipher = AESCipher()

try:
    decrypted = cipher.decrypt(ciphertext, password)
except DecryptionError as e:
    print(f"Decryption failed: {e}")
    if "password" in str(e).lower():
        print("Try with correct password")

FileOperationError

Raised when file I/O operations fail.

Causes: - File not found - Permission denied - Directory not found - Disk full - File read/write failure - Invalid file path

Example: 

from encryptocli.services import EncryptionService
from encryptocli.util.exceptions import FileOperationError

service = EncryptionService()

try:
    encrypted = service.encrypt_file("/path/to/file.txt", "password")
except FileOperationError as e:
    print(f"File operation failed: {e}")
    if "not found" in str(e).lower():
        print("File does not exist")
    elif "permission" in str(e).lower():
        print("Permission denied - check file permissions")

InvalidInputError

Raised when input validation fails.

Causes: - Empty input - Invalid format - Unsupported algorithm - Invalid email address - Data too large - Missing required parameters

Example: 

from encryptocli.services import HashingService
from encryptocli.util.exceptions import InvalidInputError

service = HashingService()

try:
    hash_result = service.hash_text(data, "INVALID_ALGORITHM")
except InvalidInputError as e:
    print(f"Invalid input: {e}")
    print(f"Supported algorithms: {service.ALGORITHMS.keys()}")

Error Handling Patterns

Basic Try-Except

from encryptocli.services import EncryptionService
from encryptocli.util.exceptions import (
    EncryptionError,
    InvalidInputError
)

service = EncryptionService()

try:
    result = service.encrypt_text(secret, password)
except EncryptionError as e:
    print(f"Encryption error: {e}")
except InvalidInputError as e:
    print(f"Invalid input: {e}")

Catch All EncryptoCLI Errors

from encryptocli.services import EncryptionService
from encryptocli.util.exceptions import EncryptoCLIException

service = EncryptionService()

try:
    result = service.encrypt_file(path, password)
except EncryptoCLIException as e:
    print(f"EncryptoCLI error: {e}")
    # Handle any EncryptoCLI error

Multi-Level Error Handling

from encryptocli.services import DecryptionService
from encryptocli.util.exceptions import (
    DecryptionError,
    FileOperationError,
    EncryptoCLIException
)

service = DecryptionService()

try:
    result = service.decrypt_file(encrypted_path, password)
except FileOperationError as e:
    print(f"Cannot read file: {e}")
except DecryptionError as e:
    print(f"Wrong password or corrupted data: {e}")
except EncryptoCLIException as e:
    print(f"Other error: {e}")

With Cleanup

from encryptocli.services import EncryptionService
from encryptocli.util.exceptions import EncryptoCLIException
import tempfile

service = EncryptionService()
temp_file = None

try:
    temp_file = tempfile.NamedTemporaryFile(delete=False)
    encrypted = service.encrypt_file(source, password)
    temp_file.write(encrypted)
    print("Encryption successful")
except EncryptoCLIException as e:
    print(f"Error: {e}")
finally:
    if temp_file:
        temp_file.close()
        # Optional: clean up temp file

Exception Messages

Exception messages are descriptive and actionable:

try:
    # Missing file
    encrypt_file("missing.txt", "password")
except FileOperationError as e:
    # e.message: "File not found: missing.txt"
    print(e)

Best Practices

1. Specific Exception Handling

Good: 

try:
    decrypt_text(data, password)
except DecryptionError as e:
    print("Wrong password")

Bad: 

try:
    decrypt_text(data, password)
except Exception as e:
    print("Something went wrong")

2. Log Exception Information

import logging
from encryptocli.util.exceptions import EncryptoCLIException

logger = logging.getLogger(__name__)

try:
    operation()
except EncryptoCLIException as e:
    logger.error(f"Operation failed: {e}", exc_info=True)

3. Provide Context

try:
    encrypted = service.encrypt_file(path, password)
except FileOperationError as e:
    print(f"Cannot encrypt {path}: {e}")
except Exception as e:
    print(f"Encryption failed: {e}")

4. Retry Logic

from encryptocli.util.exceptions import DecryptionError

def decrypt_with_retry(data, max_attempts=3):
    for attempt in range(max_attempts):
        try:
            password = input("Enter password: ")
            return decrypt_text(data, password)
        except DecryptionError:
            if attempt < max_attempts - 1:
                print("Wrong password, try again")
            else:
                print("Failed - wrong password")
                raise

See Also