earthsnake/earthsnake/identity.py

"""Identity management"""

import re
from typing import Optional

import bip39
from nacl.encoding import RawEncoder
from nacl.exceptions import BadSignatureError
from nacl.signing import SigningKey, VerifyKey

from .base32 import base32_bytes_to_string, base32_string_to_bytes
from .exc import ValidationError
from .types import ALPHA_LOWER, ALPHA_LOWER_OR_DIGIT, B32_CHAR


class Identity:
    """Class representing and Earthstar identity

    .. code-block:: python

       identity = Identity()
       mnemonic = identity.mnemonic
       identity = Identity.from_mnemonic(mnemonic)
    """

    _KEY_PATTERN = f'b[{B32_CHAR}]{{52}}'
    _NAME_PATTERN = f'[{ALPHA_LOWER}][{ALPHA_LOWER_OR_DIGIT}]{{3}}'
    _SECRET_PATTERN = f'^{_KEY_PATTERN}$'
    PATTERN = f'^@{_NAME_PATTERN}\\.{_KEY_PATTERN}$'

    def __init__(
        self,
        name: str,
        verify_key: Optional[VerifyKey] = None,
        sign_key: Optional[SigningKey] = None,
    ) -> None:
        if not self.valid_name(name):
            raise ValidationError(f'Invalid name: {name}')

        if sign_key and verify_key and sign_key.verify_key != verify_key:
            raise ValidationError('Signing and verifying keys don’t match')

        if sign_key and not verify_key:
            verify_key = sign_key.verify_key

        if not verify_key:
            raise ValidationError('At least verify_key must be present')

        self.name = name
        self.verify_key = verify_key
        self.sign_key = sign_key

    def __str__(self) -> str:
        key = base32_bytes_to_string(self.verify_key.encode(RawEncoder))

        return f'@{self.name}.{key}'

    def __repr__(self) -> str:
        if self.sign_key:
            return f'<Identity (signer) {self}>'

        return f'<Identity {self}>'

    def __eq__(self, other: object) -> bool:
        if isinstance(other, str):
            return str(self) == other

        if isinstance(other, Identity):
            return str(self) == str(other)

        raise TypeError(
            'Don’t know how to compare {self.__class__.__name__} and {other.__class__.__name__}'
        )

    @classmethod
    def from_address(cls, address: str) -> 'Identity':
        """Load an identity from an author address"""

        if not cls.valid_address(address):
            raise ValidationError(f'Invalid address {address}')

        address = address[1:]
        name, verify_key_data = address.split('.')
        verify_key_bytes = base32_string_to_bytes(verify_key_data)
        verify_key = VerifyKey(verify_key_bytes)

        return cls(name, verify_key=verify_key)

    @classmethod
    def valid_name(cls, name: str) -> bool:
        """Validate an address’ name part"""

        return bool(re.match(f'^{cls._NAME_PATTERN}$', name))

    @classmethod
    def valid_address(cls, address: str) -> bool:
        """Validate an author address"""

        if not address.startswith('@'):
            return False

        address = address[1:]

        try:
            name, verify_key_data = address.split('.')
        except ValueError:
            return False

        try:
            verify_key_bytes = base32_string_to_bytes(verify_key_data)
            VerifyKey(verify_key_bytes)
        except BaseException:  # pylint: disable=broad-except
            return False

        return cls.valid_name(name)

    @classmethod
    def generate(cls, name: str) -> 'Identity':
        """Generate a new entity"""

        sign_key = SigningKey.generate()
        verify_key = sign_key.verify_key

        return cls(name, verify_key=verify_key, sign_key=sign_key)

    @classmethod
    def from_mnemonic(cls, mnemonic: str) -> 'Identity':
        """Load an identity from a mnemonic"""

        name, mnemonic = mnemonic.split(' ', 1)
        seed = bip39.decode_phrase(mnemonic)
        sign_key = SigningKey(seed)

        return cls(name, sign_key=sign_key)

    @property
    def mnemonic(self) -> Optional[str]:
        """Convert the identify to a BIP39 mnemonic

        If the identity doesn’t have a stored signing (secret) key, it returns None."""

        if self.sign_key is None:
            return None

        seed = self.sign_key.encode()
        mnemonic = bip39.encode_bytes(seed)

        return f'{self.name} {mnemonic}'

    @property
    def can_sign(self) -> bool:
        return bool(self.sign_key)

    def sign(self, data: str) -> str:
        """Sign data"""

        if not self.sign_key:
            raise TypeError('This identity doesn’t have a signing key')

        signed_message = self.sign_key.sign(data.encode('utf-8'))

        return base32_bytes_to_string(signed_message.signature)

    def verify(self, data: str, signature: str) -> bool:
        """Verify if data is signed by us"""

        signature_bytes = base32_string_to_bytes(signature)

        try:
            self.verify_key.verify(data.encode('utf-8'), signature_bytes)
        except BadSignatureError:
            return False

        return True

    def hash(self) -> int:
        return hash(str(self))