from datetime import datetime, timedelta, timezone
from typing import Tuple

from cryptography import x509
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.x509.oid import NameOID


def make_tls_cert(hostname: str) -> Tuple[x509.Certificate, rsa.RSAPrivateKey]:
    key = rsa.generate_private_key(
        public_exponent=65537, key_size=2048, backend=default_backend()
    )
    subject = issuer = x509.Name(
        [
            x509.NameAttribute(NameOID.COMMON_NAME, hostname),
        ]
    )
    cert = (
        x509.CertificateBuilder()
        .subject_name(subject)
        .issuer_name(issuer)
        .public_key(key.public_key())
        .serial_number(x509.random_serial_number())
        .not_valid_before(datetime.now(timezone.utc))
        .not_valid_after(datetime.now(timezone.utc) + timedelta(days=10))
        .add_extension(
            x509.SubjectAlternativeName([x509.DNSName(hostname)]),
            critical=False,
        )
        .sign(key, hashes.SHA256(), default_backend())
    )
    return cert, key


def serialize_key(key: rsa.RSAPrivateKey) -> bytes:
    return key.private_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PrivateFormat.TraditionalOpenSSL,
        encryption_algorithm=serialization.NoEncryption(),
    )


def serialize_cert(cert: x509.Certificate) -> bytes:
    return cert.public_bytes(serialization.Encoding.PEM)
