import os, os.path
import random 
import sys
import datetime

from pyseeder.utils import PyseederException

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

def keygen(pub_key, priv_key, priv_key_password, user_id):
    """Generate new private key and certificate RSA_SHA512_4096"""
    for f in [pub_key, priv_key]:
        if not os.access(os.path.dirname(f) or ".", os.W_OK):
            raise PyseederException("Can't write {}, access forbidden").format(f)

    # Generate our key
    key = rsa.generate_private_key(public_exponent=65537, key_size=4096,
                                            backend=default_backend())

    # Write our key to disk for safe keeping
    with open(priv_key, "wb") as f:
        f.write(key.private_bytes(
            encoding=serialization.Encoding.PEM,
            format=serialization.PrivateFormat.TraditionalOpenSSL,
            encryption_algorithm=serialization.BestAvailableEncryption(
                                                            priv_key_password),
        ))

    # Various details about who we are. For a self-signed certificate the
    # subject and issuer are always the same.
    subject = issuer = x509.Name([
        x509.NameAttribute(NameOID.COUNTRY_NAME, "XX"),
        x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, "XX"),
        x509.NameAttribute(NameOID.LOCALITY_NAME, "XX"),
        x509.NameAttribute(NameOID.ORGANIZATION_NAME, "I2P Anonymous Network"),
        x509.NameAttribute(NameOID.ORGANIZATIONAL_UNIT_NAME, "I2P"),
        x509.NameAttribute(NameOID.COMMON_NAME, user_id),
    ])

    cert = x509.CertificateBuilder() \
        .subject_name(subject) \
        .issuer_name(issuer) \
        .public_key(key.public_key()) \
        .not_valid_before(datetime.datetime.utcnow()) \
        .not_valid_after(
            datetime.datetime.utcnow() + datetime.timedelta(days=365*10)
        ) \
        .serial_number(random.randrange(1000000000, 2000000000)) \
        .add_extension(
            x509.SubjectKeyIdentifier.from_public_key(key.public_key()),
            critical=False,
        ).sign(key, hashes.SHA512(), default_backend())

    with open(pub_key, "wb") as f:
        f.write(cert.public_bytes(serialization.Encoding.PEM))


def append_signature(target_file, priv_key, priv_key_password):
    """Append signature to the end of file"""
    if not os.path.exists(priv_key):
        raise PyseederException("Wrong private key path")

    if not os.access(priv_key, os.R_OK):
        raise PyseederException("Can't read private key, access forbidden")

    with open(target_file, "rb") as f:
        contents = f.read()

    with open(priv_key, "rb") as kf:
        private_key = serialization.load_pem_private_key(
            kf.read(), password=priv_key_password, backend=default_backend())

    signature = private_key.sign(contents, padding.PKCS1v15(), hashes.SHA512())

    with open(target_file, "ab") as f:
        f.write(signature)