import re
import unicodedata

from cryptography import x509
from flask import current_app
from lemur.extensions import sentry
from lemur.constants import SAN_NAMING_TEMPLATE, DEFAULT_NAMING_TEMPLATE


def text_to_slug(value):
    """Normalize a string to a "slug" value, stripping character accents and removing non-alphanum characters."""

    # Strip all character accents (ä => a): decompose Unicode characters and then drop combining chars.
    value = ''.join(c for c in unicodedata.normalize('NFKD', value) if not unicodedata.combining(c))

    # Replace all remaining non-alphanumeric characters with '-'. Multiple characters get collapsed into a single dash.
    # Except, keep 'xn--' used in IDNA domain names as is.
    value = re.sub(r'[^A-Za-z0-9.]+(?<!xn--)', '-', value)

    # '-' in the beginning or end of string looks ugly.
    return value.strip('-')


def certificate_name(common_name, issuer, not_before, not_after, san):
    """
    Create a name for our certificate. A naming standard
    is based on a series of templates. The name includes
    useful information such as Common Name, Validation dates,
    and Issuer.

    :param san:
    :param common_name:
    :param not_after:
    :param issuer:
    :param not_before:
    :rtype: str
    :return:
    """
    if san:
        t = SAN_NAMING_TEMPLATE
    else:
        t = DEFAULT_NAMING_TEMPLATE

    temp = t.format(
        subject=common_name,
        issuer=issuer.replace(' ', ''),
        not_before=not_before.strftime('%Y%m%d'),
        not_after=not_after.strftime('%Y%m%d')
    )

    temp = temp.replace('*', "WILDCARD")
    return text_to_slug(temp)


def signing_algorithm(cert):
    return cert.signature_hash_algorithm.name


def common_name(cert):
    """
    Attempts to get a sane common name from a given certificate.

    :param cert:
    :return: Common name or None
    """
    try:
        return cert.subject.get_attributes_for_oid(
            x509.OID_COMMON_NAME
        )[0].value.strip()
    except Exception as e:
        sentry.captureException()
        current_app.logger.error("Unable to get common name! {0}".format(e))


def organization(cert):
    """
    Attempt to get the organization name from a given certificate.
    :param cert:
    :return:
    """
    try:
        return cert.subject.get_attributes_for_oid(
            x509.OID_ORGANIZATION_NAME
        )[0].value.strip()
    except Exception as e:
        sentry.captureException()
        current_app.logger.error("Unable to get organization! {0}".format(e))


def organizational_unit(cert):
    """
    Attempt to get the organization unit from a given certificate.
    :param cert:
    :return:
    """
    try:
        return cert.subject.get_attributes_for_oid(
            x509.OID_ORGANIZATIONAL_UNIT_NAME
        )[0].value.strip()
    except Exception as e:
        sentry.captureException()
        current_app.logger.error("Unable to get organizational unit! {0}".format(e))


def country(cert):
    """
    Attempt to get the country from a given certificate.
    :param cert:
    :return:
    """
    try:
        return cert.subject.get_attributes_for_oid(
            x509.OID_COUNTRY_NAME
        )[0].value.strip()
    except Exception as e:
        sentry.captureException()
        current_app.logger.error("Unable to get country! {0}".format(e))


def state(cert):
    """
    Attempt to get the from a given certificate.
    :param cert:
    :return:
    """
    try:
        return cert.subject.get_attributes_for_oid(
            x509.OID_STATE_OR_PROVINCE_NAME
        )[0].value.strip()
    except Exception as e:
        sentry.captureException()
        current_app.logger.error("Unable to get state! {0}".format(e))


def location(cert):
    """
    Attempt to get the location name from a given certificate.
    :param cert:
    :return:
    """
    try:
        return cert.subject.get_attributes_for_oid(
            x509.OID_LOCALITY_NAME
        )[0].value.strip()
    except Exception as e:
        sentry.captureException()
        current_app.logger.error("Unable to get location! {0}".format(e))


def domains(cert):
    """
    Attempts to get an domains listed in a certificate.
    If 'subjectAltName' extension is not available we simply
    return the common name.

    :param cert:
    :return: List of domains
    """
    domains = []
    try:
        ext = cert.extensions.get_extension_for_oid(x509.OID_SUBJECT_ALTERNATIVE_NAME)
        entries = ext.value.get_values_for_type(x509.DNSName)
        for entry in entries:
            domains.append(entry)
    except x509.ExtensionNotFound:
        if current_app.config.get("LOG_SSL_SUBJ_ALT_NAME_ERRORS", True):
            sentry.captureException()
    except Exception as e:
        sentry.captureException()

    return domains


def serial(cert):
    """
    Fetch the serial number from the certificate.

    :param cert:
    :return: serial number
    """
    return cert.serial


def san(cert):
    """
    Determines if a given certificate is a SAN certificate.
    SAN certificates are simply certificates that cover multiple domains.

    :param cert:
    :return: Bool
    """
    if len(domains(cert)) > 1:
        return True


def is_wildcard(cert):
    """
    Determines if certificate is a wildcard certificate.

    :param cert:
    :return: Bool
    """
    d = domains(cert)
    if len(d) == 1 and d[0][0:1] == "*":
        return True

    if cert.subject.get_attributes_for_oid(x509.OID_COMMON_NAME)[0].value[0:1] == "*":
        return True


def bitstrength(cert):
    """
    Calculates a certificates public key bit length.

    :param cert:
    :return: Integer
    """
    try:
        return cert.public_key().key_size
    except AttributeError:
        sentry.captureException()
        current_app.logger.debug('Unable to get bitstrength.')


def issuer(cert):
    """
    Gets a sane issuer name from a given certificate.

    :param cert:
    :return: Issuer
    """
    delchars = ''.join(c for c in map(chr, range(256)) if not c.isalnum())
    try:
        # Try organization name or fall back to CN
        issuer = (cert.issuer.get_attributes_for_oid(x509.OID_ORGANIZATION_NAME)
                  or cert.issuer.get_attributes_for_oid(x509.OID_COMMON_NAME))
        issuer = str(issuer[0].value)
        for c in delchars:
            issuer = issuer.replace(c, "")
        return issuer
    except Exception as e:
        sentry.captureException()
        current_app.logger.error("Unable to get issuer! {0}".format(e))
        return "Unknown"


def not_before(cert):
    """
    Gets the naive datetime of the certificates 'not_before' field.
    This field denotes the first date in time which the given certificate
    is valid.

    :param cert:
    :return: Datetime
    """
    return cert.not_valid_before


def not_after(cert):
    """
    Gets the naive datetime of the certificates 'not_after' field.
    This field denotes the last date in time which the given certificate
    is valid.

    :return: Datetime
    """
    return cert.not_valid_after