import logging
import os
import re
import socket
import struct
import tempfile
import time
from contextlib import contextmanager
from xml.etree import ElementTree

from cloudinit import util


LOG = logging.getLogger(__name__)


@contextmanager
def cd(newdir):
    prevdir = os.getcwd()
    os.chdir(os.path.expanduser(newdir))
    try:
        yield
    finally:
        os.chdir(prevdir)


class AzureEndpointHttpClient(object):

    headers = {
        'x-ms-agent-name': 'WALinuxAgent',
        'x-ms-version': '2012-11-30',
    }

    def __init__(self, certificate):
        self.extra_secure_headers = {
            "x-ms-cipher-name": "DES_EDE3_CBC",
            "x-ms-guest-agent-public-x509-cert": certificate,
        }

    def get(self, url, secure=False):
        headers = self.headers
        if secure:
            headers = self.headers.copy()
            headers.update(self.extra_secure_headers)
        return util.read_file_or_url(url, headers=headers)

    def post(self, url, data=None, extra_headers=None):
        headers = self.headers
        if extra_headers is not None:
            headers = self.headers.copy()
            headers.update(extra_headers)
        return util.read_file_or_url(url, data=data, headers=headers)


class GoalState(object):

    def __init__(self, xml, http_client):
        self.http_client = http_client
        self.root = ElementTree.fromstring(xml)
        self._certificates_xml = None

    def _text_from_xpath(self, xpath):
        element = self.root.find(xpath)
        if element is not None:
            return element.text
        return None

    @property
    def container_id(self):
        return self._text_from_xpath('./Container/ContainerId')

    @property
    def incarnation(self):
        return self._text_from_xpath('./Incarnation')

    @property
    def instance_id(self):
        return self._text_from_xpath(
            './Container/RoleInstanceList/RoleInstance/InstanceId')

    @property
    def certificates_xml(self):
        if self._certificates_xml is None:
            url = self._text_from_xpath(
                './Container/RoleInstanceList/RoleInstance'
                '/Configuration/Certificates')
            if url is not None:
                self._certificates_xml = self.http_client.get(
                    url, secure=True).contents
        return self._certificates_xml


class OpenSSLManager(object):

    certificate_names = {
        'private_key': 'TransportPrivate.pem',
        'certificate': 'TransportCert.pem',
    }

    def __init__(self):
        self.tmpdir = tempfile.mkdtemp()
        self.certificate = None
        self.generate_certificate()

    def clean_up(self):
        util.del_dir(self.tmpdir)

    def generate_certificate(self):
        LOG.debug('Generating certificate for communication with fabric...')
        if self.certificate is not None:
            LOG.debug('Certificate already generated.')
            return
        with cd(self.tmpdir):
            util.subp([
                'openssl', 'req', '-x509', '-nodes', '-subj',
                '/CN=LinuxTransport', '-days', '32768', '-newkey', 'rsa:2048',
                '-keyout', self.certificate_names['private_key'],
                '-out', self.certificate_names['certificate'],
            ])
            certificate = ''
            for line in open(self.certificate_names['certificate']):
                if "CERTIFICATE" not in line:
                    certificate += line.rstrip()
            self.certificate = certificate
        LOG.debug('New certificate generated.')

    def parse_certificates(self, certificates_xml):
        tag = ElementTree.fromstring(certificates_xml).find(
            './/Data')
        certificates_content = tag.text
        lines = [
            b'MIME-Version: 1.0',
            b'Content-Disposition: attachment; filename="Certificates.p7m"',
            b'Content-Type: application/x-pkcs7-mime; name="Certificates.p7m"',
            b'Content-Transfer-Encoding: base64',
            b'',
            certificates_content.encode('utf-8'),
        ]
        with cd(self.tmpdir):
            with open('Certificates.p7m', 'wb') as f:
                f.write(b'\n'.join(lines))
            out, _ = util.subp(
                'openssl cms -decrypt -in Certificates.p7m -inkey'
                ' {private_key} -recip {certificate} | openssl pkcs12 -nodes'
                ' -password pass:'.format(**self.certificate_names),
                shell=True)
        private_keys, certificates = [], []
        current = []
        for line in out.splitlines():
            current.append(line)
            if re.match(r'[-]+END .*?KEY[-]+$', line):
                private_keys.append('\n'.join(current))
                current = []
            elif re.match(r'[-]+END .*?CERTIFICATE[-]+$', line):
                certificates.append('\n'.join(current))
                current = []
        keys = []
        for certificate in certificates:
            with cd(self.tmpdir):
                public_key, _ = util.subp(
                    'openssl x509 -noout -pubkey |'
                    'ssh-keygen -i -m PKCS8 -f /dev/stdin',
                    data=certificate,
                    shell=True)
            keys.append(public_key)
        return keys


class WALinuxAgentShim(object):

    REPORT_READY_XML_TEMPLATE = '\n'.join([
        '<?xml version="1.0" encoding="utf-8"?>',
        '<Health xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"'
        ' xmlns:xsd="http://www.w3.org/2001/XMLSchema">',
        '  <GoalStateIncarnation>{incarnation}</GoalStateIncarnation>',
        '  <Container>',
        '    <ContainerId>{container_id}</ContainerId>',
        '    <RoleInstanceList>',
        '      <Role>',
        '        <InstanceId>{instance_id}</InstanceId>',
        '        <Health>',
        '          <State>Ready</State>',
        '        </Health>',
        '      </Role>',
        '    </RoleInstanceList>',
        '  </Container>',
        '</Health>'])

    def __init__(self):
        LOG.debug('WALinuxAgentShim instantiated...')
        self.endpoint = self.find_endpoint()
        self.openssl_manager = None
        self.values = {}

    def clean_up(self):
        if self.openssl_manager is not None:
            self.openssl_manager.clean_up()

    @staticmethod
    def get_ip_from_lease_value(lease_value):
        unescaped_value = lease_value.replace('\\', '')
        if len(unescaped_value) > 4:
            hex_string = ''
            for hex_pair in unescaped_value.split(':'):
                if len(hex_pair) == 1:
                    hex_pair = '0' + hex_pair
                hex_string += hex_pair
            packed_bytes = struct.pack(
                '>L', int(hex_string.replace(':', ''), 16))
        else:
            packed_bytes = unescaped_value.encode('utf-8')
        return socket.inet_ntoa(packed_bytes)

    @staticmethod
    def find_endpoint():
        LOG.debug('Finding Azure endpoint...')
        content = util.load_file('/var/lib/dhcp/dhclient.eth0.leases')
        value = None
        for line in content.splitlines():
            if 'unknown-245' in line:
                value = line.strip(' ').split(' ', 2)[-1].strip(';\n"')
        if value is None:
            raise Exception('No endpoint found in DHCP config.')
        endpoint_ip_address = WALinuxAgentShim.get_ip_from_lease_value(value)
        LOG.debug('Azure endpoint found at %s', endpoint_ip_address)
        return endpoint_ip_address

    def register_with_azure_and_fetch_data(self):
        self.openssl_manager = OpenSSLManager()
        http_client = AzureEndpointHttpClient(self.openssl_manager.certificate)
        LOG.info('Registering with Azure...')
        attempts = 0
        while True:
            try:
                response = http_client.get(
                    'http://{0}/machine/?comp=goalstate'.format(self.endpoint))
            except Exception:
                if attempts < 10:
                    time.sleep(attempts + 1)
                else:
                    raise
            else:
                break
            attempts += 1
        LOG.debug('Successfully fetched GoalState XML.')
        goal_state = GoalState(response.contents, http_client)
        public_keys = []
        if goal_state.certificates_xml is not None:
            LOG.debug('Certificate XML found; parsing out public keys.')
            public_keys = self.openssl_manager.parse_certificates(
                goal_state.certificates_xml)
        data = {
            'public-keys': public_keys,
        }
        self._report_ready(goal_state, http_client)
        return data

    def _report_ready(self, goal_state, http_client):
        LOG.debug('Reporting ready to Azure fabric.')
        document = self.REPORT_READY_XML_TEMPLATE.format(
            incarnation=goal_state.incarnation,
            container_id=goal_state.container_id,
            instance_id=goal_state.instance_id,
        )
        http_client.post(
            "http://{0}/machine?comp=health".format(self.endpoint),
            data=document,
            extra_headers={'Content-Type': 'text/xml; charset=utf-8'},
        )
        LOG.info('Reported ready to Azure fabric.')


def get_metadata_from_fabric():
    shim = WALinuxAgentShim()
    try:
        return shim.register_with_azure_and_fetch_data()
    finally:
        shim.clean_up()
