# stdlib
import socket
import re
import logging
import subprocess
import types

# datadog
from datadog.util.compat import url_lib, is_p3k, iteritems, json
from datadog.util.config import get_config, get_os, CfgNotFound

VALID_HOSTNAME_RFC_1123_PATTERN = re.compile(r"^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$")  # noqa
MAX_HOSTNAME_LEN = 255

log = logging.getLogger('datadog.api')


def is_valid_hostname(hostname):
    if hostname.lower() in set([
        'localhost',
        'localhost.localdomain',
        'localhost6.localdomain6',
        'ip6-localhost',
    ]):
        log.warning("Hostname: %s is local" % hostname)
        return False
    if len(hostname) > MAX_HOSTNAME_LEN:
        log.warning("Hostname: %s is too long (max length is  %s characters)"
                    % (hostname, MAX_HOSTNAME_LEN))
        return False
    if VALID_HOSTNAME_RFC_1123_PATTERN.match(hostname) is None:
        log.warning("Hostname: %s is not complying with RFC 1123" % hostname)
        return False
    return True


def get_hostname():
    """
    Get the canonical host name this agent should identify as. This is
    the authoritative source of the host name for the agent.

    Tries, in order:

      * agent config (datadog.conf, "hostname:")
      * 'hostname -f' (on unix)
      * socket.gethostname()
    """

    hostname = None
    config = None

    # first, try the config
    try:
        config = get_config()
        config_hostname = config.get('hostname')
        if config_hostname and is_valid_hostname(config_hostname):
            return config_hostname
    except CfgNotFound:
        log.info("No agent or invalid configuration file found")

    # Try to get GCE instance name
    if hostname is None:
        gce_hostname = GCE.get_hostname(config)
        if gce_hostname is not None:
            if is_valid_hostname(gce_hostname):
                return gce_hostname
    # then move on to os-specific detection
    if hostname is None:
        def _get_hostname_unix():
            try:
                # try fqdn
                p = subprocess.Popen(['/bin/hostname', '-f'], stdout=subprocess.PIPE)
                out, err = p.communicate()
                if p.returncode == 0:
                    if is_p3k():
                        return out.decode("utf-8").strip()
                    else:
                        return out.strip()
            except Exception:
                return None

        os_name = get_os()
        if os_name in ['mac', 'freebsd', 'linux', 'solaris']:
            unix_hostname = _get_hostname_unix()
            if unix_hostname and is_valid_hostname(unix_hostname):
                hostname = unix_hostname

    # if we have an ec2 default hostname, see if there's an instance-id available
    if hostname is not None and True in [hostname.lower().startswith(p) for p in [u'ip-', u'domu']]:
        instanceid = EC2.get_instance_id(config)
        if instanceid:
            hostname = instanceid

    # fall back on socket.gethostname(), socket.getfqdn() is too unreliable
    if hostname is None:
        try:
            socket_hostname = socket.gethostname()
        except socket.error:
            socket_hostname = None
        if socket_hostname and is_valid_hostname(socket_hostname):
            hostname = socket_hostname

    if hostname is None:
        log.warning(
            u"Unable to reliably determine host name. You can define one in your `hosts` file, "
            u"or in `datadog.conf` file if you have Datadog Agent installed."
        )

    return hostname


def get_ec2_instance_id():
    try:
        # Remember the previous default timeout
        old_timeout = socket.getdefaulttimeout()

        # Try to query the EC2 internal metadata service, but fail fast
        socket.setdefaulttimeout(0.25)

        try:
            return url_lib.urlopen(url_lib.Request("http://169.254.169.254/latest/"
                                                   "meta-data/instance-id")).read()
        finally:
            # Reset the previous default timeout
            socket.setdefaulttimeout(old_timeout)
    except:
        return socket.gethostname()


class GCE(object):
    URL = "http://169.254.169.254/computeMetadata/v1/?recursive=true"
    TIMEOUT = 0.1  # second
    SOURCE_TYPE_NAME = 'google cloud platform'
    metadata = None

    @staticmethod
    def _get_metadata(agentConfig):
        if GCE.metadata is not None:
            return GCE.metadata

        if not agentConfig['collect_instance_metadata']:
            log.info("Instance metadata collection is disabled. Not collecting it.")
            GCE.metadata = {}
            return GCE.metadata

        socket_to = None
        try:
            socket_to = socket.getdefaulttimeout()
            socket.setdefaulttimeout(GCE.TIMEOUT)
        except Exception:
            pass

        try:
            opener = url_lib.build_opener()
            opener.addheaders = [('X-Google-Metadata-Request', 'True')]
            GCE.metadata = json.loads(opener.open(GCE.URL).read().strip())

        except Exception:
            GCE.metadata = {}

        try:
            if socket_to is None:
                socket_to = 3
            socket.setdefaulttimeout(socket_to)
        except Exception:
            pass
        return GCE.metadata

    @staticmethod
    def get_hostname(agentConfig):
        try:
            host_metadata = GCE._get_metadata(agentConfig)
            return host_metadata['instance']['hostname'].split('.')[0]
        except Exception:
            return None


class EC2(object):
    """Retrieve EC2 metadata
    """
    URL = "http://169.254.169.254/latest/meta-data"
    TIMEOUT = 0.1  # second
    metadata = {}

    @staticmethod
    def get_tags(agentConfig):
        if not agentConfig['collect_instance_metadata']:
            log.info("Instance metadata collection is disabled. Not collecting it.")
            return []

        socket_to = None
        try:
            socket_to = socket.getdefaulttimeout()
            socket.setdefaulttimeout(EC2.TIMEOUT)
        except Exception:
            pass

        try:
            iam_role = url_lib.urlopen(EC2.URL + "/iam/security-credentials").read().strip()
            iam_params = json.loads(url_lib.urlopen(EC2.URL + "/iam/security-credentials" + "/" +
                                    str(iam_role)).read().strip())
            from boto.ec2.connection import EC2Connection
            connection = EC2Connection(aws_access_key_id=iam_params['AccessKeyId'],
                                       aws_secret_access_key=iam_params['SecretAccessKey'],
                                       security_token=iam_params['Token'])
            instance_object = connection.get_only_instances([EC2.metadata['instance-id']])[0]

            EC2_tags = [u"%s:%s" % (tag_key, tag_value) for tag_key, tag_value
                        in iteritems(instance_object.tags)]

        except Exception:
            log.exception("Problem retrieving custom EC2 tags")
            EC2_tags = []

        try:
            if socket_to is None:
                socket_to = 3
            socket.setdefaulttimeout(socket_to)
        except Exception:
            pass

        return EC2_tags

    @staticmethod
    def get_metadata(agentConfig):
        """Use the ec2 http service to introspect the instance. This adds latency \
        if not running on EC2
        """
        # >>> import urllib2
        # >>> urllib2.urlopen('http://169.254.169.254/latest/', timeout=1).read()
        # 'meta-data\nuser-data'
        # >>> urllib2.urlopen('http://169.254.169.254/latest/meta-data', timeout=1).read()
        # 'ami-id\nami-launch-index\nami-manifest-path\nhostname\ninstance-id\nlocal-ipv4\
        # npublic-keys/\nreservation-id\nsecurity-groups'
        # >>> urllib2.urlopen('http://169.254.169.254/latest/meta-data/instance-id',
        # timeout=1).read()
        # 'i-deadbeef'

        # Every call may add TIMEOUT seconds in latency so don't abuse this call
        # python 2.4 does not support an explicit timeout argument so force it here
        # Rather than monkey-patching urllib2, just lower the timeout globally for these calls

        if not agentConfig['collect_instance_metadata']:
            log.info("Instance metadata collection is disabled. Not collecting it.")
            return {}

        socket_to = None
        try:
            socket_to = socket.getdefaulttimeout()
            socket.setdefaulttimeout(EC2.TIMEOUT)
        except Exception:
            pass

        for k in ('instance-id', 'hostname', 'local-hostname', 'public-hostname', 'ami-id',
                  'local-ipv4', 'public-keys', 'public-ipv4', 'reservation-id', 'security-groups'):
            try:
                v = url_lib.urlopen(EC2.URL + "/" + str(k)).read().strip()
                assert type(v) in (types.StringType, types.UnicodeType) and len(v) > 0, \
                    "%s is not a string" % v
                EC2.metadata[k] = v
            except Exception:
                pass

        try:
            if socket_to is None:
                socket_to = 3
            socket.setdefaulttimeout(socket_to)
        except Exception:
            pass

        return EC2.metadata

    @staticmethod
    def get_instance_id(agentConfig):
        try:
            return EC2.get_metadata(agentConfig).get("instance-id", None)
        except Exception:
            return None