#!/usr/bin/python
#
# Copyright 2016 Canonical Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#  http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import ast
import pcmk
import maas
import os
import subprocess
import socket
import fcntl
import struct
import xml.etree.ElementTree as ET

from base64 import b64decode

from charmhelpers.core.hookenv import (
    local_unit,
    log,
    DEBUG,
    INFO,
    WARNING,
    relation_get,
    related_units,
    relation_ids,
    config,
    unit_get,
    status_set,
)
from charmhelpers.contrib.openstack.utils import (
    get_host_ip,
    set_unit_paused,
    clear_unit_paused,
    is_unit_paused_set,
)
from charmhelpers.contrib.openstack.ha.utils import (
    assert_charm_supports_dns_ha
)
from charmhelpers.core.host import (
    mkdir,
    rsync,
    service_start,
    service_stop,
    service_restart,
    service_running,
    write_file,
    file_hash,
    lsb_release
)
from charmhelpers.fetch import (
    apt_install,
    add_source,
    apt_update,
)
from charmhelpers.contrib.hahelpers.cluster import (
    peer_ips,
)
from charmhelpers.contrib.network import ip as utils

try:
    import netifaces
except ImportError:
    apt_install('python-netifaces')
    import netifaces

try:
    from netaddr import IPNetwork
except ImportError:
    apt_install('python-netaddr', fatal=True)
    from netaddr import IPNetwork


try:
    import jinja2
except ImportError:
    apt_install('python-jinja2', fatal=True)
    import jinja2


TEMPLATES_DIR = 'templates'
COROSYNC_CONF = '/etc/corosync/corosync.conf'
COROSYNC_DEFAULT = '/etc/default/corosync'
COROSYNC_AUTHKEY = '/etc/corosync/authkey'
COROSYNC_HACLUSTER_ACL_DIR = '/etc/corosync/uidgid.d'
COROSYNC_HACLUSTER_ACL = COROSYNC_HACLUSTER_ACL_DIR + '/hacluster'
COROSYNC_CONF_FILES = [
    COROSYNC_DEFAULT,
    COROSYNC_AUTHKEY,
    COROSYNC_CONF,
    COROSYNC_HACLUSTER_ACL,
]
SUPPORTED_TRANSPORTS = ['udp', 'udpu', 'multicast', 'unicast']


class MAASConfigIncomplete(Exception):
    pass


def disable_upstart_services(*services):
    for service in services:
        with open("/etc/init/{}.override".format(service), "w") as override:
            override.write("manual")


def enable_upstart_services(*services):
    for service in services:
        path = '/etc/init/{}.override'.format(service)
        if os.path.exists(path):
            os.remove(path)


def disable_lsb_services(*services):
    for service in services:
        subprocess.check_call(['update-rc.d', '-f', service, 'remove'])


def enable_lsb_services(*services):
    for service in services:
        subprocess.check_call(['update-rc.d', '-f', service, 'defaults'])


def get_iface_ipaddr(iface):
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    return socket.inet_ntoa(fcntl.ioctl(
        s.fileno(),
        0x8919,  # SIOCGIFADDR
        struct.pack('256s', iface[:15])
    )[20:24])


def get_iface_netmask(iface):
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    return socket.inet_ntoa(fcntl.ioctl(
        s.fileno(),
        0x891b,  # SIOCGIFNETMASK
        struct.pack('256s', iface[:15])
    )[20:24])


def get_netmask_cidr(netmask):
    netmask = netmask.split('.')
    binary_str = ''
    for octet in netmask:
        binary_str += bin(int(octet))[2:].zfill(8)
    return str(len(binary_str.rstrip('0')))


def get_network_address(iface):
    if iface:
        iface = str(iface)
        network = "{}/{}".format(get_iface_ipaddr(iface),
                                 get_netmask_cidr(get_iface_netmask(iface)))
        ip = IPNetwork(network)
        return str(ip.network)
    else:
        return None


def get_ipv6_network_address(iface):
    # Behave in same way as ipv4 get_network_address() above if iface is None.
    if not iface:
        return None

    try:
        ipv6_addr = utils.get_ipv6_addr(iface=iface)[0]
        all_addrs = netifaces.ifaddresses(iface)

        for addr in all_addrs[netifaces.AF_INET6]:
            if ipv6_addr == addr['addr']:
                network = "{}/{}".format(addr['addr'], addr['netmask'])
                return str(IPNetwork(network).network)

    except ValueError:
        msg = "Invalid interface '%s'" % iface
        status_set('blocked', msg)
        raise Exception(msg)

    msg = "No valid network found for interface '%s'" % iface
    status_set('blocked', msg)
    raise Exception(msg)


def get_corosync_id(unit_name):
    # Corosync nodeid 0 is reserved so increase all the nodeids to avoid it
    off_set = 1000
    return off_set + int(unit_name.split('/')[1])


def nulls(data):
    """Returns keys of values that are null (but not bool)"""
    return [k for k in data.iterkeys()
            if not isinstance(data[k], bool) and not data[k]]


def get_corosync_conf():
    if config('prefer-ipv6'):
        ip_version = 'ipv6'
        bindnetaddr = get_ipv6_network_address
    else:
        ip_version = 'ipv4'
        bindnetaddr = get_network_address

    transport = get_transport()

    # NOTE(jamespage) use local charm configuration over any provided by
    # principle charm
    conf = {
        'ip_version': ip_version,
        'ha_nodes': get_ha_nodes(),
        'transport': transport,
    }

    # NOTE(jamespage): only populate multicast configuration if udp is
    #                  configured
    if transport == 'udp':
        conf.update({
            'corosync_bindnetaddr': bindnetaddr(config('corosync_bindiface')),
            'corosync_mcastport': config('corosync_mcastport'),
            'corosync_mcastaddr': config('corosync_mcastaddr')
        })

    if config('prefer-ipv6'):
        conf['nodeid'] = get_corosync_id(local_unit())

    if config('netmtu'):
        conf['netmtu'] = config('netmtu')

    if config('debug'):
        conf['debug'] = config('debug')

    if not nulls(conf):
        log("Found sufficient values in local config to populate "
            "corosync.conf", level=DEBUG)
        return conf

    conf = {}
    for relid in relation_ids('ha'):
        for unit in related_units(relid):
            conf = {
                'ip_version': ip_version,
                'ha_nodes': get_ha_nodes(),
                'transport': transport,
            }

            # NOTE(jamespage): only populate multicast configuration if udpu is
            #                  configured
            if transport == 'udp':
                bindiface = relation_get('corosync_bindiface',
                                         unit, relid)
                conf.update({
                    'corosync_bindnetaddr': bindnetaddr(bindiface),
                    'corosync_mcastport': relation_get('corosync_mcastport',
                                                       unit, relid),
                    'corosync_mcastaddr': config('corosync_mcastaddr'),
                })

            if config('prefer-ipv6'):
                conf['nodeid'] = get_corosync_id(local_unit())

            if config('netmtu'):
                conf['netmtu'] = config('netmtu')

            if config('debug'):
                conf['debug'] = config('debug')

            # Values up to this point must be non-null
            if nulls(conf):
                continue

            return conf

    missing = [k for k, v in conf.iteritems() if v is None]
    log('Missing required configuration: %s' % missing)
    return None


def emit_corosync_conf():
    corosync_conf_context = get_corosync_conf()
    if corosync_conf_context:
        write_file(path=COROSYNC_CONF,
                   content=render_template('corosync.conf',
                                           corosync_conf_context))
        return True

    return False


def emit_base_conf():
    if not os.path.isdir(COROSYNC_HACLUSTER_ACL_DIR):
        os.mkdir(COROSYNC_HACLUSTER_ACL_DIR)
    corosync_default_context = {'corosync_enabled': 'yes'}
    write_file(path=COROSYNC_DEFAULT,
               content=render_template('corosync',
                                       corosync_default_context))

    write_file(path=COROSYNC_HACLUSTER_ACL,
               content=render_template('hacluster.acl', {}))

    corosync_key = config('corosync_key')
    if corosync_key:
        write_file(path=COROSYNC_AUTHKEY,
                   content=b64decode(corosync_key),
                   perms=0o400)
        return True

    return False


def render_template(template_name, context, template_dir=TEMPLATES_DIR):
    templates = jinja2.Environment(
        loader=jinja2.FileSystemLoader(template_dir)
    )
    template = templates.get_template(template_name)
    return template.render(context)


def assert_charm_supports_ipv6():
    """Check whether we are able to support charms ipv6."""
    if lsb_release()['DISTRIB_CODENAME'].lower() < "trusty":
        msg = "IPv6 is not supported in the charms for Ubuntu " \
              "versions less than Trusty 14.04"
        status_set('blocked', msg)
        raise Exception(msg)


def get_transport():
    transport = config('corosync_transport')
    _deprecated_transport_values = {"multicast": "udp", "unicast": "udpu"}
    val = _deprecated_transport_values.get(transport, transport)
    if val not in ['udp', 'udpu']:
        msg = ("Unsupported corosync_transport type '%s' - supported "
               "types are: %s" % (transport, ', '.join(SUPPORTED_TRANSPORTS)))
        status_set('blocked', msg)
        raise ValueError(msg)

    return val


def get_ipv6_addr():
    """Exclude any ip addresses configured or managed by corosync."""
    excludes = []
    for rid in relation_ids('ha'):
        for unit in related_units(rid):
            resources = parse_data(rid, unit, 'resources')
            for res in resources.itervalues():
                if 'ocf:heartbeat:IPv6addr' in res:
                    res_params = parse_data(rid, unit, 'resource_params')
                    res_p = res_params.get(res)
                    if res_p:
                        for k, v in res_p.itervalues():
                            if utils.is_ipv6(v):
                                log("Excluding '%s' from address list" % v,
                                    level=DEBUG)
                                excludes.append(v)

    return utils.get_ipv6_addr(exc_list=excludes)[0]


def get_ha_nodes():
    ha_units = peer_ips(peer_relation='hanode')
    ha_nodes = {}
    for unit in ha_units:
        corosync_id = get_corosync_id(unit)
        addr = ha_units[unit]
        if config('prefer-ipv6'):
            if not utils.is_ipv6(addr):
                # Not an error since cluster may still be forming/updating
                log("Expected an ipv6 address but got %s" % (addr),
                    level=WARNING)

            ha_nodes[corosync_id] = addr
        else:
            ha_nodes[corosync_id] = get_host_ip(addr)

    corosync_id = get_corosync_id(local_unit())
    if config('prefer-ipv6'):
        addr = get_ipv6_addr()
    else:
        addr = get_host_ip(unit_get('private-address'))

    ha_nodes[corosync_id] = addr

    return ha_nodes


def get_cluster_nodes():
    hosts = []
    if config('prefer-ipv6'):
        hosts.append(get_ipv6_addr())
    else:
        hosts.append(unit_get('private-address'))

    for relid in relation_ids('hanode'):
        for unit in related_units(relid):
            if relation_get('ready', rid=relid, unit=unit):
                hosts.append(relation_get('private-address', unit, relid))

    hosts.sort()
    return hosts


def parse_data(relid, unit, key):
    """Simple helper to ast parse relation data"""
    data = relation_get(key, unit, relid)
    if data:
        return ast.literal_eval(data)

    return {}


def configure_stonith():
    if config('stonith_enabled') not in ['true', 'True', True]:
        log('Disabling STONITH', level=INFO)
        cmd = "crm configure property stonith-enabled=false"
        pcmk.commit(cmd)
    else:
        log('Enabling STONITH for all nodes in cluster.', level=INFO)
        # configure stontih resources for all nodes in cluster.
        # note: this is totally provider dependent and requires
        # access to the MAAS API endpoint, using endpoint and credentials
        # set in config.
        url = config('maas_url')
        creds = config('maas_credentials')
        if None in [url, creds]:
            msg = 'maas_url and maas_credentials must be set ' \
                  'in config to enable STONITH.'
            status_set('blocked', msg)
            raise Exception(msg)

        nodes = maas.MAASHelper(url, creds).list_nodes()
        if not nodes:
            msg = 'Could not obtain node inventory from ' \
                  'MAAS @ %s.' % url
            status_set('blocked', msg)
            raise Exception(msg)

        cluster_nodes = pcmk.list_nodes()
        for node in cluster_nodes:
            rsc, constraint = pcmk.maas_stonith_primitive(nodes, node)
            if not rsc:
                msg = 'Failed to determine STONITH primitive for ' \
                      'node %s' % node
                status_set('blocked', msg)
                raise Exception(msg)

            rsc_name = str(rsc).split(' ')[1]
            if not pcmk.is_resource_present(rsc_name):
                log('Creating new STONITH primitive %s.' % rsc_name,
                    level=DEBUG)
                cmd = 'crm -F configure %s' % rsc
                pcmk.commit(cmd)
                if constraint:
                    cmd = 'crm -F configure %s' % constraint
                    pcmk.commit(cmd)
            else:
                log('STONITH primitive already exists for node.', level=DEBUG)

        pcmk.commit("crm configure property stonith-enabled=true")


def configure_monitor_host():
    """Configure extra monitor host for better network failure detection"""
    log('Checking monitor host configuration', level=DEBUG)
    monitor_host = config('monitor_host')
    if monitor_host:
        if not pcmk.crm_opt_exists('ping'):
            log('Implementing monitor host configuration (host: %s)' %
                monitor_host, level=DEBUG)
            monitor_interval = config('monitor_interval')
            cmd = ('crm -w -F configure primitive ping '
                   'ocf:pacemaker:ping params host_list="%s" '
                   'multiplier="100" op monitor interval="%s" ' %
                   (monitor_host, monitor_interval))
            pcmk.commit(cmd)
            cmd = ('crm -w -F configure clone cl_ping ping '
                   'meta interleave="true"')
            pcmk.commit(cmd)
        else:
            log('Reconfiguring monitor host configuration (host: %s)' %
                monitor_host, level=DEBUG)
            cmd = ('crm -w -F resource param ping set host_list="%s"' %
                   monitor_host)
    else:
        if pcmk.crm_opt_exists('ping'):
            log('Disabling monitor host configuration', level=DEBUG)
            pcmk.commit('crm -w -F resource stop ping')
            pcmk.commit('crm -w -F configure delete ping')


def configure_cluster_global():
    """Configure global cluster options"""
    log('Applying global cluster configuration', level=DEBUG)
    if int(config('cluster_count')) >= 3:
        # NOTE(jamespage) if 3 or more nodes, then quorum can be
        # managed effectively, so stop if quorum lost
        log('Configuring no-quorum-policy to stop', level=DEBUG)
        cmd = "crm configure property no-quorum-policy=stop"
    else:
        # NOTE(jamespage) if less that 3 nodes, quorum not possible
        # so ignore
        log('Configuring no-quorum-policy to ignore', level=DEBUG)
        cmd = "crm configure property no-quorum-policy=ignore"

    pcmk.commit(cmd)
    cmd = ('crm configure rsc_defaults $id="rsc-options" '
           'resource-stickiness="100"')
    pcmk.commit(cmd)


def restart_corosync_on_change():
    """Simple decorator to restart corosync if any of its config changes"""
    def wrap(f):
        def wrapped_f(*args, **kwargs):
            checksums = {}
            for path in COROSYNC_CONF_FILES:
                checksums[path] = file_hash(path)
            return_data = f(*args, **kwargs)
            # NOTE: this assumes that this call is always done around
            # configure_corosync, which returns true if configuration
            # files where actually generated
            if return_data:
                for path in COROSYNC_CONF_FILES:
                    if checksums[path] != file_hash(path):
                        restart_corosync()
                        break

            return return_data
        return wrapped_f
    return wrap


@restart_corosync_on_change()
def configure_corosync():
    log('Configuring and (maybe) restarting corosync', level=DEBUG)
    return emit_base_conf() and emit_corosync_conf()


def restart_corosync():
    if service_running("pacemaker"):
        service_stop("pacemaker")

    if not is_unit_paused_set():
        service_restart("corosync")
        service_start("pacemaker")


def validate_dns_ha():
    """Validate the DNS HA

    Assert the charm will support DNS HA
    Check MAAS related configuration options are properly set
    """

    # Will raise an exception if unable to continue
    assert_charm_supports_dns_ha()

    if config('maas_url') and config('maas_credentials'):
        return True
    else:
        msg = ("DNS HA is requested but the maas_url or maas_credentials "
               "settings are not set")
        status_set('blocked', msg)
        raise MAASConfigIncomplete(msg)


def setup_maas_api():
    """Install MAAS PPA and packages for accessing the MAAS API.
    """
    add_source(config('maas_source'))
    apt_update(fatal=True)
    apt_install('python3-maas-client', fatal=True)


def setup_ocf_files():
    """Setup OCF resrouce agent files
    """

    # TODO (thedac) Eventually we want to package the OCF files.
    # Bundle with the charm until then.
    mkdir('/usr/lib/ocf/resource.d/ceph')
    mkdir('/usr/lib/ocf/resource.d/maas')
    # Xenial corosync is not creating this directory
    mkdir('/etc/corosync/uidgid.d')

    rsync('ocf/ceph/rbd', '/usr/lib/ocf/resource.d/ceph/rbd')
    rsync('ocf/maas/dns', '/usr/lib/ocf/resource.d/maas/dns')
    rsync('ocf/maas/maas_dns.py', '/usr/lib/heartbeat/maas_dns.py')
    rsync('ocf/maas/maasclient/', '/usr/lib/heartbeat/maasclient/')


def is_in_standby_mode(node_name):
    """Check if node is in standby mode in pacemaker

    @param node_name: The name of the node to check
    @returns boolean - True if node_name is in standby mode
    """
    out = subprocess.check_output(['crm', 'node', 'status', node_name])
    root = ET.fromstring(out)

    standby_mode = False
    for nvpair in root.iter('nvpair'):
        if (nvpair.attrib.get('name') == 'standby' and
                nvpair.attrib.get('value') == 'on'):
            standby_mode = True
    return standby_mode


def get_hostname():
    """Return the hostname of this unit

    @returns hostname
    """
    return socket.gethostname()


def enter_standby_mode(node_name, duration='forever'):
    """Put this node into standby mode in pacemaker

    @returns None
    """
    subprocess.check_call(['crm', 'node', 'standby', node_name, duration])


def leave_standby_mode(node_name):
    """Take this node out of standby mode in pacemaker

    @returns None
    """
    subprocess.check_call(['crm', 'node', 'online', node_name])


def node_has_resources(node_name):
    """Check if this node is running resources

    @param node_name: The name of the node to check
    @returns boolean - True if node_name has resources
    """
    out = subprocess.check_output(['crm_mon', '-X'])
    root = ET.fromstring(out)
    has_resources = False
    for resource in root.iter('resource'):
        for child in resource:
            if child.tag == 'node' and child.attrib.get('name') == node_name:
                has_resources = True
    return has_resources


def set_unit_status():
    """Set the workload status for this unit

    @returns None
    """
    status_set(*assess_status_helper())


def resume_unit():
    """Resume services on this unit and update the units status

    @returns None
    """
    node_name = get_hostname()
    messages = []
    leave_standby_mode(node_name)
    if is_in_standby_mode(node_name):
        messages.append("Node still in standby mode")
    if messages:
        raise Exception("Couldn't resume: {}".format("; ".join(messages)))
    else:
        clear_unit_paused()
        set_unit_status()


def pause_unit():
    """Pause services on this unit and update the units status

    @returns None
    """
    node_name = get_hostname()
    messages = []
    enter_standby_mode(node_name)
    if not is_in_standby_mode(node_name):
        messages.append("Node not in standby mode")
    if node_has_resources(node_name):
        messages.append("Resources still running on unit")
    status, message = assess_status_helper()
    if status != 'active':
        messages.append(message)
    if messages:
        raise Exception("Couldn't pause: {}".format("; ".join(messages)))
    else:
        set_unit_paused()
        status_set("maintenance",
                   "Paused. Use 'resume' action to resume normal service.")


def assess_status_helper():
    """Assess status of unit

    @returns status, message - status is workload status and message is any
                               corresponding messages
    """
    node_count = int(config('cluster_count'))
    status = 'active'
    message = 'Unit is ready and clustered'
    for relid in relation_ids('hanode'):
        if len(related_units(relid)) + 1 < node_count:
            status = 'blocked'
            message = ("Insufficient peer units for ha cluster "
                       "(require {})".format(node_count))
    return status, message