# Copyright (C) 2015-2016 Red Hat, Inc. All rights reserved.
#
# This copyrighted material is made available to anyone wishing to use,
# modify, copy, or redistribute it subject to the terms and conditions
# of the GNU General Public License v.2.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

import xml.etree.ElementTree as Et
import sys
import inspect
import collections
import ctypes
import errno
import fcntl
import os
import stat
import string
import datetime
import tempfile

import dbus
from lvmdbusd import cfg
# noinspection PyUnresolvedReferences
from gi.repository import GLib
import threading
import traceback
import signal

STDOUT_TTY = os.isatty(sys.stdout.fileno())


def _handle_execute(rc, out, err, interface):
	if rc == 0:
		cfg.load()
	else:
		# Need to work on error handling, need consistent
		raise dbus.exceptions.DBusException(
			interface, 'Exit code %s, stderr = %s' % (str(rc), err))


def rtype(dbus_type):
	"""
	Decorator making sure that the decorated function returns a value of
	specified type.
	:param dbus_type: The specific dbus type to return value as
	"""

	def decorator(fn):
		def decorated(*args, **kwargs):
			return dbus_type(fn(*args, **kwargs))

		return decorated

	return decorator


# Field is expected to be a number, handle the corner cases when parsing
@rtype(dbus.UInt64)
def n(v):
	if not v:
		return 0
	return int(float(v))


@rtype(dbus.UInt32)
def n32(v):
	if not v:
		return 0
	return int(float(v))


@rtype(dbus.Double)
def d(v):
	if not v:
		return 0.0
	return float(v)


def _snake_to_pascal(s):
	return ''.join(x.title() for x in s.split('_'))


# noinspection PyProtectedMember
def init_class_from_arguments(
		obj_instance, begin_suffix=None, snake_to_pascal=False):
	for k, v in list(sys._getframe(1).f_locals.items()):
		if k != 'self':
			nt = k

			# If the current attribute has a value, but the incoming does
			# not, don't overwrite it.  Otherwise, the default values on the
			# property decorator don't work as expected.
			cur = getattr(obj_instance, nt, v)

			# print 'Init class %s = %s' % (nt, str(v))
			if not (cur and len(str(cur)) and (v is None or len(str(v))) == 0)\
					and (begin_suffix is None or nt.startswith(begin_suffix)):

				if begin_suffix and nt.startswith(begin_suffix):
					name = nt[len(begin_suffix):]
					if snake_to_pascal:
						name = _snake_to_pascal(name)

					setattr(obj_instance, name, v)
				else:
					setattr(obj_instance, nt, v)


def get_properties(f):
	"""
	Walks through an object instance, or it's parent class(es) and determines
	which attributes are properties and if they were created to be used for
	dbus.
	:param f:   Object to inspect
	:return:    A dictionary of tuples with each tuple being:
				0 = An array of dicts with the keys being: p_t, p_name,
				p_access(type, name, access)
				1 = Hash of property names and current value
	"""
	interfaces = dict()

	for c in inspect.getmro(f.__class__):

		h = vars(c)
		for p, value in h.items():
			if isinstance(value, property):
				# We found a property, see if it has a metadata type
				key = attribute_type_name(p)
				if key in h:
					interface = h[key][1]

					if interface not in interfaces:
						interfaces[interface] = ([], {})

					access = ''
					if getattr(f.__class__, p).fget:
						access += 'read'
					if getattr(f.__class__, p).fset:
						access += 'write'

					interfaces[interface][0].append(
						dict(
							p_t=getattr(f, key)[0],
							p_name=p,
							p_access=access))

					interfaces[interface][1][p] = getattr(f, p)

	return interfaces


def get_object_property_diff(o_prop, n_prop):
	"""
	Walk through each object properties and report what has changed and with
	the new values
	:param o_prop:   Old keys/values
	:param n_prop:   New keys/values
	:return: hash of properties that have changed and their new value
	"""
	rc = {}

	for intf_k, intf_v in o_prop.items():
		for k, v in list(intf_v[1].items()):
			# print('Comparing %s:%s to %s:%s' %
			#      (k, o_prop[intf_k][1][k], k, str(n_prop[intf_k][1][k])))
			if o_prop[intf_k][1][k] != n_prop[intf_k][1][k]:
				new_value = n_prop[intf_k][1][k]

				if intf_k not in rc:
					rc[intf_k] = dict()

				rc[intf_k][k] = new_value
	return rc


def add_properties(xml, interface, props):
	"""
	Given xml that describes the interface, add property values to the XML
	for the specified interface.
	:param xml:         XML to edit
	:param interface:   Interface to add the properties too
	:param props:       Output from get_properties
	:return: updated XML string
	"""
	if props:
		root = Et.fromstring(xml)
		interface_element = None

		# Check to see if interface is present
		for c in root:
			if c.attrib['name'] == interface:
				interface_element = c
				break

		# Interface is not present, lets create it, so we have something to
		# attach the properties too
		if interface_element is None:
			interface_element = Et.Element("interface", name=interface)
			root.append(interface_element)

		# Add the properties
		for p in props:
			temp = '<property type="%s" name="%s" access="%s"/>\n' % \
				(p['p_t'], p['p_name'], p['p_access'])
			interface_element.append(Et.fromstring(temp))

		return Et.tostring(root, encoding='utf8')
	return xml


def attribute_type_name(name):
	"""
	Given the property name, return string of the attribute type
	:param name:
	:return:
	"""
	return "_%s_meta" % name


_type_map = dict(
	s=dbus.String,
	o=dbus.ObjectPath,
	t=dbus.UInt64,
	x=dbus.Int64,
	u=dbus.UInt32,
	i=dbus.Int32,
	n=dbus.Int16,
	q=dbus.UInt16,
	d=dbus.Double,
	y=dbus.Byte,
	b=dbus.Boolean)


def _pass_through(v):
	"""
	If we have something which is not a simple type we return the original
	value un-wrapped.
	:param v:
	:return:
	"""
	return v


def _dbus_type(t, value):
	return _type_map.get(t, _pass_through)(value)


def dbus_property(interface_name, name, dbus_type, doc=None):
	"""
	Creates the get/set properties for the given name.  It assumes that the
	actual attribute is '_' + name and the attribute metadata is stuffed in
	_name_type.

	There is probably a better way todo this.
	:param interface_name:  Dbus interface this property is associated with
	:param name:            Name of property
	:param dbus_type:       dbus string type eg. s,t,i,x
	:param doc:             Python __doc__ for the property
	:return:
	"""
	attribute_name = '_' + name

	def getter(self):
		t = getattr(self, attribute_name + '_meta')[0]
		return _dbus_type(t, getattr(self.state, attribute_name[1:]))

	prop = property(getter, None, None, doc)

	def decorator(cls):
		setattr(cls, attribute_name + '_meta', (dbus_type, interface_name))
		setattr(cls, name, prop)
		return cls

	return decorator


def parse_tags(tags):
	if len(tags):
		if ',' in tags:
			return tags.split(',')
		return dbus.Array(sorted([tags]), signature='s')
	return dbus.Array([], signature='s')


class DebugMessages(object):

	def __init__(self, size=5000):
		self.queue = collections.deque(maxlen=size)
		self.lock = threading.RLock()

	def add(self, message):
		with self.lock:
			self.queue.append(message)

	def dump(self):
		if cfg.args and not cfg.args.debug:
			with self.lock:
				if len(self.queue):
					log_error("LVM dbus debug messages START last (%d max) messages" % self.queue.maxlen)
					for m in self.queue:
						print(m)
					log_error("LVM dbus debug messages END")
					self.queue.clear()


def _format_log_entry(msg):
	tid = ctypes.CDLL('libc.so.6').syscall(186)

	if not cfg.systemd and STDOUT_TTY:
		msg = "%s: %d:%d - %s" % \
			(datetime.datetime.now().strftime("%b %d %H:%M:%S.%f"),
			os.getpid(), tid, msg)

	else:
		if cfg.systemd:
			# Systemd already puts the daemon pid in the log, we'll just add the tid
			msg = "[%d]: %s" % (tid, msg)
		else:
			msg = "[%d:%d]: %s" % (os.getpid(), tid, msg)
	return msg


def _common_log(msg, *attributes):
	msg = _format_log_entry(msg)

	cfg.stdout_lock.acquire()

	if STDOUT_TTY and attributes:
		print(color(msg, *attributes))
	else:
		print(msg)

	sys.stdout.flush()
	cfg.stdout_lock.release()


# Serializes access to stdout to prevent interleaved output
# @param msg    Message to output to stdout
# @return None
def log_debug(msg, *attributes):
	if cfg.args and cfg.args.debug:
		_common_log(msg, *attributes)
	else:
		if cfg.debug:
			cfg.debug.add(_format_log_entry(msg))


def log_error(msg, *attributes):
	_common_log(msg, *attributes)


def log_msg(msg, *attributes):
	_common_log(msg, *attributes)


def dump_threads_stackframe():
	ident_to_name = {}

	for thread_object in threading.enumerate():
		ident_to_name[thread_object.ident] = thread_object

	stacks = []
	for thread_ident, frame in sys._current_frames().items():
		stack = traceback.format_list(traceback.extract_stack(frame))

		# There is a possibility that a thread gets created after we have
		# enumerated all threads, so this lookup table may be incomplete, so
		# account for this
		if thread_ident in ident_to_name:
			thread_name = ident_to_name[thread_ident].name
		else:
			thread_name = "unknown"

		stacks.append("Thread: %s" % (thread_name))
		stacks.append("".join(stack))

	log_error("Dumping thread stack frames!\n" + "\n".join(stacks))


# noinspection PyUnusedLocal
def handler(signum):
	try:
		# signal 10
		if signum == signal.SIGUSR1:
			cfg.debug.dump()
			dump_threads_stackframe()
		# signal 12
		elif signum == signal.SIGUSR2:
			cfg.debug.dump()
			cfg.flightrecorder.dump()
		else:
			# If we are getting a SIGTERM, and we sent one to the lvm shell we
			# will ignore this and keep running.
			if signum == signal.SIGTERM and cfg.ignore_sigterm:
				# Clear the flag, so we will exit on SIGTERM if we didn't
				# send it.
				cfg.ignore_sigterm = False
				return True

			# If lvm shell is in use, tell it to exit
			if cfg.SHELL_IN_USE is not None:
				cfg.SHELL_IN_USE.exit_shell()
			cfg.run.value = 0
			log_error('Exiting daemon with signal %d' % signum)
			if cfg.loop is not None:
				cfg.loop.quit()
	except BaseException as be:
		st = extract_stack_trace(be)
		log_error("signal handler: exception (logged, not reported!) \n %s" % st)

	# It's important we report that we handled the exception for the exception
	# handler to continue to work, especially for signal 10 (SIGUSR1)
	return True


def pv_obj_path_generate():
	return cfg.PV_OBJ_PATH + "/%d" % next(cfg.pv_id)


def vg_obj_path_generate():
	return cfg.VG_OBJ_PATH + "/%d" % next(cfg.vg_id)


def lv_object_path_method(name, meta):
	if name[0] == '[':
		return _hidden_lv_obj_path_generate
	elif meta[0][0] == 't':
		return _thin_pool_obj_path_generate
	elif meta[0][0] == 'd':
		return _vdo_pool_object_path_generate
	elif meta[0][0] == 'C' and 'pool' in meta[1]:
		return _cache_pool_obj_path_generate

	return _lv_obj_path_generate


# Note: None of the individual LV path generate functions should be called
# directly, they should only be dispatched through lv_object_path_method

def _lv_obj_path_generate():
	return cfg.LV_OBJ_PATH + "/%d" % next(cfg.lv_id)


def _thin_pool_obj_path_generate():
	return cfg.THIN_POOL_PATH + "/%d" % next(cfg.thin_id)


def _vdo_pool_object_path_generate():
	return cfg.VDO_POOL_PATH + "/%d" % next(cfg.vdo_id)


def _cache_pool_obj_path_generate():
	return cfg.CACHE_POOL_PATH + "/%d" % next(cfg.cache_pool_id)


def _hidden_lv_obj_path_generate():
	return cfg.HIDDEN_LV_PATH + "/%d" % next(cfg.hidden_lv)


def job_obj_path_generate():
	return cfg.JOB_OBJ_PATH + "/%d" % next(cfg.job_id)


def color(text, *user_styles):
	styles = {
		# styles
		'reset': '\033[0m',
		'bold': '\033[01m',
		'disabled': '\033[02m',
		'underline': '\033[04m',
		'reverse': '\033[07m',
		'strike_through': '\033[09m',
		'invisible': '\033[08m',
		# text colors
		'fg_black': '\033[30m',
		'fg_red': '\033[31m',
		'fg_green': '\033[32m',
		'fg_orange': '\033[33m',
		'fg_blue': '\033[34m',
		'fg_purple': '\033[35m',
		'fg_cyan': '\033[36m',
		'fg_light_grey': '\033[37m',
		'fg_dark_grey': '\033[90m',
		'fg_light_red': '\033[91m',
		'fg_light_green': '\033[92m',
		'fg_yellow': '\033[93m',
		'fg_light_blue': '\033[94m',
		'fg_pink': '\033[95m',
		'fg_light_cyan': '\033[96m',
		# background colors
		'bg_black': '\033[40m',
		'bg_red': '\033[41m',
		'bg_green': '\033[42m',
		'bg_orange': '\033[43m',
		'bg_blue': '\033[44m',
		'bg_purple': '\033[45m',
		'bg_cyan': '\033[46m',
		'bg_light_grey': '\033[47m'
	}

	color_text = ''
	for style in user_styles:
		try:
			color_text += styles[style]
		except KeyError:
			return 'def color: parameter {} does not exist'.format(style)
	color_text += text
	return '\033[0m{0}\033[0m'.format(color_text)


def pv_range_append(cmd, device, start, end):
	if (start, end) == (0, 0):
		cmd.append(device)
	else:
		if start != 0 and end == 0:
			cmd.append("%s:%d-" % (device, start))
		else:
			cmd.append(
				"%s:%d-%d" %
				(device, start, end))


def pv_dest_ranges(cmd, pv_dest_range_list):
	if len(pv_dest_range_list):
		for i in pv_dest_range_list:
			pv_range_append(cmd, *i)


def round_size(size_bytes):
	bs = 512
	remainder = size_bytes % bs
	if not remainder:
		return size_bytes
	return size_bytes + bs - remainder


_ALLOWABLE_CH = string.ascii_letters + string.digits + '#+-.:=@_\/%'
_ALLOWABLE_CH_SET = set(_ALLOWABLE_CH)

_ALLOWABLE_VG_LV_CH = string.ascii_letters + string.digits + '.-_+'
_ALLOWABLE_VG_LV_CH_SET = set(_ALLOWABLE_VG_LV_CH)
_LV_NAME_RESERVED = ("_cdata", "_cmeta", "_corig", "_mimage", "_mlog",
	"_pmspare", "_rimage", "_rmeta", "_tdata", "_tmeta", "_vorigin", "_vdata")

# Tags can have the characters, based on the code
# a-zA-Z0-9._-+/=!:&#
_ALLOWABLE_TAG_CH = string.ascii_letters + string.digits + "._-+/=!:&#"
_ALLOWABLE_TAG_CH_SET = set(_ALLOWABLE_TAG_CH)


def _allowable_tag(tag_name):
	# LVM should impose a length restriction
	return set(tag_name) <= _ALLOWABLE_TAG_CH_SET


def _allowable_vg_name(vg_name):
	if vg_name is None:
		raise ValueError("VG name is None or empty")

	vg_len = len(vg_name)
	if vg_len == 0 or vg_len > 127:
		raise ValueError("VG name (%s) length (%d) not in the domain 1..127" %
			(vg_name, vg_len))

	if not set(vg_name) <= _ALLOWABLE_VG_LV_CH_SET:
		raise ValueError("VG name (%s) contains invalid character, "
			"allowable set(%s)" % (vg_name, _ALLOWABLE_VG_LV_CH))

	if vg_name == "." or vg_name == "..":
		raise ValueError('VG name (%s) cannot be "." or ".."' % (vg_name))


def _allowable_lv_name(vg_name, lv_name):

	if lv_name is None:
		raise ValueError("LV name is None or empty")

	lv_len = len(lv_name)

	# This length is derived from empirical testing
	if lv_len == 0 or (len(vg_name) + lv_len) > 125:
		raise ValueError("LV name (%s) length (%d) + VG name length "
			"not in the domain 1..125" % (lv_name, lv_len))

	if not set(lv_name) <= _ALLOWABLE_VG_LV_CH_SET:
		raise ValueError("LV name (%s) contains invalid character, "
			"allowable (%s)" % (lv_name, _ALLOWABLE_VG_LV_CH))

	if any(x in lv_name for x in _LV_NAME_RESERVED):
		raise ValueError("LV name (%s) contains a reserved word, "
			"reserved set(%s)" % (lv_name, str(_LV_NAME_RESERVED)))

	if lv_name.startswith("snapshot") or lv_name.startswith("pvmove"):
		raise ValueError("LV name (%s) starts with a reserved word, "
			"reserved set(%s)" % (lv_name, str(["snapshot", "pvmove"])))

	if lv_name[0] == '-':
		raise ValueError("LV name (%s) cannot start with a '-' "
				"character" % lv_name)


def validate_device_path(interface, device):
	if not set(device) <= _ALLOWABLE_CH_SET:
		raise dbus.exceptions.DBusException(
			interface, 'Device path (%s) has invalid characters, '
			'allowable (%s)' % (device, _ALLOWABLE_CH))


def validate_vg_name(interface, vg_name):
	try:
		_allowable_vg_name(vg_name)
	except ValueError as ve:
		raise dbus.exceptions.DBusException(
			interface, str(ve))


def validate_lv_name(interface, vg_name, lv_name):
	try:
		_allowable_lv_name(vg_name, lv_name)
	except ValueError as ve:
		raise dbus.exceptions.DBusException(
			interface, str(ve))


def validate_tag(interface, tag):
	if not _allowable_tag(tag):
		raise dbus.exceptions.DBusException(
			interface, 'tag (%s) contains invalid character, allowable set(%s)'
			% (tag, _ALLOWABLE_TAG_CH))


def add_config_option(cmdline, key, value):
	if 'help' in cmdline:
		return cmdline

	if key in cmdline:
		for i, arg in enumerate(cmdline):
			if arg == key:
				if len(cmdline) <= i + 1:
					raise dbus.exceptions.DBusException("Missing value for --config option.")
				cmdline[i + 1] += " %s" % value
				break
	else:
		cmdline.extend([key, value])

	return cmdline


def add_no_notify(cmdline):
	"""
	Given a command line to execute we will see if `--config` is present, if it
	is we will add the global/notify_dbus=0 to it, otherwise we will append it
	to the end of the list.
	:param: cmdline: The command line to inspect
	:type: cmdline: list
	:return: cmdline with notify_dbus config option present
	:rtype: list
	"""

	# Only after we have seen an external event will we disable lvm from sending
	# us one when we call lvm
	rv = cmdline
	if cfg.got_external_event:
		rv = add_config_option(rv, "--config", "global/notify_dbus=0")

	return rv


# The methods below which start with mt_* are used to execute the desired code
# on the main thread of execution to alleviate any issues the dbus-python
# library with regard to multithreaded access.  Essentially, we are trying to
# ensure all dbus library interaction is done from the same thread!


def _async_handler(call_back, parameters):
	params_str = ", ".join(str(x) for x in parameters)
	log_debug('Main thread execution, callback = %s, parameters = (%s)' %
				(str(call_back), params_str))

	try:
		if parameters:
			call_back(*parameters)
		else:
			call_back()
	except BaseException as be:
		log_error("mt_async_call: exception (logged, not reported!) \n %s" % extract_stack_trace(be))


# Execute the function on the main thread with the provided parameters, do
# not return *any* value or wait for the execution to complete!
def mt_async_call(function_call_back, *parameters):
	GLib.idle_add(_async_handler, function_call_back, parameters)


# Run the supplied function and arguments on the main thread and wait for them
# to complete while allowing the ability to get the return value too.
#
# Example:
# result = MThreadRunner(foo, arg1, arg2).done()
#
class MThreadRunner(object):

	@staticmethod
	def runner(obj):
		# noinspection PyProtectedMember
		obj._run()
		with obj.cond:
			obj.function_complete = True
			obj.cond.notify_all()

	def __init__(self, function, *args):
		self.f = function
		self.rc = None
		self.exception = None
		self.args = args
		self.function_complete = False
		self.cond = threading.Condition(threading.Lock())

	def done(self):
		GLib.idle_add(MThreadRunner.runner, self)
		with self.cond:
			if not self.function_complete:
				self.cond.wait()
		if self.exception:
			raise self.exception
		return self.rc

	def _run(self):
		try:
			if self.args:
				self.rc = self.f(*self.args)
			else:
				self.rc = self.f()
		except BaseException as be:
			self.exception = be


def _remove_objects(dbus_objects_rm):
	for o in dbus_objects_rm:
		cfg.om.remove_object(o, emit_signal=True)


# Remove dbus objects from main thread
def mt_remove_dbus_objects(objs):
	MThreadRunner(_remove_objects, objs).done()


# Make stream non-blocking
def make_non_block(stream):
	flags = fcntl.fcntl(stream, fcntl.F_GETFL)
	fcntl.fcntl(stream, fcntl.F_SETFL, flags | os.O_NONBLOCK)


def read_decoded(stream):
	tmp = stream.read()
	if tmp:
		return tmp.decode("utf-8")
	return ''


class LockFile(object):
	"""
	Simple lock file class
	Based on Pg.1144 "The Linux Programming Interface" by Michael Kerrisk
	"""
	def __init__(self, lock_file):
		self.fd = 0
		self.lock_file = lock_file

	def __enter__(self):
		try:
			self.fd = os.open(self.lock_file, os.O_CREAT | os.O_RDWR, stat.S_IRUSR | stat.S_IWUSR)

			# Get and set the close on exec and lock the file
			flags = fcntl.fcntl(self.fd, fcntl.F_GETFD)
			flags |= fcntl.FD_CLOEXEC
			fcntl.fcntl(self.fd, fcntl.F_SETFL, flags)
			fcntl.lockf(self.fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
		except OSError as e:
			if e.errno == errno.EAGAIN:
				log_error("Daemon already running, exiting!")
			else:
				log_error("Error during creation of lock file(%s): errno(%d), exiting!" % (self.lock_file, e.errno))
			sys.exit(114)

	def __exit__(self, _type, _value, _traceback):
		os.close(self.fd)


def extract_stack_trace(exception):
	return ''.join(traceback.format_exception(None, exception, exception.__traceback__))


def lvm_column_key(key):
	# Check LV
	if key.startswith("lv_") or key.startswith("vg_") or key.startswith("pool_") or \
			key.endswith("_percent") or key.startswith("move_") or key.startswith("vdo_") or \
			key in ["origin_uuid", "segtype", "origin", "data_lv", "metadata_lv"]:
		return True
	# Check VG
	if key.startswith("vg_") or key.startswith("lv_") or key.startswith("pv_") or \
			key in ["max_lv", "max_pv", "snap_count"]:
		return True
	# Check PV
	if key.startswith("pv") or key.startswith("vg") or (key in ['dev_size', 'pe_start']):
		return True
	return False

class LvmBug(RuntimeError):
	"""
	Things that are clearly a bug with lvm itself.
	"""
	def __init__(self, msg):
		super().__init__(msg)

	def __str__(self):
		return "lvm bug encountered: %s" % ' '.join(self.args)


class LvmDebugData:
	def __init__(self, do_collection):
		self.fd = -1
		self.fn = None
		self.collect = do_collection
		if self.collect:
			log_msg("Collecting lvm debug data!")

	def _remove_file(self):
		if self.fn is not None:
			os.unlink(self.fn)
			self.fn = None

	def _close_fd(self):
		if self.fd != -1:
			os.close(self.fd)
			self.fd = -1

	def setup(self):
		# Create a secure filename
		if self.collect:
			self.fd, self.fn = tempfile.mkstemp(suffix=".log", prefix="lvmdbusd.lvm.debug.")
			return self.fn
		return None

	def lvm_complete(self):
		# Remove the file ASAP, so we decrease our odds of leaving it
		# around if the daemon gets killed by a signal -9
		self._remove_file()

	def dump(self):
		# Read the file and log it to log_err
		if self.fd != -1:
			# How big could the verbose debug get?
			debug = os.read(self.fd, 1024*1024*5)
			debug_txt = debug.decode("utf-8")
			for line in debug_txt.split("\n"):
				log_error("lvm debug >>> %s" % line)
			self._close_fd()
		# In case lvm_complete doesn't get called.
		self._remove_file()

	def complete(self):
		self._close_fd()
		# In case lvm_complete doesn't get called.
		self._remove_file()


def get_error_msg(report_json):
	# Get the error message from the returned JSON
	if 'log' in report_json:
		error_msg = ""
		# Walk the entire log array and build an error string
		for log_entry in report_json['log']:
			if log_entry['log_type'] == "error":
				if error_msg:
					error_msg += ', ' + log_entry['log_message']
				else:
					error_msg = log_entry['log_message']

		return error_msg

	return None