Squashed commit of the following:

commit 91cf4b74105f69f16a80825581a0d2d34d15d155
Merge: 30ceaea 90b42ed
Author: nico <nico.wellpott@uni-oldenburg.de>
Date:   Wed Oct 3 22:34:42 2018 +0200

    Merge remote-tracking branch 'origin/xep' into xep

commit 30ceaea56a77ed95deba30c4fe65e238ea5960ac
Author: nico <nico.wellpott@uni-oldenburg.de>
Date:   Wed Oct 3 22:34:33 2018 +0200

    Initial Version XEP query

    + added initial version of xep query class

    Init Implementation

    + added xep plugin to bot class

    * reworked validation function
    * updated .gitignore file
    + added xep plugin

commit 90b42edb9b8e92eba3bb67030d5f919b1e71d0bc
Author: nico <nico.wellpott@uni-oldenburg.de>
Date:   Wed Oct 3 22:34:21 2018 +0200

    * reworked validation function
    * updated .gitignore file
    + added xep plugin

commit 25c78807731417867840d6fe4abf598e64aded28
Author: nico <nico@magicbroccoli.de>
Date:   Wed Oct 3 10:54:02 2018 +0200

    Init Implementation

    + added xep plugin to bot class

commit fe711f44d40671d927e9b946fb66679b297272c8
Author: nico <nico@magicbroccoli.de>
Date:   Tue Oct 2 21:20:08 2018 +0200

    Initial Version XEP query

    + added initial version of xep query class

5 files changed, 128 insertions, 17 deletions

diff --git a/.gitignore b/.gitignore
index 2da8adf..103d4a6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -60,4 +60,6 @@ target/
 
 # .idea
 .idea
+.etag
 bot\.cfg
+xeplist.xml
diff --git a/classes/functions.py b/classes/functions.py
index 08d6146..a8ed356 100644
--- a/classes/functions.py
+++ b/classes/functions.py
@@ -93,7 +93,7 @@ class ContactInfo:
 
 # class handeling XMPPError exeptions
 class HandleError:
-	def __init__(self, error, msg, key, target):
+	def __init__(self, error, msg, key, target="target missing"):
 		self.error = error
 		self.message = msg
 		self.key = key
diff --git a/classes/strings.py b/classes/strings.py
index ade0520..6866a31 100644
--- a/classes/strings.py
+++ b/classes/strings.py
@@ -12,7 +12,8 @@ class StaticAnswers:
 			'help':		'!help -- display this text',
 			'version':	'!version domain.tld  -- receive XMPP server version',
 			'uptime':	'!uptime domain.tld -- receive XMPP server uptime',
-			'contact':	'!contact domain.tld -- receive XMPP server contact address info'}
+			'contact':	'!contact domain.tld -- receive XMPP server contact address info',
+			'xep': 		'!xep XEP Number -- recieve information about the specified XEP'}
 		self.possible_answers = {
 			'1': 'I heard that, %s.',
 			'2': 'I am sorry for that %s.',
@@ -22,8 +23,10 @@ class StaticAnswers:
 			'2': 'not a valid target'
 		}
 		self.keywords = {
-			"keywords": ["!help", "!uptime", "!version", "!contact"],
-			"no_arg_keywords": ["!help"]
+			"keywords": ["!help", "!uptime", "!version", "!contact", "!xep"],
+			"domain_keywords": ["!uptime", "!version", "!contact"],
+			"no_arg_keywords": ["!help"],
+			"number_keywords": ["!xep"]
 		}
 
 	def keys(self, arg="", keyword='keywords'):
diff --git a/classes/xep.py b/classes/xep.py
new file mode 100644
index 0000000..6293c27
--- /dev/null
+++ b/classes/xep.py
@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+import requests
+import xml.etree.ElementTree as ET
+
+
+class XEPRequest:
+	def __init__(self, msg, xepnumber):
+		"""
+		class which requests the header of the referenced xep
+		:param xepnumber: number int or str to request the xep for
+		"""
+		self.message_type = msg['type']
+		self.muc_nick = msg['mucnick']
+
+		self.reqxep = str(xepnumber)
+		self.xeplist = None
+		self.acceptedxeps = list()
+
+	def req_xeplist(self):
+		"""
+		query and save the current xep list to reduce network bandwidth
+		"""
+		try:
+			with open(".etag") as file:
+				local_etag = file.read()
+		except FileExistsError:
+			local_etag = ""
+			pass
+
+		with requests.Session() as s:
+			s.headers.update({'Accept': 'application/xml'})
+			head = s.head("https://xmpp.org/extensions/xeplist.xml")
+			etag = head.headers['etag']
+
+			if local_etag == etag:
+				with open("xeplist.xml", "r") as file:
+					self.xeplist = ET.fromstring(file.read())
+			else:
+				r = s.get("https://xmpp.org/extensions/xeplist.xml")
+				r.encoding = 'utf-8'
+				local_etag = head.headers['etag']
+
+				with open("xeplist.xml", "w") as file:
+					file.write(r.content.decode())
+					self.xeplist = ET.fromstring(r.content.decode())
+
+				with open('.etag', 'w') as string:
+					string.write(local_etag)
+
+		# populate xep comparison list
+		for xep in self.xeplist.findall(".//*[@accepted='true']/number"):
+			self.acceptedxeps.append(xep.text)
+
+	def get(self):
+		"""
+		function to query the xep entry if xepnumber is present in xeplist
+		:return: nicely formatted xep header information
+		"""
+		# check if xeplist is accurate
+		self.req_xeplist()
+
+		result = list()
+		# if requested number is inside acceptedxeps continou
+		if self.reqxep in self.acceptedxeps:
+			searchstring = ".//*[@accepted='true']/[number='%s']" % self.reqxep
+
+			for item in self.xeplist.findall(searchstring):
+				for x in range(1,5):
+					result.append(item[x].tag + " : " + item[x].text)
+
+		else:
+			if self.message_type == "groupchat":
+				result.append(self.muc_nick + " : " + "XEP-" + str(self.reqxep) + " : is not available.")
+			else:
+				result.append("XEP-" + str(self.reqxep) + " : is not available.")
+
+		return result
+
+	def format(self):
+		reply = self.get()
+		if self.message_type == "groupchat":
+			text = "%s: " % self.muc_nick
+			reply[0] = text + reply[0]
+
+		text = '\n'.join(reply)
+
+		return text
diff --git a/main.py b/main.py
index 13cfb4c..2625728 100644
--- a/main.py
+++ b/main.py
@@ -19,6 +19,7 @@ from slixmpp.exceptions import XMPPError
 
 from classes.strings import StaticAnswers
 from classes.functions import Version, LastActivity, ContactInfo, HandleError
+from classes.xep import XEPRequest
 
 
 class QueryBot(slixmpp.ClientXMPP):
@@ -36,7 +37,7 @@ class QueryBot(slixmpp.ClientXMPP):
 
 	def start(self, event):
 		"""
-		:param str event -- An empty dictionary. The session_start event does not provide any additional data.
+		:param event -- An empty dictionary. The session_start event does not provide any additional data.
 		"""
 		self.send_presence()
 		self.get_roster()
@@ -47,27 +48,41 @@ class QueryBot(slixmpp.ClientXMPP):
 
 	def validate_domain(self, wordlist, index):
 		"""
-		validation method to reduce connection attemps to unvalid domains
-		:param wordlist: words seperated by " " from the message
+		validation method to reduce malformed querys and unnecessary connection attempts
+		:param wordlist: words separated by " " from the message
 		:param index: keyword index inside the message
 		:return: true if valid
 		"""
 		# keyword inside the message
 		argument = wordlist[index]
 
-		# if the argument is not inside the no_arg_keywords target is index + 1
-		if argument not in StaticAnswers().keys(arg='list', keyword="no_arg_keywords"):
-			try:
-				target = wordlist[index + 1]
-				if validators.domain(target):
+		# check if argument is in the argument list
+		if argument in StaticAnswers().keys(arg='list'):
+			# if argument uses a domain check for occurence in list and check domain
+			if argument in StaticAnswers().keys(arg='list', keyword='domain_keywords'):
+				try:
+					target = wordlist[index + 1]
+					if validators.domain(target):
+						return True
+				except IndexError:
+					# except an IndexError if a keywords is the last word in the message
+					return False
+
+			# check if number keyword is used if true check if target is assignable
+			elif argument in StaticAnswers().keys(arg='list', keyword='number_keywords'):
+				try:
+					target = wordlist[index + 1]
 					return True
-			except IndexError:
-				# except an IndexError if a keywords is the last word in the message
+				except IndexError:
+					# except an IndexError if target is not assignable
+					return False
+			# check if argument is inside no_arg list
+			elif argument in StaticAnswers().keys(arg='list', keyword="no_arg_keywords"):
+				return True
+			else:
 				return False
-		elif argument in StaticAnswers().keys(arg='list', keyword="no_arg_keywords"):
-			return True
 		else:
-			return
+			return False
 
 	def deduplicate(self, reply):
 		"""
@@ -136,6 +151,9 @@ class QueryBot(slixmpp.ClientXMPP):
 						contact = yield from self['xep_0030'].get_info(jid=target, cached=False)
 						reply.append(ContactInfo(contact, msg, target).format_contact())
 
+					elif keyword == "!xep":
+						reply.append(XEPRequest(msg, target).format())
+
 				except XMPPError as error:
 					reply.append(HandleError(error, msg, key, target).build_report())