diff --git a/diagrams.py b/diagrams.py
new file mode 100644
index 0000000..3afcc93
--- /dev/null
+++ b/diagrams.py
@@ -0,0 +1,315 @@
+from subprocess import Popen, PIPE
+import sys
+from sys import platform
+from os.path import expanduser
+from pathlib import Path
+import os.path
+import zlib
+import re
+import json
+
+
+class Example(object):
+		""" Example handling """
+
+		@staticmethod
+		def get(generator):
+				scriptdir = os.path.dirname(os.path.abspath(__file__))
+				example = scriptdir + "/../web/examples/example.%s" % generator
+				if os.path.isfile(example):
+						txt = Path(example).read_text()
+				else:
+						txt = "no example for %s found" % generator
+				return txt
+
+
+class Command(object):
+		""" a command to be run using the shell environment """
+
+		def __init__(self, cmd, versionOption="--version", timeout=5, debug=False):
+				""" construct me """
+				self.cmd = cmd
+				self.timeout = timeout
+				self.versionOption = versionOption
+				self.cmdpath = None
+				self.debug = debug
+
+		def call(self, args):
+				""" call me with the given args"""
+				return self.docall(self.cmdpath, self.cmd, args)
+
+		def callalias(self, alias, args):
+				""" call me with the given args"""
+				#print ("callalias cmdpath %s\nalias %s\nargs %s" % (self.cmdpath, alias, args), file=sys.stderr)
+				return self.docall(self.cmdpath, alias, args)
+
+		def docall(self, cmdpath, cmd, args):
+				""" call with a specific path and command"""
+				cmdline = "%s%s %s" % (cmdpath, cmd, str(args))
+				if self.debug:
+						print ("calling %s" % cmdline, file=sys.stderr)
+				process = Popen(cmdline, shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE)
+				try:
+						stdout, stderr = process.communicate(timeout=self.timeout)
+						if self.debug:
+								if stdout is not None:
+										print ("stdout: %s" % stdout.decode('utf-8'), file=sys.stderr)
+								if stderr is not None:
+										print ("stderr: %s" % stderr.decode('utf-8'), file=sys.stderr)
+						return stdout, stderr
+				except Exception:
+						process.kill()
+						return None, None
+
+		def check(self):
+				cmdpaths = []
+				# do we know the cmdpath?
+				if self.cmdpath is None:
+						# no we need to try multiple options in a specific order
+						# prio #1: $HOME/bin
+						home = expanduser("~")
+						cmdpaths.append(home + "/bin/")
+						# prio #2: e.g. Macports
+						if platform == "darwin":
+								cmdpaths.append("/opt/local/bin/")
+						# prio #3: default path / no path
+						# no path - use default PATH
+						cmdpaths.append("")
+				else:
+						# we know the valid path
+						cmdpaths.append(self.cmdpath)
+				for cmdpath in cmdpaths:
+						stdout, stderr = self.docall(cmdpath, self.cmd, self.versionOption)
+						stdoutTxt = None
+						stderrTxt = None
+						if stdout is not None:
+								stdoutTxt = stdout.decode("utf-8")
+						if stderr is not None:
+								stderrTxt = stderr.decode("utf-8")
+						if not "not found" in stderrTxt and not "No such file or directory" in stderrTxt:
+								self.cmdpath = cmdpath
+								return stdoutTxt, stderrTxt
+				return None, None
+
+
+class Generators(object):
+		generatorDict = {}
+		""" the available generators """
+
+		@staticmethod
+		def get(generator):
+				if len(Generators.generatorDict) is 0:
+						for gen in Generators.generators():
+								Generators.generatorDict[gen.id] = gen
+				gen = None
+				if generator in Generators.generatorDict:
+						gen = Generators.generatorDict[generator]
+				return gen
+
+		@staticmethod
+		def generatorIdForAlias(alias):
+				for gen in Generators.generators():
+						if alias in gen.aliases:
+								return gen.id
+				return None
+
+		@staticmethod
+		def generators():
+				scriptdir = os.path.dirname(os.path.abspath(__file__))
+				for plantumlpath in [".", ".."]:
+						plantumljar = scriptdir + "/" + plantumlpath + "/plantuml.jar";
+						if os.path.isfile(plantumljar):
+								break;
+				if plantumljar is None:
+						raise Exception("plantuml.jar not found in %s or .. of it", scriptdir)
+				#else
+				gens = [
+						Generator("graphviz", "GraphViz", "dot", "-V", logo="https://graphviz.gitlab.io/_pages/Resources/app.png", url="https://www.graphviz.org/",
+										  aliases=[ 'dot', 'neato', 'twopi', 'circo', 'fdp', 'sfdp', 'patchwork', 'osage' ],
+										  defaultType='png',
+										  outputTypes=['dot', 'xdot', 'ps', 'pdf', 'svg', 'fig', 'png', 'gif', 'jpg', 'json', 'imap', 'cmapx']
+										 ),
+						Generator("mscgen", "Mscgen", "mscgen", "", logo="http://www.mcternan.me.uk/mscgen/img/msc-sig.png", url="http://www.mcternan.me.uk/mscgen/", defaultType='png', outputTypes=['png', 'eps', 'svg', 'ismap']),
+						Generator("plantuml", "PlantUML", "java -jar " + plantumljar, "-version", aliases=['plantuml'],
+										  logo="https://useblocks.com/assets/img/posts/plantuml_logo.png",
+										  url="https://plantuml.com",
+						   defaultType='png',
+						   download="http://sourceforge.net/projects/plantuml/files/plantuml.jar/download",
+						   outputTypes=['png', 'svg', 'eps', 'pdf', 'vdx', 'xmi', 'scxml', 'html', 'txt', 'utxt',
+						'latex', 'latex:nopreamble'])
+				]
+				return gens
+
+
+class GenerateResult(object):
+
+		def __init__(self, crc32, outputType, path, stdout, stderr):
+				""" construct me """
+				self.crc32 = crc32;
+				self.outputType = outputType;
+				self.path = path;
+				self.stdout = stdout
+				self.stderr = stderr
+
+		def errMsg(self):
+				""" decode my stdout and stderr to an error message"""
+				msg = ""
+				if self.stdout is not None:
+						msg = msg + self.stdout.decode('utf-8')
+				if self.stderr is not None:
+						msg = msg + self.stderr.decode('utf-8')
+				return msg
+
+		def asHtml(self):
+				""" return me as HTML"""
+				url = '/render/%s/%s' % (self.outputType, self.crc32)
+				if self.outputType in ['gif', 'jpg', 'png', 'svg']:
+						return "<img src='%s'>" % url;
+				elif self.outputType in ['pdf']:
+						return "<object data='%s' width='640' height='640'></object>" % url;
+				else:
+						return "<a href='%s'>%s %s</a>" % (url, self.outputType, self.crc32)
+
+		def isValid(self):
+				""" check if i am valid"""
+				valid = os.path.isfile(self.path) and not self.errMsg()
+				return valid
+
+		def asJson(self, baseurl):
+				""" return my result as JSON for the Mediawiki diagrams extension"""
+				errMsg=self.errMsg();
+				if errMsg:
+						jsonTxt="""{
+						   "error": "generating %s failed",
+						   "message": %s
+						}""" % (self.outputType,json.dumps(errMsg))
+				else:
+						jsonTxt = """{
+  "diagrams": {
+		"png": {
+		  "url": "%s/png/%s.png"
+		}
+  }
+}""" % (baseurl,self.crc32)
+				return jsonTxt
+
+
+class Generator(object):
+		""" a diagram generator """
+
+		@staticmethod
+		def getOutputDirectory():
+				home = expanduser("~")
+				outputDir = home + "/.diagrams/"
+				if not os.path.isdir(outputDir):
+						os.mkdir(outputDir);
+				return outputDir
+
+		def __init__(self, genid, name, cmd, versionOption, logo=None, url=None, download=None, defaultType=None, aliases=None, outputTypes=None, debug=False):
+				""" construct me """
+				self.id = genid
+				self.name = name
+				self.cmd = cmd
+				self.gencmd = None
+				self.logo = logo
+				self.url = url
+				self.htmlInfo = None
+				self.download = download
+				self.versionOption = versionOption;
+				if aliases is None:
+						self.aliases = [cmd]
+				else:
+						self.aliases = aliases
+				self.defaultType = defaultType
+				self.selectedType = defaultType
+				self.outputTypes = outputTypes
+				self.debug = debug
+				pass
+
+		def getHtmlInfo(self):
+				""" get info on this generator to be displayed via  HTML"""
+				# cache the info since getVersion is a costly process
+				if self.htmlInfo is None:
+						version = self.getVersion()
+						self.htmlInfo = "<a href='%s' title='%s:%s'><img src='%s'/></a>" % (self.url, self.name, version, self.logo)
+				return self.htmlInfo
+
+		def check(self):
+				""" check my version"""
+				self.gencmd = Command(self.cmd, self.versionOption, debug=self.debug)
+				return self.gencmd.check()
+
+		def getVersion(self):
+				stdOutText, stdErrText = self.check()
+				if stdOutText is None:
+						stdOutText = ''
+				if stdErrText is None:
+						stdErrText = ''
+				outputText = stdOutText + stdErrText
+				found = re.search(r'version.*[,)]', outputText)
+				if found:
+						version = found.group()
+				else:
+						# actually an error message
+						version = outputText
+						# invalidate gencmd
+						self.gencmd = None
+				return version
+
+		@staticmethod
+		def getHash(txt):
+				hashValue = zlib.crc32(txt.encode()) & 0xffffffff
+				hashId = hex(hashValue)
+				#print ("txt %s\nhashValue %s\nhashId %s" % (txt, hashValue, hashId), file=sys.stderr)
+				return hashId
+
+		def wrap(self,txt):
+				""" wraot the given text"""
+				if self.id == "plantuml":
+						txt="@startuml\n%s\n@enduml\n" % txt
+				return txt
+
+		def generate(self, alias, txt, outputType, renderer, useCached=True):
+				""" generate """
+				txt=self.wrap(txt)
+				hashId = Generator.getHash(txt)
+				inputPath = "%s%s.%s" % (Generator.getOutputDirectory(), hashId, 'txt')
+				stdout = None
+				stderr = None
+				if not (os.path.isfile(inputPath) and useCached):
+						text_file = open(inputPath, "wt", encoding='utf-8')
+						try:
+								if self.debug:
+										print ("txt %s" % txt, file=sys.stderr)
+								text_file.write("%s" % txt)
+						except Exception as e:
+								print ("exception %s" % e, file=sys.stderr)
+						finally:
+								text_file.close()
+				outputPath = "%s%s.%s" % (Generator.getOutputDirectory(), hashId, outputType)
+				if os.path.isfile(outputPath) and useCached:
+						if self.debug:
+								print ("cached %s #%s from %s" % (outputType, hashId, outputPath), file=sys.stderr)
+				#else:
+				if True:
+						if self.debug:
+								print ("generating %s #%s to %s" % (outputType, hashId, outputPath), file=sys.stderr)
+						if self.id == "graphviz":
+								args = "-T%s %s -o  %s" % (outputType, inputPath, outputPath)
+								if len(renderer) != 0: #exists and not empty
+										alias = renderer
+								else:
+										alias = "dot"
+								#print ("renderer %s\nalias %s" % (renderer, alias), file=sys.stderr)
+						elif self.id == "mscgen":
+								args = "-T%s -i %s -o  %s" % (outputType, inputPath, outputPath)
+						elif self.id == "plantuml":
+								args = "-charset UTF-8 -t%s %s" % (outputType, inputPath)
+								alias = "java -jar /var/diagrams/plantuml.jar"
+						else:
+								print ("unknown generator %s" % self.id, file=sys.stderr)
+						if self.gencmd is None:
+								self.check()
+						stdout, stderr = self.gencmd.callalias(alias, args)
+				result = GenerateResult(hashId, outputType, outputPath, stdout, stderr)
+				return result