Experiments/EditorSim.icl

+module EditorSim
+/**
+* Simulation of messages passing between editors to figure out the design details
+*/
+import iTasks
+import Data.Maybe, Data.Either, Data.Tuple, Data.Functor, Data.List, Data.Func, Data.Error
+import qualified Data.Map as DM
+import Text, Text.HTML
+from StdFunc import seqList, :: St(..)
+from Data.Foldable import maximumBy
+import StdArray
+import Data.Map.GenJSON
+
+import qualified Graphics.Scalable.Image as GI
+from Graphics.Scalable.Image import :: FillAttr(..), <@<,  :: Image, :: Host(..)
+from Graphics.Scalable.Image import class tuneImage, instance tuneImage FillAttr
+from Graphics.Scalable.Image import class margin, instance margin (!Span, !Span, !Span, !Span), instance margin Span
+import iTasks.Extensions.SVG.SVGEditor
+import StdMisc, StdDebug
+
+//TODOS:
+// - Model an example with input field validation for mandatory fields etc. such as 'empty','validated', etc
+
+//PROBLEMS:
+// - Link methods not complete enough yet... (impossible to react to refreshes on server...)
+
+//Definition of editors
+
+// p: The parameter set (same as in sds)
+// r: Data read from an external source (sds) based on p. Data will arrive with some delay and can be updated later
+// w: Data to be written back to the external source (sds)
+
+// s: Server-side state
+// c: Client-side state
+// m: Messages exchanged to synchronize between client and server (and potentially between sub editors)
+
+:: NxtEditor p r w s c m =
+  { client :: NxtEditorClient p c m
+  , server :: NxtEditorServer p r w s m
+  }
+
+:: NxtEditorClient p c m =
+  { init      :: p -> NxtDOM
+  , state     :: NxtDOM -> c
+  , onEvent   :: NxtDOMRef String NxtDOM -> ([NxtClientOutMessage m],NxtDOM)
+  , onMessage :: (NxtClientInMessage m) NxtDOM -> ([NxtClientOutMessage m],NxtDOM)
+  }
+
+:: NxtEditorServer p r w s m =
+  { init      :: p NxtMajorVersion -> (s, NxtVersionTree)
+  , parameter :: s -> p
+  , value     :: s -> Maybe w
+  , onRefresh :: r NxtMajorVersion s NxtVersionTree -> ([NxtServerOutMessage m], s, NxtVersionTree, NxtWrite) 
+  , onMessage :: (NxtServerInMessage m) s NxtVersionTree -> ([NxtServerOutMessage m], s, NxtVersionTree, Bool)
+  }
+
+:: NxtWrite :== Bool //The Bool is a 'write' signal that indicates if something significant has changed
+
+:: NxtVersion :== (!NxtMajorVersion,!NxtMinorVersion) //First: which read from sds, Second: which revision by edits
+:: NxtMajorVersion :== Int
+:: NxtMinorVersion :== Int
+
+//Together with the served side state we need to track all versions explicitly
+//(the client versions are encoded in the DOM)
+:: NxtVersionTree
+	= NVTBasic     !NxtVersion
+	| NVTGlue      !NxtVersionTree !NxtVersionTree
+	| NVTMultiple  !NxtVersion [NxtVersionTree]
+
+//Messages commonly only affect part of a datastructure, so no complete version tree is communicated
+:: NxtPartialVersionTree 
+	= NVPVersion !(Maybe NxtVersion) ![(Int,NxtPartialVersionTree)]
+
+:: NxtWithPartialVersion m = { message :: m, version :: NxtPartialVersionTree }
+:: NxtWithPartialVersions m = { message :: m, oldVersion :: NxtPartialVersionTree, newVersion :: NxtPartialVersionTree}
+
+:: NxtClientInMessage m
+	= NxtClientInRemote m NxtPartialVersionTree NxtPartialVersionTree //(message, oldVersion, newVersion)
+	| NxtClientInLocal m //local loopback on client
+
+:: NxtClientOutMessage m = NxtClientOut m NxtPartialVersionTree //(message, version)
+
+:: NxtServerInMessage m
+	= NxtServerInRemote m NxtPartialVersionTree
+	| NxtServerInLocal m NxtMajorVersion //When we feedback messages, we need to pass along the major version of message that created the feedback
+
+:: NxtServerOutMessage m = NxtServerOut m NxtPartialVersionTree NxtPartialVersionTree
+
+instance Functor NxtServerInMessage
+where
+	fmap f (NxtServerInRemote m v) = NxtServerInRemote (f m) v
+	fmap f (NxtServerInLocal m v) = NxtServerInLocal (f m) v
+
+instance Functor NxtClientInMessage
+where
+	fmap f (NxtClientInRemote m ov nv) = NxtClientInRemote (f m) ov nv
+	fmap f (NxtClientInLocal m) = NxtClientInLocal (f m)
+
+//TODO: this is not minimal enough: We create a partial version info structure, but it actually contains all versions!
+toPartialVersion (NVTBasic v) = NVPVersion (Just v) []
+toPartialVersion (NVTGlue v1 v2) = NVPVersion Nothing [(0,toPartialVersion v1),(1,toPartialVersion v2)]
+toPartialVersion (NVTMultiple v vs) = NVPVersion (Just v) [(n,toPartialVersion cv) \\ cv <- vs & n <- [0..]]
+
+emptyPartialVersion = NVPVersion Nothing []
+selectPartialVersion pos (NVPVersion _ items) = case [v \\ (i,v) <- items | i == pos] of
+	[v:_] = v
+	_     = emptyPartialVersion
+
+maxMajorVersion (NVPVersion mbv vs) = foldr max (maybe 0 fst mbv) (map (maxMajorVersion o snd) vs)
+
+getVersion:: NxtVersionTree -> NxtVersion
+getVersion (NVTBasic v) = v
+getVersion (NVTMultiple v _) = v
+
+//Simulated DOM/JSWorld
+:: NxtDOMRef :== [Int]
+:: NxtDOM :== NxtDOMNode
+
+:: NxtDOMNode = 
+	{ attributes :: Map String String
+	, children   :: [NxtDOMNode]
+	, history    :: [(NxtVersion,NxtDOMNode)] //Would normally be tracked in JS outside the DOM
+	}
+
+:: VersionedServerState s =
+	{ state            :: s
+	, readVersion      :: NxtMajorVersion //Increments each time the linked sds refreshes
+	, stateVersion     :: NxtVersionTree //Holds the versions of all parts of an editor
+	}
+
+//Untyped clientside configuration
+:: NxtUI = { attributes  :: Map String String, children :: [NxtUI]}
+
+//Untyped message for transfer and configuration
+:: NxtChange
+  = NxtNoChange
+  | NxtReplace NxtUI
+  | NxtChange [NxtAttrChange] [NxtStructureChange]
+
+:: NxtAttrChange = NxtSetAttr String String | NxtDelAttr String
+:: NxtStructureChange
+  = NxtAddChild Int NxtUI
+  | NxtRemChild Int
+  | NxtUpdChild Int NxtChange
+
+derive class iTask NxtDOMNode, VersionedServerState, NxtUI, NxtChange, NxtAttrChange, NxtStructureChange
+derive class iTask NxtWithPartialVersion, NxtWithPartialVersions, NxtVersionTree, NxtPartialVersionTree
+derive class iTask NxtServerInMessage, NxtServerOutMessage, NxtClientInMessage, NxtClientOutMessage
+
+derive JSEncode NxtDOMNode, Map
+derive JSDecode NxtDOMNode, Map
+
+//Typed messages for dynamic editors that contain children
+//TODO add messages for the container itself..
+:: ContainerMsg p m
+	= NxtInsertChild Position p
+	| NxtRemoveChild Position
+	| NxtUpdateChild Position m
+
+:: Position :== Int
+
+derive class iTask ContainerMsg
+
+class EditMessage m
+where
+  encodeEditMessage :: m -> NxtChange
+  decodeEditMessage :: NxtChange -> m
+
+class EditUI c
+where
+  encodeEditUI :: c -> NxtUI
+  decodeEditUI :: NxtUI -> c
+
+nextRevision (version,revision) = (version, revision + 1)
+
+checkRevision (NVPVersion (Just (v1,r1)) _) (v2,r2) = (v1 == v2) && (r1 == r2 + 1) //Only accept the next revision
+checkRevision _ _ = False
+
+getVersionFromDOM {NxtDOMNode|attributes}
+	# major = maybe 0 toInt ('DM'.get "major-version" attributes)
+	# minor = maybe 0 toInt ('DM'.get "minor-version" attributes)
+	= (major,minor) 
+
+setVersionInDOM (major,minor) dom=:{NxtDOMNode|attributes}
+	# attributes = 'DM'.put "major-version" (toString major) attributes
+	# attributes = 'DM'.put "minor-version" (toString minor) attributes
+	= {NxtDOMNode|dom & attributes = attributes}
+
+pushHistoryInDOM dom=:{attributes,children,history}
+	# version = getVersionFromDOM dom
+	= {NxtDOMNode|attributes = attributes, children = children, history = [(version,dom):history]}
+
+resetHistoryInDOM dom = {NxtDOMNode|dom & history = []}
+
+//Get the version of a child element in a compound structure
+childversion pos mv = case [v \\ (n,v) <- mv | n == pos] of
+	[] = NVPVersion Nothing []
+	vs = last vs
+
+//Definitions of a test editor
+nxtNumberField :: NxtEditor () Int Int String String String
+nxtNumberField = {client=client,server=server}
+where
+ client = {init=init,onEvent=onEvent,onMessage=onMessage,state=state}
+ where
+  init ()
+    = {NxtDOMNode|attributes = 'DM'.fromList [("type","numberfield"),("value","")], children = [], history = []}
+
+  state dom=:{NxtDOMNode|attributes} = fromMaybe "" ('DM'.get "value" attributes)
+
+  onEvent [] e dom=:{NxtDOMNode|attributes}
+	# version = nextRevision $ getVersionFromDOM dom
+    # msg = [NxtClientOut e (NVPVersion (Just version) [])]
+	# dom = pushHistoryInDOM dom
+    # dom = setVersionInDOM version {NxtDOMNode|dom & attributes = 'DM'.put "value" (fromString e) attributes}
+    = (msg,dom)
+  onEvent _ _ dom = ([],dom)
+
+  onMessage (NxtClientInLocal message) dom=:{NxtDOMNode|attributes,history}
+	# version = nextRevision $ getVersionFromDOM dom
+    # msg = [NxtClientOut message (NVPVersion (Just version) [])]
+	# dom = pushHistoryInDOM dom
+    # dom = setVersionInDOM version {NxtDOMNode|dom & attributes = 'DM'.put "value" message attributes}
+    = (msg,dom)
+
+  onMessage (NxtClientInRemote message (NVPVersion (Just oldVersion) _) (NVPVersion (Just newVersion) _)) dom=:{NxtDOMNode|attributes,history}
+	# version = getVersionFromDOM dom
+	| version <> oldVersion //The server was not up-to date, mitigate potential conflict
+		# curValue = fromJust ('DM'.get "value" attributes)
+		# oldValue = firstJust ['DM'.get "value" attributes \\ (v,{NxtDOMNode|attributes}) <- history | v == oldVersion]
+		//If we only extended the message, we can add the extension 
+		| startsWith oldValue curValue
+			# extension = subString (textSize oldValue) (textSize curValue) curValue
+			# newValue = message +++ extension
+			//Set message value as first step in history
+			# dom = setVersionInDOM newVersion dom
+			# dom = {NxtDOMNode|dom & attributes = 'DM'.put "value" message attributes}
+			# dom = pushHistoryInDOM $ resetHistoryInDOM dom
+			//Retore the extension and set as message
+			# newVersion = nextRevision newVersion
+			# dom = setVersionInDOM newVersion dom
+			# dom = {NxtDOMNode|dom & attributes = 'DM'.put "value" newValue attributes}
+    		# msg = [NxtClientOut newValue (NVPVersion (Just newVersion) [])]
+			= (msg,dom)
+		| otherwise //Too bad, we have lost our edits, best notify the user somehow by a visual or audible cue
+			# dom = {NxtDOMNode|dom & attributes = 'DM'.put "value" message attributes}
+			# dom = setVersionInDOM newVersion dom
+			# dom = resetHistoryInDOM dom
+			= ([],dom)
+	| otherwise //Everything was as expected
+		# dom = {NxtDOMNode|dom & attributes = 'DM'.put "value" message attributes}
+		# dom = setVersionInDOM newVersion dom
+		# dom = resetHistoryInDOM dom
+		= ([],dom)
+  where
+    firstJust [Just x:_] = x
+
+  onMessage msg dom=:{NxtDOMNode|attributes,history}
+	= abort (toString (toJSON msg))
+
+ server = {init=init,parameter=parameter,value=value,onRefresh=onRefresh,onMessage=onMessage}
+ where
+  init () v = ("",NVTBasic (v,0))
+  parameter _ = ()
+  value s = Just (toInt s)
+
+  onRefresh r rv  _ (NVTBasic v)
+	= ([NxtServerOut (toString r) (NVPVersion (Just v) []) (NVPVersion (Just (rv,0)) [])], toString r,NVTBasic (rv,0), False)
+
+  onMessage (NxtServerInRemote message version) c (NVTBasic v )
+	| checkRevision version v = ([], message, NVTBasic (nextRevision v), True)
+	| otherwise               = ([], c, NVTBasic v, False)
+
+nxtButton :: NxtEditor String Bool Bool (String,Bool) (String,Bool) Bool
+nxtButton = {client=client,server=server}
+where
+ client = {init=init,state=state,onEvent=onEvent,onMessage=onMessage}
+ where
+  init label
+	= {NxtDOMNode|attributes = 'DM'.fromList [("type","button"),("label",label),("clicked","false")],children = [], history = []}
+
+  state dom=:{NxtDOMNode|attributes}
+	# clicked = case 'DM'.get "clicked" attributes of
+		(Just "true") = True
+		_             = False
+	# label = fromJust ('DM'.get "label" attributes)
+	= (label,clicked)
+
+  onEvent [] value dom=:{NxtDOMNode|attributes}
+	# clicked = value == "click"
+	# major = maybe 0 toInt ('DM'.get "major-version" attributes)
+	# minor = maybe 1 (inc o toInt) ('DM'.get "minor-version" attributes)
+    # msg = [NxtClientOut clicked (NVPVersion (Just (major,minor)) [])]
+    # dom = {NxtDOMNode|dom & attributes = 'DM'.put "minor-version" (toString minor) $'DM'.put "clicked" (if clicked "true" "false") attributes}
+    = (msg,dom)
+  onEvent _ _ dom
+	= ([],dom)
+
+  onMessage (NxtClientInLocal value) dom=:{NxtDOMNode|attributes} //Similar to onEvent, but can also set value to False
+	# major = maybe 0 toInt ('DM'.get "major-version" attributes)
+	# minor = maybe 1 (inc o toInt) ('DM'.get "minor-version" attributes)
+    # msg = [NxtClientOut value (NVPVersion (Just (major,minor)) [])]
+    # dom = {NxtDOMNode|dom & attributes = 'DM'.put "minor-version" (toString minor) $'DM'.put "clicked" (if value "true" "false") attributes}
+    = (msg,dom)
+
+  onMessage (NxtClientInRemote message oldVersion newVersion) dom=:{NxtDOMNode|attributes}
+	# attributes = 'DM'.put "clicked" (if message "true" "false") attributes
+	//Update version
+	# attributes = case newVersion of
+		(NVPVersion (Just (major,minor)) _)
+			= 'DM'.put "minor-version" (toString minor) $ 'DM'.put "major-version" (toString major) attributes
+		_ 
+			= attributes
+    = ([],{NxtDOMNode|dom & attributes = attributes})
+
+ server = {init=init,parameter=parameter,value=value,onRefresh=onRefresh,onMessage=onMessage}
+ where
+  init label v = ((label,False),NVTBasic (v,0))
+  parameter (l,_) = l
+  value s = Just (snd s)
+
+  onRefresh r rv (l,_) (NVTBasic v) = ([NxtServerOut r (NVPVersion (Just v) []) (NVPVersion (Just (rv,0)) [])], (l,r), NVTBasic (rv,0), False)
+
+  onMessage (NxtServerInRemote message version) (l,c) (NVTBasic v)
+	| checkRevision version v = ([], (l,message), NVTBasic (nextRevision v), True)
+	| otherwise               = ([], (l,c), NVTBasic v, False)
+
+
+toVersionAttr (x,y) = toString x +++ "-" +++ toString y
+
+fromVersionAttr s = case split "-" s of
+	[x,y:_] = (toInt x,toInt y)
+	_       = (0,0)
+
+addVersionAttr key (Just version) (NxtNoChange) = NxtChange [NxtSetAttr key (toVersionAttr version)] []
+addVersionAttr key (Just version) (NxtChange attrChanges childChanges) = NxtChange (attrChanges ++ [NxtSetAttr key (toVersionAttr version)]) childChanges
+addVersionAttr key (Just version) (NxtReplace ui=:{NxtUI|attributes}) = NxtReplace {NxtUI|ui & attributes = 'DM'.put key (toVersionAttr version) attributes}
+addVersionAttr key Nothing message = message
+
+getVersionAttr key (NxtChange attrChanges childChanges)
+	= case [fromVersionAttr v \\ NxtSetAttr k v <- attrChanges | key == k] of
+		[] =  Nothing
+		versions = Just (last versions)
+getVersionAttr key (NxtReplace {NxtUI|attributes}) 
+	= fmap fromVersionAttr ('DM'.get key attributes)
+getVersionAttr key enc = Nothing
+
+class overlayVersions a :: String NxtPartialVersionTree a -> a
+
+instance overlayVersions NxtChange
+where
+	overlayVersions key (NVPVersion Nothing []) (NxtNoChange) = NxtNoChange
+	overlayVersions key (NVPVersion mbv cvs) (NxtNoChange) = NxtChange attrChanges childChanges
+	where
+		attrChanges = maybe [] (\version -> [NxtSetAttr key (toVersionAttr version)]) mbv
+		childChanges = [NxtUpdChild n (overlayVersions key cv NxtNoChange) \\ (n,cv) <- cvs]
+
+	overlayVersions key (NVPVersion mbv cvs) (NxtChange attrChanges childChanges) = NxtChange attrChanges` childChanges`
+	where
+		attrChanges` = attrChanges ++ maybe [] (\version -> [NxtSetAttr key (toVersionAttr version)]) mbv
+		childChanges` = map overlayChild childChanges
+		where
+			overlayChild (NxtUpdChild n change) = NxtUpdChild n (overlayVersions key (fromMaybe empty ('DM'.get n cvsMap)) change)
+			overlayChild c = c
+			empty = NVPVersion Nothing []
+
+		cvsMap = 'DM'.fromList cvs
+
+	overlayVersions key version=:(NVPVersion mbv cvs) (NxtReplace ui) = NxtReplace (overlayVersions key version ui)
+
+instance overlayVersions NxtUI
+where
+	overlayVersions key (NVPVersion mbv cvs) {NxtUI|attributes,children} = {NxtUI|attributes=attributes`,children=children`}
+	where 
+		attributes` = maybe attributes (\version -> 'DM'.put key (toVersionAttr version) attributes) mbv
+		children` = [maybe c (\v -> overlayVersions key v c) ('DM'.get i cvsMap) \\ c <- children & i <- [0..]]
+		cvsMap = 'DM'.fromList cvs
+
+class getOverlayedVersions a :: String a -> NxtPartialVersionTree
+
+instance getOverlayedVersions NxtChange 
+where
+	getOverlayedVersions key NxtNoChange = NVPVersion Nothing []
+	getOverlayedVersions key (NxtReplace ui) = getOverlayedVersions key ui
+	getOverlayedVersions key (NxtChange attrChanges childChanges)
+		# version = foldl setVersion Nothing attrChanges
+		# childVersions = [(n, getOverlayedVersions key change) \\ (NxtUpdChild n change) <- childChanges]
+		= NVPVersion version (filter (not o emptyChange o snd) childVersions)
+	where
+		setVersion cur (NxtSetAttr k v) = if (k == key) (Just (fromVersionAttr v)) cur
+		setVersion cur _ = cur
+
+		emptyChange (NVPVersion Nothing []) = True
+		emptyChange _ = False
+
+instance getOverlayedVersions NxtUI
+where
+	getOverlayedVersions key {NxtUI|attributes,children}
+	 	# mbv = fmap fromVersionAttr ('DM'.get key attributes)
+		# cvs = filter (not o emptyVersion o snd) [(i,getOverlayedVersions key c) \\ c <- children & i <- [0..]]
+		= NVPVersion mbv cvs
+	where
+		emptyVersion (NVPVersion Nothing []) = True	
+		emptyVersion _ = False
+
+instance EditMessage (NxtServerOutMessage m) | EditMessage m
+where
+	encodeEditMessage (NxtServerOut message oldVersion newVersion)
+//		| not (trace_tn (toJSON oldVersion)) = undef
+		= overlayVersions "old-version" oldVersion
+		$ overlayVersions "new-version" newVersion
+		$ encodeEditMessage message
+
+	decodeEditMessage enc
+		= let  message = decodeEditMessage enc
+		       oldVersion = getOverlayedVersions "old-version" enc
+		       newVersion = getOverlayedVersions "new-version" enc
+		  in (NxtServerOut message oldVersion newVersion)
+
+instance EditMessage (NxtClientOutMessage m) | EditMessage m
+where
+	encodeEditMessage (NxtClientOut message version)
+		= overlayVersions "version" version
+		$ encodeEditMessage message
+
+	decodeEditMessage enc
+		= let message = decodeEditMessage enc
+		      version = getOverlayedVersions "version" enc
+		  in (NxtClientOut message version)
+
+instance EditMessage (Either a b) | EditMessage a & EditMessage b
+where
+  encodeEditMessage (Left value) = case encodeEditMessage value of
+	(NxtChange attrChanges childChanges) = NxtChange [NxtSetAttr "either" "left":attrChanges] childChanges
+	(NxtReplace ui=:{NxtUI|attributes}) = NxtReplace {NxtUI|ui & attributes = 'DM'.put "either" "left" attributes}
+  encodeEditMessage (Right value) = case encodeEditMessage value of
+	(NxtChange attrChanges childChanges) = NxtChange [NxtSetAttr "either" "right":attrChanges] childChanges
+	(NxtReplace ui=:{NxtUI|attributes}) = NxtReplace {NxtUI|ui & attributes = 'DM'.put "either" "right" attributes}
+
+  decodeEditMessage (NxtChange [NxtSetAttr "either" "left":attrChanges] childChanges)
+		= Left (decodeEditMessage (NxtChange attrChanges childChanges))
+  decodeEditMessage (NxtChange [NxtSetAttr "either" "right":attrChanges] childChanges)
+		= Right (decodeEditMessage (NxtChange attrChanges childChanges))
+
+  decodeEditMessage (NxtReplace ui=:{NxtUI|attributes}) = case 'DM'.get "either" attributes of
+	(Just "left") = Left (decodeEditMessage (NxtReplace {NxtUI|ui & attributes = 'DM'.del "either" attributes}))
+	_             = Right (decodeEditMessage (NxtReplace {NxtUI|ui & attributes = 'DM'.del "either" attributes}))
+
+instance EditUI ()
+where
+  encodeEditUI _ = {NxtUI|attributes='DM'.newMap ,children=[]}
+  decodeEditUI _ = () 
+
+instance EditMessage String //If strings are used as edit type, it's just the value attribute
+where
+  encodeEditMessage value = NxtChange [NxtSetAttr "value" value] []
+  decodeEditMessage (NxtChange [NxtSetAttr "value" value:_] []) = value
+
+instance EditUI String
+where
+  encodeEditUI value = {NxtUI|attributes='DM'.fromList [("value",value)],children=[]}
+  decodeEditUI {NxtUI|attributes} = fromJust ('DM'.get "value" attributes)
+
+instance EditMessage Bool //If strings are used as edit type, it's just the value attribute
+where
+  encodeEditMessage value = NxtChange [NxtSetAttr "value" (if value "true" "false")] []
+
+  decodeEditMessage (NxtChange [NxtSetAttr "value" "true":_] []) = True
+  decodeEditMessage (NxtChange [NxtSetAttr "value" "false":_] []) = False
+
+instance EditUI Bool
+where
+  encodeEditUI value = {NxtUI|attributes='DM'.fromList [("value",if value "true" "false")],children=[]}
+  decodeEditUI {NxtUI|attributes} = case ('DM'.get "value" attributes) of (Just "true") = True; _ = False
+
+instance EditMessage (Maybe a,Maybe b) | EditMessage a & EditMessage b
+where
+  encodeEditMessage (mba, mbb)
+	= NxtChange [] (maybe [] (\a -> [NxtUpdChild 0 (encodeEditMessage a)]) mba
+		 ++ maybe [] (\b -> [NxtUpdChild 1 (encodeEditMessage b)]) mbb)
+
+  decodeEditMessage (NxtChange _ [NxtUpdChild 0 enca,NxtUpdChild 1 encb:_])
+		= (Just (decodeEditMessage enca), Just (decodeEditMessage encb))
+  decodeEditMessage (NxtChange _ [NxtUpdChild 0 enca:_]) = (Just (decodeEditMessage enca),Nothing)
+  decodeEditMessage (NxtChange _ [NxtUpdChild 1 encb:_]) = (Nothing,Just (decodeEditMessage encb))
+  decodeEditMessage _ = (Nothing,Nothing)
+
+instance EditUI (Maybe a) | EditUI a
+where
+	encodeEditUI Nothing = {NxtUI|attributes='DM'.newMap,children=[]}
+	encodeEditUI (Just x) = {NxtUI|attributes='DM'.newMap,children=[encodeEditUI x]}
+
+	decodeEditUI {NxtUI|children=[]} = Nothing
+	decodeEditUI {NxtUI|children=[m]} = Just (decodeEditUI m)
+
+instance EditUI (a, b) | EditUI a & EditUI b
+where
+  encodeEditUI (a,b) = {NxtUI|attributes='DM'.newMap,children = [encodeEditUI a,encodeEditUI b]}
+  decodeEditUI m = (decodeEditUI m,decodeEditUI m)
+
+instance EditMessage (ContainerMsg p m) | EditUI p & EditMessage m
+where
+	encodeEditMessage (NxtInsertChild pos p) = NxtChange [] [NxtAddChild pos (encodeEditUI p)]
+	encodeEditMessage (NxtRemoveChild pos) = NxtChange [] [NxtRemChild pos]
+	encodeEditMessage (NxtUpdateChild pos m) = NxtChange [] [NxtUpdChild pos (encodeEditMessage m)]
+
+	decodeEditMessage (NxtChange _ [NxtAddChild pos p:_]) = NxtInsertChild pos (decodeEditUI p)
+	decodeEditMessage (NxtChange _ [NxtRemChild pos:_]) = NxtRemoveChild pos
+	decodeEditMessage (NxtChange _ [NxtUpdChild pos m:_]) = NxtUpdateChild pos (decodeEditMessage m)
+
+instance EditUI (Either a b) | EditUI a & EditUI b
+where
+	encodeEditUI (Left a) = markleft (encodeEditUI a)
+	where
+		markleft {NxtUI|attributes,children} = {NxtUI|attributes='DM'.put "either" "left" attributes,children=children}
+
+	encodeEditUI (Right b) = markright (encodeEditUI b)
+	where
+		markright {NxtUI|attributes,children} = {NxtUI|attributes='DM'.put "either" "right" attributes,children=children}
+
+	decodeEditUI enc = if (isLeft enc) (Left (decodeEditUI enc)) (Right (decodeEditUI enc))
+	where
+		isLeft {NxtUI|attributes} = maybe False ((==) "left") ('DM'.get "either" attributes) //TODO: This doesn't work for nested eithers
+
+// ### Composition
+
+//Combine two editors into one that can do both
+//Based on the initial parameter, the appropriate one is selected
+//The editor is biased left 
+alternative :: 
+	(NxtEditor p1 r1 w1 s1 c1 m1)
+	(NxtEditor p2 r2 w2 s2 c2 m2)
+    ->
+	(NxtEditor (Either p1 p2) (Either r1 r2) (Either w1 w2) (Either s1 s2) (Either c1 c2) (Either m1 m2))
+alternative e1 e2 = {NxtEditor|server=server,client=client} 
+where
+	server = {init = init, parameter = parameter, value=value, onRefresh = onRefresh, onMessage = onMessage}
+	where
+		init (Left p) mv = appFst Left (e1.server.NxtEditorServer.init p mv)
+		init (Right p) mv = appFst Right (e2.server.NxtEditorServer.init p mv)
+
+		parameter (Left s) = Left (e1.server.NxtEditorServer.parameter s)
+		parameter (Right s) = Right (e2.server.NxtEditorServer.parameter s)
+
+		value (Left s) = fmap Left (e1.server.NxtEditorServer.value s)
+		value (Right s) = fmap Right (e2.server.NxtEditorServer.value s)
+
+		onRefresh (Left r) rv (Left s) sv
+			# (ms,s,sv,w) = e1.server.NxtEditorServer.onRefresh r rv s sv
+			= ([NxtServerOut (Left message) oldVersion newVersion \\ (NxtServerOut message oldVersion newVersion) <- ms], Left s, sv, w)
+		onRefresh (Right r) rv (Right s) sv
+			# (ms,s,sv,w) = e2.server.NxtEditorServer.onRefresh r rv s sv
+			= ([NxtServerOut (Right message) oldVersion newVersion \\ (NxtServerOut message oldVersion newVersion) <- ms], Right s, sv, w)
+
+		onRefresh _ rv _ sv
+			= abort "alternative editor switched type dynamically"
+
+		onMessage (NxtServerInRemote (Left m) version) (Left s) sv 
+			# (ms,s,sv,w) = e1.server.NxtEditorServer.onMessage (NxtServerInRemote m version) s sv
+			= ([NxtServerOut (Left message) oldVersion newVersion \\ (NxtServerOut message oldVersion newVersion) <- ms], Left s, sv, w)
+		onMessage (NxtServerInRemote (Right m) version) (Right s) sv
+			# (ms,s,sv,w) = e2.server.NxtEditorServer.onMessage (NxtServerInRemote m version) s sv
+			= ([NxtServerOut (Right message) oldVersion newVersion \\ (NxtServerOut message oldVersion newVersion) <- ms], Right s, sv, w)
+
+    client = {init = init, onEvent = onEvent, onMessage = onMessage, state = state}
+	where
+		init (Left p)
+			# dom=:{NxtDOMNode|attributes} = e1.client.NxtEditorClient.init p
+			= {NxtDOMNode|dom & attributes = 'DM'.put "alternative" "left" attributes}
+		init (Right p)
+			# dom=:{NxtDOMNode|attributes} = e2.client.NxtEditorClient.init p
+			= {NxtDOMNode|dom & attributes = 'DM'.put "alternative" "right" attributes}
+
+		state dom=:{NxtDOMNode|attributes}
+    		# alt = fromJust ('DM'.get "alternative" attributes)
+			| alt == "left"
+				= Left (e1.client.NxtEditorClient.state dom)
+			| otherwise
+				= Right (e2.client.NxtEditorClient.state dom)
+	
+		onEvent ref event dom=:{NxtDOMNode|attributes}
+    		# alt = fromJust ('DM'.get "alternative" attributes)
+			| alt == "left"
+				# (ms,dom) = e1.client.NxtEditorClient.onEvent ref event dom 
+				= ([NxtClientOut (Left message) version \\ (NxtClientOut message version) <- ms], dom)
+			| otherwise
+				# (ms,dom) = e2.client.NxtEditorClient.onEvent ref event dom 
+				= ([NxtClientOut (Right message) version \\ (NxtClientOut message version) <- ms], dom)
+
+		onMessage (NxtClientInRemote (Left m) oldVersion newVersion) dom 
+			# (ms,dom) = e1.client.NxtEditorClient.onMessage (NxtClientInRemote m oldVersion newVersion) dom 
+			= ([NxtClientOut (Left message) version \\ (NxtClientOut message version) <- ms], dom)
+		onMessage (NxtClientInRemote (Right m) oldVersion newVersion) dom 
+			# (ms,dom) = e2.client.NxtEditorClient.onMessage (NxtClientInRemote m oldVersion newVersion) dom 
+			= ([NxtClientOut (Right message) version \\ (NxtClientOut message version) <- ms], dom)
+
+multiple :: (NxtEditor p r w s c m) -> (NxtEditor [p] [Maybe r] [Maybe w] [s] [c] (ContainerMsg p m)) | gDefault{|*|} p
+multiple editor = {NxtEditor|server=server,client=client}
+where
+	server = {init = init, parameter = parameter, value=value, onRefresh = onRefresh, onMessage = onMessage}
+	where
+		init ps v
+			# (ss,vs) = unzip [editor.server.NxtEditorServer.init p v \\ p <- ps]
+			= (ss,NVTMultiple (v,0) vs)
+
+		parameter ss = map editor.server.NxtEditorServer.parameter ss 
+		value ss = Just (map editor.server.NxtEditorServer.value ss)
+
+		onRefresh mbrs rv ss (NVTMultiple stv vs)//A naive linear side by side diff to see what needs updating
+			# (msgs,ss,vs,write) = compare 0 ss vs mbrs
+			= (msgs, ss, NVTMultiple stv vs, False)//By default we need to do a diff
+		where
+			//Compare first items side by side
+			compare i [s:ss] [v:vs] [Nothing:mbrs]
+				# (msgs, ss, vs, write) = compare (i + 1) ss vs mbrs
+				= (msgs, [s:ss], [v:vs], write)
+
+			compare i [s:ss] [vo:vs] [Just r:mbrs]
+				# (ms, s, vn, writes) = editor.server.NxtEditorServer.onRefresh r rv s vo
+				# (msgs, ss, vs, writess) = compare (i + 1) ss vs mbrs
+				= ([NxtServerOut (NxtUpdateChild i message) (wrapVersion i oldVersion) (wrapVersion i newVersion) \\ (NxtServerOut message oldVersion newVersion) <- ms] ++ msgs
+				  , [s:ss], [vn:vs], writes || writess)
+			where
+				wrapVersion n v = NVPVersion Nothing [(n,v)]
+
+			//New read list has more items
+			//TODO: When items are edited or removed, it is a structural change that needs to bump the version on the container itself
+			compare i [] _ mbrs
+				# (msgs, ss, vs, ws) = unzip4 [create i` mbr \\ mbr <- mbrs & i` <- [i..]]
+				= (flatten msgs, ss, vs, or ws)
+			where
+				create i mbr
+					# (s,vi) = editor.server.NxtEditorServer.init defaultValue (fst stv)
+					# (ms, s, v, write) = maybe ([],s,vi,False) (\r -> editor.server.NxtEditorServer.onRefresh r rv s vi) mbr 
+					= ([NxtServerOut (NxtInsertChild i defaultValue) emptyPartialVersion (toPartialVersion vi)
+					   :[NxtServerOut (NxtUpdateChild i message) (NVPVersion Nothing [(i,oldVersion)]) (NVPVersion Nothing [(i,newVersion)]) \\ (NxtServerOut message oldVersion newVersion) <- ms]], s, v, write)
+
+			//New read list has less (remove existing)
+			compare i ss _ [] = (repeatn (length ss) (NxtServerOut (NxtRemoveChild i) emptyPartialVersion emptyPartialVersion),[],[],False) //TODO: versions...
+
+
+		onMessage (NxtServerInRemote (NxtUpdateChild pos m) (NVPVersion _ mv)) ss (NVTMultiple stv vs)//Route to the corresponding child
+			| pos >= length ss || pos < 0 = ([],ss,NVTMultiple stv vs,False) //Out of bounds, (maybe abort instead for the simulation)
+			# (ms,s,v,write) = editor.server.NxtEditorServer.onMessage (NxtServerInRemote m (childversion pos mv)) (ss !! pos) (vs !! pos)
+			= ([NxtServerOut (NxtUpdateChild pos message) (multiversion pos oldVersion) (multiversion pos newVersion)
+			   \\ (NxtServerOut message oldVersion newVersion) <-ms ], updateAt pos s ss, NVTMultiple stv (updateAt pos v vs), write)
+			//TODO: create the right version structure
+            where
+				multiversion pos v = NVPVersion Nothing [(pos,v)]
+
+		onMessage (NxtServerInRemote (NxtRemoveChild pos) (NVPVersion _ mv)) ss (NVTMultiple stv vs)
+			| pos >= length ss || pos < 0 = ([],ss,NVTMultiple stv vs, False) //Out of bounds, (maybe abort instead for the simulation)
+			= ([], removeAt pos ss, NVTMultiple stv (removeAt pos vs), True)
+
+
+		onMessage (NxtServerInRemote (NxtInsertChild pos pn) (NVPVersion _ mv)) ss (NVTMultiple stv vs)
+			| pos > length ss || pos < 0 = ([],ss,NVTMultiple stv vs, False) //Out of bounds, (maybe abort instead for the simulation)
+			# (s,v) = editor.server.NxtEditorServer.init pn (fst stv) 
+			= ([], insertAt pos s ss, NVTMultiple stv (insertAt pos v vs), True)
+
+
+    client = {init = init, onEvent = onEvent, onMessage = onMessage, state = state}
+	where
+		init ps
+			= {NxtDOMNode|attributes = attributes, children = [editor.client.NxtEditorClient.init p \\ p <- ps], history = []}
+		where	
+			attributes = 'DM'.fromList [("type","multiple")]
+
+		onEvent [n:ref] event dom=:{NxtDOMNode|children}
+			| n < 0 || n >= length children = ([],dom)
+			# (ms,child) = editor.client.NxtEditorClient.onEvent ref event (children !! n)
+			= ([NxtClientOut (NxtUpdateChild n message) (NVPVersion Nothing [(n,version)]) \\ (NxtClientOut message version) <- ms], {NxtDOMNode|dom & children = updateAt n child children})
+		onEvent _ _ dom
+			= ([],dom)
+
+		onMessage (NxtClientInRemote (NxtInsertChild pos pn) oldVersion newVersion) dom=:{NxtDOMNode|children} //TODO: Check structure versions...
+			# child = editor.client.NxtEditorClient.init pn
+			= ([],{NxtDOMNode|dom & children = insertAt pos child children})
+
+		onMessage (NxtClientInLocal (NxtInsertChild pos c)) dom=:{NxtDOMNode|children} //TODO: Revert and versioning
+			# child = editor.client.NxtEditorClient.init c
+			= ([NxtClientOut (NxtInsertChild pos c) emptyPartialVersion],{NxtDOMNode|dom & children = insertAt pos child children})
+
+		onMessage (NxtClientInRemote (NxtRemoveChild pos) oldVersion newVersion) dom=:{NxtDOMNode|children} //TODO: Check structure versions...
+			= ([],{NxtDOMNode|dom & children = removeAt pos children})
+
+		onMessage (NxtClientInLocal (NxtRemoveChild pos)) dom=:{NxtDOMNode|children} //TODO: should be able to revert to older version and send versions...
+			= ([NxtClientOut (NxtRemoveChild pos) emptyPartialVersion],{NxtDOMNode|dom & children = removeAt pos children})
+
+		onMessage (NxtClientInRemote (NxtUpdateChild pos m) oldVersion newVersion) dom=:{NxtDOMNode|children}
+			# (ms,child) = editor.client.NxtEditorClient.onMessage
+				(NxtClientInRemote m (selectPartialVersion pos oldVersion) (selectPartialVersion pos newVersion)) (children !! pos)
+			= ([(NxtClientOut (NxtUpdateChild pos message) emptyPartialVersion) \\ (NxtClientOut message version) <- ms] //TODO: Determine version
+			  ,{NxtDOMNode|dom & children = updateAt pos child children})
+
+		onMessage (NxtClientInLocal m) dom
+			= trace_n "UNIMPLEMENTED" ([],dom)
+
+		state dom=:{NxtDOMNode|children}
+			= map editor.client.NxtEditorClient.state children
+
+//Compose by juxtaposition, no need to specify interdependency
+glue ::
+		(NxtEditor p1 r1 w1 s1 c1 m1)
+        (NxtEditor p2 r2 w2 s2 c2 m2)
+        ->
+        (NxtEditor (p1,p2) (Maybe r1,Maybe r2) (Maybe w1, Maybe w2) (s1,s2) (c1,c2) (Maybe m1, Maybe m2))
+glue e1 e2 = {NxtEditor|server=server,client=client}
+where
+  server = {init=init,parameter=parameter,value=value,onRefresh=onRefresh,onMessage=onMessage}
+  where
+	init (p1,p2) mv
+		# (s1,vs1) = e1.server.NxtEditorServer.init p1 mv
+		# (s2,vs2) = e2.server.NxtEditorServer.init p2 mv
+		= ((s1,s2),NVTGlue vs1 vs2)
+
+	parameter (s1,s2) = (e1.server.NxtEditorServer.parameter s1, e2.server.NxtEditorServer.parameter s2)
+
+	value (s1,s2) = case (e1.server.NxtEditorServer.value s1, e2.server.NxtEditorServer.value s2) of
+		(Nothing,Nothing) = Nothing
+		(mb1,mb2) = Just (mb1,mb2)
+
+    onRefresh (mbr1,mbr2) rv (s1,s2) (NVTGlue sv1 sv2)
+       # (m1, s1, sv1, w1) = maybe ([],s1,sv1,False) (\r1 -> e1.server.NxtEditorServer.onRefresh r1 rv s1 sv1) mbr1
+       # (m2, s2, sv2, w2) = maybe ([],s2,sv2,False) (\r2 -> e2.server.NxtEditorServer.onRefresh r2 rv s2 sv2) mbr2
+       = (zipMessagesWithVersions m1 m2, (s1,s2), NVTGlue sv1 sv2, w1 || w2)
+
+    onMessage (NxtServerInLocal (mb1,mb2) vm) (s1,s2) (NVTGlue sv1 sv2)
+       # (ms1, s1, sv1, w1) = maybe ([],s1,sv1,False) (\m1 -> e1.server.NxtEditorServer.onMessage (NxtServerInLocal m1 vm) s1 sv1) mb1
+       # (ms2, s2, sv2, w2) = maybe ([],s2,sv2,False) (\m2 -> e2.server.NxtEditorServer.onMessage (NxtServerInLocal m2 vm) s2 sv2) mb2
+       = (zipMessagesWithVersions ms1 ms2, (s1,s2), NVTGlue sv1 sv2, w1 || w2)
+
+    onMessage (NxtServerInRemote (mb1,mb2) (NVPVersion _ cvs)) (s1,s2) (NVTGlue sv1 sv2)
+       # (ms1, s1, sv1, w1) = maybe ([],s1,sv1,False) (\m1 -> e1.server.NxtEditorServer.onMessage (NxtServerInRemote m1 (childversion 0 cvs)) s1 sv1) mb1
+       # (ms2, s2, sv2, w2) = maybe ([],s2,sv2,False) (\m2 -> e2.server.NxtEditorServer.onMessage (NxtServerInRemote m2 (childversion 1 cvs)) s2 sv2) mb2
+       = (zipMessagesWithVersions ms1 ms2, (s1,s2), NVTGlue sv1 sv2, w1 || w2)
+	
+  zipMessagesWithVersions [NxtServerOut x ovx nvx:xs] [NxtServerOut y ovy nvy:ys]
+	= [NxtServerOut (Just x, Just y) (NVPVersion Nothing [(0,ovx),(1,ovy)]) (NVPVersion Nothing [(0,nvx),(1,nvy)]):zipMessagesWithVersions xs ys]
+  zipMessagesWithVersions [] ys
+	= [NxtServerOut (Nothing,Just y) (NVPVersion Nothing [(1,ovy)]) (NVPVersion Nothing [(1,nvy)]) \\ (NxtServerOut y ovy nvy) <- ys]
+  zipMessagesWithVersions xs []
+	= [NxtServerOut (Just x,Nothing) (NVPVersion Nothing [(0,ovx)]) (NVPVersion Nothing [(0,nvx)]) \\ (NxtServerOut x ovx nvx) <- xs]
+ 
+  client = {init=init,onEvent=onEvent,onMessage=onMessage,state=state}
+  where
+    init (p1,p2)
+		= {NxtDOMNode|attributes=attributes,children = [e1.client.NxtEditorClient.init p1, e2.client.NxtEditorClient.init p2], history = []}
+	attributes = 'DM'.fromList [("type","glue")]
+
+    onEvent [0:ref] event dom=:{NxtDOMNode|children=[c1,c2]}
+      # (m1,c1) = e1.client.NxtEditorClient.onEvent ref event c1
+	  = ([NxtClientOut (Just message,Nothing) (NVPVersion Nothing [(0,version)]) \\ (NxtClientOut message version) <-m1],{NxtDOMNode|dom & children = [c1,c2]})
+    onEvent [1:ref] event dom=:{NxtDOMNode|children=[c1,c2]}
+      # (m2,c2) = e2.client.NxtEditorClient.onEvent ref event c2
+	  = ([NxtClientOut (Nothing,Just message) (NVPVersion Nothing [(1,version)]) \\ (NxtClientOut message version) <-m2],{NxtDOMNode|dom & children = [c1,c2]})
+	onEvent _ _ dom = ([],dom)
+
+    onMessage (NxtClientInLocal (mb1,mb2)) dom=:{NxtDOMNode|children=[c1,c2]}
+      # (m1,c1) = maybe ([],c1) (\m1 -> e1.client.NxtEditorClient.onMessage (NxtClientInLocal m1) c1) mb1
+      # (m2,c2) = maybe ([],c2) (\m2 -> e2.client.NxtEditorClient.onMessage (NxtClientInLocal m2) c2) mb2
+      = (zipClientOutMessages m1 m2, {NxtDOMNode|dom & children = [c1,c2]})
+
+    onMessage (NxtClientInRemote (mb1,mb2) (NVPVersion _ omvs) (NVPVersion _ nmvs)) dom=:{NxtDOMNode|children=[c1,c2]}
+      # (m1,c1) = maybe ([],c1) (\m1 -> e1.client.NxtEditorClient.onMessage (NxtClientInRemote m1 (childversion 0 omvs) (childversion 0 nmvs)) c1) mb1
+      # (m2,c2) = maybe ([],c2) (\m2 -> e2.client.NxtEditorClient.onMessage (NxtClientInRemote m2 (childversion 1 omvs) (childversion 1 nmvs)) c2) mb2
+      = (zipClientOutMessages m1 m2, {NxtDOMNode|dom & children = [c1,c2]})
+
+    state dom=:{NxtDOMNode|children=[c1,c2]}
+	  = (e1.client.NxtEditorClient.state c1, e2.client.NxtEditorClient.state c2)
+
+  zipClientOutMessages [NxtClientOut x vx:xs] [NxtClientOut y vy:ys]
+	= [NxtClientOut (Just x, Just y) (NVPVersion Nothing [(0,vx),(1,vy)]):zipClientOutMessages xs ys]
+  zipClientOutMessages [] ys
+	= [NxtClientOut (Nothing,Just y) (NVPVersion Nothing [(1,vy)]) \\ (NxtClientOut y vy) <- ys]
+  zipClientOutMessages xs []
+	= [NxtClientOut (Just x,Nothing) (NVPVersion Nothing [(0,vx)]) \\ (NxtClientOut x vx) <- xs]
+ 
+linkm ::
+	([s] (ContainerMsg p m) -> (Bool, [ContainerMsg p m]))
+	([c] (ContainerMsg p m) -> (Bool, [ContainerMsg p m]))
+	(NxtEditor [p] [Maybe r] [Maybe w] [s] [c] (ContainerMsg p m))
+	->
+	(NxtEditor [p] [Maybe r] [Maybe w] [s] [c] (ContainerMsg p m))
+linkm mserver mclient editor = {NxtEditor|server=server,client=client}
+where
+	server = {init=init,parameter=parameter,value=value,onRefresh=onRefresh,onMessage=onMessage}
+	where
+		init = editor.server.NxtEditorServer.init
+		parameter = editor.server.NxtEditorServer.parameter
+		value = editor.server.NxtEditorServer.value
+
+    	onRefresh rs rv ss (NVTMultiple v vs)
+			# (msgs, ss, NVTMultiple v vs, mbw)  = editor.server.NxtEditorServer.onRefresh rs rv ss (NVTMultiple v vs)
+			# (msgs, ss, v, vs, mbwm) = foldl modifyMsg ([],ss,v,vs,False) msgs
+			= (msgs, ss, NVTMultiple v vs, mbw || mbwm)
+
+		onMessage m ss (NVTMultiple v vs)
+			# (msgs, ss, NVTMultiple v vs, mbw) = editor.server.NxtEditorServer.onMessage m ss (NVTMultiple v vs)
+			# (msgs, ss,v,vs,mbwm) = foldl modifyMsg ([],ss,v,vs,False) msgs
+			= (msgs, ss, NVTMultiple v vs, mbw || mbwm)
+
+		modifyMsg (msgs,ss,v,vs,mbw) msg=:(NxtServerOut message oldVersion newVersion)
+			//Modify the outgoing messages
+			# (passOn,feedBack) = mserver ss message
+			//Feedback messages
+			# (feedbackOutput,ss,v,vs,mbwm) = foldl (feedBackMsg (maxMajorVersion newVersion)) ([],ss,v,vs,False) feedBack
+			= (msgs ++ (if passOn [NxtServerOut message oldVersion newVersion] []) ++ feedbackOutput, ss, v, vs, mbw || mbwm)
+
+		feedBackMsg vm (msgs,ss,v,vs,mbw) msg
+			# (emsgs,ss,NVTMultiple v vs,mbwm) = onMessage (NxtServerInLocal msg vm) ss (NVTMultiple v vs)
+			= (msgs ++ emsgs,ss,v,vs,mbw || mbwm)
+
+	client = {init=init,onEvent=onEvent,onMessage=onMessage,state=state}
+	where
+		init = editor.client.NxtEditorClient.init
+		state = editor.client.NxtEditorClient.state
+
+    	onEvent ref event dom
+			# (msgs,dom) = editor.client.NxtEditorClient.onEvent ref event dom
+			# (msgs,dom) = foldl modifyMsg ([],dom) msgs
+			= (msgs,dom)
+
+		onMessage msg dom
+			# (msgs,dom) = editor.client.NxtEditorClient.onMessage msg dom
+			# (msgs,dom) = foldl modifyMsg ([],dom) msgs
+			= (msgs,dom)
+
+		modifyMsg (msgs,dom) (NxtClientOut message version)
+			# cs = state dom
+			# (passOn,feedBack) = mclient cs message
+			# (feedbackOutput,dom) = foldl feedBackMsg ([],dom) feedBack
+			= (msgs ++ (if passOn [NxtClientOut message version] []) ++ feedbackOutput, dom)
+
+		feedBackMsg (msgs,dom) msg
+			# (emsgs,dom) = onMessage (NxtClientInLocal msg) dom
+			= (msgs ++ emsgs,dom)
+
+//Define the dependencies by defining feedback on messages
+//NOTE: Only one the last 'writes' to the data source are be returned, is this ok?
+linkg ::
+        //Rewrite from server to client with feedback to server
+        (s1 s2 (Maybe m1, Maybe m2) -> (Bool, [(Maybe m1, Maybe m2)]))
+        //Rewrite from client to server with feedback to client
+        (c1 c2 (Maybe m1, Maybe m2) -> (Bool, [(Maybe m1, Maybe m2)])) //Pass on, feedback message
+        (NxtEditor p (Maybe r1,Maybe r2) (Maybe w1, Maybe w2) (s1,s2) (c1,c2) (Maybe m1, Maybe m2))
+        ->
+        (NxtEditor p (Maybe r1,Maybe r2) (Maybe w1, Maybe w2) (s1,s2) (c1,c2) (Maybe m1, Maybe m2))
+
+linkg modServerToClient modClientToServer editor = {NxtEditor|server=server,client=client}
+where
+	server = {init=init,parameter=parameter,value=value,onRefresh=onRefresh,onMessage=onMessage}
+	where
+		init = editor.server.NxtEditorServer.init
+		parameter = editor.server.NxtEditorServer.parameter
+		value = editor.server.NxtEditorServer.value
+
+    	onRefresh (r1,r2) rv (s1,s2) (NVTGlue v1 v2)
+			# (msgs,(s1,s2),NVTGlue v1 v2,mbw) = editor.server.NxtEditorServer.onRefresh (r1,r2) rv (s1,s2) (NVTGlue v1 v2)
+			# (msgs,(s1,s2),(v1,v2),mbwm) = foldl modifyMsg ([],(s1,s2),(v1,v2),False) msgs
+			= (msgs, (s1,s2),NVTGlue v1 v2, mbw || mbwm)
+
+		onMessage m (s1,s2) (NVTGlue v1 v2)
+			# (msgs,(s1,s2), NVTGlue v1 v2, mbw) = editor.server.NxtEditorServer.onMessage m (s1,s2) (NVTGlue v1 v2)
+			# (msgs,(s1,s2), (v1,v2), mbwm) = foldl modifyMsg ([],(s1,s2),(v1,v2),False) msgs 
+			= (msgs,(s1,s2), NVTGlue v1 v2,  mbw || mbwm)
+
+		modifyMsg (msgs,(s1,s2),(v1,v2),mbw) msg=:(NxtServerOut message oldVersion newVersion)
+			//Modify the outgoing messages
+			# (passOn,feedBack) = modServerToClient s1 s2 message
+			# (feedbackOutput,(s1,s2),(v1,v2),mbwm) = foldl (feedBackMsg (maxMajorVersion newVersion)) ([], (s1,s2),(v1,v2), False) feedBack
+			= (msgs ++ (if passOn [NxtServerOut message oldVersion newVersion] []) ++ feedbackOutput, (s1,s2), (v1,v2), mbw || mbwm)
+
+		feedBackMsg vm (msgs,(s1,s2),(v1,v2),mbw) msg
+			# (emsgs,(s1,s2),NVTGlue v1 v2,mbwm) = onMessage (NxtServerInLocal msg vm) (s1,s2) (NVTGlue v1 v2)
+			= (msgs ++ emsgs,(s1,s2),(v1,v2), mbw || mbwm)
+
+	client = {init=init,onEvent=onEvent,onMessage=onMessage,state=state}
+	where
+		init = editor.client.NxtEditorClient.init
+		state = editor.client.NxtEditorClient.state
+
+    	onEvent ref event dom
+			# (msgs,dom) = editor.client.NxtEditorClient.onEvent ref event dom
+			# (msgs,dom) = foldl modifyMsg ([],dom) msgs
+			= (msgs,dom)
+
+		onMessage msg dom
+			# (msgs,dom) = editor.client.NxtEditorClient.onMessage msg dom
+			# (msgs,dom) = foldl modifyMsg ([],dom) msgs
+			= (msgs,dom)
+
+		modifyMsg (msgs,dom) (NxtClientOut message version)
+			# (c1,c2) = state dom
+			# (passOn,feedBack) = modClientToServer c1 c2 message
+			# (feedbackOutput,dom) = foldl feedBackMsg ([],dom) feedBack
+			= (msgs ++ (if passOn [NxtClientOut message version] []) ++ feedbackOutput, dom)
+
+		feedBackMsg (msgs,dom) msg
+			# (emsgs,dom) = onMessage (NxtClientInLocal msg) dom
+			= (msgs ++ emsgs,dom)
+
+mapp :: (pa -> pb, pb -> pa) (NxtEditor pa r w s c m) -> (NxtEditor pb r w s c m) 
+mapp (t,f) e = {NxtEditor|server = server, client = client}
+where
+	server = {init = init, parameter = parameter, value = e.server.NxtEditorServer.value
+		, onRefresh = e.server.NxtEditorServer.onRefresh, onMessage = e.server.NxtEditorServer.onMessage}
+    where
+		init p = e.server.NxtEditorServer.init (f p)
+		parameter s = t (e.server.NxtEditorServer.parameter s)
+
+	client = {init = init, onEvent = e.client.NxtEditorClient.onEvent
+		, onMessage = e.client.NxtEditorClient.onMessage, state = e.client.NxtEditorClient.state }
+	where
+		init p = e.client.NxtEditorClient.init (f p)
+
+mapr :: (rb -> ra) (NxtEditor p ra w s c m) -> (NxtEditor p rb w s c m) 
+mapr t e = {NxtEditor|server = server, client = e.client}
+where
+	server = {init = e.server.NxtEditorServer.init, parameter = e.server.NxtEditorServer.parameter, value = e.server.NxtEditorServer.value
+		, onRefresh = onRefresh, onMessage = e.server.NxtEditorServer.onMessage}
+	where
+		onRefresh r s = e.server.NxtEditorServer.onRefresh (t r) s
+
+mapw :: (wa -> Maybe wb) (NxtEditor p r wa s c m) -> (NxtEditor p r wb s c m)
+mapw f e = {NxtEditor|server = server, client = e.client}
+where
+	server = {init = e.server.NxtEditorServer.init, parameter = e.server.NxtEditorServer.parameter, value = value
+		, onRefresh = e.server.NxtEditorServer.onRefresh, onMessage = e.server.NxtEditorServer.onMessage}
+	where
+		value s = maybe Nothing f (e.server.NxtEditorServer.value s)
+
+maps :: (sa -> sb, sb -> sa) (NxtEditor p r w sa c m) -> (NxtEditor p r w sb c m)
+maps (t,f) e = {NxtEditor|server = server, client = e.client}
+where
+	server = {init = init, parameter = parameter, value = value, onRefresh = onRefresh, onMessage = onMessage}
+	where
+		init p rv
+			# (s,v) = e.server.NxtEditorServer.init p rv
+			= (t s,v)
+
+		parameter s = e.server.NxtEditorServer.parameter (f s)
+		value s = e.server.NxtEditorServer.value (f s)
+		onRefresh r rv s v
+			# (ms,s,v, w) = e.server.NxtEditorServer.onRefresh r rv (f s) v
+			= (ms,t s,v, w)
+		onMessage m s v
+			# (ms,s,v,w) = e.server.NxtEditorServer.onMessage m (f s) v
+			= (ms,t s,v,w)
+
+mapc :: (ca -> cb, cb -> ca) (NxtEditor p r w s ca m) -> (NxtEditor p r w s cb m)
+mapc (t,_) e = {NxtEditor|server = e.server, client = client}
+where
+	client = {init = init, onEvent = e.client.NxtEditorClient.onEvent
+		, onMessage = e.client.NxtEditorClient.onMessage, state = state }
+	where
+		init p = e.client.NxtEditorClient.init p
+		state dom = t (e.client.NxtEditorClient.state dom)
+
+//FIXME: This can't be right, version information should be mapped together with the messages
+mapm :: (ma -> mb, mb -> ma) (NxtEditor p r w s c ma) -> (NxtEditor p r w s c mb)
+mapm (t,f) e = {NxtEditor|server = server, client = client}
+where
+	server = {init = e.server.NxtEditorServer.init, parameter = e.server.NxtEditorServer.parameter, value = e.server.NxtEditorServer.value
+		, onRefresh = onRefresh, onMessage = onMessage}
+	where
+		onRefresh r rv s v
+			# (ms,s,v,w) = e.server.NxtEditorServer.onRefresh r rv s v
+			= ([NxtServerOut (t m) oldVersion newVersion \\ NxtServerOut m oldVersion newVersion <- ms], s,v,w)
+
+		onMessage m s v
+			# m = case m of 
+				(NxtServerInRemote mm mv) = NxtServerInRemote (f mm) mv
+				(NxtServerInLocal mm rv) = NxtServerInLocal (f mm) rv
+			# (ms,s,v,w) = e.server.NxtEditorServer.onMessage m s v
+			= ([NxtServerOut (t m) oldVersion newVersion \\ NxtServerOut m oldVersion newVersion <- ms],s,v,w)
+
+	client = {init = e.client.NxtEditorClient.init, onEvent = onEvent
+		, onMessage = onMessage, state = e.client.NxtEditorClient.state }
+	where
+		onEvent ref ev dom
+			# (ms,dom) = e.client.NxtEditorClient.onEvent ref ev dom
+			= ([NxtClientOut (t m) version \\ NxtClientOut m version <- ms],dom)
+		onMessage m dom
+			# m = case m of 
+				(NxtClientInRemote mm ov nv) = NxtClientInRemote (f mm) ov nv
+				(NxtClientInLocal mm) = NxtClientInLocal (f mm)
+			# (ms,dom) = e.client.NxtEditorClient.onMessage m dom
+			= ([NxtClientOut (t m) version \\ NxtClientOut m version <- ms],dom)
+mapg ::
+		((p1,p2) -> p, p -> (p1,p2))                                       //Fuse parameter
+		((Maybe w1, Maybe w2) -> Maybe w, r -> (r1,r2))                          //Fuse read/write
+        ((c1,c2) -> c, c -> (c1,c2))                                       //Fuse client configuration
+        ((s1,s2) -> s, s -> (s1,s2))                                       //Fuse server state
+        ((Maybe m1, Maybe m2) -> (Maybe m), m -> (Maybe m1, Maybe m2))     //Fuse messages
+
+        (NxtEditor (p1,p2) (r1,r2) (Maybe w1, Maybe w2) (s1,s2) (c1,c2) (Maybe m1, Maybe m2))
+        ->
+        (NxtEditor p r w s c m)
+mapg mp (mw,mr) mc ms (mmt,mmf) editor
+	= mapm (fromJust o mmt, mmf) $ maps ms $ mapc mc $ mapw mw $ mapr mr $ mapp mp $ editor
+
+validate :: (s -> Bool) (NxtEditor p r w s c m) -> (NxtEditor p r w (s,Bool) (c,Bool) (Either m Bool))
+validate checkfun editor = {client=client,server=server}
+where
+	server = {init=init,parameter=parameter,value=value,onRefresh=onRefresh,onMessage=onMessage}
+	where
+		init p rv
+			# (s,v) = editor.server.NxtEditorServer.init p rv
+			= ((s,checkfun s),v)
+
+		parameter s
+			= editor.server.NxtEditorServer.parameter (fst s) 
+		value (s,valid)
+			= if (not valid) Nothing (editor.server.NxtEditorServer.value s)
+
+    	onRefresh rs rv (s,valid) v
+			# (msgs, s, v`, mbw)  = editor.server.NxtEditorServer.onRefresh rs rv s v
+			# valid` = checkfun s
+			# msgs` = [NxtServerOut (Left m) ov nv \\ (NxtServerOut m ov nv) <- msgs]
+					++ if (valid <> valid`) [NxtServerOut (Right valid`) (toPartialVersion v) (toPartialVersion v`)] []
+			= (msgs`, (s,valid`), v`, mbw)
+
+		onMessage (NxtServerInRemote (Left m) mv) (s,valid) v
+			# (msgs, s, v`, mbw)  = editor.server.NxtEditorServer.onMessage (NxtServerInRemote m mv) s v 
+			# valid` = checkfun s
+			# msgs` = [NxtServerOut (Left m) ov nv \\ (NxtServerOut m ov nv) <- msgs]
+					++ if (valid <> valid`) [NxtServerOut (Right valid`) (toPartialVersion v) (toPartialVersion v`)] []
+			= (msgs`, (s,valid`), v`, mbw)
+
+	client = {init=init,onEvent=onEvent,onMessage=onMessage,state=state}
+	where
+		init p
+			# dom = editor.client.NxtEditorClient.init p
+			= {NxtDOMNode|dom & attributes = 'DM'.put "valid" "true" dom.NxtDOMNode.attributes}
+
+		state dom = (editor.client.NxtEditorClient.state dom, False)
+
+    	onEvent ref event dom
+			# (msgs,dom) = editor.client.NxtEditorClient.onEvent ref event dom
+			= ([NxtClientOut (Left m) v \\ (NxtClientOut m v) <- msgs],dom)
+
+		onMessage (NxtClientInRemote (Right valid) ov nv) dom
+			= ([],{NxtDOMNode|dom & attributes = 'DM'.put "valid" (if valid "true" "false") dom.NxtDOMNode.attributes})
+		onMessage (NxtClientInRemote (Left m) ov nv) dom
+			# (msgs,dom) = editor.client.NxtEditorClient.onMessage (NxtClientInRemote m ov nv) dom
+			= ([NxtClientOut (Left m) v \\ (NxtClientOut m v) <- msgs],dom)
+
+//Simulation
+simulate :: (NxtEditor p r w s c m) p (Maybe r) -> Task () | iTask r & iTask w & iTask s & iTask c & iTask m & EditMessage m
+simulate editor p mbr
+  = withShared initNetworkState
+  \networkState ->
+    withShared initServerState
+  \serverState ->
+    withShared initClientState
+  \clientState ->
+       allTasks
+		[simulateServer editor serverState networkState <<@ Title "Server" @! ()
+		,viewNetwork networkState <<@ Title "Network" @! ()
+		,simulateClient editor clientState networkState <<@ Title "Client" @! ()			
+		] <<@ ArrangeHorizontal @! ()
+where
+	(initClientState,initServerState,initNetworkState) = initStates
+	where
+		initReadVersion = 0
+		initStates
+			# (s,v) = editor.server.NxtEditorServer.init p initReadVersion
+			# cs = editor.client.NxtEditorClient.init p 
+			# (s2c,s,sv,rv) = case mbr of
+				Nothing = ([],s,v,initReadVersion)
+				Just r
+					# rv = initReadVersion + 1
+					# (ms,s,sv,_) = editor.server.NxtEditorServer.onRefresh r rv s v
+					= (ms,s,sv,rv)
+			= (cs,initVersions s rv sv, (map encodeEditMessage s2c,[]))
+
+		initVersions s rv sv = {state = s, readVersion = rv, stateVersion = sv}
+
+simulateServer editor serverState networkState
+   = viewSharedInformation () [ViewAs serverView] serverState
+   >^* [OnAction (Action "Refresh") (always (doServerRefresh <<@ InWindow))
+       ,OnAction (Action "Message") (always doServerMessage)
+       ]
+where
+	serverView s = (s,editor.server.NxtEditorServer.value s.VersionedServerState.state)
+
+	doServerRefresh
+		=  enterInformation "Enter the refresh value" []
+		>>= \v -> upd (setStates v) (serverState >*< networkState)
+	where
+		setStates