package-lock.json

@@ -24,6 +24,7 @@
         "@types/react": "^19.1.13",
         "@types/react-dom": "^19.1.9",
         "@vitejs/plugin-react": "^5.0.3",
+        "baseline-browser-mapping": "^2.9.11",
         "eslint": "^9.36.0",
         "eslint-plugin-react-hooks": "^5.2.0",
         "eslint-plugin-react-refresh": "^0.4.20",
@@ -3698,9 +3699,9 @@
       "license": "MIT"
     },
     "node_modules/baseline-browser-mapping": {
-      "version": "2.8.6",
-      "resolved": "https://registry.npmjs.org/baseline-browser-mapping/-/baseline-browser-mapping-2.8.6.tgz",
-      "integrity": "sha512-wrH5NNqren/QMtKUEEJf7z86YjfqW/2uw3IL3/xpqZUC95SSVIFXYQeeGjL6FT/X68IROu6RMehZQS5foy2BXw==",
+      "version": "2.9.11",
+      "resolved": "https://registry.npmjs.org/baseline-browser-mapping/-/baseline-browser-mapping-2.9.11.tgz",
+      "integrity": "sha512-Sg0xJUNDU1sJNGdfGWhVHX0kkZ+HWcvmVymJbj6NSgZZmW/8S9Y2HQ5euytnIgakgxN6papOAWiwDo1ctFDcoQ==",
       "dev": true,
       "license": "Apache-2.0",
       "bin": {
@@ -4869,9 +4870,9 @@
       }
     },
     "node_modules/glob": {
-      "version": "10.4.5",
-      "resolved": "https://registry.npmjs.org/glob/-/glob-10.4.5.tgz",
-      "integrity": "sha512-7Bv8RF0k6xjo7d4A/PxYLbUCfb6c+Vpd2/mB2yRDlew7Jb5hEXiCD9ibfO7wpk8i4sevK6DFny9h7EYbM3/sHg==",
+      "version": "10.5.0",
+      "resolved": "https://registry.npmjs.org/glob/-/glob-10.5.0.tgz",
+      "integrity": "sha512-DfXN8DfhJ7NH3Oe7cFmu3NCu1wKbkReJ8TorzSAFbSKrlNaQSKfIzqYqVY8zlbs2NLBbWpRiU52GX2PbaBVNkg==",
       "dev": true,
       "license": "ISC",
       "dependencies": {

package.json

@@ -28,6 +28,7 @@
     "@types/react": "^19.1.13",
     "@types/react-dom": "^19.1.9",
     "@vitejs/plugin-react": "^5.0.3",
+    "baseline-browser-mapping": "^2.9.11",
     "eslint": "^9.36.0",
     "eslint-plugin-react-hooks": "^5.2.0",
     "eslint-plugin-react-refresh": "^0.4.20",

src/pages/VisProgPage/visualProgrammingUI/HandleRuleLogic.ts

@@ -0,0 +1,110 @@
+import {type Connection} from "@xyflow/react";
+import {useEffect} from "react";
+import useFlowStore from "./VisProgStores.tsx";
+
+export type ConnectionContext = {
+  connectionCount: number;
+  source: {
+    id: string;
+    handleId: string;
+  }
+  target: {
+    id: string;
+    handleId: string;
+  }
+}
+
+export type HandleRule = (
+  connection: Connection,
+  context: ConnectionContext
+) => RuleResult;
+
+/**
+ * A RuleResult describes the outcome of validating a HandleRule
+ *
+ * if a rule is not satisfied, the RuleResult includes a message that is used inside a tooltip
+ * that tells the user why their attempted connection is not possible
+ */
+export type RuleResult =
+  | { isSatisfied: true }
+  | { isSatisfied: false, message: string };
+
+/**
+ * default RuleResults, can be used to create more readable handleRule definitions
+ */
+export const ruleResult = {
+  satisfied: { isSatisfied: true } as RuleResult,
+  unknownError: {isSatisfied: false, message: "Unknown Error" } as RuleResult,
+  notSatisfied: (message: string) : RuleResult => { return {isSatisfied: false, message: message } }
+}
+
+
+const evaluateRules = (
+  rules: HandleRule[],
+  connection: Connection,
+  context: ConnectionContext
+) : RuleResult => {
+  // evaluate the rules and check if there is at least one unsatisfied rule
+  const failedRule = rules
+    .map(rule => rule(connection, context))
+    .find(result => !result.isSatisfied);
+
+  return failedRule ? ruleResult.notSatisfied(failedRule.message) : ruleResult.satisfied;
+}
+
+
+/**
+ * !DOCUMENTATION NOT FINISHED!
+ *
+ * - The output is a single RuleResult, meaning we only show one error message.
+ * Error messages are prioritised by listOrder; Thus, if multiple HandleRules evaluate to false,
+ * we only send the error message of the first failed rule in the target's registered list of rules.
+ *
+ * @param {string} nodeId
+ * @param {string} handleId
+ * @param type
+ * @param {HandleRule[]} rules
+ * @returns {(c: Connection) => RuleResult} a function that validates an attempted connection
+ */
+export function useHandleRules(
+  nodeId: string,
+  handleId: string,
+  type: "source" | "target",
+  rules: HandleRule[],
+) : (c: Connection) => RuleResult {
+  const edges = useFlowStore.getState().edges;
+  const registerRules = useFlowStore((state) => state.registerRules);
+
+
+  useEffect(() => {
+    registerRules(nodeId, handleId, rules);
+    // the following eslint disable is required as it wants us to use all possible dependencies for the useEffect statement,
+    // however this would result in an infinite loop because it would change one of its own dependencies
+    // so we only use those dependencies that we don't change ourselves
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [handleId, nodeId, registerRules]);
+
+  return (connection: Connection) => {
+    // inside this function we consider the target to be the target of the isValidConnection event
+    // and not the target in the actual connection
+    const { target, targetHandle } = type === "source"
+      ? connection
+      : { target: connection.source, targetHandle: connection.sourceHandle };
+
+    if (!targetHandle) {throw new Error("No target handle was provided");}
+
+    const targetConnections = edges.filter(edge => edge.target === target && edge.targetHandle === targetHandle);
+
+
+    // we construct the connectionContext
+    const context: ConnectionContext = {
+      connectionCount: targetConnections.length,
+      source: {id: nodeId, handleId: handleId},
+      target: {id: target, handleId: targetHandle},
+    };
+    const targetRules = useFlowStore.getState().getTargetRules(target, targetHandle);
+
+    // finally we return a function that evaluates all rules using the created context
+    return evaluateRules(targetRules, connection, context);
+  };
+}

src/pages/VisProgPage/visualProgrammingUI/HandleRules.ts

@@ -0,0 +1,45 @@
+import {
+  type HandleRule,
+  ruleResult
+} from "./HandleRuleLogic.ts";
+import useFlowStore from "./VisProgStores.tsx";
+
+
+/**
+ * this specifies what types of nodes can make a connection to a handle that uses this rule
+ */
+export function allowOnlyConnectionsFromType(nodeTypes: string[]) : HandleRule  {
+  return ((_, {source}) => {
+    const sourceType = useFlowStore.getState().nodes.find(node => node.id === source.id)!.type!;
+    return nodeTypes.find(type => sourceType === type)
+      ? ruleResult.satisfied
+      : ruleResult.notSatisfied(`the target doesn't allow connections from nodes with type: ${sourceType}`);
+  })
+}
+
+/**
+ * similar to allowOnlyConnectionsFromType,
+ * this is a more specific variant that allows you to restrict connections to specific handles on each nodeType
+ */
+//
+export function allowOnlyConnectionsFromHandle(handles: {nodeType: string, handleId: string}[]) : HandleRule  {
+  return ((_, {source}) => {
+    const sourceNode = useFlowStore.getState().nodes.find(node => node.id === source.id)!;
+    return handles.find(handle => sourceNode.type === handle.nodeType && source.handleId === handle.handleId)
+      ? ruleResult.satisfied
+      : ruleResult.notSatisfied(`the target doesn't allow connections from nodes with type: ${sourceNode.type}`);
+  })
+}
+
+
+/**
+ * This rule prevents a node from making a connection between its own handles
+ */
+export const noSelfConnections : HandleRule =
+  (connection, _) => {
+    return connection.source !== connection.target
+      ? ruleResult.satisfied
+      : ruleResult.notSatisfied("nodes are not allowed to connect to themselves");
+  }
+
+

src/pages/VisProgPage/visualProgrammingUI/VisProgStores.tsx

@@ -8,6 +8,7 @@ import {
   type Edge,
   type XYPosition,
 } from '@xyflow/react';
+import '@xyflow/react/dist/style.css';
 import type { FlowState } from './VisProgTypes';
 import {
   NodeDefaults,
@@ -50,8 +51,9 @@ function createNode(id: string, type: string, position: XYPosition, data: Record
 
   const initialNodes : Node[] = [startNode, endNode, initialPhaseNode,];
 
-// * Initial edges * /
-const initialEdges: Edge[] = []; // no initial edges as edge connect events don't fire when using initial edges
+// Initial edges, leave empty as setting initial edges...
+// ...breaks logic that is dependent on connection events
+const initialEdges: Edge[] = [];
 
 
 /**
@@ -84,8 +86,9 @@ const useFlowStore = create<FlowState>(UndoRedo((set, get) => ({
    */
   onNodesChange: (changes) => set({nodes: applyNodeChanges(changes, get().nodes)}),
 
-  onEdgesDelete: (edges) => {
+  onNodesDelete: (nodes) => nodes.forEach(node => get().unregisterNodeRules(node.id)),
 
+  onEdgesDelete: (edges) => {
     // we make sure any affected nodes get updated to reflect removal of edges
     edges.forEach((edge) => {
         const nodes = get().nodes;
@@ -231,6 +234,79 @@ const useFlowStore = create<FlowState>(UndoRedo((set, get) => ({
   past: [],
   future: [],
   isBatchAction: false,
+
+  // handleRuleRegistry definitions
+  /**
+   * stores registered rules for handle connection validation
+   */
+  ruleRegistry: new Map(),
+
+  /**
+   * gets the rules registered by that handle described by the given node and handle ids
+   *
+   * @param {string} targetNodeId
+   * @param {string} targetHandleId
+   * @returns {HandleRule[]}
+   */
+  getTargetRules: (targetNodeId, targetHandleId) => {
+    const key = `${targetNodeId}:${targetHandleId}`;
+    const rules = get().ruleRegistry.get(key);
+
+    // helper function that handles a situation where no rules were registered
+    const missingRulesResponse = () => {
+      console.warn(
+        `No rules were registered for the following handle "${key}"!
+          returning and empty handleRule[] to avoid crashing`);
+      return []
+    }
+
+    return rules
+      ? rules
+      : missingRulesResponse()
+  },
+
+  /**
+   * registers a handle's connection rules
+   *
+   * @param {string} nodeId
+   * @param {string} handleId
+   * @param {HandleRule[]} rules
+   */
+  registerRules: (nodeId, handleId, rules) => {
+      const registry = get().ruleRegistry;
+      registry.set(`${nodeId}:${handleId}`, rules);
+      set({ ruleRegistry: registry }) ;
+  },
+
+  /**
+   * unregisters a handles connection rules
+   *
+   * @param {string} nodeId
+   * @param {string} handleId
+   */
+  unregisterHandleRules: (nodeId, handleId) => {
+    set( () => {
+      const registry = get().ruleRegistry;
+      registry.delete(`${nodeId}:${handleId}`);
+      return { ruleRegistry: registry };
+    })
+  },
+
+  /**
+   * unregisters connection rules for all handles on the given node
+   * used for cleaning up rules on node deletion
+   *
+   * @param {string} nodeId
+   */
+  unregisterNodeRules: (nodeId) => {
+    set(() => {
+      const registry = get().ruleRegistry;
+      registry.forEach((_,key) => {
+        if (key.startsWith(`${nodeId}:`)) registry.delete(key)
+      })
+      return { ruleRegistry: registry };
+    })
+  }
   }))
 );
 

src/pages/VisProgPage/visualProgrammingUI/VisProgTypes.tsx

@@ -1,5 +1,15 @@
 // VisProgTypes.ts
-import type {Edge, OnNodesChange, OnEdgesChange, OnConnect, OnReconnect, Node, OnEdgesDelete} from '@xyflow/react';
+import type {
+  Edge,
+  OnNodesChange,
+  OnEdgesChange,
+  OnConnect,
+  OnReconnect,
+  Node,
+  OnEdgesDelete,
+  OnNodesDelete
+} from '@xyflow/react';
+import type {HandleRule} from "./HandleRuleLogic.ts";
 import type { NodeTypes } from './NodeRegistry';
 import type {FlowSnapshot} from "./EditorUndoRedo.ts";
 
@@ -31,6 +41,8 @@ export type FlowState = {
   /** Handler for changes to nodes triggered by ReactFlow */
   onNodesChange: OnNodesChange;
 
+  onNodesDelete: OnNodesDelete;
+
   onEdgesDelete: OnEdgesDelete;
 
   /** Handler for changes to edges triggered by ReactFlow */
@@ -82,7 +94,9 @@ export type FlowState = {
    * @param node - the Node object to add
    */
   addNode: (node: Node) => void;
+} & UndoRedoState & HandleRuleRegistry;
 
+export type UndoRedoState = {
   // UndoRedo Types
   past: FlowSnapshot[];
   future: FlowSnapshot[];
@@ -92,4 +106,27 @@ export type FlowState = {
   endBatchAction: () => void;
   undo: () => void;
   redo: () => void;
-};
+}
+
+export type HandleRuleRegistry = {
+  ruleRegistry: Map<string, HandleRule[]>;
+
+  getTargetRules: (
+    targetNodeId: string,
+    targetHandleId: string
+  ) => HandleRule[];
+
+  registerRules: (
+    nodeId: string,
+    handleId: string,
+    rules: HandleRule[]
+  ) => void;
+
+  unregisterHandleRules: (
+    nodeId: string,
+    handleId: string
+  ) => void;
+
+  // cleans up all registered rules of all handles of the provided node
+  unregisterNodeRules: (nodeId: string) => void
+}

src/pages/VisProgPage/visualProgrammingUI/components/CustomNodeHandles.tsx

@@ -1,30 +0,0 @@
-import {
-  Handle,
-  useNodeConnections,
-  type HandleType,
-  type Position
-} from '@xyflow/react';
-
-
-const LimitedConnectionCountHandle = (props: {
-  node_id: string,
-  type: HandleType,
-  position: Position,
-  connection_count: number,
-  id?: string
-}) => {
-  const connections = useNodeConnections({
-    id: props.node_id,
-    handleType: props.type,
-    handleId: props.id,
-  });
-
-  return (
-    <Handle
-      {...props}
-      isConnectable={connections.length < props.connection_count}
-    />
-  );
-};
-
-export default LimitedConnectionCountHandle;

src/pages/VisProgPage/visualProgrammingUI/components/RuleBasedHandle.module.css

@@ -0,0 +1,34 @@
+:global(.react-flow__handle.connected) {
+    background: lightgray;
+    border-color: green;
+    filter: drop-shadow(0 0 0.25rem green);
+}
+
+:global(.singleConnectionHandle.connected) {
+    background: #55dd99;
+}
+
+:global(.react-flow__handle.unconnected){
+    background: lightgray;
+    border-color: gray;
+}
+
+:global(.singleConnectionHandle.unconnected){
+    background: lightsalmon;
+    border-color: #ff6060;
+    filter: drop-shadow(0 0 0.25rem #ff6060);
+}
+
+:global(.react-flow__handle.connectingto) {
+    background: #ff6060;
+    border-color: coral;
+    filter: drop-shadow(0 0 0.25rem coral);
+}
+
+:global(.react-flow__handle.valid) {
+    background: #55dd99;
+    border-color: green;
+    filter: drop-shadow(0 0 0.25rem green);
+}
+
+

src/pages/VisProgPage/visualProgrammingUI/components/RuleBasedHandle.tsx

@@ -0,0 +1,88 @@
+import {
+  Handle,
+  type HandleProps,
+  type Connection,
+  useNodeId, useNodeConnections
+} from '@xyflow/react';
+import {useState} from 'react';
+import { type HandleRule, useHandleRules} from "../HandleRuleLogic.ts";
+import "./RuleBasedHandle.module.css";
+
+
+
+export function MultiConnectionHandle({
+  id,
+  type,
+  rules = [],
+  ...otherProps
+} : HandleProps & { rules?: HandleRule[]}) {
+  let nodeId = useNodeId();
+  // this check is used to make sure that the handle code doesn't break when used inside a test,
+  // since useNodeId would be undefined if the handle is not used inside a node
+  nodeId = nodeId ? nodeId : "mockId";
+  const validate = useHandleRules(nodeId, id!, type!, rules);
+
+
+  const connections = useNodeConnections({
+    id: nodeId,
+    handleType: type,
+    handleId: id!
+  })
+
+  // initialise the handles state with { isValid: true } to show that connections are possible
+  const [handleState, setHandleState] = useState<{ isSatisfied: boolean, message?: string }>({ isSatisfied: true });
+
+  return (
+    <Handle
+      {...otherProps}
+      id={id}
+      type={type}
+      className={"multiConnectionHandle" + (connections.length === 0 ? " unconnected" : " connected")}
+      isValidConnection={(connection) => {
+        const result = validate(connection as Connection);
+        setHandleState(result);
+        return result.isSatisfied;
+      }}
+      title={handleState.message}
+    />
+  );
+}
+
+export function SingleConnectionHandle({
+  id,
+  type,
+  rules = [],
+  ...otherProps
+} : HandleProps & { rules?: HandleRule[]}) {
+  let nodeId = useNodeId();
+  // this check is used to make sure that the handle code doesn't break when used inside a test,
+  // since useNodeId would be undefined if the handle is not used inside a node
+  nodeId = nodeId ? nodeId : "mockId";
+  const validate = useHandleRules(nodeId, id!, type!, rules);
+
+  const connections = useNodeConnections({
+    id: nodeId,
+    handleType: type,
+    handleId: id!
+  })
+
+  // initialise the handles state with { isValid: true } to show that connections are possible
+  const [handleState, setHandleState] = useState<{ isSatisfied: boolean, message?: string }>({ isSatisfied: true });
+
+  return (
+    <Handle
+      {...otherProps}
+      id={id}
+      type={type}
+      className={"singleConnectionHandle" + (connections.length === 0 ? " unconnected" : " connected")}
+      isConnectable={connections.length === 0}
+      isValidConnection={(connection) => {
+        const result = validate(connection as Connection);
+        setHandleState(result);
+        return result.isSatisfied;
+      }}
+      title={handleState.message}
+    />
+  );
+}
+

src/pages/VisProgPage/visualProgrammingUI/nodes/BasicBeliefNode.tsx

@@ -1,11 +1,12 @@
 import {
-  Handle,
   type NodeProps,
   Position,
   type Node,
 } from '@xyflow/react';
 import { Toolbar } from '../components/NodeComponents';
 import styles from '../../VisProg.module.css';
+import {MultiConnectionHandle} from "../components/RuleBasedHandle.tsx";
+import {allowOnlyConnectionsFromType} from "../HandleRules.ts";
 import useFlowStore from '../VisProgStores';
 import { TextField } from '../../../../components/TextField';
 import { MultilineTextField } from '../../../../components/MultilineTextField';
@@ -183,7 +184,9 @@ export default function BasicBeliefNode(props: NodeProps<BasicBeliefNode>) {
                       />
           </div>
           )}
-        <Handle type="source" position={Position.Right} id="source"/>
+        <MultiConnectionHandle type="source" position={Position.Right} id="source" rules={[
+          allowOnlyConnectionsFromType(["norm", "trigger"]),
+        ]}/>
       </div>
     </>
   );

src/pages/VisProgPage/visualProgrammingUI/nodes/EndNode.tsx

@@ -3,9 +3,11 @@ import {
   Position,
   type Node,
 } from '@xyflow/react';
-import LimitedConnectionCountHandle from "../components/CustomNodeHandles.tsx";
 import { Toolbar } from '../components/NodeComponents';
 import styles from '../../VisProg.module.css';
+import {SingleConnectionHandle} from "../components/RuleBasedHandle.tsx";
+import {allowOnlyConnectionsFromType} from "../HandleRules.ts";
+
 
 
 /**
@@ -32,13 +34,9 @@ export default function EndNode(props: NodeProps<EndNode>) {
         <div className={"flex-row gap-sm"}>
         End
         </div>
-        <LimitedConnectionCountHandle
-          node_id={props.id}
-          type="target"
-          position={Position.Left}
-          connection_count={1}
-          id="target"
-        />
+        <SingleConnectionHandle type="target" position={Position.Left} id="target" rules={[
+          allowOnlyConnectionsFromType(["phase"])
+        ]}/>
       </div>
     </>
   );

src/pages/VisProgPage/visualProgrammingUI/nodes/GoalNode.tsx

@@ -1,5 +1,4 @@
 import {
-  Handle,
   type NodeProps,
   Position,
   type Node,
@@ -7,6 +6,8 @@ import {
 import { Toolbar } from '../components/NodeComponents';
 import styles from '../../VisProg.module.css';
 import { TextField } from '../../../../components/TextField';
+import {MultiConnectionHandle} from "../components/RuleBasedHandle.tsx";
+import {allowOnlyConnectionsFromHandle} from "../HandleRules.ts";
 import useFlowStore from '../VisProgStores';
 import { DoesPlanIterate, PlanReduce, type Plan } from '../components/Plan';
 import PlanEditorDialog from '../components/PlanEditor';
@@ -111,7 +112,9 @@ export default function GoalNode({id, data}: NodeProps<GoalNode>) {
                   description={data.name}
         />
       </div>
-      <Handle type="source" position={Position.Right} id="GoalSource"/>
+      <MultiConnectionHandle type="source" position={Position.Right} id="GoalSource" rules={[
+        allowOnlyConnectionsFromHandle([{nodeType:"phase",handleId:"data"}]),
+      ]}/>
     </div>
   </>;
 }

src/pages/VisProgPage/visualProgrammingUI/nodes/NormNode.tsx

@@ -1,5 +1,4 @@
 import {
-  Handle,
   type NodeProps,
   Position,
   type Node,
@@ -7,6 +6,8 @@ import {
 import { Toolbar } from '../components/NodeComponents';
 import styles from '../../VisProg.module.css';
 import { TextField } from '../../../../components/TextField';
+import {MultiConnectionHandle} from "../components/RuleBasedHandle.tsx";
+import {allowOnlyConnectionsFromHandle, allowOnlyConnectionsFromType} from "../HandleRules.ts";
 import useFlowStore from '../VisProgStores';
 import { BasicBeliefReduce } from './BasicBeliefNode';
 
@@ -75,9 +76,13 @@ export default function NormNode(props: NodeProps<NormNode>) {
         <label htmlFor={checkbox_id}>Condition/ Belief attached.</label>
       </div>)}
 
-  
-      <Handle type="source" position={Position.Right} id="norms"/>
-      <Handle type="target" position={Position.Bottom} id="norms"/>
+
+      <MultiConnectionHandle type="source" position={Position.Right} id="norms" rules={[
+        allowOnlyConnectionsFromHandle([{nodeType:"phase",handleId:"data"}])
+      ]}/>
+      <MultiConnectionHandle type="target" position={Position.Bottom} id="beliefs" rules={[
+        allowOnlyConnectionsFromType(["basic_belief"])
+      ]}/>
     </div>
   </>;
 };
@@ -86,7 +91,7 @@ export default function NormNode(props: NodeProps<NormNode>) {
 /**
  * Reduces each Norm, including its children down into its relevant data.
  * @param node The Node Properties of this node.
- * @param _nodes all the nodes in the graph
+ * @param nodes all the nodes in the graph
  */
 export function NormReduce(node: Node, nodes: Node[]) {
   const data = node.data as NormNodeData;

src/pages/VisProgPage/visualProgrammingUI/nodes/PhaseNode.tsx

@@ -1,15 +1,15 @@
 import {
-  Handle,
   type NodeProps,
   Position,
   type Node
 } from '@xyflow/react';
 import { Toolbar } from '../components/NodeComponents';
 import styles from '../../VisProg.module.css';
+import {SingleConnectionHandle, MultiConnectionHandle} from "../components/RuleBasedHandle.tsx";
+import {allowOnlyConnectionsFromType, noSelfConnections} from "../HandleRules.ts";
 import { NodeReduces, NodesInPhase, NodeTypes} from '../NodeRegistry';
 import useFlowStore from '../VisProgStores';
 import { TextField } from '../../../../components/TextField';
-import LimitedConnectionCountHandle from "../components/CustomNodeHandles.tsx";
 
 /**
  * The default data dot a phase node
@@ -54,21 +54,17 @@ export default function PhaseNode(props: NodeProps<PhaseNode>) {
             placeholder={"Phase ..."}
           />
         </div>
-        <LimitedConnectionCountHandle
-          node_id={props.id}
-          type="target"
-          position={Position.Left}
-          connection_count={1}
-          id="target"
-        />
-        <Handle type="target" position={Position.Bottom} id="norms"/>
-        <LimitedConnectionCountHandle
-          node_id={props.id}
-          type="source"
-          position={Position.Right}
-          connection_count={1}
-          id="source"
-        />
+        <SingleConnectionHandle type="target" position={Position.Left} id="target" rules={[
+          noSelfConnections,
+          allowOnlyConnectionsFromType(["phase", "start"]),
+        ]}/>
+        <MultiConnectionHandle type="target" position={Position.Bottom} id="data" rules={[
+          allowOnlyConnectionsFromType(["norm", "goal", "trigger"])
+        ]}/>
+        <SingleConnectionHandle type="source" position={Position.Right} id="source" rules={[
+          noSelfConnections,
+          allowOnlyConnectionsFromType(["phase", "end"]),
+        ]}/>
       </div>
     </>
   );

src/pages/VisProgPage/visualProgrammingUI/nodes/StartNode.tsx

@@ -3,9 +3,10 @@ import {
   Position,
   type Node,
 } from '@xyflow/react';
-import LimitedConnectionCountHandle from "../components/CustomNodeHandles.tsx";
 import { Toolbar } from '../components/NodeComponents';
 import styles from '../../VisProg.module.css';
+import {SingleConnectionHandle} from "../components/RuleBasedHandle.tsx";
+import {allowOnlyConnectionsFromHandle} from "../HandleRules.ts";
 
 
 export type StartNodeData = {
@@ -31,13 +32,9 @@ export default function StartNode(props: NodeProps<StartNode>) {
         <div className={"flex-row gap-sm"}>
           Start
         </div>
-        <LimitedConnectionCountHandle
-          node_id={props.id}
-          type="source"
-          position={Position.Right}
-          connection_count={1}
-          id="source"
-        />
+        <SingleConnectionHandle type="source" position={Position.Right} id="source" rules={[
+          allowOnlyConnectionsFromHandle([{nodeType:"phase",handleId:"target"}])
+        ]}/>
       </div>
     </>
   );

src/pages/VisProgPage/visualProgrammingUI/nodes/TriggerNode.tsx

@@ -1,5 +1,4 @@
 import {
-  Handle,
   type NodeProps,
   Position,
   type Connection,
@@ -8,6 +7,8 @@ import {
 } from '@xyflow/react';
 import { Toolbar } from '../components/NodeComponents';
 import styles from '../../VisProg.module.css';
+import {MultiConnectionHandle} from "../components/RuleBasedHandle.tsx";
+import {allowOnlyConnectionsFromHandle} from "../HandleRules.ts";
 import useFlowStore from '../VisProgStores';
 import { PlanReduce, type Plan } from '../components/Plan';
 import PlanEditorDialog from '../components/PlanEditor';  
@@ -61,8 +62,9 @@ export default function TriggerNode(props: NodeProps<TriggerNode>) {
       <div className={"flex-row gap-md"}>Triggers when the condition is met.</div>
       <div className={"flex-row gap-md"}>Condition/ Belief is currently {data.condition ? "" : "not"} set. {data.condition ? "🟢" : "🔴"}</div>
       <div className={"flex-row gap-md"}>Plan{data.plan ? (": " + data.plan.name) : ""} is currently {data.plan ? "" : "not"} set. {data.plan ? "🟢" : "🔴"}</div>
-      <Handle type="source" position={Position.Right} id="TriggerSource"/>
-      <Handle type="target" position={Position.Bottom} id="ConditionTarget"/>
+      <MultiConnectionHandle type="source" position={Position.Right} id="TriggerSource" rules={[
+        allowOnlyConnectionsFromHandle([{nodeType:"phase",handleId:"data"}]),
+      ]}/>
       <PlanEditorDialog
           plan={data.plan}
           onSave={(plan) => {

test/pages/visProgPage/visualProgrammingUI/HandleRuleLogic.test.ts

@@ -0,0 +1,86 @@
+import {renderHook} from "@testing-library/react";
+import type {Connection} from "@xyflow/react";
+import {
+  ruleResult,
+  type RuleResult,
+  useHandleRules
+} from "../../../../src/pages/VisProgPage/visualProgrammingUI/HandleRuleLogic.ts";
+import useFlowStore from "../../../../src/pages/VisProgPage/visualProgrammingUI/VisProgStores.tsx";
+
+describe('useHandleRules', () => {
+  it('should register rules on mount and validate connection', () => {
+    const rules = [() => ({ isSatisfied: true } as RuleResult)];
+
+    const { result } = renderHook(() => useHandleRules('node1', 'h1', 'target', rules));
+
+    // Confirm rules registered
+    const storedRules = useFlowStore.getState().getTargetRules('node1', 'h1');
+    expect(storedRules).toEqual(rules);
+
+    // Validate a connection
+    const connection = { source: 'node2', sourceHandle: 'h2', target: 'node1', targetHandle: 'h1' };
+    const validation = result.current(connection);
+    expect(validation).toEqual(ruleResult.satisfied);
+  });
+
+  it('should throw error if targetHandle missing', () => {
+    const rules: any[] = [];
+    const { result } = renderHook(() => useHandleRules('node1', 'h1', 'target', rules));
+
+    expect(() =>
+      result.current({ source: 'a', target: 'b', targetHandle: null, sourceHandle: null })
+    ).toThrow('No target handle was provided');
+  });
+});
+
+describe('useHandleRules with multiple failed rules', () => {
+  it('should return the first failed rule message and consider connectionCount', () => {
+    // Mock rules for the target handle
+    const failingRules = [
+      (_conn: any, ctx: any) => {
+        if (ctx.connectionCount >= 1) {
+          return { isSatisfied: false, message: 'Max connections reached' } as RuleResult;
+        }
+        return { isSatisfied: true } as RuleResult;
+      },
+      () => ({ isSatisfied: false, message: 'Other rule failed' } as RuleResult),
+      () => ({ isSatisfied: true } as RuleResult),
+    ];
+
+    // Register rules for the target handle
+    useFlowStore.getState().registerRules('targetNode', 'targetHandle', failingRules);
+
+    // Add one existing edge to simulate connectionCount
+    useFlowStore.setState({
+      edges: [
+        {
+          id: 'edge-1',
+          source: 'sourceNode',
+          sourceHandle: 'sourceHandle',
+          target: 'targetNode',
+          targetHandle: 'targetHandle',
+        },
+      ],
+    });
+
+    // Create hook for a source node handle
+    const rulesForSource = [
+      (_c: Connection) => ({ isSatisfied: true } as RuleResult)
+    ];
+    const { result } = renderHook(() =>
+      useHandleRules('sourceNode', 'sourceHandle', 'source', rulesForSource)
+    );
+
+    const connection = {
+      source: 'sourceNode',
+      sourceHandle: 'sourceHandle',
+      target: 'targetNode',
+      targetHandle: 'targetHandle',
+    };
+
+    const validation = result.current(connection);
+
+    // Should fail with first failing rule message
+    expect(validation).toEqual(ruleResult.notSatisfied('Max connections reached'));
+  });
+});

test/pages/visProgPage/visualProgrammingUI/HandleRules.test.ts

@@ -0,0 +1,84 @@
+import {ruleResult} from "../../../../src/pages/VisProgPage/visualProgrammingUI/HandleRuleLogic.ts";
+import {
+  allowOnlyConnectionsFromType,
+  allowOnlyConnectionsFromHandle, noSelfConnections
+} from "../../../../src/pages/VisProgPage/visualProgrammingUI/HandleRules.ts";
+import useFlowStore from "../../../../src/pages/VisProgPage/visualProgrammingUI/VisProgStores.tsx";
+
+beforeEach(() => {
+  useFlowStore.setState({
+    nodes: [
+      { id: 'nodeA', type: 'typeA', position: { x: 0, y: 0 }, data: {} },
+      { id: 'nodeB', type: 'typeB', position: { x: 0, y: 0 }, data: {} },
+    ],
+  });
+});
+
+describe('allowOnlyConnectionsFromType', () => {
+  it('should allow connection from allowed node type', () => {
+    const rule = allowOnlyConnectionsFromType(['typeA']);
+    const connection = { source: 'nodeA', sourceHandle: 'h1', target: 'nodeB', targetHandle: 'h2' };
+    const context = { connectionCount: 0, source: { id: 'nodeA', handleId: 'h1' }, target: { id: 'nodeB', handleId: 'h2' } };
+
+    const result = rule(connection, context);
+    expect(result).toEqual(ruleResult.satisfied);
+  });
+
+  it('should not allow connection from disallowed node type', () => {
+    const rule = allowOnlyConnectionsFromType(['typeA']);
+    const connection = { source: 'nodeB', sourceHandle: 'h1', target: 'nodeA', targetHandle: 'h2' };
+    const context = { connectionCount: 0, source: { id: 'nodeB', handleId: 'h1' }, target: { id: 'nodeA', handleId: 'h2' } };
+
+    const result = rule(connection, context);
+    expect(result).toEqual(ruleResult.notSatisfied("the target doesn't allow connections from nodes with type: typeB"));
+  });
+});
+describe('allowOnlyConnectionsFromHandle', () => {
+  it('should allow connection from node with correct type and handle', () => {
+    const rule = allowOnlyConnectionsFromHandle([{ nodeType: 'typeA', handleId: 'h1' }]);
+    const connection = { source: 'nodeA', sourceHandle: 'h1', target: 'nodeB', targetHandle: 'h2' };
+    const context = { connectionCount: 0, source: { id: 'nodeA', handleId: 'h1' }, target: { id: 'nodeB', handleId: 'h2' } };
+
+    const result = rule(connection, context);
+    expect(result).toEqual(ruleResult.satisfied);
+  });
+
+  it('should not allow connection from node with wrong handle', () => {
+    const rule = allowOnlyConnectionsFromHandle([{ nodeType: 'typeA', handleId: 'h1' }]);
+    const connection = { source: 'nodeA', sourceHandle: 'wrongHandle', target: 'nodeB', targetHandle: 'h2' };
+    const context = { connectionCount: 0, source: { id: 'nodeA', handleId: 'wrongHandle' }, target: { id: 'nodeB', handleId: 'h2' } };
+
+    const result = rule(connection, context);
+    expect(result).toEqual(ruleResult.notSatisfied("the target doesn't allow connections from nodes with type: typeA"));
+  });
+
+  it('should not allow connection from node with wrong type', () => {
+    const rule = allowOnlyConnectionsFromHandle([{ nodeType: 'typeA', handleId: 'h1' }]);
+    const connection = { source: 'nodeB', sourceHandle: 'h1', target: 'nodeA', targetHandle: 'h2' };
+    const context = { connectionCount: 0, source: { id: 'nodeB', handleId: 'h1' }, target: { id: 'nodeA', handleId: 'h2' } };
+
+    const result = rule(connection, context);
+    expect(result).toEqual(ruleResult.notSatisfied("the target doesn't allow connections from nodes with type: typeB"));
+  });
+});
+
+describe('noSelfConnections', () => {
+  it('should allow connection from node with other type and handle', () => {
+    const rule = noSelfConnections;
+    const connection = { source: 'nodeA', sourceHandle: 'h1', target: 'nodeB', targetHandle: 'h2' };
+    const context = { connectionCount: 0, source: { id: 'nodeA', handleId: 'h1' }, target: { id: 'nodeB', handleId: 'h2' } };
+
+    const result = rule(connection, context);
+    expect(result).toEqual(ruleResult.satisfied);
+  });
+
+  it('should not allow connection from other handle on same node', () => {
+    const rule = noSelfConnections;
+    const connection = { source: 'nodeA', sourceHandle: 'h1', target: 'nodeA', targetHandle: 'h2' };
+    const context = { connectionCount: 0, source: { id: 'nodeA', handleId: 'h1' }, target: { id: 'nodeB', handleId: 'h2' } };
+
+    const result = rule(connection, context);
+    expect(result).toEqual(ruleResult.notSatisfied("nodes are not allowed to connect to themselves"));
+  });
+
+});

test/pages/visProgPage/visualProgrammingUI/VisProgStores.test.tsx

@@ -1,5 +1,6 @@
 import {act} from '@testing-library/react';
 import type {Connection, Edge, Node} from "@xyflow/react";
+import type {HandleRule, RuleResult} from "../../../../src/pages/VisProgPage/visualProgrammingUI/HandleRuleLogic.ts";
 import { NodeDisconnections } from "../../../../src/pages/VisProgPage/visualProgrammingUI/NodeRegistry.ts";
 import type {PhaseNodeData} from "../../../../src/pages/VisProgPage/visualProgrammingUI/nodes/PhaseNode.tsx";
 import useFlowStore from '../../../../src/pages/VisProgPage/visualProgrammingUI/VisProgStores.tsx';
@@ -594,5 +595,48 @@ describe('FlowStore Functionality', () => {
       expect(updatedState.nodes).toHaveLength(1);
       expect(updatedState.nodes[0]).toMatchObject(expected.node);
     })
-  })
+  describe('Handle Rule Registry', () => {
+    it('should register and retrieve rules', () => {
+      const mockRules: HandleRule[] = [() => ({ isSatisfied: true } as RuleResult)];
+
+      useFlowStore.getState().registerRules('node1', 'handleA', mockRules);
+      const rules = useFlowStore.getState().getTargetRules('node1', 'handleA');
+
+      expect(rules).toEqual(mockRules);
+    });
+
+    it('should warn and return empty array if rules are missing', () => {
+      const consoleSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+
+      const rules = useFlowStore.getState().getTargetRules('missingNode', 'missingHandle');
+      expect(rules).toEqual([]);
+      expect(consoleSpy).toHaveBeenCalledWith(expect.stringContaining('No rules were registered'));
+
+      consoleSpy.mockRestore();
+    });
+
+    it('should unregister a specific handle rule', () => {
+      const mockRules: HandleRule[] = [() => ({ isSatisfied: true } as RuleResult)];
+      useFlowStore.getState().registerRules('node1', 'handleA', mockRules);
+
+      useFlowStore.getState().unregisterHandleRules('node1', 'handleA');
+      const rules = useFlowStore.getState().getTargetRules('node1', 'handleA');
+
+      expect(rules).toEqual([]);
+    });
+
+    it('should unregister all rules for a node', () => {
+      const mockRules: HandleRule[] = [() => ({ isSatisfied: true } as RuleResult)];
+      useFlowStore.getState().registerRules('node1', 'handleA', mockRules);
+      useFlowStore.getState().registerRules('node1', 'handleB', mockRules);
+      useFlowStore.getState().registerRules('node2', 'handleC', mockRules);
+
+      useFlowStore.getState().unregisterNodeRules('node1');
+
+      expect(useFlowStore.getState().getTargetRules('node1', 'handleA')).toEqual([]);
+      expect(useFlowStore.getState().getTargetRules('node1', 'handleB')).toEqual([]);
+      expect(useFlowStore.getState().getTargetRules('node2', 'handleC')).toEqual(mockRules);
+    });
+  });
+})
 });

test/setupFlowTests.ts

@@ -78,7 +78,8 @@ beforeAll(() => {
     past: [],
     future: [],
     isBatchAction: false,
-    edgeReconnectSuccessful: true
+    edgeReconnectSuccessful: true,
+    ruleRegistry: new Map()
   });
 });
 
@@ -90,7 +91,8 @@ afterEach(() => {
     past: [],
     future: [],
     isBatchAction: false,
-    edgeReconnectSuccessful: true
+    edgeReconnectSuccessful: true,
+    ruleRegistry: new Map()
   });
 });