fix: wrong socket was highlighted when dragging node

The old code had a bug that highlighted a socket from a node to which a
edge already exists which could not be connected to

app/src/lib/graph-interface/test-utils.ts

@@ -0,0 +1,86 @@
+import type { NodeDefinition, NodeId, NodeRegistry } from '@nodarium/types';
+
+export function createMockNodeRegistry(nodes: NodeDefinition[]): NodeRegistry {
+  const nodesMap = new Map(nodes.map(n => [n.id, n]));
+  return {
+    status: 'ready' as const,
+    load: async (nodeIds: NodeId[]) => {
+      const loaded: NodeDefinition[] = [];
+      for (const id of nodeIds) {
+        if (nodesMap.has(id)) {
+          loaded.push(nodesMap.get(id)!);
+        }
+      }
+      return loaded;
+    },
+    getNode: (id: string) => nodesMap.get(id as NodeId),
+    getAllNodes: () => Array.from(nodesMap.values()),
+    register: async () => {
+      throw new Error('Not implemented in mock');
+    }
+  };
+}
+
+export const mockFloatOutputNode: NodeDefinition = {
+  id: 'test/node/output',
+  inputs: {},
+  outputs: ['float'],
+  meta: { title: 'Float Output' },
+  execute: () => new Int32Array()
+};
+
+export const mockFloatInputNode: NodeDefinition = {
+  id: 'test/node/input',
+  inputs: { value: { type: 'float' } },
+  outputs: [],
+  meta: { title: 'Float Input' },
+  execute: () => new Int32Array()
+};
+
+export const mockGeometryOutputNode: NodeDefinition = {
+  id: 'test/node/geometry',
+  inputs: {},
+  outputs: ['geometry'],
+  meta: { title: 'Geometry Output' },
+  execute: () => new Int32Array()
+};
+
+export const mockPathInputNode: NodeDefinition = {
+  id: 'test/node/path',
+  inputs: { input: { type: 'path', accepts: ['geometry'] } },
+  outputs: [],
+  meta: { title: 'Path Input' },
+  execute: () => new Int32Array()
+};
+
+export const mockVec3OutputNode: NodeDefinition = {
+  id: 'test/node/vec3',
+  inputs: {},
+  outputs: ['vec3'],
+  meta: { title: 'Vec3 Output' },
+  execute: () => new Int32Array()
+};
+
+export const mockIntegerInputNode: NodeDefinition = {
+  id: 'test/node/integer',
+  inputs: { value: { type: 'integer' } },
+  outputs: [],
+  meta: { title: 'Integer Input' },
+  execute: () => new Int32Array()
+};
+
+export const mockBooleanOutputNode: NodeDefinition = {
+  id: 'test/node/boolean',
+  inputs: {},
+  outputs: ['boolean'],
+  meta: { title: 'Boolean Output' },
+  execute: () => new Int32Array()
+};
+
+export const mockBooleanInputNode: NodeDefinition = {
+  id: 'test/node/boolean-input',
+  inputs: { value: { type: 'boolean' } },
+  outputs: [],
+  meta: { title: 'Boolean Input' },
+  execute: () => new Int32Array()
+};