apps/simulator/src/agents/graphEngine.ts

/**
 * Workflow Graph Engine (IR Layer) — UPGRADED
 * Builds an internal graph representation BEFORE compiling to n8n JSON
 * Provider-agnostic LLM Gateway — NO direct OpenAI dependency
 * Validates all node types against the real Node Registry before returning
 */
import { type LLMGateway } from '@wfo/integrations/llm-providers/index';
import type { WorkflowIntent, WorkflowArchitecturePlan, WorkflowGraph } from '../types/workflow';
import { GRAPH_ENGINE_PROMPT } from '../prompts/graphEngine';
import { isValidNodeType, getRegistryNodeList } from '../knowledge/nodeRegistry';

export class WorkflowGraphEngine {
  private llm: LLMGateway;

  constructor(llm: LLMGateway) {
    this.llm = llm;
  }

  async buildGraph(
    userRequest: string,
    intent: WorkflowIntent,
    plan: WorkflowArchitecturePlan,
  ): Promise<WorkflowGraph> {
    const registryList = getRegistryNodeList();

    const graph = await this.llm.completeJSON<WorkflowGraph>([
      { role: 'system', content: GRAPH_ENGINE_PROMPT },
      {
        role: 'user',
        content: `Build a WorkflowGraph IR for this workflow:

REQUEST: ${userRequest}

INTENT:
${JSON.stringify(intent, null, 2)}

ARCHITECTURE PLAN:
${JSON.stringify(plan, null, 2)}

AVAILABLE NODE TYPES (USE ONLY THESE — NO OTHERS):
${registryList}

CRITICAL RULES:
- Every node MUST have n8nNodeType from the list above ONLY
- NEVER invent node types not in the list
- Every non-trigger node MUST have at least one incoming edge
- Every node MUST have meaningful parameters — NO empty nodes
- DataContracts must define what JSON fields flow between nodes
- Use real expressions: {{$json?.field ?? ""}} — NOT placeholder text
- Position nodes in clean left-to-right layout (x increases by 220 per step)
- Return a complete WorkflowGraph JSON`,
      },
    ], {
      temperature: 0.0,
      retries: 3,
    });

    return this.validateAndOptimizeGraph(graph);
  }

  /**
   * Validates all node types against registry, removes unknown nodes,
   * optimises graph structure (orphan removal, position cleanup)
   */
  private validateAndOptimizeGraph(graph: WorkflowGraph): WorkflowGraph {
    const unknownNodes: string[] = [];

    // Filter out any hallucinated node types
    const validNodes = graph.nodes.filter((node) => {
      if (!isValidNodeType(node.n8nNodeType)) {
        unknownNodes.push(`${node.label} (${node.n8nNodeType})`);
        return false;
      }
      return true;
    });

    if (unknownNodes.length > 0) {
      console.warn(
        `[GraphEngine] REJECTED ${unknownNodes.length} unknown node type(s): ${unknownNodes.join(', ')}`,
      );
    }

    const validNodeIds = new Set(validNodes.map((n) => n.id));

    // Remove edges that reference removed nodes
    const validEdges = graph.edges.filter(
      (e) => validNodeIds.has(e.sourceNodeId) && validNodeIds.has(e.targetNodeId),
    );

    // Remove orphaned non-trigger nodes
    const optimizedNodes = validNodes.filter((node) => {
      const hasIncoming = validEdges.some((e) => e.targetNodeId === node.id);
      const hasOutgoing = validEdges.some((e) => e.sourceNodeId === node.id);
      const isTrigger = node.layer === 'trigger';
      return isTrigger || hasIncoming || hasOutgoing;
    });

    return {
      ...graph,
      nodes: optimizedNodes,
      edges: validEdges,
      metadata: {
        ...graph.metadata,
        version: '2.0.0',
        createdAt: new Date().toISOString(),
        unknownNodesRejected: unknownNodes,
      },
    };
  }
}