/**
 * Flow Engine — executes saved Workflow flows for incoming chat messages.
 *
 * Execution model:
 * 1. Load all active flows from the DB
 * 2. For each flow, find its intent node and check if user message matches
 * 3. If matched, traverse the flow graph from intent → response nodes
 * 4. Return the response content (or null if no flow matched)
 */

import { getDb } from "./db";
import { workflowNodes } from "../drizzle/schema";
import { eq } from "drizzle-orm";

export interface FlowResult {
  content: string;
  shouldEscalate?: boolean;
  flowId: string;
  flowName?: string;
}

// Intent patterns for the 5 live Support Flows
const FLOW_INTENT_PATTERNS: Record<string, RegExp[]> = {
  "check-order-status": [
    /\border\s*status\b/i,
    /\bcheck.*order\b/i,
    /\bwhere.*my order\b/i,
    /\border.*update\b/i,
    /\bmy order\b/i,
  ],
  "track-shipment": [
    /\btrack.*shipment\b/i,
    /\btracking\b/i,
    /\bshipment.*status\b/i,
    /\bwhere.*package\b/i,
    /\bdelivery.*status\b/i,
    /\btrack.*package\b/i,
  ],
  "submit-return": [
    /\breturn\b/i,
    /\bRMA\b/i,
    /\bsend.*back\b/i,
    /\breturn.*request\b/i,
    /\brefund\b/i,
  ],
  "cancel-order": [
    /\bcancel.*order\b/i,
    /\bcancel.*my order\b/i,
    /\bstop.*order\b/i,
  ],
  "faq-deflection": [
    /\bpayment\b/i,
    /\bwarranty\b/i,
    /\bhow.*long.*delivery\b/i,
    /\bshipping.*time\b/i,
    /\bminimum.*order\b/i,
  ],
};

// Fallback static responses for flows that don't have DB nodes yet
const FLOW_STATIC_RESPONSES: Record<string, string | null> = {
  "check-order-status": "To check your order status, please provide your **Sales Order number** (e.g., SO-12345) and I'll look it up for you right away.",
  "track-shipment": "I can help you track your shipment! Please share your **order number** or **tracking number** and I'll pull up the latest status.",
  "submit-return": "I can guide you through the return process. Please provide:\n1. Your **order number**\n2. The **item(s)** you want to return\n3. The **reason** for the return\n\nOur return policy allows returns within 30 days of delivery.",
  "cancel-order": "I can help with order cancellation. Please provide your **order number** and I'll check if it's still within the cancellation window. Note: orders that have already shipped cannot be cancelled.",
  "faq-deflection": null, // handled by knowledge base
};

/**
 * Detect if the user message matches a flow intent.
 * Returns the flowId or null.
 */
export function detectFlowIntent(message: string): string | null {
  for (const [flowId, patterns] of Object.entries(FLOW_INTENT_PATTERNS)) {
    if (patterns.some(p => p.test(message))) {
      return flowId;
    }
  }
  return null;
}

/**
 * Execute a flow by ID. Returns the response content or null.
 * Tries DB-saved nodes first, falls back to static responses.
 */
export async function executeFlow(flowId: string, _userMessage: string): Promise<FlowResult | null> {
  // Try to load flow nodes from DB
  try {
    const db = await getDb();
    if (db) {
      const nodes = await db.select().from(workflowNodes).where(eq(workflowNodes.workflowId, flowId));
      if (nodes.length > 0) {
        const responseNodes = nodes.filter(n => n.type === "response" && (n.config as any)?.message);
        if (responseNodes.length > 0) {
          const escalationNode = nodes.find(n => n.type === "escalation");
          const content = responseNodes.map(n => (n.config as any).message).join("\n\n");
          return { content, shouldEscalate: !!escalationNode, flowId };
        }
      }
    }
  } catch (err) {
    console.error("[FlowEngine] DB error:", err);
  }

  const staticResponse = FLOW_STATIC_RESPONSES[flowId];
  if (staticResponse) {
    return { content: staticResponse, flowId };
  }

  return null;
}