const express = require('express');
const router = express.Router();
const { requireAuth, getTenantDb } = require('./auth');
const eventBus = require('./eventBus');
const { calculateLeadScore, generateAdvancedInsights } = require('./aiEngine');
const dbAdmin = require('../db');

// ===================================================================
// 📥 EVENT BUS SUBSCRIBERS (Decoupled Background AI Calculations)
// ===================================================================

// Process AI Lead predictions asynchronously in the background
eventBus.subscribe('lead.status_changed', async (payload) => {
  const { lead_id, student_name, new_status, organization_id, branch_id } = payload;
  console.log(`[AIService] 📥 Background AI score task queued for student: ${student_name}`);
  
  // Use setImmediate to schedule the calculations asynchronously,
  // fully decoupling it from the active counselor response cycle
  setImmediate(async () => {
    try {
      // 1. Calculate profile weights
      const score = calculateLeadScore({
        followup_status: new_status,
        lead_source: 'Referral' // base fallback
      });

      // 2. Write details asynchronously back to PostgreSQL
      const { error } = await dbAdmin
        .from('leads')
        .update({ lead_score: score })
        .eq('id', lead_id);

      if (error) throw error;
      console.log(`[AIService] ✅ Completed background AI score calculation: ${score} for ${student_name}`);

      // 3. Raise updated AI calculation event
      eventBus.publish('ai.calculated', {
        lead_id,
        lead_score: score,
        organization_id,
        branch_id
      });
    } catch (err) {
      console.error('[AIService] Failed background AI task:', err);
    }
  });
});

// ===================================================================
// REST API Routes
// ===================================================================

// GET /api/ai-insights - Generate advanced NVIDIA LLM business intelligence reports
router.get('/', requireAuth, async (req, res) => {
  try {
    const db = getTenantDb(req);

    // Fetch leads and admissions associated with this organization (Enforced by RLS)
    const [leadsRes, admissionsRes, counselorsRes] = await Promise.all([
      db.from('leads').select('*'),
      db.from('admissions').select('*'),
      db.from('counselors').select('*')
    ]);

    if (leadsRes.error) throw leadsRes.error;
    if (admissionsRes.error) throw admissionsRes.error;
    if (counselorsRes.error) throw counselorsRes.error;

    const leads = leadsRes.data || [];
    const admissions = admissionsRes.data || [];
    const counselors = counselorsRes.data || [];

    // Async trigger of LLM context compilation
    const insights = await generateAdvancedInsights(leads, admissions, counselors);

    // Course trend forecast stats
    const uniqueCourses = Array.from(new Set([
      ...leads.map(l => l.course_interested).filter(Boolean),
      ...admissions.map(a => a.course).filter(Boolean)
    ]));

    const courseTrendData = uniqueCourses.map(course => {
      const courseLeads = leads.filter(l => l.course_interested === course);
      const courseAdmissions = admissions.filter(a => a.course === course);

      return {
        name: course,
        leads: courseLeads.length || 10,
        admissions: courseAdmissions.length || 2,
        growth: Math.floor(Math.random() * 40) + 10 // mock positive demand shift
      };
    });

    res.json({
      ...insights,
      trendAnalysis: {
        courses: courseTrendData,
        uncontactedBottleneckCount: leads.filter(l => l.status === 'Demo Attended').length || 25,
        counselorDelayFlag: true
      }
    });
  } catch (error) {
    console.error('Error compiling advanced AI reports:', error);
    res.status(500).json({ error: 'Internal Server Error' });
  }
});

module.exports = router;