/**
 * ALWAS ML-Enhanced Bottleneck Scanner
 * Drop-in replacement for the existing node-cron bottleneck scanner.
 * Uses ML models instead of simple 48h threshold.
 * 
 * Place in: server/cron/mlBottleneckScanner.js
 * 
 * Setup in server/app.js:
 *   const cron = require('node-cron');
 *   const mlScanner = require('./cron/mlBottleneckScanner');
 *   cron.schedule('0 * * * *', () => mlScanner(io)); // hourly
 */

const ml = require('../utils/alwas-ml-client');
const Block = require('../models/Block');
const Notification = require('../models/Notification');
const User = require('../models/User');

async function mlBottleneckScanner(io) {
  console.log('[ML Scanner] Starting hourly bottleneck scan...');
  
  try {
    // Get all in-progress blocks
    const blocks = await Block.find({ 
      status: { $nin: ['Not Started', 'Completed'] } 
    }).populate('assignedTo');

    let highRisk = 0;
    let mediumRisk = 0;
    let alerts = [];

    for (const block of blocks) {
      try {
        // Calculate days in current stage
        const lastTransition = block.transitions?.[block.transitions.length - 1];
        const daysSince = lastTransition 
          ? (Date.now() - new Date(lastTransition.timestamp)) / (1000 * 60 * 60 * 24)
          : 0;

        const riskData = ml.constructor.formatForBottleneck(block, daysSince);
        const risk = await ml.predictBottleneck(riskData);

        if (risk.risk_level === 'High') {
          highRisk++;
          
          // Create notification for assigned engineer
          if (block.assignedTo) {
            const notification = await Notification.create({
              user: block.assignedTo._id || block.assignedTo,
              type: 'stuck',
              message: `⚠️ ML Alert: ${block.name} has HIGH bottleneck risk`,
              data: {
                blockId: block._id,
                risk: risk.risk_level,
                confidence: risk.confidence,
                recommendations: risk.recommendations,
                hours_over_budget: risk.hours_over_budget_ratio,
              }
            });

            // Real-time socket notification
            io.emit('newNotification', {
              userId: block.assignedTo._id || block.assignedTo,
              notification: notification,
            });
          }

          // Also notify managers
          const managers = await User.find({ role: 'manager' });
          for (const manager of managers) {
            await Notification.create({
              user: manager._id,
              type: 'stuck',
              message: `🔴 ML Bottleneck Alert: ${block.name} (${block.status}) — ${risk.recommendations[0] || 'High risk detected'}`,
              data: {
                blockId: block._id,
                risk: risk.risk_level,
                confidence: risk.confidence,
                recommendations: risk.recommendations,
                engineer: block.assignedTo?.name || 'Unassigned',
              }
            });
          }

          alerts.push({
            block: block.name,
            stage: block.status,
            risk: risk.risk_level,
            confidence: risk.confidence,
            reason: risk.recommendations[0] || 'High risk',
          });

        } else if (risk.risk_level === 'Medium') {
          mediumRisk++;
        }
      } catch (blockError) {
        console.error(`[ML Scanner] Error scanning block ${block._id}:`, blockError.message);
      }
    }

    console.log(`[ML Scanner] Scan complete: ${blocks.length} blocks scanned, ${highRisk} high risk, ${mediumRisk} medium risk`);
    
    if (alerts.length > 0) {
      console.log('[ML Scanner] High-risk blocks:');
      alerts.forEach(a => console.log(`  - ${a.block} (${a.stage}): ${a.reason}`));
    }

    return { scanned: blocks.length, highRisk, mediumRisk, alerts };

  } catch (error) {
    console.error('[ML Scanner] Fatal error:', error.message);
    return { error: error.message };
  }
}

module.exports = mlBottleneckScanner;