Re_Backend/Business_Days_Calculation_Recommendations.md

Business Days Calculation - Current Issues & Recommendations

🔴 CRITICAL ISSUE: TAT Processor Using Wrong Calculation

Current Problem:

In Re_Backend/src/queues/tatProcessor.ts (lines 64-65), the TAT calculation uses simple calendar hours:

const elapsedMs = now.getTime() - new Date(levelStartTime).getTime();
const elapsedHours = elapsedMs / (1000 * 60 * 60);

This is WRONG because:

• ❌ Counts ALL hours (24/7), including nights, weekends, holidays
• ❌ Doesn't respect working hours (9 AM - 6 PM)
• ❌ Doesn't exclude weekends for STANDARD priority
• ❌ Doesn't exclude holidays
• ❌ Causes incorrect TAT breach alerts

✅ Solution Available:

You already have a proper function calculateElapsedWorkingHours() in tatTimeUtils.ts that:

• ✅ Respects working hours (9 AM - 6 PM)
• ✅ Excludes weekends for STANDARD priority
• ✅ Excludes holidays
• ✅ Handles EXPRESS vs STANDARD differently
• ✅ Uses minute-by-minute precision

🔧 Fix Required:

Update tatProcessor.ts to use proper working hours calculation:

// BEFORE (WRONG):
const elapsedMs = now.getTime() - new Date(levelStartTime).getTime();
const elapsedHours = elapsedMs / (1000 * 60 * 60);

// AFTER (CORRECT):
import { calculateElapsedWorkingHours } from '@utils/tatTimeUtils';
const priority = ((workflow as any).priority || 'STANDARD').toString().toLowerCase();
const elapsedHours = await calculateElapsedWorkingHours(levelStartTime, now, priority);

---

📊 Business Days Calculation for Workflow Aging Report

Current Situation:

• ✅ You have calculateElapsedWorkingHours() - calculates hours
• ❌ You DON'T have calculateBusinessDays() - calculates days

Need:

For the Workflow Aging Report, you need to show "Days Open" as business days (excluding weekends and holidays), not calendar days.

🔧 Solution: Add Business Days Function

Add this function to Re_Backend/src/utils/tatTimeUtils.ts:

/**
 * Calculate business days between two dates
 * Excludes weekends and holidays
 * @param startDate - Start date
 * @param endDate - End date (defaults to now)
 * @param priority - 'express' or 'standard' (express includes weekends, standard excludes)
 * @returns Number of business days
 */
export async function calculateBusinessDays(
  startDate: Date | string,
  endDate: Date | string | null = null,
  priority: string = 'standard'
): Promise<number> {
  await loadWorkingHoursCache();
  await loadHolidaysCache();
  
  let start = dayjs(startDate).startOf('day');
  const end = dayjs(endDate || new Date()).startOf('day');
  
  // In test mode, use calendar days
  if (isTestMode()) {
    return end.diff(start, 'day') + 1;
  }
  
  const config = workingHoursCache || {
    startHour: TAT_CONFIG.WORK_START_HOUR,
    endHour: TAT_CONFIG.WORK_END_HOUR,
    startDay: TAT_CONFIG.WORK_START_DAY,
    endDay: TAT_CONFIG.WORK_END_DAY
  };
  
  let businessDays = 0;
  let current = start;
  
  // Count each day from start to end (inclusive)
  while (current.isBefore(end) || current.isSame(end, 'day')) {
    const dayOfWeek = current.day(); // 0 = Sunday, 6 = Saturday
    const dateStr = current.format('YYYY-MM-DD');
    
    // For express priority: count all days (including weekends) but exclude holidays
    // For standard priority: count only working days (Mon-Fri) and exclude holidays
    const isWorkingDay = priority === 'express' 
      ? true  // Express includes weekends
      : (dayOfWeek >= config.startDay && dayOfWeek <= config.endDay);
    
    const isNotHoliday = !holidaysCache.has(dateStr);
    
    if (isWorkingDay && isNotHoliday) {
      businessDays++;
    }
    
    current = current.add(1, 'day');
    
    // Safety check to prevent infinite loops
    if (current.diff(start, 'day') > 730) { // 2 years
      console.error('[TAT] Safety break - exceeded 2 years in business days calculation');
      break;
    }
  }
  
  return businessDays;
}

---

📋 Summary of Issues & Fixes

Issue 1: TAT Processor Using Calendar Hours ✅ FIXED

• File: Re_Backend/src/queues/tatProcessor.ts
• Line: 64-65 (now 66-77)
• Problem: Uses simple calendar hours instead of working hours
• Impact: Incorrect TAT breach calculations
• Fix: ✅ Replaced with calculateElapsedWorkingHours() and addWorkingHours()/addWorkingHoursExpress()
• Status: ✅ COMPLETED - Now uses proper working hours calculation

Issue 2: Missing Business Days Function ✅ FIXED

• File: Re_Backend/src/utils/tatTimeUtils.ts
• Problem: No function to calculate business days count
• Impact: Workflow Aging Report shows calendar days instead of business days
• Fix: ✅ Added calculateBusinessDays() function (lines 697-758)
• Status: ✅ COMPLETED - Function implemented and exported

Issue 3: Workflow Aging Report Using Calendar Days ✅ FIXED

• File: Re_Backend/src/services/dashboard.service.ts
• Problem: Will use calendar days if not fixed
• Impact: Incorrect "Days Open" calculation
• Fix: ✅ Uses calculateBusinessDays() in report endpoint (getWorkflowAgingReport method)
• Status: ✅ COMPLETED - Report now uses business days calculation

---

🛠️ Implementation Steps ✅ ALL COMPLETED

Step 1: Fix TAT Processor (CRITICAL) ✅ DONE

1. ✅ Opened Re_Backend/src/queues/tatProcessor.ts
2. ✅ Imported calculateElapsedWorkingHours, addWorkingHours, addWorkingHoursExpress from @utils/tatTimeUtils
3. ✅ Replaced lines 64-65 with proper working hours calculation (now lines 66-77)
4. ✅ Gets priority from workflow
5. ⏳ TODO: Test TAT breach alerts

Step 2: Add Business Days Function ✅ DONE

1. ✅ Opened Re_Backend/src/utils/tatTimeUtils.ts
2. ✅ Added calculateBusinessDays() function (lines 697-758)
3. ✅ Exported the function
4. ⏳ TODO: Test with various date ranges

Step 3: Update Workflow Aging Report ✅ DONE

1. ✅ Built report endpoint using calculateBusinessDays()
2. ✅ Filters requests where businessDays > threshold
3. ✅ Displays business days instead of calendar days

---

✅ What's Already Working

• ✅ calculateElapsedWorkingHours() - Properly calculates working hours
• ✅ calculateSLAStatus() - Comprehensive SLA calculation
• ✅ Working hours configuration (from admin settings)
• ✅ Holiday support (from database)
• ✅ Priority-based calculation (express vs standard)
• ✅ Used correctly in approval.service.ts and dashboard.service.ts

---

🎯 Priority Order

1. 🔴 CRITICAL: Fix TAT Processor (affects all TAT calculations)
2. 🟡 HIGH: Add Business Days Function (needed for reports)
3. 🟡 HIGH: Update Workflow Aging Report to use business days

---

📝 Code Example: Fixed TAT Processor

// In tatProcessor.ts, around line 60-70
import { calculateElapsedWorkingHours } from '@utils/tatTimeUtils';

// ... existing code ...

const tatHours = Number((approvalLevel as any).tatHours || 0);
const levelStartTime = (approvalLevel as any).levelStartTime || (approvalLevel as any).createdAt;
const now = new Date();

// FIXED: Use proper working hours calculation
const priority = ((workflow as any).priority || 'STANDARD').toString().toLowerCase();
const elapsedHours = await calculateElapsedWorkingHours(levelStartTime, now, priority);
const remainingHours = Math.max(0, tatHours - elapsedHours);
const expectedCompletionTime = dayjs(levelStartTime).add(tatHours, 'hour').toDate();

// ... rest of code ...

---

🧪 Testing Recommendations

1. Test TAT Breach Calculation:

   • Create a request with 8-hour TAT
   • Submit on Friday 5 PM
   • Should NOT breach until Monday 1 PM (next working hour)
   • Currently will breach on Saturday 1 AM (wrong!)

2. Test Business Days:

   • Start: Monday, Jan 1
   • End: Friday, Jan 5
   • Should return: 5 business days (not 5 calendar days if there are holidays)

3. Test Express vs Standard:

   • Express: Should count weekends
   • Standard: Should exclude weekends

---

📚 Related Files

• Re_Backend/src/queues/tatProcessor.ts - ✅ FIXED - Now uses calculateElapsedWorkingHours() and proper deadline calculation
• Re_Backend/src/utils/tatTimeUtils.ts - ✅ FIXED - Added calculateBusinessDays() function
• Re_Backend/src/services/approval.service.ts - ✅ Already using correct calculation
• Re_Backend/src/services/dashboard.service.ts - ✅ FIXED - Uses calculateBusinessDays() in Workflow Aging Report
• Re_Backend/src/services/workflow.service.ts - ✅ Already using correct calculation