From f12818cfddea4bf0e79744ce26e0a8508f05bc49 Mon Sep 17 00:00:00 2001
From: Jake Kasper <jake.kasper@hpe.com>
Date: Sat, 23 Aug 2025 14:02:09 -0400
Subject: [PATCH] calcs again

---
 backend/src/utils/applicationCalculations.js | 74 ++++++++++++++------
 1 file changed, 52 insertions(+), 22 deletions(-)

diff --git a/backend/src/utils/applicationCalculations.js b/backend/src/utils/applicationCalculations.js
index d260e1e..6ba9149 100644
--- a/backend/src/utils/applicationCalculations.js
+++ b/backend/src/utils/applicationCalculations.js
@@ -27,57 +27,87 @@ function calculateLiquidApplication(areaSquareFeet, rateAmount, rateUnit, equipm
     Equipment: ${equipment?.categoryName}
     Nozzle GPM: ${nozzle?.flowRateGpm || 'N/A'}`);
 
+  // Calculate application speed first based on equipment and nozzle
+  if (equipment && nozzle && nozzle.flowRateGpm && equipment.sprayWidthFeet) {
+    const sprayWidthFeet = equipment.sprayWidthFeet;
+    const nozzleGpm = nozzle.flowRateGpm;
+    
+    // For liquid applications, we need to determine optimal speed based on target carrier rate
+    // Let's use a reasonable default carrier rate of 20 GPA (gallons per acre)
+    const targetGallonsPerAcre = 20;
+    const targetGallonsPerSqft = targetGallonsPerAcre / 43560;
+    
+    // Formula: Speed (MPH) = GPM / (width_ft × target_rate_gal_per_sqft × 88)
+    // Where 88 converts MPH to ft/min
+    applicationSpeedMph = nozzleGpm / (sprayWidthFeet * targetGallonsPerSqft * 88);
+    
+    // Limit speed to reasonable range (1-8 MPH for lawn applications)
+    applicationSpeedMph = Math.max(1, Math.min(8, applicationSpeedMph));
+  } else {
+    applicationSpeedMph = 3; // Default speed
+  }
+
+  // Now calculate actual carrier (water) rate using the calculated speed
+  // Formula: Rate (gal/sqft) = flow (GPM) / (width (ft) × speed (ft/min))
+  // Where speed (ft/min) = speed (MPH) × 88
+  let carrierRateGalPerSqft = 0;
+  
+  if (equipment && nozzle && nozzle.flowRateGpm && equipment.sprayWidthFeet) {
+    const flowGpm = nozzle.flowRateGpm;
+    const widthFt = equipment.sprayWidthFeet;
+    const speedFtPerMin = applicationSpeedMph * 88; // Convert MPH to ft/min
+    
+    carrierRateGalPerSqft = flowGpm / (widthFt * speedFtPerMin);
+    waterGallons = carrierRateGalPerSqft * areaSquareFeet;
+    
+    console.log('Carrier rate calculation:', {
+      flowGpm,
+      widthFt,
+      speedMph: applicationSpeedMph,
+      speedFtPerMin,
+      carrierRateGalPerSqft,
+      areaSquareFeet,
+      totalWaterGallons: waterGallons,
+      carrierRateGalPer1000Sqft: carrierRateGalPerSqft * 1000
+    });
+  } else {
+    // Fallback to area-based calculation if equipment data is missing
+    console.log('Using fallback water calculation - missing equipment/nozzle data');
+    waterGallons = area1000sqft * 0.164; // Use your example: 0.164 gal/1000sqft
+  }
+
   // Calculate product amount based on rate unit
   if (rateUnit.includes('oz/gal')) {
     // Rate is ounces per gallon of spray solution
-    // Need to determine gallons of water needed first
-    const gallonsPerAcre = 20; // Default 20 GPA for lawn applications
-    waterGallons = areaAcres * gallonsPerAcre;
     productOunces = waterGallons * rateAmount;
   } else if (rateUnit.includes('oz/1000sqft') || rateUnit.includes('oz per 1000sqft')) {
     // Rate is ounces per 1000 square feet
     productOunces = area1000sqft * rateAmount;
-    // Calculate water needed (typical lawn application is 0.5-1 gallon per 1000 sqft)
-    waterGallons = area1000sqft * 0.75; // 0.75 gal per 1000 sqft default
   } else if (rateUnit.includes('oz/acre')) {
     // Rate is ounces per acre
     productOunces = areaAcres * rateAmount;
-    waterGallons = areaAcres * 20; // 20 GPA default
   } else if (rateUnit.includes('fl oz/1000sqft') || rateUnit.includes('fl oz per 1000sqft')) {
     // Rate is fluid ounces per 1000 square feet
     productOunces = area1000sqft * rateAmount;
-    waterGallons = area1000sqft * 0.75;
   } else {
     // Fallback: assume rate is per 1000 sq ft
     productOunces = area1000sqft * rateAmount;
-    waterGallons = area1000sqft * 0.75;
   }
 
-  // Calculate application speed based on equipment and nozzle
-  if (equipment && nozzle) {
-    const sprayWidthFeet = equipment.sprayWidthFeet || 3; // Default 3 ft width
-    const nozzleGpm = nozzle.flowRateGpm || 0.25; // Default 0.25 GPM
-    const gallonsPerAcre = (waterGallons / areaAcres) || 20;
-    
-    // Speed calculation: MPH = (GPM × 5940) / (Width × GPA)
-    // Where 5940 is a conversion constant
-    applicationSpeedMph = (nozzleGpm * 5940) / (sprayWidthFeet * gallonsPerAcre);
-    
-    // Limit speed to reasonable range (1-8 MPH for lawn applications)
-    applicationSpeedMph = Math.max(1, Math.min(8, applicationSpeedMph));
-  }
 
   const result = {
     productAmountOunces: Math.round(productOunces * 100) / 100, // Round to 2 decimals
     waterAmountGallons: Math.round(waterGallons * 100) / 100,
     applicationSpeedMph: Math.round(applicationSpeedMph * 100) / 100,
     gallonsPerAcre: Math.round((waterGallons / areaAcres) * 100) / 100,
+    carrierRateGalPer1000Sqft: Math.round(carrierRateGalPerSqft * 1000 * 1000) / 1000, // Rate per 1000 sqft
     calculationDetails: {
       areaSquareFeet,
       areaAcres: Math.round(areaAcres * 1000) / 1000,
       area1000sqft: Math.round(area1000sqft * 10) / 10,
       rateAmount,
-      rateUnit
+      rateUnit,
+      carrierRateGalPerSqft: carrierRateGalPerSqft
     }
   };