Add a linear CoB / absorption model

Trio.xcodeproj/project.pbxproj

@@ -258,6 +258,7 @@
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 		3B4BA7902D8DC0EC0069D5B8 /* TidepoolServiceKitUI.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 3B4BA7892D8DC0EC0069D5B8 /* TidepoolServiceKitUI.framework */; };
 		3B4BA7912D8DC0EC0069D5B8 /* TidepoolServiceKitUI.framework in Embed Frameworks */ = {isa = PBXBuildFile; fileRef = 3B4BA7892D8DC0EC0069D5B8 /* TidepoolServiceKitUI.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
+		3B4FD3D22E05E40700EDDB1E /* SimpleCob.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3B4FD3D12E05E40300EDDB1E /* SimpleCob.swift */; };
 		3B5CD1EC2D4912A600CE213C /* OpenAPSSwift.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3B5CD1E92D4912A600CE213C /* OpenAPSSwift.swift */; };
 		3B5CD1ED2D4912A600CE213C /* JSONBridge.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3B5CD1EA2D4912A600CE213C /* JSONBridge.swift */; };
 		3B5CD2982D4AEA3C00CE213C /* Carbs.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3B5CD2922D4AEA3C00CE213C /* Carbs.swift */; };
@@ -1139,6 +1140,7 @@
 		3B4BA7692D8DBD690069D5B8 /* RileyLinkKitUI.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; path = RileyLinkKitUI.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		3B4BA7882D8DC0EC0069D5B8 /* TidepoolServiceKit.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; path = TidepoolServiceKit.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		3B4BA7892D8DC0EC0069D5B8 /* TidepoolServiceKitUI.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; path = TidepoolServiceKitUI.framework; sourceTree = BUILT_PRODUCTS_DIR; };
+		3B4FD3D12E05E40300EDDB1E /* SimpleCob.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SimpleCob.swift; sourceTree = "<group>"; };
 		3B5CD1E92D4912A600CE213C /* OpenAPSSwift.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = OpenAPSSwift.swift; sourceTree = "<group>"; };
 		3B5CD1EA2D4912A600CE213C /* JSONBridge.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = JSONBridge.swift; sourceTree = "<group>"; };
 		3B5CD2912D4AEA3C00CE213C /* Basal.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Basal.swift; sourceTree = "<group>"; };
@@ -3691,6 +3693,7 @@
 				DD9E6DA42D5A66B500514CEC /* MealGenerator.swift */,
 				DD9E6DA12D59A12200514CEC /* MealHistory.swift */,
 				DD9E6DA62D5A694900514CEC /* MealTotal.swift */,
+				3B4FD3D12E05E40300EDDB1E /* SimpleCob.swift */,
 			);
 			path = Meal;
 			sourceTree = "<group>";
@@ -4577,6 +4580,7 @@
 				3811DE5D25C9D4D500A708ED /* Publisher.swift in Sources */,
 				E00EEC0727368630002FF094 /* APSAssembly.swift in Sources */,
 				BD249D8A2D42FC1200412DEB /* GlucosePercentileChart.swift in Sources */,
+				3B4FD3D22E05E40700EDDB1E /* SimpleCob.swift in Sources */,
 				38B4F3AF25E2979F00E76A18 /* IndexedCollection.swift in Sources */,
 				58D08B222C8DAA8E00AA37D3 /* OverrideView.swift in Sources */,
 				BD0B2EF32C5998E600B3298F /* MealPresetView.swift in Sources */,

Trio/Sources/APS/OpenAPSSwift/Meal/SimpleCob.swift

@@ -0,0 +1,48 @@
+import Foundation
+
+struct SimpleCob {
+    /// Calculate COB using simple piecewise linear absorption
+    /// Returns (totalCarbs, currentCOB)
+    static func calculate(
+        treatments: [MealInput],
+        currentTime: Date,
+        absorptionHours: Decimal = 3  // Default 3 hours
+    ) -> (carbs: Decimal, cob: Decimal) {
+        
+        var totalCarbs: Decimal = 0
+        var totalCOB: Decimal = 0
+        
+        let absorptionMinutes = absorptionHours * 60
+        let delayMinutes: Decimal = 15     // 15 min delay before absorption starts
+        let peakMinutes: Decimal = 60      // Peak at 1 hour (50% absorbed)
+        
+        for treatment in treatments {
+            guard let carbs = treatment.carbs, carbs > 0 else { continue }
+            
+            let minutesSinceMeal = Decimal(currentTime.timeIntervalSince(treatment.timestamp) / 60)
+            
+            // Skip future meals or fully absorbed meals
+            guard minutesSinceMeal >= 0, minutesSinceMeal <= absorptionMinutes else { continue }
+            
+            totalCarbs += carbs
+            
+            // Calculate absorption fraction
+            let absorbed: Decimal
+            if minutesSinceMeal < delayMinutes {
+                // No absorption yet
+                absorbed = 0
+            } else if minutesSinceMeal < peakMinutes {
+                // Linear ramp to 50% at peak
+                absorbed = 0.5 * (minutesSinceMeal - delayMinutes) / (peakMinutes - delayMinutes)
+            } else {
+                // Linear ramp from 50% to 100%
+                absorbed = 0.5 + 0.5 * (minutesSinceMeal - peakMinutes) / (absorptionMinutes - peakMinutes)
+            }
+            
+            let remaining = carbs * (1 - absorbed)
+            totalCOB += remaining
+        }
+        
+        return (totalCarbs, max(0, totalCOB))
+    }
+}