Merge pull request #430 from kingst/iob-chart-scale-fix

Account for scaled IoB in chart axis

Trio/Sources/Modules/Home/HomeStateModel+Setup/ChartAxisSetup.swift

@@ -93,9 +93,8 @@ extension Home.StateModel {
 
             // Ensure min and max IOB values exist, or set defaults
             if let minIob = minIob, let maxIob = maxIob {
-                let adjustedMin = minIob < 0 ? minIob - 2 : 0
                 Task {
-                    await self.updateIobChartBounds(minValue: adjustedMin, maxValue: maxIob + 2)
+                    await self.updateIobChartBounds(minValue: minIob, maxValue: maxIob)
                 }
             } else {
                 Task {

Trio/Sources/Modules/Home/View/Chart/ChartElements/CobIobChart.swift

@@ -54,8 +54,10 @@ extension MainChartView {
     }
 
     func combinedYDomain() -> ClosedRange<Double> {
-        let minValue = min(state.minValueCobChart, state.minValueIobChart)
-        let maxValue = max(state.maxValueCobChart, state.maxValueIobChart)
+        let iobMin = scaleIobAmountForChart(state.minValueIobChart)
+        let iobMax = scaleIobAmountForChart(state.maxValueIobChart)
+        let minValue = min(state.minValueCobChart, iobMin)
+        let maxValue = max(state.maxValueCobChart, iobMax)
         return Double(minValue) ... Double(maxValue)
     }
 
@@ -79,6 +81,17 @@ extension MainChartView {
         .position(by: .value("Axis", axis))
     }
 
+    /// Scales IOB amounts for chart display.
+    ///
+    /// As IOB and COB share the same Y axis and COB is usually >> IOB,
+    /// we need to visually weigh IOB by multiplying it by a scaling factor:
+    ///
+    /// - Parameter rawAmount: The unscaled IOB amount
+    /// - Returns: The scaled IOB amount for visual representation
+    private func scaleIobAmountForChart<T: Numeric & Comparable>(_ rawAmount: T) -> T where T: ExpressibleByIntegerLiteral {
+        rawAmount > 0 ? rawAmount * 8 : rawAmount * 9
+    }
+
     func drawCOBIOBChart() -> some ChartContent {
         // Filter out duplicate entries by `deliverAt`,
         // We sometimes get two determinations when editing carbs, one without the entry-to-be-edited and then another one after editing the entry.
@@ -115,9 +128,7 @@ extension MainChartView {
             // MARK: - IOB line and area mark
 
             let rawAmount = item.iob?.doubleValue ?? 0
-
-            // as iob and cob share the same y axis and cob is usually >> iob we need to weigh iob visually
-            let amountIOB: Double = rawAmount > 0 ? rawAmount * 8 : rawAmount * 9
+            let amountIOB: Double = scaleIobAmountForChart(rawAmount)
 
             AreaMark(x: .value("Time", date), y: .value("Amount", amountIOB))
                 .foregroundStyle(by: .value("Type", "IOB"))