Base fixes and test harness

PortfolioJournal/ViewModels/DashboardViewModel.swift

@@ -195,7 +195,11 @@ class DashboardViewModel: ObservableObject {
             snapshots: allSnapshots
         )
         updateEvolutionData(from: completedSnapshots, categories: categories)
-        latestPortfolioChange = calculateLatestChange(from: evolutionData)
+        latestPortfolioChange = calculateLatestCheckInChange(
+            sources: sources,
+            snapshots: allSnapshots,
+            fallback: evolutionData
+        )
 
         // Calculate portfolio forecast
         updatePortfolioForecast()
@@ -360,7 +364,7 @@ class DashboardViewModel: ObservableObject {
         snapshots: [Snapshot]
     ) -> [Snapshot] {
         guard let lastCompleted = MonthlyCheckInStore.latestCompletionDate()?.startOfMonth else {
-            return []
+            return snapshots
         }
 
         let completedMonthsAfter = completedMonthKeys(
@@ -371,6 +375,10 @@ class DashboardViewModel: ObservableObject {
 
         return snapshots.filter { snapshot in
             let monthDate = snapshot.date.startOfMonth
+            if let completionDate = MonthlyCheckInStore.completionDate(for: monthDate),
+               snapshot.date > completionDate {
+                return false
+            }
             if monthDate <= lastCompleted {
                 return true
             }
@@ -382,7 +390,7 @@ class DashboardViewModel: ObservableObject {
 
     private func calculateLatestChange(from data: [(date: Date, value: Decimal)]) -> PortfolioChange {
         guard data.count >= 2 else {
-            return PortfolioChange(absolute: 0, percentage: 0, label: "since last update")
+            return PortfolioChange(absolute: 0, percentage: 0, label: "since last check-in")
         }
         let last = data[data.count - 1]
         let previous = data[data.count - 2]
@@ -390,7 +398,58 @@ class DashboardViewModel: ObservableObject {
         let percentage = previous.value > 0
             ? NSDecimalNumber(decimal: absolute / previous.value).doubleValue * 100
             : 0
-        return PortfolioChange(absolute: absolute, percentage: percentage, label: "since last update")
+        return PortfolioChange(absolute: absolute, percentage: percentage, label: "since last check-in")
+    }
+
+    private func calculateLatestCheckInChange(
+        sources: [InvestmentSource],
+        snapshots: [Snapshot],
+        fallback: [(date: Date, value: Decimal)]
+    ) -> PortfolioChange {
+        let completedMonths = MonthlyCheckInStore.allEntries()
+            .compactMap { entry -> Date? in
+                entry.entry.completionDate != nil ? entry.date.startOfMonth : nil
+            }
+            .sorted()
+
+        guard completedMonths.count >= 2 else {
+            return calculateLatestChange(from: fallback)
+        }
+
+        let lastMonth = completedMonths[completedMonths.count - 1]
+        let previousMonth = completedMonths[completedMonths.count - 2]
+        let lastCompletion = MonthlyCheckInStore.completionDate(for: lastMonth) ?? lastMonth.endOfMonth
+        let previousCompletion = MonthlyCheckInStore.completionDate(for: previousMonth) ?? previousMonth.endOfMonth
+
+        let lastValue = totalPortfolioValue(asOf: lastCompletion, sources: sources, snapshots: snapshots)
+        let previousValue = totalPortfolioValue(asOf: previousCompletion, sources: sources, snapshots: snapshots)
+        let absolute = lastValue - previousValue
+        let percentage = previousValue > 0
+            ? NSDecimalNumber(decimal: absolute / previousValue).doubleValue * 100
+            : 0
+
+        return PortfolioChange(absolute: absolute, percentage: percentage, label: "since last check-in")
+    }
+
+    private func totalPortfolioValue(
+        asOf date: Date,
+        sources: [InvestmentSource],
+        snapshots: [Snapshot]
+    ) -> Decimal {
+        let snapshotsBySource = Dictionary(grouping: snapshots) { $0.source?.id }
+        var total = Decimal.zero
+
+        for source in sources {
+            let sourceId = source.id
+            guard let sourceSnapshots = snapshotsBySource[sourceId] else { continue }
+            if let latest = sourceSnapshots
+                .filter({ $0.date <= date })
+                .max(by: { $0.date < $1.date }) {
+                total += latest.decimalValue
+            }
+        }
+
+        return total
     }
 
     private func updatePortfolioForecast() {