イベント詳細表示と日付変更検知によるカレンダーのUX向上

- イベント行にポップアップによる詳細ビュー（EventDetailView）を追加し、イベントの場所・メモ・URLなどをリッチに表示
- ボタン化によりイベントタップ時の操作性を改善
- NotificationCenterでNSCalendarDayChangedに対応し、日付変更時にイベントリストを自動更新するよう拡張
- 日時や区切りの表示、日本語ロケールへの対応などイベント詳細情報のUIを最適化

Sources/CalendarService.swift

@@ -27,6 +27,14 @@ class CalendarService: ObservableObject {
         ) { [weak self] _ in
             self?.handleEventStoreChanged()
         }
+
+        NotificationCenter.default.addObserver(
+            forName: .NSCalendarDayChanged,
+            object: nil,
+            queue: .main
+        ) { [weak self] _ in
+            self?.handleDayChanged()
+        }
     }
 
     @MainActor
@@ -35,6 +43,11 @@ class CalendarService: ObservableObject {
         loadEvents()
     }
 
+    @MainActor
+    private func handleDayChanged() {
+        loadEvents()
+    }
+
     @MainActor
     func requestAccess() async {
         do {

Sources/ContentView.swift

@@ -126,34 +126,45 @@ struct DayGroup {
 
 struct EventRow: View {
     let event: EKEvent
+    @State private var showingDetail = false
 
     var body: some View {
-        VStack(alignment: .leading, spacing: 4) {
-            HStack {
-                if event.isAllDay {
-                    Text("終日")
-                        .font(.caption)
-                        .foregroundColor(.secondary)
-                } else {
-                    Text(timeString(from: event.startDate, to: event.endDate))
+        Button(action: {
+            showingDetail = true
+        }) {
+            VStack(alignment: .leading, spacing: 4) {
+                HStack {
+                    if event.isAllDay {
+                        Text("終日")
+                            .font(.caption)
+                            .foregroundColor(.secondary)
+                    } else {
+                        Text(timeString(from: event.startDate, to: event.endDate))
+                            .font(.caption)
+                            .foregroundColor(.secondary)
+                    }
+                    if let calendar = event.calendar {
+                        Circle()
+                            .fill(Color(calendar.color))
+                            .frame(width: 8, height: 8)
+                    }
+                }
+                Text(event.title ?? "無題のイベント")
+                    .font(.body)
+                if let location = event.location, !location.isEmpty {
+                    Text(location)
                         .font(.caption)
                         .foregroundColor(.secondary)
                 }
-                if let calendar = event.calendar {
-                    Circle()
-                        .fill(Color(calendar.color))
-                        .frame(width: 8, height: 8)
-                }
-            }
-            Text(event.title ?? "無題のイベント")
-                .font(.body)
-            if let location = event.location, !location.isEmpty {
-                Text(location)
-                    .font(.caption)
-                    .foregroundColor(.secondary)
             }
+            .padding(.vertical, 4)
+            .frame(maxWidth: .infinity, alignment: .leading)
+            .contentShape(Rectangle())
+        }
+        .buttonStyle(.plain)
+        .popover(isPresented: $showingDetail) {
+            EventDetailView(event: event)
         }
-        .padding(.vertical, 4)
     }
 
     private func timeString(from start: Date, to end: Date) -> String {
@@ -162,3 +173,88 @@ struct EventRow: View {
         return "\(formatter.string(from: start)) - \(formatter.string(from: end))"
     }
 }
+
+struct EventDetailView: View {
+    let event: EKEvent
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 12) {
+            HStack {
+                if let calendar = event.calendar {
+                    Circle()
+                        .fill(Color(calendar.color))
+                        .frame(width: 12, height: 12)
+                    Text(calendar.title)
+                        .font(.caption)
+                        .foregroundColor(.secondary)
+                }
+            }
+
+            Text(event.title ?? "無題のイベント")
+                .font(.headline)
+
+            Divider()
+
+            VStack(alignment: .leading, spacing: 8) {
+                if event.isAllDay {
+                    HStack {
+                        Image(systemName: "clock")
+                            .foregroundColor(.secondary)
+                            .frame(width: 20)
+                        Text("終日")
+                    }
+                } else {
+                    HStack(alignment: .top) {
+                        Image(systemName: "clock")
+                            .foregroundColor(.secondary)
+                            .frame(width: 20)
+                        VStack(alignment: .leading, spacing: 2) {
+                            Text(formatDateTime(event.startDate))
+                            Text("〜")
+                                .foregroundColor(.secondary)
+                                .font(.caption)
+                            Text(formatDateTime(event.endDate))
+                        }
+                    }
+                }
+
+                if let location = event.location, !location.isEmpty {
+                    HStack(alignment: .top) {
+                        Image(systemName: "location")
+                            .foregroundColor(.secondary)
+                            .frame(width: 20)
+                        Text(location)
+                    }
+                }
+
+                if let notes = event.notes, !notes.isEmpty {
+                    HStack(alignment: .top) {
+                        Image(systemName: "note.text")
+                            .foregroundColor(.secondary)
+                            .frame(width: 20)
+                        Text(notes)
+                            .textSelection(.enabled)
+                    }
+                }
+
+                if let url = event.url {
+                    HStack(alignment: .top) {
+                        Image(systemName: "link")
+                            .foregroundColor(.secondary)
+                            .frame(width: 20)
+                        Link(url.absoluteString, destination: url)
+                    }
+                }
+            }
+        }
+        .padding()
+        .frame(minWidth: 300, maxWidth: 400)
+    }
+
+    private func formatDateTime(_ date: Date) -> String {
+        let formatter = DateFormatter()
+        formatter.dateFormat = "M月d日(E) HH:mm"
+        formatter.locale = Locale(identifier: "ja_JP")
+        return formatter.string(from: date)
+    }
+}