implement multi stopwatch

MultiChrono/ContentView.swift

@@ -6,16 +6,73 @@
 //
 
 import SwiftUI
+import Combine
+
+class ContentViewModel: ObservableObject {
+    @Published var stopwatches: [Stopwatch] = []
+    
+    func addStopwatch(name: String) {
+        let newStopwatch = Stopwatch(name: name)
+        stopwatches.append(newStopwatch)
+    }
+    
+    func deleteStopwatch(at index: Int) {
+        stopwatches[index].pause() // Ensure timer is stopped
+        stopwatches.remove(at: index)
+    }
+    
+    func deleteStopwatch(id: UUID) {
+        if let index = stopwatches.firstIndex(where: { $0.id == id }) {
+            deleteStopwatch(at: index)
+        }
+    }
+}
 
 struct ContentView: View {
+    @StateObject private var viewModel = ContentViewModel()
+    @State private var isShowingAddSheet = false
+    
     var body: some View {
-        VStack {
-            Image(systemName: "globe")
-                .imageScale(.large)
-                .foregroundStyle(.tint)
-            Text("Hello, world!")
+        NavigationStack {
+            List {
+                ForEach(viewModel.stopwatches) { stopwatch in
+                    StopwatchRow(stopwatch: stopwatch, onDelete: {
+                        viewModel.deleteStopwatch(id: stopwatch.id)
+                    })
+                }
+                .onDelete { indexSet in
+                    for index in indexSet {
+                        viewModel.deleteStopwatch(at: index)
+                    }
+                }
+            }
+            .listStyle(.plain)
+            .navigationTitle("MultiChrono")
+            .toolbar {
+                ToolbarItem(placement: .primaryAction) {
+                    Button(action: {
+                        isShowingAddSheet = true
+                    }) {
+                        Image(systemName: "plus")
+                    }
+                }
+            }
+            .sheet(isPresented: $isShowingAddSheet) {
+                AddStopwatchView { name in
+                    viewModel.addStopwatch(name: name)
+                    isShowingAddSheet = false
+                }
+            }
+            .overlay {
+                if viewModel.stopwatches.isEmpty {
+                    ContentUnavailableView(
+                        "No Stopwatches",
+                        systemImage: "timer",
+                        description: Text("Tap the + button to create a stopwatch.")
+                    )
+                }
+            }
         }
-        .padding()
     }
 }