Allow reordering custom metrics sources

LocalPackage/Sources/Model/Stores/CustomMetricsSettings.swift

@@ -115,6 +115,19 @@ public final class CustomMetricsSettings: Composable {
         case .removingCustomMetricsSourceCancelled:
             pendingRemovalSourceID = nil
 
+        case let .customMetricsSourceMoved(sourceID, destinationID):
+            guard let sourceIndex = customMetricsSources.firstIndex(where: { $0.id == sourceID }),
+                  let destinationIndex = customMetricsSources.firstIndex(where: { $0.id == destinationID }),
+                  sourceIndex != destinationIndex else {
+                return
+            }
+            let source = customMetricsSources.remove(at: sourceIndex)
+            customMetricsSources.insert(source, at: destinationIndex)
+            var configuration = userDefaultsRepository.customMetricsConfiguration
+            configuration.sources = customMetricsSources
+            userDefaultsRepository.customMetricsConfiguration = configuration
+            customMetricsService.emitConfigurationChange()
+
         case let .customMetricsSourceLinkTapped(source):
             do {
                 try customMetricsService.perform(
@@ -150,6 +163,7 @@ public final class CustomMetricsSettings: Composable {
         case removeCustomMetricsSourceButtonTapped(UUID)
         case removingCustomMetricsSourceConfirmed
         case removingCustomMetricsSourceCancelled
+        case customMetricsSourceMoved(UUID, UUID)
         case customMetricsSourceLinkTapped(CustomMetricsSource)
         case onError(RCNError)
     }

LocalPackage/Sources/UserInterface/Views/Settings/MetricsSettings/CustomMetricsSettingsSectionView.swift

@@ -18,25 +18,45 @@
  limitations under the License.
  */
 
+import AppKit
 import Model
+import Observation
 import SwiftUI
+import UniformTypeIdentifiers
 
 struct CustomMetricsSettingsSectionView: View {
     @State var store: CustomMetricsSettings
+    @State private var dragState = CustomMetricsSourceDragState()
 
     var body: some View {
         Section {
             ForEach(store.customMetricsSources) { source in
                 CustomMetricsSourceRowView(
                     source: source,
                     isErrorDetected: store.failedCustomMetricsSourceIDs.contains(source.id),
+                    dragStarted: {
+                        dragState.begin(sourceID: source.id)
+                    },
                     removeButtonTapped: {
                         await store.send(.removeCustomMetricsSourceButtonTapped(source.id))
                     },
                     sourceLinkTapped: {
                         await store.send(.customMetricsSourceLinkTapped(source))
                     }
                 )
+                .opacity(dragState.hiddenSourceID == source.id ? 0 : 1)
+                .onDrop(
+                    of: [.text],
+                    delegate: CustomMetricsSourceDropDelegate(
+                        destinationSourceID: source.id,
+                        dragState: dragState,
+                        move: { sourceID, destinationID in
+                            Task {
+                                await store.send(.customMetricsSourceMoved(sourceID, destinationID))
+                            }
+                        }
+                    )
+                )
             }
             HStack {
                 Spacer()
@@ -116,9 +136,70 @@ struct CustomMetricsSettingsSectionView: View {
             await store.send(.task)
         }
         .onDisappear {
+            dragState.end()
             Task {
                 await store.send(.onDisappear)
             }
         }
     }
 }
+
+@MainActor @Observable
+private final class CustomMetricsSourceDragState {
+    var sourceID: UUID?
+    var hiddenSourceID: UUID?
+
+    @ObservationIgnored private var mouseUpMonitor: Any?
+    @ObservationIgnored private var revealTask: Task<Void, Never>?
+
+    func begin(sourceID: UUID) {
+        revealTask?.cancel()
+        self.sourceID = sourceID
+        hiddenSourceID = sourceID
+        guard mouseUpMonitor == nil else { return }
+        mouseUpMonitor = NSEvent.addLocalMonitorForEvents(matching: .leftMouseUp) { [weak self] event in
+            self?.end()
+            return event
+        }
+    }
+
+    func end() {
+        let wasDragging = sourceID != nil
+        sourceID = nil
+        if let mouseUpMonitor {
+            NSEvent.removeMonitor(mouseUpMonitor)
+            self.mouseUpMonitor = nil
+        }
+        guard wasDragging else { return }
+        revealTask?.cancel()
+        revealTask = Task { [weak self] in
+            try? await Task.sleep(for: .milliseconds(200))
+            guard !Task.isCancelled else { return }
+            self?.hiddenSourceID = nil
+            self?.revealTask = nil
+        }
+    }
+}
+
+private struct CustomMetricsSourceDropDelegate: DropDelegate {
+    var destinationSourceID: UUID
+    var dragState: CustomMetricsSourceDragState
+    var move: (UUID, UUID) -> Void
+
+    func dropEntered(info: DropInfo) {
+        guard let draggedSourceID = dragState.sourceID,
+              draggedSourceID != destinationSourceID else {
+            return
+        }
+        move(draggedSourceID, destinationSourceID)
+    }
+
+    func dropUpdated(info: DropInfo) -> DropProposal? {
+        DropProposal(operation: .move)
+    }
+
+    func performDrop(info: DropInfo) -> Bool {
+        dragState.end()
+        return true
+    }
+}

LocalPackage/Sources/UserInterface/Views/Settings/MetricsSettings/CustomMetricsSourceRowView.swift

@@ -22,22 +22,32 @@ import DataSource
 import SwiftUI
 
 struct CustomMetricsSourceRowView: View {
+    private let controlWidth: CGFloat = 24
+    private let controlSpacing: CGFloat = 8
+
     var source: CustomMetricsSource
     var isErrorDetected: Bool
+    var dragStarted: () -> Void
     var removeButtonTapped: () async -> Void
     var sourceLinkTapped: () async -> Void
 
     var body: some View {
         LabeledContent {
-            Button(role: .destructive) {
-                Task {
-                    await removeButtonTapped()
+            HStack(spacing: controlSpacing) {
+                Image(systemName: "line.3.horizontal")
+                    .foregroundStyle(.secondary)
+                    .frame(width: controlWidth)
+                Button(role: .destructive) {
+                    Task {
+                        await removeButtonTapped()
+                    }
+                } label: {
+                    Image(systemName: "minus.circle")
+                        .foregroundStyle(Color.red)
                 }
-            } label: {
-                Image(systemName: "minus.circle")
-                    .foregroundStyle(Color.red)
+                .buttonStyle(.borderless)
+                .frame(width: controlWidth)
             }
-            .buttonStyle(.borderless)
         } label: {
             Text(source.displayName)
                 .truncationMode(.middle)
@@ -55,5 +65,31 @@ struct CustomMetricsSourceRowView: View {
                 }
             }
         }
+        .contentShape(
+            .interaction,
+            CustomMetricsSourceDragHandleShape(
+                width: controlWidth,
+                trailingInset: controlWidth + controlSpacing
+            )
+        )
+        .contentShape(.dragPreview, Rectangle())
+        .onDrag {
+            dragStarted()
+            return NSItemProvider(object: source.id.uuidString as NSString)
+        }
+    }
+}
+
+private struct CustomMetricsSourceDragHandleShape: Shape {
+    var width: CGFloat
+    var trailingInset: CGFloat
+
+    func path(in rect: CGRect) -> Path {
+        Path(CGRect(
+            x: rect.maxX - trailingInset - width,
+            y: rect.minY,
+            width: width,
+            height: rect.height
+        ))
     }
 }

LocalPackage/Tests/ModelTests/StoreTests/CustomMetricsSettingsTests.swift

@@ -234,6 +234,30 @@ struct CustomMetricsSettingsTests {
         #expect(sut.customMetricsSources.count == 1)
     }
 
+    @MainActor @Test
+    func send_customMetricsSourceMoved_reorders_sources_persists_and_emits_change() async {
+        let appState = AllocatedUnfairLock<AppState>(initialState: .init())
+        let sources = (1...3).map {
+            CustomMetricsSource(
+                id: UUID($0),
+                displayName: "Source \($0)",
+                fileURL: URL(filePath: "/tmp/source-\($0).json"),
+                bookmark: Data(),
+                createdAt: Date(timeIntervalSince1970: 0)
+            )
+        }
+        let storage = UserDefaultsClient.storage(initialSources: sources)
+        let sut = CustomMetricsSettings(.testDependencies(
+            appStateClient: .testDependency(appState),
+            userDefaultsClient: storage.client
+        ))
+        await sut.send(.customMetricsSourceMoved(sources[0].id, sources[2].id))
+        let expectedSources = [sources[1], sources[2], sources[0]]
+        #expect(sut.customMetricsSources == expectedSources)
+        #expect(storage.currentConfiguration()?.sources == expectedSources)
+        #expect(appState.withLock(\.customMetricsConfigurationChanges.latestValue) != nil)
+    }
+
     @MainActor @Test
     func send_customMetricsSourceLinkTapped_activates_file_viewer_with_resolved_url() async {
         let resolvedURL = URL(filePath: "/tmp/resolved.json")