Handle empty state and resetting the script

Source/Yasba/Views/Sieve Script Builder/SieveScriptBuilderView.swift

@@ -7,24 +7,21 @@ import AppKit
 // MARK: - Root
 
 struct SieveScriptBuilderView: View {
-    @State var model: SieveScriptViewModel
+    @StateObject var model: SieveScriptViewModel
     @State private var libraryWidth: CGFloat = 320
     @State private var shouldPresentSheet = false
     @State private var renderedScriptText: String = ""
+    @State private var shouldShowClearConfirmation = false
 
     var body: some View {
         HSplitView {
             ZStack(alignment: .topLeading) {
                 Color.primary.colorInvert()
                     .ignoresSafeArea()
 
-                Toolbar() {
-                    renderedScriptText = model.render()
-                    shouldPresentSheet = true
-                }
-                .ignoresSafeArea()
+                toolbar
 
-                SieveScriptView(viewModel: $model)
+                SieveScriptView(viewModel: model)
                     .padding([.leading, .top], 24)
                     .frame(minWidth: 420,
                            maxWidth: .infinity,
@@ -49,30 +46,68 @@ struct SieveScriptBuilderView: View {
         } content: {
             RenderedSieveScriptView(scriptText: $renderedScriptText)
         }
+        .alert("Clear Script?", isPresented: $shouldShowClearConfirmation) {
+            Button("Cancel", role: .cancel) { }
+            Button("Clear", role: .destructive) {
+                model.clear()
+            }
+        } message: {
+            Text("This will remove all commands from the script. This action cannot be undone.")
+        }
+    }
+
+    @ViewBuilder
+    private var toolbar: some View {
+        Toolbar {
+            if !model.rowTokens.isEmpty {
+                ToolbarButton(icon: "trash") {
+                    shouldShowClearConfirmation = true
+                }
+            }
+            ToolbarButton(icon: "note.text") {
+                renderedScriptText = model.render()
+                shouldPresentSheet = true
+            }
+        }
+        .ignoresSafeArea()
     }
 }
 
-private struct Toolbar: View {
-    var onRender: (() -> Void)
+private struct Toolbar<Content: View>: View {
+    var content: Content
+
+    init(@ViewBuilder content: () -> Content) {
+        self.content = content()
+    }
 
     var body: some View {
-        HStack {
+        HStack(spacing: 32) {
             Spacer()
-            Button {
-                onRender()
-            } label: {
-                Image(systemName: "note.text")
-                    .resizable()
-                    .frame(width: 18, height: 18)
-            }
-            .buttonStyle(.plain)
-
+            content
         }
         .padding(.trailing, 24)
         .frame(height: 50)
     }
 }
 
+private struct ToolbarButton: View {
+    private let size: CGFloat = 22
+
+    let icon: String
+    let action: () -> Void
+
+    var body: some View {
+        Button {
+            action()
+        } label: {
+            Image(systemName: icon)
+                .resizable()
+                .frame(width: size, height: size)
+        }
+        .buttonStyle(.plain)
+    }
+}
+
 #Preview {
     SieveScriptBuilderView(model: SieveScriptViewModel())
         .frame(width: 1120, height: 720)

Source/Yasba/Views/Sieve Script/SieveScriptView.swift

@@ -2,7 +2,7 @@ import SwiftUI
 import UniformTypeIdentifiers
 
 struct SieveScriptView: View {
-    @Binding private var viewModel: SieveScriptViewModel
+    @ObservedObject private var viewModel: SieveScriptViewModel
     @State private var draggedRange: Range<Int>? = nil
     @State private var dropGapIndex: Int? = nil
     @State private var rowHeights: [Int: CGFloat] = [:]
@@ -12,6 +12,10 @@ struct SieveScriptView: View {
     var tokens: [RowToken] { viewModel.rowTokens }
     var indents: [Int] { viewModel.indentation(for: tokens) }
 
+    init(viewModel: SieveScriptViewModel) {
+        self.viewModel = viewModel
+    }
+
     var filteredIndices: [Int] {
         if let span = draggedRange { return Array(tokens.indices).filter { !span.contains($0) } }
         return Array(tokens.indices)
@@ -29,22 +33,52 @@ struct SieveScriptView: View {
         return CGFloat(indents.last ?? 0) * 24
     }
 
-    init(viewModel: Binding<SieveScriptViewModel>) {
-        self._viewModel = viewModel
-    }
-
     var body: some View {
         ZStack(alignment: .center) {
             HStack {
                 Spacer()
-                scriptList
-                    .frame(maxWidth: 1000)
+                if viewModel.rowTokens.isEmpty {
+                    emptyDropArea
+                        .frame(maxWidth: 1000)
+                } else {
+                    scriptList
+                        .frame(maxWidth: 1000)
+                }
                 Spacer()
             }
             .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .top)
         }
         .frame(maxWidth: .infinity, maxHeight: .infinity)
     }
+
+    @ViewBuilder
+        private var emptyDropArea: some View {
+            VStack(spacing: 12) {
+                if dropGapIndex != nil || draggedRange != nil {
+                    PlaceholderRowView()
+                        .padding(.leading, 0)
+                        .transition(.opacity)
+                } else {
+                    Text("Drag a command from the sidebar to start writing your script.")
+                        .font(.title2)
+                        .foregroundStyle(Color.secondary)
+                        .multilineTextAlignment(.center)
+                        .padding(.horizontal, 24)
+                }
+            }
+            .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .top)
+            .contentShape(Rectangle())
+            .onDrop(
+                of: [UTType.utf8PlainText],
+                delegate: UnifiedDropDelegate(
+                    target: .fixedGap(0),
+                    draggedRange: $draggedRange,
+                    dropGapIndex: $dropGapIndex,
+                    rowHeights: $rowHeights,
+                    viewModel: viewModel
+                )
+            )
+        }
 
     @ViewBuilder
     var scriptList: some View {
@@ -151,7 +185,32 @@ struct SieveScriptView: View {
     }
 }
 
-#Preview {
+#Preview("Not empty") {
+    @Previewable @State var viewModel = SieveScriptViewModel(script: [
+        AddFlagCommand(tag: "Spam"),
+        IfCommand(
+            quantifier: .any,
+            tests: [
+                .header(["from"], match: .contains, keys: ["[email protected]"]),
+                .exists(["x-marked-spam"])
+            ],
+            thenChildren: [
+                AddFlagCommand(tag: "Label 1"),
+                AddFlagCommand(tag: "Label 2")
+            ],
+            elseChildren: [
+                AddFlagCommand(tag: "Tag 1")
+            ]
+        ),
+        FileIntoCommand(mailbox: "Social"),
+        AddFlagCommand(tag: "Tag 1"),
+        AddFlagCommand(tag: "Tag 2"),
+        StopCommand()
+    ])
+    SieveScriptView(viewModel: viewModel)
+}
+
+#Preview("Empty") {
     @Previewable @State var viewModel = SieveScriptViewModel()
-    SieveScriptView(viewModel: $viewModel)
+    SieveScriptView(viewModel: viewModel)
 }

Source/Yasba/Views/Sieve Script/SieveScriptViewModel.swift

@@ -2,27 +2,7 @@ import Combine
 
 final class SieveScriptViewModel: ObservableObject {
 
-    private var script: [AnySieveCommand] = [
-        AddFlagCommand(tag: "Spam"),
-        IfCommand(
-            quantifier: .any,
-            tests: [
-                .header(["from"], match: .contains, keys: ["[email protected]"]),
-                .exists(["x-marked-spam"])
-            ],
-            thenChildren: [
-                AddFlagCommand(tag: "Label 1"),
-                AddFlagCommand(tag: "Label 2")
-            ],
-            elseChildren: [
-                AddFlagCommand(tag: "Tag 1")
-            ]
-        ),
-        FileIntoCommand(mailbox: "Social"),
-        AddFlagCommand(tag: "Tag 1"),
-        AddFlagCommand(tag: "Tag 2"),
-        StopCommand()
-    ]
+    private var script: [AnySieveCommand] = []
 
     private let mapper: RowTokenMapping
     private let editor: RowTokenEditing
@@ -32,9 +12,11 @@ final class SieveScriptViewModel: ObservableObject {
         mapper.tokens(from: script)
     }
 
-    init(mapper: RowTokenMapping = RowTokenMapper(),
+    init(script: [AnySieveCommand] = [],
+         mapper: RowTokenMapping = RowTokenMapper(),
          editor: RowTokenEditing = RowTokenEditor(),
          scriptRenderer: SieveScriptRenderer = .default) {
+        self.script = script
         self.mapper = mapper
         self.editor = editor
         self.scriptRenderer = scriptRenderer
@@ -70,8 +52,15 @@ final class SieveScriptViewModel: ObservableObject {
     func render() -> String {
         return scriptRenderer.render(commands: script)
     }
+
+    func clear() {
+        applyTokenEdit { tokens in
+            tokens = []
+        }
+    }
 
     private func applyTokenEdit(_ transform: (inout [RowToken]) -> Void) {
+        objectWillChange.send()
         var tokens = mapper.tokens(from: script)
         transform(&tokens)
         self.script = mapper.script(from: tokens)