blowup now locks out subsequent rolls, unit tests added

Bunch-O--Dice/MainView.swift

@@ -226,14 +226,16 @@ struct MainView: View {
                 VStack {
                     Text("Blow Up")
                     VStack {
-                        Button(action: {current.dice.blowup(dice: .six)})
-                        {Image(systemName: "die.face.6")
+                        Button(action: { current.applyBlowup(face: .six) }) {
+                            Image(systemName: "die.face.6")
                                 .foregroundColor(.primary)
                         }
-                        Button(action: {current.dice.blowup(dice: .five)})
-                        {Image(systemName: "die.face.5")
+                        .disabled(current.blowupUsed)
+                        Button(action: { current.applyBlowup(face: .five) }) {
+                            Image(systemName: "die.face.5")
                                 .foregroundColor(.primary)
                         }
+                        .disabled(current.blowupUsed)
                     }
                     .padding()
                     .font(.system(size: controlSize))

Bunch-O--Dice/Model/RollState.swift

@@ -150,6 +150,8 @@ class Roll: ObservableObject {
     @Published var hitHasRerolled = false
     @Published var woundHasRerolled = false
     @Published var saveHasRerolled = false
+
+    @Published var blowupUsed = false
   
     // calculated variables
     var totalDigits: [Int] {
@@ -341,6 +343,7 @@ class Roll: ObservableObject {
             self.total = save
             self.state = .hit
             hitHasRerolled = false
+            blowupUsed = false
         }
         self.dice.roll(howMany: self.total)
     }
@@ -349,6 +352,20 @@ class Roll: ObservableObject {
     func resetPool() {
         dice.roll(howMany: total)
         hitHasRerolled = false
+        blowupUsed = false
+    }
+
+    func applyBlowup(face: Dice.DiceType) {
+        guard !blowupUsed else { return }
+        switch face {
+        case .six:
+            dice.blowup(dice: .six)
+        case .five:
+            dice.blowup(dice: .five)
+        default:
+            break
+        }
+        blowupUsed = true
     }
 
     func applyReroll() {

Bunch-O--Dice/OnboardingView.swift

@@ -8,14 +8,14 @@
 import SwiftUI
 
 struct OnboardingView: View {
-    private var courses = DTCourse.pages
+    private let courses = DTCourse.pages
     @State private var selection = 0
     @EnvironmentObject var current: Roll
     
     var body: some View {
         VStack {
             TabView(selection: $selection) {
-                ForEach(courses.indices) { idx in
+                ForEach(courses.indices, id: \.self) { idx in
                     VStack(spacing: 0) {
                         Spacer()
                         Text(courses[idx].title)