Paywalls: extracted intro eligibility out of templates (#2901)

This simplifies template views further. Before they needed to get the
`TrialOrIntroEligibilityChecker` environment and call the appropriate
method.

Now they just need to inject the new `IntroEligibilityViewModel`, and
extract either `.allEligibility` or `singleEligibility` based on the
type of template. Everything else is done automatically outside of
templates.

RevenueCatUI/Data/IntroEligibilityViewModel.swift

@@ -0,0 +1,45 @@
+//
+//  IntroEligibilityViewModel.swift
+//  
+//
+//  Created by Nacho Soto on 7/26/23.
+//
+
+import RevenueCat
+import SwiftUI
+
+/// Holds the state for dynamically computed `IntroEligibilityStatus`
+/// for single or multi-package templates, depending on `PackageConfiguration`.
+@available(iOS 16.0, macOS 13.0, tvOS 16.0, *)
+@MainActor
+final class IntroEligibilityViewModel: ObservableObject {
+
+    typealias PackageConfiguration = TemplateViewConfiguration.PackageConfiguration
+
+    private let introEligibilityChecker: TrialOrIntroEligibilityChecker
+
+    init(introEligibilityChecker: TrialOrIntroEligibilityChecker) {
+        self.introEligibilityChecker = introEligibilityChecker
+    }
+
+    @Published
+    private(set) var allEligibility: [Package: IntroEligibilityStatus] = [:]
+    @Published
+    private(set) var singleEligibility: IntroEligibilityStatus?
+
+}
+
+@available(iOS 16.0, macOS 13.0, tvOS 16.0, *)
+extension IntroEligibilityViewModel {
+
+    func computeEligibility(for packages: PackageConfiguration) async {
+        switch packages {
+        case let .single(package):
+            self.singleEligibility = await self.introEligibilityChecker.eligibility(for: package.content)
+
+        case let .multiple(_, _, packages):
+            self.allEligibility = await self.introEligibilityChecker.eligibility(for: packages.map(\.content))
+        }
+    }
+
+}

RevenueCatUI/PaywallView.swift

@@ -134,8 +134,9 @@ struct LoadedOfferingPaywallView: View {
     private let offering: Offering
     private let paywall: PaywallData
     private let mode: PaywallViewMode
-    private let introEligibility: TrialOrIntroEligibilityChecker
 
+    @StateObject
+    private var introEligibility: IntroEligibilityViewModel
     @ObservedObject
     private var purchaseHandler: PurchaseHandler
 
@@ -152,13 +153,18 @@ struct LoadedOfferingPaywallView: View {
         self.offering = offering
         self.paywall = paywall
         self.mode = mode
-        self.introEligibility = introEligibility
+        self._introEligibility = .init(
+            wrappedValue: .init(introEligibilityChecker: introEligibility)
+        )
         self.purchaseHandler = purchaseHandler
     }
 
     var body: some View {
         let view = self.paywall
-            .createView(for: self.offering, mode: self.mode, locale: self.locale)
+            .createView(for: self.offering,
+                        mode: self.mode,
+                        introEligibility: self.introEligibility,
+                        locale: self.locale)
             .environmentObject(self.introEligibility)
             .environmentObject(self.purchaseHandler)
             .hidden(if: self.shouldHidePaywall)

RevenueCatUI/Templates/MultiPackageBoldTemplate.swift

@@ -5,25 +5,16 @@ import SwiftUI
 struct MultiPackageBoldTemplate: TemplateViewType {
 
     private let configuration: TemplateViewConfiguration
-
     @EnvironmentObject
-    private var introEligibilityChecker: TrialOrIntroEligibilityChecker
-
-    @State
-    private var introEligibility: [Package: IntroEligibilityStatus] = [:]
+    private var introEligibility: IntroEligibilityViewModel
 
     init(_ configuration: TemplateViewConfiguration) {
         self.configuration = configuration
     }
 
     var body: some View {
         MultiPackageTemplateContent(configuration: self.configuration,
-                                    introEligibility: self.introEligibility)
-        .task(id: self.configuration.packages) {
-            self.introEligibility = await self.introEligibilityChecker.eligibility(
-                for: self.configuration.packages.all.map(\.content)
-            )
-        }
+                                    introEligibility: self.introEligibility.allEligibility)
     }
 
 }

RevenueCatUI/Templates/SinglePackageStandardTemplate.swift

@@ -5,27 +5,16 @@ import SwiftUI
 struct SinglePackageStandardTemplate: TemplateViewType {
 
     private let configuration: TemplateViewConfiguration
-
     @EnvironmentObject
-    private var introEligibilityChecker: TrialOrIntroEligibilityChecker
-
-    @State
-    private var introEligibility: IntroEligibilityStatus?
+    private var introEligibility: IntroEligibilityViewModel
 
     init(_ configuration: TemplateViewConfiguration) {
         self.configuration = configuration
     }
 
     var body: some View {
         SinglePackageTemplateContent(configuration: self.configuration,
-                                     introEligibility: self.introEligibility)
-        .task(id: self.package) {
-            self.introEligibility = await self.introEligibilityChecker.eligibility(for: self.package)
-        }
-    }
-
-    private var package: Package {
-        return self.configuration.packages.single.content
+                                     introEligibility: self.introEligibility.singleEligibility)
     }
 
 }

RevenueCatUI/Templates/TemplateViewType.swift

@@ -25,10 +25,16 @@ private extension PaywallTemplate {
 extension PaywallData {
 
     @ViewBuilder
-    func createView(for offering: Offering, mode: PaywallViewMode, locale: Locale) -> some View {
+    func createView(for offering: Offering,
+                    mode: PaywallViewMode,
+                    introEligibility: IntroEligibilityViewModel,
+                    locale: Locale) -> some View {
         switch self.configuration(for: offering, mode: mode, locale: locale) {
         case let .success(configuration):
             Self.createView(template: self.template, configuration: configuration)
+                .task(id: offering) {
+                    await introEligibility.computeEligibility(for: configuration.packages)
+                }
                 .background(
                     Rectangle()
                         .foregroundColor(