Paywalls: added ability to calculate and localize subscription disc…

…ounts (#2943)

![Screenshot 2023-08-02 at 08 17
45](https://github.com/RevenueCat/purchases-ios/assets/685609/0c3ee7b8-1b37-4e6d-81d0-4b2d18086d82)

Useful for template 4, but also for others.

RevenueCatUI/Data/Localization.swift

@@ -89,6 +89,20 @@ enum Localization {
         return path.flatMap(Bundle.init(path:)) ?? containerBundle
     }
 
+    /// - Returns: localized string for a discount. Example: "37% off"
+    static func localized(
+        discount: Double,
+        locale: Locale
+    ) -> String {
+        assert(discount >= 0, "Invalid discount: \(discount)")
+
+        let number = Int((discount * 100).rounded(.toNearestOrAwayFromZero))
+        let format = self.localizedBundle(locale)
+            .localizedString(forKey: "%d%% off", value: nil, table: nil)
+
+        return String(format: format, number)
+    }
+
 }
 
 // MARK: - Private

RevenueCatUI/Data/TemplateViewConfiguration.swift

@@ -30,6 +30,7 @@ extension TemplateViewConfiguration {
 
         let content: RevenueCat.Package
         let localization: ProcessedLocalizedConfiguration
+        let discountRelativeToMostExpensivePerMonth: Double?
 
     }
 
@@ -107,33 +108,64 @@ extension TemplateViewConfiguration.PackageConfiguration {
         guard !packages.isEmpty else { throw TemplateError.noPackages }
         guard !filter.isEmpty else { throw TemplateError.emptyPackageList }
 
-        let filtered = TemplateViewConfiguration
-            .filter(packages: packages, with: filter)
+        let filtered = TemplateViewConfiguration.filter(packages: packages, with: filter)
+        let mostExpensivePricePerMonth = Self.mostExpensivePricePerMonth(in: filtered)
+
+        let filteredPackages = filtered
             .map { package in
                 TemplateViewConfiguration.Package(
                     content: package,
-                    localization: localization.processVariables(with: package, locale: locale)
+                    localization: localization.processVariables(with: package, locale: locale),
+                    discountRelativeToMostExpensivePerMonth: Self.discount(
+                        from: package.storeProduct.pricePerMonth?.doubleValue,
+                        relativeTo: mostExpensivePricePerMonth
+                    )
                 )
             }
 
-        guard let firstPackage = filtered.first else {
+        guard let firstPackage = filteredPackages.first else {
             throw TemplateError.couldNotFindAnyPackages(expectedTypes: filter)
         }
 
         switch setting {
         case .single:
             return .single(firstPackage)
         case .multiple:
-            let defaultPackage = filtered
+            let defaultPackage = filteredPackages
                 .first { $0.content.packageType == `default` }
                 ?? firstPackage
 
             return .multiple(first: firstPackage,
                              default: defaultPackage,
-                             all: filtered)
+                             all: filteredPackages)
         }
     }
 
+    private static func mostExpensivePricePerMonth(in packages: [Package]) -> Double? {
+        return packages
+            .lazy
+            .map(\.storeProduct)
+            .compactMap { product in
+                product.pricePerMonth.map {
+                    return (
+                        product: product,
+                        pricePerMonth: $0
+                    )
+                }
+            }
+            .max { productA, productB in
+                return productA.pricePerMonth.doubleValue < productB.pricePerMonth.doubleValue
+            }
+            .map(\.pricePerMonth.doubleValue)
+    }
+
+    private static func discount(from pricePerMonth: Double?, relativeTo mostExpensive: Double?) -> Double? {
+        guard let pricePerMonth, let mostExpensive else { return nil }
+        guard pricePerMonth < mostExpensive else { return nil }
+
+        return (mostExpensive - pricePerMonth) / mostExpensive
+    }
+
 }
 
 @available(iOS 16.0, macOS 13.0, tvOS 16.0, *)

RevenueCatUI/Resources/en.lproj/Localizable.strings

@@ -13,3 +13,5 @@
 "PackageType.twoMonth" = "2 month";
 "PackageType.monthly" = "Monthly";
 "PackageType.weekly" = "Weekly";
+
+"%d%% off" = "%d%% off";

RevenueCatUI/Resources/es.lproj/Localizable.strings

@@ -13,3 +13,5 @@
 "PackageType.twoMonth" = "2 meses";
 "PackageType.monthly" = "Mensual";
 "PackageType.weekly" = "Semanal";
+
+"%d%% off" = "Ahorra %d%%";

Tests/RevenueCatUITests/Data/TemplateViewConfigurationTests.swift

@@ -54,6 +54,7 @@ class TemplateViewConfigurationCreationTests: BaseTemplateViewConfigurationTests
         switch result {
         case let .single(package):
             expect(package.content) === TestData.monthlyPackage
+            expect(package.discountRelativeToMostExpensivePerMonth).to(beNil())
             Self.verifyLocalizationWasProcessed(package.localization, for: TestData.monthlyPackage)
         case .multiple:
             fail("Invalid result: \(result)")
@@ -80,10 +81,13 @@ class TemplateViewConfigurationCreationTests: BaseTemplateViewConfigurationTests
 
             let annual = packages[0]
             expect(annual.content) === TestData.annualPackage
+            expect(annual.discountRelativeToMostExpensivePerMonth)
+                .to(beCloseTo(0.55, within: 0.01))
             Self.verifyLocalizationWasProcessed(annual.localization, for: TestData.annualPackage)
 
             let monthly = packages[1]
             expect(monthly.content) === TestData.monthlyPackage
+            expect(monthly.discountRelativeToMostExpensivePerMonth).to(beNil())
             Self.verifyLocalizationWasProcessed(monthly.localization, for: TestData.monthlyPackage)
         }
     }

Tests/RevenueCatUITests/LocalizationTests.swift

@@ -180,6 +180,51 @@ class PackageTypeOtherLanguageLocalizationTests: BaseLocalizationTests {
     }
 }
 
+// MARK: - Discount
+
+@available(iOS 16.0, macOS 13.0, tvOS 16.0, *)
+class DiscountEnglishLocalizationTests: BaseLocalizationTests {
+
+    override var locale: Locale { return .init(identifier: "en_US") }
+
+    func testLocalization() {
+        verify(0, "0% off")
+        verify(0.1, "10% off")
+        verify(0.331, "33% off")
+        verify(0.5, "50% off")
+        verify(1, "100% off")
+        verify(1.1, "110% off")
+    }
+
+}
+
+@available(iOS 16.0, macOS 13.0, tvOS 16.0, *)
+class DiscountSpanishLocalizationTests: BaseLocalizationTests {
+
+    override var locale: Locale { return .init(identifier: "es_ES") }
+
+    func testLocalization() {
+        verify(0, "Ahorra 0%")
+        verify(0.1, "Ahorra 10%")
+        verify(0.331, "Ahorra 33%")
+        verify(0.5, "Ahorra 50%")
+        verify(1, "Ahorra 100%")
+        verify(1.1, "Ahorra 110%")
+    }
+
+}
+
+@available(iOS 16.0, macOS 13.0, tvOS 16.0, *)
+class DiscountOtherLanguageLocalizationTests: BaseLocalizationTests {
+
+    override var locale: Locale { return .init(identifier: "fr") }
+
+    func testLocalizationDefaultsToEnglish() {
+        verify(1, "100% off")
+    }
+
+}
+
 // MARK: - Private
 
 @available(iOS 16.0, macOS 13.0, tvOS 16.0, *)
@@ -219,4 +264,15 @@ private extension BaseLocalizationTests {
         expect(file: file, line: line, result) == expected
     }
 
+    func verify(
+        _ discount: Double,
+        _ expected: String,
+        file: StaticString = #file,
+        line: UInt = #line
+    ) {
+        let result = Localization.localized(discount: discount,
+                                            locale: self.locale)
+        expect(file: file, line: line, result) == expected
+    }
+
 }