/**
 Type-erased View
 */
protocol AnyView: AnyObject { }
protocol ViewBuilder {
    func makeView() -> AnyView
}

/**
 Configurable View. It requires that the type has an associated
 Configuration type which is used to build the AnyView instances
 (due to ViewBuilder requirement)
 */
protocol ConfigurableView: AnyView, PreviewProvider {
    associatedtype Configuration: ViewConfiguration
    var configuration: Configuration { get }
    init(_ configuration: Configuration)
}

protocol ViewConfiguration: ViewBuilder {
    associatedtype View: ConfigurableView where View.Configuration == Self
}

protocol PreviewProvider {
    static var previewConfigurations: [ViewBuilder] { get }
}

extension ViewConfiguration {
    // Implementing the ViewBuilder protocol.
    func makeView() -> AnyView {
        View(self)
    }
}

/**
 An example of a simple `ConfigurableView` implementation.
 Think of it as a simple Label view that can render a line of text with
 configurable font size.
 */
class Label: ConfigurableView {
    var configuration: Configuration
    required init(_ configuration: Configuration) {
        self.configuration = configuration
    }
    struct Configuration: ViewConfiguration {
        typealias View = Label
        let text: String
        let fontSize: Int
    }
}

extension Label {
    static var previewConfigurations: [ViewBuilder] { [
        Label.Configuration(text: "Regular size label", fontSize: 1),
        Label.Configuration(text: "Bigger label", fontSize: 2),
        Label.Configuration(text: "Even bigger label", fontSize: 3),
    ] }
}

/**
 An example of a `ConfigurableView` implementation using generics.
 Think of it as a scrollable collection of configurable views.
 */
class CarouselView<Component: ConfigurableView>: ConfigurableView {
    var configuration: Configuration
    required init(_ configuration: Configuration) {
        self.configuration = configuration
    }
    struct Configuration: ViewConfiguration {
        typealias View = CarouselView<Component>
        let items: [Component.Configuration]
    }
}

extension CarouselView {
    static var previewConfigurations: [ViewBuilder] { [ ] }
}

extension CarouselView where Component == Label {
    static var previewConfigurations: [ViewBuilder] { [
        CarouselView.Configuration(
            items: [
                Label.Configuration(text: "Hello", fontSize: 1),
                Label.Configuration(text: "World", fontSize: 1),
            ])
    ] }
}

import XCTest
@testable import DynamicDispatchIssue

final class DynamicDispatchIssueTests: XCTestCase {
    func testCallingStaticMemberDirectly() {
        XCTAssertEqual(Label.previewConfigurations.count, 3)
        XCTAssertEqual(CarouselView<Label>.previewConfigurations.count, 1)
        XCTAssertEqual(CarouselView<Label>.self.previewConfigurations.count, 1)
    }
    
    func testCallingStaticMemberOnDowncastType() {
        XCTAssertEqual((CarouselView<Label>.self as PreviewProvider.Type).previewConfigurations.count, 1)
        // This assert fails because of (CarouselView<Label>.self as PreviewProvider.Type)
    }
    
    static var allTests = [
        ("testCallingStaticMemberDirectly", testCallingStaticMemberDirectly),
        ("testCallingStaticMemberOnDowncastType", testCallingStaticMemberOnDowncastType),
    ]
}