import CWinRT
import CWinAppSDK
import WindowsFoundation
import WinSDK

public enum ThreadingModel {
    case single
    case multi
}

/// WindowsAppRuntimeInitializer is used to properly initialize the Windows App SDK runtime, along with the Windows Runtime.
/// The runtime is initalized for the lifetime of the object, and is deinitialized when the object is deallocated.
/// Example usage:
/// ```
/// public static func main() {
///        do {
///            try withExtendedLifetime(WindowsAppRuntimeInitializer()) {
///                initialization code here
///            }
///        }
///        catch {
///            fatalError("Failed to initialize WindowsAppRuntimeInitializer: \(error)")
///        }
///    }
/// ```
public class WindowsAppRuntimeInitializer {
    // TODO: Figure out how to properly link against delayimp.lib so that we can delay load the bootstrap dll.
    private typealias pfnMddBootstrapInitialize2 = @convention(c) (UInt32, PCWSTR?, PACKAGE_VERSION, MddBootstrapInitializeOptions) -> HRESULT
    private typealias pfnMddBootstrapShutdown = @convention(c) () -> Void
    private let bootsrapperDll = LoadLibraryA("swift-windowsappsdk_CWinAppSDK.resources\\Microsoft.WindowsAppRuntime.Bootstrap.dll")

    private lazy var Initialize: pfnMddBootstrapInitialize2 = {
        let pfn = GetProcAddress(bootsrapperDll, "MddBootstrapInitialize2")
        return unsafeBitCast(pfn, to: pfnMddBootstrapInitialize2.self)
    }()

    private lazy var Shutdown: pfnMddBootstrapShutdown = {
        let pfn = GetProcAddress(bootsrapperDll, "MddBootstrapShutdown")
        return unsafeBitCast(pfn, to: pfnMddBootstrapShutdown.self)
    }()

    private func processHasIdentity() -> Bool {
        var length: UInt32 = 0
        return GetCurrentPackageFullName(&length, nil) != APPMODEL_ERROR_NO_PACKAGE
    }

    public init(threadingModel: ThreadingModel = .single) throws  {
        let roInitParam = switch threadingModel {
            case .single: RO_INIT_SINGLETHREADED
            case .multi: RO_INIT_MULTITHREADED
        }

        try CHECKED(RoInitialize(roInitParam))

        try CHECKED(SetProcessDpiAwareness(PROCESS_PER_MONITOR_DPI_AWARE))

        guard !processHasIdentity() else {
            return
        }

        try CHECKED(Initialize(
            UInt32(WINDOWSAPPSDK_RELEASE_MAJORMINOR),
            WINDOWSAPPSDK_RELEASE_VERSION_TAG_SWIFT,
            .init(),
            MddBootstrapInitializeOptions(
                MddBootstrapInitializeOptions_OnNoMatch_ShowUI.rawValue
            )
        ))
    }

    deinit {
        RoUninitialize()
        if !processHasIdentity() {
            Shutdown()
        }
        FreeLibrary(bootsrapperDll)
    }
}