// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
//
//
 
using System.IO;
using System.Runtime.InteropServices;
using System.Windows.Interop;
 
namespace MS.Internal.WindowsRuntime
{
    namespace Windows.UI.ViewManagement
    {
        /// <summary>
        /// DevDiv:1193138
        /// This class wraps the corresponding WinRT APIs for InputPane.  This is used to show the touch keyboard.
        /// Note that WinRT events belonging to this class are not included for simplicity.
        /// 
        /// This class uses RCWs for WinRT objects in order to properly cast from a WinRT IActivationFactory and
        /// therefore implements IDisposable in order to allow for fast RCW cleanup.
        /// </summary>
        internal class InputPane : IDisposable
        {
            #region Fields
 
            /// <summary>
            /// Bool to check if the WinRT input pane is supported
            /// </summary>
            private static readonly bool _isSupported;
 
 
            /// <summary>
            /// Activation factory to instantiate InputPane RCWs
            /// </summary>
            private static object _winRtActivationFactory;
 
            /// <summary>
            /// The appropriate RCW for calling TryShow/Hide
            /// </summary>
            private InputPaneRcw.IInputPane2 _inputPane;
 
            #endregion
 
            #region Constructors
 
            /// <summary>
            /// Acquires the InputPane type from the winmd
            /// </summary>
            [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes")]
            static InputPane()
            {
                // We don't want to throw here - so wrap in try..catch
                try
                {
                    // If we cannot get a new activation factory, then we cannot support
                    // this platform.  As such, null out the type to guard instantiations.
                    if (GetWinRtActivationFactory(forceInitialization: true) == null)
                    {
                        _isSupported = false;
                    }
                    _isSupported = true;
                }
                catch
                {
                    _isSupported = false;
                }
            }
 
            /// <summary>
            /// Checks that the InputPane type was loaded and gets a new InputPane for the parent window.
            /// </summary>
            /// <exception cref="PlatformNotSupportedException"></exception>
            private InputPane(IntPtr? hwnd)
            {
                if (!_isSupported)
                {
                    throw new PlatformNotSupportedException();
                }
 
                try
                {
                    if (hwnd.HasValue)
                    {
                        InputPaneRcw.IInputPaneInterop inputPaneInterop;
 
                        try
                        {
                            // Get the IActivationFactory and cast to IInputPaneInterop.  The WinRT pattern for
                            // static factory types implements an activation factory that allows casting to one
                            // or more COM interfaces containing "static" methods to use as initialization.  In 
                            // the case of InputPane this is an interop class that contains an init function
                            // designed to take an HWND.  This interface is cloaked and not part of the WinRT
                            // projections and therefore cannot be seen by reflecting on the type.
                            inputPaneInterop = GetWinRtActivationFactory() as InputPaneRcw.IInputPaneInterop;
                        }
                        catch (COMException)
                        {
                            // Do a fine grained catch here to detect the activation factory going stale.
                            // If this happens, we retry the cast querying a new factory.  If this retry fails
                            // something else is going wrong, allow the error to be handled by the outer block.
                            inputPaneInterop = GetWinRtActivationFactory(forceInitialization: true) as InputPaneRcw.IInputPaneInterop;
                        }
 
                        _inputPane = inputPaneInterop?.GetForWindow(hwnd.Value, typeof(InputPaneRcw.IInputPane2).GUID);
                    }
                }
                catch (COMException)
                {
                    // Something went wrong in acquiring/using one of the COM RCWs above.
                    // This is not a fatal error and just means that this particular attempt to initialize InputPane
                    // has failed or the platform does not support this access (this can be caught at the Type init
                    // but it is possible that is not the case).
                }
 
                if (_inputPane == null)
                {
                    throw new PlatformNotSupportedException();
                }
            }
 
            #endregion
 
            #region Member Functions
 
            /// <summary>
            /// Wraps creation in a manner analagous to the WinRT interface to this class.
            /// </summary>
            /// <returns>A new InputPane</returns>
            /// <exception cref="PlatformNotSupportedException"></exception>
            internal static InputPane GetForWindow(HwndSource source)
            {
                return new InputPane(source?.Handle ?? null);
            }
 
            /// <summary>
            /// Attempts to show the touch keyboard
            /// </summary>
            /// <returns>True if successful, false otherwise</returns>
            internal bool TryShow()
            {
                bool result = false;
 
                try
                {
                    result = _inputPane?.TryShow() ?? false;
                }
                catch (COMException)
                {
                    // It's possible that the IInputPane2 has gone stale for some reason
                    // in that case we should catch the exception here and simply return
                    // false indicating that the KB did not show.
                }
 
                return result;
            }
 
            /// <summary>
            /// Attempts to hide the touch keyboard
            /// </summary>
            /// <returns>True if successful, false otherwise</returns>
            internal bool TryHide()
            {
                bool result = false;
 
                try
                {
                    result = _inputPane?.TryHide() ?? false;
                }
                catch (COMException)
                {
                    // It's possible that the IInputPane2 has gone stale for some reason
                    // in that case we should catch the exception here and simply return
                    // false indicating that the KB did not show.
                }
 
                return result;
            }
 
            /// <summary>
            /// Creates, caches, and returns a WinRT activation factory for use with the InputPane runtime type.
            /// </summary>
            /// <param name="forceInitialization">If true, will create a new IActivationFactory.  If false will
            /// only create a new IActivationFactory if there is no valid cached instance available.</param>
            /// <returns>An IActivationFactory of InputPane or null if it fails to instantiate.</returns>
            private static object GetWinRtActivationFactory(bool forceInitialization = false)
            {
                if (forceInitialization || _winRtActivationFactory == null)
                {
                    try
                    {
                        _winRtActivationFactory = InputPaneRcw.GetInputPaneActivationFactory();
                    }
                    catch (Exception e) when (e is TypeLoadException
                                             || e is FileNotFoundException
                                             || e is EntryPointNotFoundException
                                             || e is DllNotFoundException
                                             || e.HResult == NativeMethods.E_NOINTERFACE
                                             || e.HResult == NativeMethods.REGDB_E_CLASSNOTREG)
                    {
                        // Catch the set of exceptions that are considered activation exceptions,
                        // as well as exception with HResults that can be returned from DllGetActivationFactory when it fails.
                        // <see cref="https://msdn.microsoft.com/en-us/library/system.runtime.interopservices.windowsruntime.windowsruntimemarshal.getactivationfactory(v=vs.110).aspx"/>
                        // On some Windows SKUs, notably ServerCore, a failing static dependency in InputPane seems to cause a
                        // FileNotFoundException during acquisition of the activation factory. We explicitly catch this exception 
                        // here to alleviate this issue.  This is not an ideal solution to the platform bug, but keeps WPF applications 
                        // from being exposed to the issue.
 
                        // We also catch an EntryPointNotFoundException and DllNotFoundExceptions for when WinRT isn't supported on the platform.
                        _winRtActivationFactory = null;
                    }
                }
 
                return _winRtActivationFactory;
            }
 
            #endregion
 
            #region IDisposable
 
            private bool _disposed = false;
 
            ~InputPane()
            {
                Dispose(false);
            }
 
            public void Dispose()
            {
                Dispose(true);
                GC.SuppressFinalize(this);
            }
 
            /// <summary>
            /// Releases the _inputPane RCW
            /// </summary>
            /// <param name="disposing">True if called from a Dispose() call, false when called from the finalizer</param>
            private void Dispose(bool disposing)
            {
                if (!_disposed)
                {
                    if (_inputPane != null)
                    {
                        try
                        {
                            // Release the input pane here
                            Marshal.ReleaseComObject(_inputPane);
                        }
                        catch
                        {
                            // Don't want to raise any exceptions in a finalizer, eat them here
                        }
 
                        _inputPane = null;
                    }
 
                    _disposed = true;
                }
            }
 
            #endregion
        }
    }
}