// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.ComTypes;
using System.Runtime.Versioning;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
 
#nullable disable
 
namespace Microsoft.Build.Execution
{
    /// <summary>
    /// Wrapper for the COM Running Object Table.
    /// </summary>
    /// <remarks>
    /// See https://docs.microsoft.com/en-us/windows/desktop/api/objidl/nn-objidl-irunningobjecttable.
    /// </remarks>
    internal class RunningObjectTable : IRunningObjectTableWrapper
    {
        private readonly Task<IRunningObjectTable> _rotTask;
 
        public RunningObjectTable()
        {
            if (!NativeMethodsShared.IsWindows)
            {
                return;
            }
 
            if (Thread.CurrentThread.GetApartmentState() == ApartmentState.MTA)
            {
                Ole32.GetRunningObjectTable(0, out var rot);
                _rotTask = Task.FromResult(rot);
            }
            else
            {
                // To avoid deadlock, create ROT in a threadpool threads which guarantees to be MTA. And the
                // object will be MTA
                _rotTask =
                Task.Run(() =>
                {
#pragma warning disable CA1416 // Validate platform compatibility: we checked above but the analyzer misses it
                    Ole32.GetRunningObjectTable(0, out var rot);
#pragma warning restore CA1416 // Validate platform compatibility
                    return rot;
                });
            }
        }
 
        /// <summary>
        /// Attempts to retrieve an item from the ROT.
        /// </summary>
        [SupportedOSPlatform("windows")]
        public object GetObject(string itemName)
        {
            var rot = _rotTask.GetAwaiter().GetResult();
            IMoniker moniker;
            if (Thread.CurrentThread.GetApartmentState() == ApartmentState.MTA)
            {
                Ole32.CreateItemMoniker("!", itemName, out moniker);
            }
            else
            {
                // To avoid deadlock, create Moniker in a threadpool threads which guarantees to be MTA. And the
                // object will be MTA
                var task = Task.Run(() =>
                {
                    Ole32.CreateItemMoniker("!", itemName, out var mk);
                    return mk;
                });
 
                moniker = task.GetAwaiter().GetResult();
            }
 
            int hr = rot.GetObject(moniker, out object obj);
            if (hr != 0)
            {
                ThrowComExceptionWithDetails(hr, itemName);
            }
 
            return obj;
        }
 
        /// <summary>
        /// Throws an exception with detailed COM error information if available.
        /// </summary>
        private static void ThrowComExceptionWithDetails(int hr, string itemName)
        {
            StringBuilder errorMessage = new StringBuilder();
            errorMessage.AppendLine($"Failed to get object '{itemName}' from Running Object Table.");
            errorMessage.AppendLine($"HRESULT: 0x{hr:X8} ({hr})");
 
            if (NativeMethodsShared.IsWindows && Ole32.GetErrorInfo(0, out IErrorInfo errorInfo) == 0 && errorInfo != null)
            {
                // Try to get IErrorInfo for detailed error information
                try
                {
                    errorInfo.GetDescription(out string description);
                    errorInfo.GetSource(out string source);
                    errorInfo.GetHelpFile(out string helpFile);
                    errorInfo.GetHelpContext(out int helpContext);
                    
                    AppendIfNotEmpty(nameof(description), description);
                    AppendIfNotEmpty(nameof(source), source);
                    AppendIfNotEmpty("help file", helpFile);
                    if (helpContext != 0)
                    {
                        errorMessage.AppendLine($"help context: {helpContext}");
                    }
                }
                catch
                {
                    // If we can't get error info details, just continue with the basic code.
                }
                finally
                {
                    Marshal.ReleaseComObject(errorInfo);
                }
            }
 
            throw new COMException(errorMessage.ToString(), hr);
 
            void AppendIfNotEmpty(string label, string value)
            {
                if (!string.IsNullOrEmpty(value))
                {
                    errorMessage.AppendLine($"{label}: {value}");
                }
            }
        }
 
        [SupportedOSPlatform("windows")]
        private static class Ole32
        {
            [DllImport(nameof(Ole32))]
            public static extern void CreateItemMoniker(
                [MarshalAs(UnmanagedType.LPWStr)] string lpszDelim,
                [MarshalAs(UnmanagedType.LPWStr)] string lpszItem,
                out IMoniker ppmk);
 
            [DllImport(nameof(Ole32))]
            public static extern void GetRunningObjectTable(
                int reserved,
                out IRunningObjectTable pprot);
 
            [DllImport(nameof(Ole32))]
            public static extern int GetErrorInfo(
                int dwReserved,
                out IErrorInfo ppIErrorInfo);
        }
 
        /// <summary>
        /// COM IErrorInfo interface for retrieving detailed error information.
        /// </summary>
        [ComImport]
        [Guid("1CF2B120-547D-101B-8E65-08002B2BD119")]
        [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        private interface IErrorInfo
        {
            void GetSource([MarshalAs(UnmanagedType.BStr)] out string pBstrSource);
 
            void GetDescription([MarshalAs(UnmanagedType.BStr)] out string pBstrDescription);
 
            void GetHelpFile([MarshalAs(UnmanagedType.BStr)] out string pBstrHelpFile);
 
            void GetHelpContext(out int pdwHelpContext);
        }
    }
}