using System;
using System.ComponentModel;
using System.Runtime.InteropServices;

[module: DefaultCharSet(CharSet.Unicode)]

public static class CredentialPrompt
{
    public readonly struct Result
    {
        public Result(string userName, string domain, string password)
        {
            UserName = userName;
            Domain = domain;
            Password = password;
        }

        public string UserName { get; }
        public string Domain { get; }
        public string Password { get; }
    }

    public static Result? ShowDialog(HandleRef owner, string caption, string message, bool previousAttemptFailed)
    {
        var authPackage = (uint)0;
        var r = CredUIPromptForWindowsCredentials(
            new CREDUI_INFO(owner.Handle, message, caption),
            previousAttemptFailed ? (uint)WinErrorCode.LogonFailure : 0,
            ref authPackage,
            pvInAuthBuffer: IntPtr.Zero,
            ulInAuthBufferSize: 0,
            out var packedResultBuffer,
            out var packedResultBufferSize,
            pfSave: IntPtr.Zero,
            CREDUIWIN.GENERIC);

        using (packedResultBuffer)
        {
            switch ((WinErrorCode)r)
            {
                case WinErrorCode.Cancelled:
                    return null;
                case WinErrorCode.Success:
                    break;
                default:
                    throw new Win32Exception(r);
            }

            unsafe
            {
                var userNameBufferSize = 128 * sizeof(char);
                var userNameBuffer = new char[userNameBufferSize];
                var domainBufferSize = 128 * sizeof(char);
                var domainBuffer = new char[domainBufferSize];
                var passwordBufferSize = 128 * sizeof(char);
                var passwordBuffer = new char[passwordBufferSize];
                fixed (char* usernamePointer = userNameBuffer)
                fixed (char* domainPointer = domainBuffer)
                fixed (char* passwordPointer = passwordBuffer)
                {
                    try
                    {
                        if (!CredUnPackAuthenticationBuffer(CRED_PACK.GENERIC_CREDENTIALS, packedResultBuffer, packedResultBufferSize, usernamePointer, ref userNameBufferSize, domainPointer, ref domainBufferSize, passwordPointer, ref passwordBufferSize))
                            throw new Win32Exception();

                        GC.KeepAlive(owner.Wrapper);

                        return new Result(
                            new string(usernamePointer),
                            new string(domainPointer),
                            new string(passwordPointer));
                    }
                    finally
                    {
                        Array.Clear(passwordBuffer, 0, passwordBuffer.Length);
                    }
                }
            }
        }
    }

#pragma warning disable IDE0052 // Remove unread private members

    private enum WinErrorCode : ushort
    {
        Success = 0,
        Cancelled = 1223,
        LogonFailure = 1326
    }

    [DllImport("credui.dll", SetLastError = true)]
    private static extern unsafe bool CredUnPackAuthenticationBuffer(CRED_PACK dwFlags, CoTaskMemSafeHandle pAuthBuffer, uint cbAuthBuffer, char* pszUserName, ref int pcchMaxUserName, char* pszDomainName, ref int pcchMaxDomainame, char* pszPassword, ref int pcchMaxPassword);

    private sealed class CoTaskMemSafeHandle : SafeHandle
    {
        private CoTaskMemSafeHandle()
            : base(invalidHandleValue: IntPtr.Zero, ownsHandle: true)
        {
        }

        public override bool IsInvalid => handle == IntPtr.Zero;

        protected override bool ReleaseHandle()
        {
            Marshal.FreeCoTaskMem(handle);
            return true;
        }
    }

    private enum CRED_PACK : uint
    {
        PROTECTED_CREDENTIALS = 0x1,
        WOW_BUFFER = 0x2,
        GENERIC_CREDENTIALS = 0x4,
        ID_PROVIDER_CREDENTIALS = 0x8
    }

    private readonly struct CREDUI_INFO
    {
        private readonly int cbSize;
        private readonly IntPtr hwndParent;
        private readonly string pszMessageText;
        private readonly string pszCaptionText;
        private readonly IntPtr hbmBanner;

        public CREDUI_INFO(IntPtr hwndParent, string pszMessageText, string pszCaptionText)
        {
            cbSize = Marshal.SizeOf<CREDUI_INFO>();
            this.hwndParent = hwndParent;
            this.pszMessageText = pszMessageText;
            this.pszCaptionText = pszCaptionText;
            hbmBanner = IntPtr.Zero;
        }
    }

    [DllImport("credui.dll")]
    private static extern int CredUIPromptForWindowsCredentials(in CREDUI_INFO pUiInfo, uint dwAuthError, ref uint pulAuthPackage, IntPtr pvInAuthBuffer, uint ulInAuthBufferSize, out CoTaskMemSafeHandle ppvOutAuthBuffer, out uint pulOutAuthBufferSize, IntPtr pfSave, CREDUIWIN dwFlags);

    private enum CREDUIWIN : uint
    {
        GENERIC = 0x00000001,
        CHECKBOX = 0x00000002,
        AUTHPACKAGE_ONLY = 0x00000010,
        IN_CRED_ONLY = 0x00000020,
        ENUMERATE_ADMINS = 0x00000100,
        ENUMERATE_CURRENT_USER = 0x00000200,
        SECURE_PROMPT = 0x00001000,
        PREPROMPTING = 0x00002000,
        PACK_32_WOW = 0x10000000
    }
}