using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.ComTypes;
using System.Text;

namespace AeroMCSetup;

/// <summary>
/// Verknüpfungen (.lnk) über die Shell-Schnittstellen – inklusive AppUserModelID, damit
/// Taskleiste und Windows-Benachrichtigungen AeroMC wie bisher zuordnen (wie beim alten NSIS-Setup).
/// </summary>
public static class Shortcut
{
    public static void Create(string link, string target, string description, string appUserModelId)
    {
        Directory.CreateDirectory(Path.GetDirectoryName(link)!);
        var shellLink = (IShellLinkW)new CShellLink();
        try
        {
            shellLink.SetPath(target);
            shellLink.SetWorkingDirectory(Path.GetDirectoryName(target)!);
            shellLink.SetIconLocation(target, 0);
            shellLink.SetDescription(description);

            var store = (IPropertyStore)shellLink;
            var key = new PropertyKey(new Guid("9F4C2855-9F79-4B39-A8D0-E1D42DE1D5F3"), 5); // PKEY_AppUserModel_ID
            var value = new PropVariant { vt = 31 /* VT_LPWSTR */, p = Marshal.StringToCoTaskMemUni(appUserModelId) };
            try
            {
                store.SetValue(ref key, ref value);
                store.Commit();
            }
            finally { Marshal.FreeCoTaskMem(value.p); }

            ((IPersistFile)shellLink).Save(link, true);
        }
        finally { Marshal.ReleaseComObject(shellLink); }
    }

    /// <summary>Ziel einer vorhandenen Verknüpfung, oder null.</summary>
    public static string? Target(string link)
    {
        if (!File.Exists(link)) return null;
        var shellLink = (IShellLinkW)new CShellLink();
        try
        {
            ((IPersistFile)shellLink).Load(link, 0);
            var sb = new StringBuilder(1024);
            shellLink.GetPath(sb, sb.Capacity, IntPtr.Zero, 0);
            return sb.ToString();
        }
        catch { return null; }
        finally { Marshal.ReleaseComObject(shellLink); }
    }

    // ---------- COM ----------

    [ComImport, Guid("00021401-0000-0000-C000-000000000046")]
    private class CShellLink { }

    [ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("000214F9-0000-0000-C000-000000000046")]
    private interface IShellLinkW
    {
        void GetPath([Out, MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszFile, int cchMaxPath, IntPtr pfd, uint fFlags);
        void GetIDList(out IntPtr ppidl);
        void SetIDList(IntPtr pidl);
        void GetDescription([Out, MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszName, int cchMaxName);
        void SetDescription([MarshalAs(UnmanagedType.LPWStr)] string pszName);
        void GetWorkingDirectory([Out, MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszDir, int cchMaxPath);
        void SetWorkingDirectory([MarshalAs(UnmanagedType.LPWStr)] string pszDir);
        void GetArguments([Out, MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszArgs, int cchMaxPath);
        void SetArguments([MarshalAs(UnmanagedType.LPWStr)] string pszArgs);
        void GetHotkey(out short pwHotkey);
        void SetHotkey(short wHotkey);
        void GetShowCmd(out int piShowCmd);
        void SetShowCmd(int iShowCmd);
        void GetIconLocation([Out, MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszIconPath, int cchIconPath, out int piIcon);
        void SetIconLocation([MarshalAs(UnmanagedType.LPWStr)] string pszIconPath, int iIcon);
        void SetRelativePath([MarshalAs(UnmanagedType.LPWStr)] string pszPathRel, uint dwReserved);
        void Resolve(IntPtr hwnd, uint fFlags);
        void SetPath([MarshalAs(UnmanagedType.LPWStr)] string pszFile);
    }

    [ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("886D8EEB-8CF2-4446-8D02-CDBA1DBDCF99")]
    private interface IPropertyStore
    {
        void GetCount(out uint cProps);
        void GetAt(uint iProp, out PropertyKey pkey);
        void GetValue(ref PropertyKey key, out PropVariant pv);
        void SetValue(ref PropertyKey key, ref PropVariant pv);
        void Commit();
    }

    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    private struct PropertyKey(Guid fmtid, uint pid)
    {
        public Guid fmtid = fmtid;
        public uint pid = pid;
    }

    // PROPVARIANT: 16 Byte (32 Bit) bzw. 24 Byte (64 Bit)
    [StructLayout(LayoutKind.Sequential)]
    private struct PropVariant
    {
        public ushort vt;
        public ushort r1, r2, r3;
        public IntPtr p;
        public IntPtr p2;
    }
}