using System.Collections.Generic;

namespace BSO
{
    /// <summary>
    /// Klassenname eines C++-Objekts aus den MSVC-Typinfos (vtable[-1] -> CompleteObjectLocator -> TypeDescriptor).
    /// So erkennen wir Spielobjekte (BaseVehicle, CarVehicle ...), ohne ihren Aufbau zu kennen.
    /// </summary>
    public static unsafe class Rtti
    {
        static readonly Dictionary<nint, string> byVtable = new();

        /// <summary>Klassenname oder null, wenn obj kein gueltiges C++-Objekt ist.</summary>
        public static string ClassName(nint obj)
        {
            if (!Mem.TryReadPtr(obj, out nint vtable) || !Mem.IsImage(vtable)) return null;
            if (byVtable.TryGetValue(vtable, out string name)) return name;
            name = Resolve(vtable);
            byVtable[vtable] = name;
            return name;
        }

        static string Resolve(nint vtable)
        {
            if (!Mem.TryReadPtr(vtable - 8, out nint col) || !Mem.IsImage(col) || !Mem.IsReadable(col, 24)) return null;
            // x64: Signatur 1, Adressen als RVA relativ zum Modul; pSelf (RVA des Locators selbst) liefert die Modulbasis
            if (*(int*)col != 1) return null;
            uint typeRva = *(uint*)(col + 12);
            uint selfRva = *(uint*)(col + 20);
            nint typeDescriptor = col - (nint)selfRva + (nint)typeRva;
            string raw = Mem.ReadAscii(typeDescriptor + 16, 256); // ".?AVBaseVehicle@@"
            return Demangle(raw);
        }

        /// <summary>".?AVFoo@Bar@@" -> "Bar::Foo".</summary>
        static string Demangle(string raw)
        {
            if (raw.Length < 6 || !raw.StartsWith(".?A")) return null;
            string body = raw.Substring(4);
            if (body.EndsWith("@@")) body = body.Substring(0, body.Length - 2);
            if (body.Contains('?')) return body; // Templates usw. roh lassen
            string[] parts = body.Split('@');
            System.Array.Reverse(parts);
            return string.Join("::", parts);
        }
    }
}