using Qrakhen.Qamp.Core.Values.Objects;
using System.Runtime.InteropServices;
using Qrakhen.Qamp.Core.Collections;

namespace Qrakhen.Qamp.Core.Values;

// generally interesting: GCHandle.ToIntPtr(GCHandle.Alloc(obj, GCHandleType.Normal));

[StructLayout(LayoutKind.Sequential, Size = sizeof(ulong))]
public readonly struct Ptr
{
   [Serialized] public readonly Address Address;

   public Obj? Value {
      get {
         if (ObjTable.Global.TryGet(Address, out Obj? obj))
            return obj;
         return null;
      }
   }

   private Ptr(Address address)
   {      
      Address = address;
   }

   public static Ptr Create(Obj obj)
   {
      return new Ptr(obj.__Address);
   }

   public T? As<T>(bool throwWhenNull = true) where T : Obj
   {
      T? value = Value as T;
      if (value == null && throwWhenNull)
         throw new RuntimeException($"Could not convert Object {Value} to target type {typeof(T)}.", Value);
      return value;
   }

   public Obj? As(Type type, bool throwWhenNull = true)
   {
      Obj? value = Convert.ChangeType(Value, type) as Obj;
      if (value == null && throwWhenNull)
         throw new RuntimeException($"Could not convert Object {Value} to target type {type}.", Value);
      return value;
   }

   public override string ToString() => $"0x{Value}";

   public static async Task __GC_Prepare()
   {
      await Task.Run(() => {
         foreach (var obj in ObjTable.Global.Entries) {
            obj.Value.__GC_Count = 0;
         }
      });
   }

   public static byte[] SerializeFunctions()
   {
      List<byte> result = new();
      foreach (var element in ObjTable.Global.Entries) {
         Obj obj = element.Value;
         if (obj == null || obj.__GC_Marked)
            continue;
         byte[] bytes;
         if (obj is Function function) {
            bytes = function.Serialize();
         } else if (obj is Context context) {
            bytes = context.Function.Serialize();
         } else {
            continue;
         }

         result.AddRange(((long)element.Key).GetBytes());
         result.AddRange(bytes.Length.GetBytes());
         result.AddRange(bytes);
         result.Add(0);
      }
      return result.ToArray();
   }
}