using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace Cosmos.IL2CPU
{
  // todo: optimize this, probably using assembler
  public static class VTablesImpl
  {
    // this field seems to be always empty, but the VTablesImpl class is embedded in the final exe.
    public static VTable[] mTypes;

    public static bool IsInstance(int aObjectType, int aDesiredObjectType)
    {
      int xCurrentType = aObjectType;
      if (aObjectType == 0)
      {
        return true;
      }
      do
      {
        if (xCurrentType == aDesiredObjectType)
        {
          return true;
        }
        if (xCurrentType == mTypes[xCurrentType].BaseTypeIdentifier)
        {
          return false;
        }
        xCurrentType = mTypes[xCurrentType].BaseTypeIdentifier;
      }
      while (xCurrentType != 0);
      return false;
    }

    public static void LoadTypeTable(int aTypeCount)
    {
      mTypes = new VTable[aTypeCount];
      if (mTypes == null)
      {
        Console.WriteLine("No array exists!");
      }
    }

    public static void SetTypeInfo(int aType, int aBaseType, int[] aMethodIndexes, int[] aMethodAddresses, int aMethodCount)
    {
      //mTypes[aType] = new VTable();
      mTypes[aType].BaseTypeIdentifier = aBaseType;
      mTypes[aType].MethodIndexes = aMethodIndexes;
      mTypes[aType].MethodAddresses = aMethodAddresses;
      mTypes[aType].MethodCount = aMethodCount;
    }

    public static void SetMethodInfo(int aType, int aMethodIndex, int aMethodIdentifier, int aMethodAddress, char[] aName)
    {
      mTypes[aType].MethodIndexes[aMethodIndex] = aMethodIdentifier;
      mTypes[aType].MethodAddresses[aMethodIndex] = aMethodAddress;
      mTypes[aType].MethodCount = aMethodIndex + 1;
    }

    private static void WriteNumber(uint aValue, byte aBitCount)
    {
      uint xValue = aValue;
      byte xCurrentBits = aBitCount;
      Console.Write("0x");
      while (xCurrentBits >= 4)
      {
        xCurrentBits -= 4;
        byte xCurrentDigit = (byte)((xValue >> xCurrentBits) & 0xF);
        string xDigitString = null;
        switch (xCurrentDigit)
        {
          case 0:
            xDigitString = "0";
            goto default;
          case 1:
            xDigitString = "1";
            goto default;
          case 2:
            xDigitString = "2";
            goto default;
          case 3:
            xDigitString = "3";
            goto default;
          case 4:
            xDigitString = "4";
            goto default;
          case 5:
            xDigitString = "5";
            goto default;
          case 6:
            xDigitString = "6";
            goto default;
          case 7:
            xDigitString = "7";
            goto default;
          case 8:
            xDigitString = "8";
            goto default;
          case 9:
            xDigitString = "9";
            goto default;
          case 10:
            xDigitString = "A";
            goto default;
          case 11:
            xDigitString = "B";
            goto default;
          case 12:
            xDigitString = "C";
            goto default;
          case 13:
            xDigitString = "D";
            goto default;
          case 14:
            xDigitString = "E";
            goto default;
          case 15:
            xDigitString = "F";
            goto default;
          default:
            Console.Write(xDigitString);
            break;
        }
      }
    }

    public static int GetMethodAddressForType(int aType, int aMethodIndex)
    {
      do
      {
        if (mTypes[aType].MethodIndexes == null)
        {
          Console.Write("Type ");
          WriteNumber((uint)aType, 32);
          Console.WriteLine(", MethodIndexes is null!");
          while (true)
            ;
        }
        for (int i = 0; i < mTypes[aType].MethodIndexes.Length; i++)
        {
          if (mTypes[aType].MethodAddresses == null)
          {
            Console.Write("Type ");
            WriteNumber((uint)aType, 32);
            Console.WriteLine(", MethodAddresses is null!");
            while (true)
              ;
          }
          if (mTypes[aType].MethodIndexes[i] == aMethodIndex)
          {
            var xResult = mTypes[aType].MethodAddresses[i];
            if (xResult < 1048576) // if pointer is under 1MB, some issue exists!
            {
              Console.Write("Type ");
              WriteNumber((uint)aType, 32);
              Console.Write(", MethodIndex = ");
              WriteNumber((uint)aMethodIndex, 32);
              Console.Write(", Result ");
              WriteNumber((uint)xResult, 32);
              Console.Write(", i ");
              WriteNumber((uint)i, 32);
              Console.WriteLine("");
              Console.WriteLine("Method found, but address invalid!");
              while (true)
                ;
            }
            return xResult;
          }
        }
        if (aType == mTypes[aType].BaseTypeIdentifier)
        {
          break;
        }
        aType = mTypes[aType].BaseTypeIdentifier;
      }
      while (true);
      //}
      Console.Write("Type ");
      WriteNumber((uint)aType, 32);
      Console.Write(", MethodIndex = ");
      WriteNumber((uint)aMethodIndex, 32);
      Console.WriteLine("");
      Console.WriteLine("Not FOUND!");
      while (true)
        ;
      throw new Exception("Cannot find virtual method!");
    }
  }

  [StructLayout(LayoutKind.Explicit, Size = 16)]
  public struct VTable
  {
    [FieldOffset(0)]
    public int BaseTypeIdentifier;

    [FieldOffset(4)]
    public int MethodCount;

    [FieldOffset(8)]
    public int[] MethodIndexes;

    [FieldOffset(12)]
    public int[] MethodAddresses;
  }
}