using System;
using Cosmos.IL2CPU.ILOpCodes;
using Cosmos.IL2CPU.X86;
using Cosmos.Compiler.Assembler;
using Cosmos.Compiler.Assembler.X86;

namespace Cosmos.IL2CPU.X86.IL
{
    [Cosmos.IL2CPU.OpCode( ILOpCode.Code.Ldarg )]
    public class Ldarg : ILOp
    {
        public Ldarg( Cosmos.Compiler.Assembler.Assembler aAsmblr )
            : base( aAsmblr )
        {
        }

        public override void Execute( MethodInfo aMethod, ILOpCode aOpCode )
        {
          var xOpVar = (OpVar)aOpCode;
          DoExecute(Assembler, aMethod, xOpVar.Value);
        }

        public static int GetArgumentDisplacement(MethodInfo aMethod, ushort aParam) {
          var xMethodBase = aMethod.MethodBase;
          if (aMethod.PluggedMethod != null) {
            xMethodBase = aMethod.PluggedMethod.MethodBase;
          }
          var xMethodInfo = xMethodBase as System.Reflection.MethodInfo;
          uint xReturnSize = 0;
          if (xMethodInfo != null) {
            xReturnSize = Align(SizeOfType(xMethodInfo.ReturnType), 4);
          }
          uint xOffset = 8;
          var xCorrectedOpValValue = aParam;
          if (!aMethod.MethodBase.IsStatic && aParam > 0) {
            // if the method has a $this, the OpCode value includes the this at index 0, but GetParameters() doesnt include the this
            xCorrectedOpValValue -= 1;
          }
          var xParams = xMethodBase.GetParameters();
          if (aParam == 0 && !xMethodBase.IsStatic) {
            // return the this parameter, which is not in .GetParameters()
              uint xCurArgSize;
              if (xMethodBase.DeclaringType.IsValueType)
              {
                  // value types get a reference passed to the actual value, so pointer:
                  xCurArgSize = 4;
              }
              else
              {
                  xCurArgSize = Align(SizeOfType(xMethodBase.DeclaringType), 4);
              }

            for (int i = xParams.Length - 1; i >= aParam; i--) {
              var xSize = Align(SizeOfType(xParams[i].ParameterType), 4);
              xOffset += xSize;
            }

            if (xReturnSize > xCurArgSize) {
				uint xExtraSize = xReturnSize - xCurArgSize;
				xOffset += xExtraSize;
            }

            return (int)(xOffset + xCurArgSize - 4);
          } else {
            for (int i = xParams.Length - 1; i > xCorrectedOpValValue; i--) {
              var xSize = Align(SizeOfType(xParams[i].ParameterType), 4);
              xOffset += xSize;
            }
            var xCurArgSize = Align(SizeOfType(xParams[xCorrectedOpValValue].ParameterType), 4);
            uint xArgSize = 0;
            foreach (var xParam in xParams) {
              xArgSize += Align(SizeOfType(xParam.ParameterType), 4);
            }
            xReturnSize = 0;

            if (xReturnSize > xArgSize) {
				uint xExtraSize = xReturnSize - xArgSize;
				xOffset += xExtraSize;
            }

            return (int)(xOffset + xCurArgSize - 4);
          }
        }

        public static void DoExecute(Assembler Assembler, MethodInfo aMethod, ushort aParam) {
          uint xArgSize = 0u;
          var xDisplacement = GetArgumentDisplacement(aMethod, aParam);
          Type xArgType;
          if (aMethod.MethodBase.IsStatic) {
            xArgType = aMethod.MethodBase.GetParameters()[aParam].ParameterType;
          } else {
            if (aParam == 0u) {
              xArgType = aMethod.MethodBase.DeclaringType;
              if (xArgType.IsValueType)
              {
                  xArgType = xArgType.MakeByRefType();
              }
            } else {
              xArgType = aMethod.MethodBase.GetParameters()[aParam - 1].ParameterType;
            }
          }
          new Comment("Ldarg");
          new Comment("Arg idx = " + aParam);
          xArgSize = Align(SizeOfType(xArgType), 4);
          new Comment("Arg type = " + xArgType.ToString());
            new Comment("Arg size = " + xArgSize);
          for (int i = 0; i < (xArgSize / 4); i++) {
            new Push {
              DestinationReg = Registers.EBP,
              DestinationIsIndirect = true,
              DestinationDisplacement = (int)(xDisplacement - (i * 4))
            };
          }
          Assembler.Stack.Push(xArgSize, xArgType);
        }
    }
}