using System;
using System.IO;
using CPU = Indy.IL2CPU.Assembler;
using CPUx86 = Indy.IL2CPU.Assembler.X86;
using Indy.IL2CPU.Assembler;

namespace Indy.IL2CPU.IL.X86 {
  [OpCode(OpCodeEnum.Stelem_Ref)]
  public class Stelem_Ref: Op {
    private string mNextLabel;
    private string mCurLabel;
    private uint mCurOffset;
    private MethodInformation mMethodInformation;
    public Stelem_Ref(ILReader aReader, MethodInformation aMethodInfo)
      : base(aReader, aMethodInfo) {
      mMethodInformation = aMethodInfo;
      mCurOffset = aReader.Position;
      mCurLabel = IL.Op.GetInstructionLabel(aReader);
      mNextLabel = IL.Op.GetInstructionLabel(aReader.NextPosition);
    }

    public static void Assemble(CPU.Assembler aAssembler, uint aElementSize, IServiceProvider aServiceProvider, string aCurrentLabel, MethodInformation aCurrentMethodInfo, uint aCurrentOffset, string aNextLabel) {
      // stack - 3 == the array
      // stack - 2 == the index
      // stack - 1 == the new value
      uint xStackSize = aElementSize;
      if (xStackSize % 4 != 0) {
        xStackSize += 4 - xStackSize % 4;
      }
      new CPUx86.Push { DestinationReg = CPUx86.Registers.ESP, DestinationIsIndirect = true, DestinationDisplacement = (int)(xStackSize + 4) };
      new CPUx86.Call { DestinationLabel = IL2CPU.Assembler.MethodInfoLabelGenerator.GenerateLabelName(GCImplementationRefs.DecRefCountRef) };
      new CPUx86.Move { DestinationReg = CPUx86.Registers.EBX, SourceReg = CPUx86.Registers.ESP, SourceIsIndirect = true, SourceDisplacement = (int)xStackSize }; // the index
      new CPUx86.Move { DestinationReg = CPUx86.Registers.ECX, SourceReg = CPUx86.Registers.ESP, SourceIsIndirect = true, SourceDisplacement = (int)xStackSize + 4 }; // the index
      new CPUx86.Add { DestinationReg = CPUx86.Registers.ECX, SourceValue = (uint)(ObjectImpl.FieldDataOffset + 4) };
      new CPUx86.Push { DestinationValue = aElementSize };
      aAssembler.StackContents.Push(new StackContent(4, true, false, true));
      new CPUx86.Push { DestinationReg = CPUx86.Registers.EBX };
      aAssembler.StackContents.Push(new StackContent(4, true, false, true));
      Multiply(aAssembler, aServiceProvider,
          aCurrentLabel, aCurrentMethodInfo, aCurrentOffset, aNextLabel);
      new CPUx86.Push { DestinationReg = CPUx86.Registers.ECX };
      aAssembler.StackContents.Push(new StackContent(4, true, false, true));
      Add(aAssembler, aServiceProvider, aCurrentLabel, aCurrentMethodInfo, aCurrentOffset, aNextLabel);
      new CPUx86.Pop { DestinationReg = CPUx86.Registers.ECX };
      aAssembler.StackContents.Pop();
      for (int i = (int)(aElementSize / 4) - 1; i >= 0; i -= 1) {
        new CPU.Comment("Start 1 dword");
        new CPUx86.Pop { DestinationReg = CPUx86.Registers.EBX };
        new CPUx86.Move { DestinationReg = CPUx86.Registers.ECX, DestinationIsIndirect = true, SourceReg = CPUx86.Registers.EBX };
        new CPUx86.Add { DestinationReg = CPUx86.Registers.ECX, SourceValue = 4 };
      }
      switch (aElementSize % 4) {
        case 1: {
            new CPU.Comment("Start 1 byte");
            new CPUx86.Pop { DestinationReg = CPUx86.Registers.EBX };
            new CPUx86.Move { DestinationReg = CPUx86.Registers.ECX, DestinationIsIndirect = true, SourceReg = CPUx86.Registers.BL };
            break;
          }
        case 2: {
            new CPU.Comment("Start 1 word");
            new CPUx86.Pop { DestinationReg = CPUx86.Registers.EBX };
            new CPUx86.Move { DestinationReg = CPUx86.Registers.ECX, DestinationIsIndirect = true, SourceReg = CPUx86.Registers.BX };
            break;
          }
        case 0: {
            break;
          }
        default:
          throw new Exception("Remainder size " + (aElementSize % 4) + " not supported!");

      }
      new CPUx86.Add { DestinationReg = CPUx86.Registers.ESP, SourceValue = 0x8 };
      aAssembler.StackContents.Pop();
      aAssembler.StackContents.Pop();
      aAssembler.StackContents.Pop();
    }

    public override void DoAssemble() {
      Assemble(Assembler, 4, GetServiceProvider(), mCurLabel, mMethodInformation, mCurOffset, mNextLabel);
    }
  }
}