using System;

using CPUx86 = Indy.IL2CPU.Assembler.X86;

namespace Indy.IL2CPU.IL.X86 {
	[OpCode(OpCodeEnum.Sub)]
	public class Sub: Op {
        private string mNextLabel;
	    private string mCurLabel;
	    private uint mCurOffset;
	    private MethodInformation mMethodInformation;
		public Sub(ILReader aReader, MethodInformation aMethodInfo)
			: base(aReader, aMethodInfo) {
             mMethodInformation = aMethodInfo;
		    mCurOffset = aReader.Position;
		    mCurLabel = IL.Op.GetInstructionLabel(aReader);
            mNextLabel = IL.Op.GetInstructionLabel(aReader.NextPosition);
		}
		public override void DoAssemble() {
			var stackTop = Assembler.StackContents.Pop();

            if (stackTop.IsFloat)
            {
                EmitNotImplementedException(Assembler, GetServiceProvider(), "Sub: Float support not yet implemented!", mCurLabel, mMethodInformation, mCurOffset, mNextLabel);
                return;
            }

			switch (stackTop.Size) {
				case 1:
				case 2:
				case 4:
                    new CPUx86.Pop { DestinationReg = CPUx86.Registers.ECX }; 
                    new CPUx86.Pop { DestinationReg = CPUx86.Registers.EAX };
                    new CPUx86.Sub { DestinationReg = CPUx86.Registers.EAX, SourceReg = CPUx86.Registers.ECX };
                    new CPUx86.Push { DestinationReg = CPUx86.Registers.EAX };
					break;
				case 8:
                    new CPUx86.Pop { DestinationReg = CPUx86.Registers.EAX };
                    new CPUx86.Pop { DestinationReg = CPUx86.Registers.EDX };
                    new CPUx86.Sub { DestinationReg = CPUx86.Registers.ESP, DestinationIsIndirect = true, SourceReg = CPUx86.Registers.EAX };
                    new CPUx86.SubWithCarry { DestinationReg = CPUx86.Registers.ESP, DestinationIsIndirect = true, DestinationDisplacement = 4, SourceReg = CPUx86.Registers.EDX };
					break;
				default:
                    EmitNotImplementedException(Assembler, GetServiceProvider(), "Sub: Size not supported: " + stackTop.Size, mCurLabel, mMethodInformation, mCurOffset, mNextLabel);
                    return;
			}
		}
	}
}