using System;

namespace NPhilosopher {
	public variant NComparison {
		| EQ
		| NE
		| GT
		| LT
		| GTE
		| LTE
	}
	
	public variant NStack {
		| Add
		| Sub
		| Mul
		| Div
		| Mod
		| Neg
		
		| And
		| Or
		| Xor
		| Not
		| Shl
		| Shr
		
		| Push {
			PushValue : object;
		}
		| PushArg {
			Arg : int;
		}
		| Pop
		| Dup
		
		| Call {
			CallTarget : object;
		}
		| CallVirt {
			VirtTarget : object;
		}
		| Ret
		
		| CondBranch {
			Taken : object;
			NotTaken : object;
			Comparison : NComparison;
			Signed : bool;
		}
	}
	
	public module CILToStack {
		public ConvertInst(inst : NIL.Inst) : NStack {
			| Inst(_, _, opcd, _, arg) =>
				match(opcd) {
					| 0x0000U => null;
					
					| 0x0002U => NStack.PushArg(0);
					| 0x0003U => NStack.PushArg(1);
					| 0x0004U => NStack.PushArg(2);
					| 0x0005U => NStack.PushArg(3);
					
					| 0x0028U => NStack.Call(CA(arg));
					| 0x002AU => NStack.Ret();
					
					| 0x0058U => NStack.Add();
					| 0x0059U => NStack.Sub();
					| 0x005AU => NStack.Mul();
					| 0x005BU => NStack.Div();
					| 0x0065U => NStack.Neg();
					
					| 0x005FU => NStack.And();
					
					| 0x006FU => NStack.CallVirt(CA(arg));
					
					| 0x0072U => NStack.Push(CA(arg));
					
					| _ => throw Exception(String.Format("Unknown opcode {0:X}", opcd));
				}
		}
		
		CA(arg : NIL) : object {
			| Int(val) => val : object;
			| UInt(val) => val : object;
			| Object(obj) => obj : object;
			| x => x;
		}
	}
}