using System;
using System.Collections.Generic;
using System.Reflection.Emit;
using System.Text;
using Sunweaver.Commands.Attributes;
using Sunweaver.VM;

namespace Sunweaver.Commands
{
    [BasePair("Multiplication")]
    public class mul : Abstracts.BinaryOperation
    {
        public override void Operation(long A, long B)
        {
            // Floating point arithmetic stores the high order digits.  Integer multiplication stores the low order
            // digits.  Since our 15 digit numbers can fit entirely in the double's 53 bit mantissa, we can abuse both
            // floating point and integer math to find the final modulo multiplication.
            //
            // See https://en.wikipedia.org/wiki/Modular_arithmetic#Example_implementations
            long a = Math.Abs(A);
            long b = Math.Abs(B);            
            var m = IntStack.Max + 1;

            double x = a;
            Int64 c = (Int64)(x * (double)b / (double)m);
            Int64 r = (a * b - c * m) % m;
            Int64 result = r < 0 ? r + m : r;
            this.VM.Stack.Push(A < 0 ^ B < 0 ? -result : result);
        }

        public override void CompileOperation(ILGenerator il, Locals locals)
        {
            throw new NotImplementedException();
        }
    }
}