using System;
using System.Collections.Generic;
using System.Reflection.Emit;
using System.Text;
using Sunweaver.DataPrototypes;

namespace Sunweaver.Commands.Abstracts
{
    public abstract class BinaryBooleanLogic : BasePair
    {
        protected VirtualMachine VM = null;
        public override void Implementation(VirtualMachine VM)
        {
            if (VM.BoolStack.Count() < 2)
                return;

            bool b = VM.BoolStack.Pop();
            bool a = VM.BoolStack.Pop();

            this.VM = VM;

            Operation(a, b);
        }

        internal override void Compile(ILGenerator il, Locals locals)
        {
            var cont = il.DefineLabel();

            il.Emit(OpCodes.Ldloc, locals[typeof(VirtualMachine)]);
            il.Emit(OpCodes.Ldfld, typeof(VirtualMachine).GetField("BoolStack"));
            il.Emit(OpCodes.Call, typeof(BoolStack).GetMethod("Count"));
            il.Emit(OpCodes.Ldc_I4_2);
            il.Emit(OpCodes.Conv_I8);
            il.Emit(OpCodes.Blt_S, cont); // We dont return, just go the end of this method

            il.Emit(OpCodes.Ldloc, locals[typeof(VirtualMachine)]);
            il.Emit(OpCodes.Ldfld, typeof(VirtualMachine).GetField("BoolStack"));
            il.Emit(OpCodes.Call, typeof(BoolStack).GetMethod("Pop"));
            il.Emit(OpCodes.Stloc, locals[typeof(bool), 1]);

            il.Emit(OpCodes.Ldloc, locals[typeof(VirtualMachine)]);
            il.Emit(OpCodes.Ldfld, typeof(VirtualMachine).GetField("BoolStack"));
            il.Emit(OpCodes.Call, typeof(BoolStack).GetMethod("Pop"));
            il.Emit(OpCodes.Stloc, locals[typeof(bool), 0]);

            CompileOperation(il, locals);

            il.MarkLabel(cont);            
        }

        /// <summary>
        /// Abstract interface that child classes implement
        /// </summary>
        /// <param name="a">Top value from the bool stack</param>
        /// <param name="b">Second to top value on the bool stack</param>
        public abstract void Operation(bool a, bool b);

        /// <summary>
        /// Abstract interface that child classes implement
        /// </summary>
        /// <remarks>
        /// The boolean variables for the operation are stored in bool0 and bool1 of locals.
        /// </remarks>
        public abstract void CompileOperation(ILGenerator il, Locals locals);
    }
}