using System;
using System.Reflection;
using System.Reflection.Metadata;

using Cosmos.Debug.Symbols;

namespace Cosmos.IL2CPU.ILOpCodes
{
    public class OpVar : ILOpCode
    {
        public readonly UInt16 Value;

        public OpVar(Code aOpCode, int aPos, int aNextPos, UInt16 aValue, ExceptionRegion aCurrentExceptionRegion)
            : base(aOpCode, aPos, aNextPos, aCurrentExceptionRegion)
        {
            Value = aValue;
        }

        public override int GetNumberOfStackPops(MethodBase aMethod)
        {
            switch (OpCode)
            {
                case Code.Ldloc:
                case Code.Ldloca:
                case Code.Ldarg:
                case Code.Ldarga:
                    return 0;
                case Code.Stloc:
                case Code.Starg:
                    return 1;
                default:
                    throw new NotImplementedException("OpCode '" + OpCode + "' not implemented!");
            }
        }

        public override int GetNumberOfStackPushes(MethodBase aMethod)
        {
            switch (OpCode)
            {
                case Code.Stloc:
                case Code.Starg:
                    return 0;
                case Code.Ldloc:
                case Code.Ldloca:
                case Code.Ldarg:
                case Code.Ldarga:
                    return 1;
                default:
                    throw new NotImplementedException("OpCode '" + OpCode + "' not implemented!");
            }
        }

        protected override void DoInitStackAnalysis(MethodBase aMethod)
        {
            base.DoInitStackAnalysis(aMethod);

            var xArgIndexCorrection = 0;
            var xBody = aMethod.GetMethodBody();
            var xParams = aMethod.GetParameters();
            switch (OpCode)
            {
                case Code.Ldloc:
                    if (xBody != null)
                    {
                        StackPushTypes[0] = xBody.GetLocalVariablesInfo()[Value].LocalType;
                        if (StackPushTypes[0].GetTypeInfo().IsEnum)
                        {
                            StackPushTypes[0] = StackPushTypes[0].GetTypeInfo().GetEnumUnderlyingType();
                        }
                    }
                    return;
                case Code.Ldloca:
                    if (xBody != null)
                    {
                        StackPushTypes[0] = xBody.GetLocalVariablesInfo()[Value].LocalType.MakeByRefType();
                    }
                    return;
                case Code.Ldarg:
                    if (!aMethod.IsStatic)
                    {
                        if (Value == 0)
                        {
                            StackPushTypes[0] = aMethod.DeclaringType;
                            if (StackPushTypes[0].GetTypeInfo().IsEnum)
                            {
                                StackPushTypes[0] = StackPushTypes[0].GetTypeInfo().GetEnumUnderlyingType();
                            }
                            else if (StackPushTypes[0].GetTypeInfo().IsValueType)
                            {
                                StackPushTypes[0] = StackPushTypes[0].MakeByRefType();
                            }
                            return;
                        }
                        xArgIndexCorrection = -1;
                    }
                    StackPushTypes[0] = xParams[Value + xArgIndexCorrection].ParameterType;
                    if (StackPushTypes[0].GetTypeInfo().IsEnum)
                    {
                        StackPushTypes[0] = StackPushTypes[0].GetTypeInfo().GetEnumUnderlyingType();
                    }
                    return;
                case Code.Ldarga:
                    if (!aMethod.IsStatic)
                    {
                        if (Value == 0)
                        {
                            if (StackPushTypes[0].GetTypeInfo().IsValueType)
                            {
                                StackPushTypes[0] = StackPushTypes[0].MakeByRefType();
                            }
                            return;
                        }
                        xArgIndexCorrection = -1;
                    }
                    StackPushTypes[0] = xParams[Value + xArgIndexCorrection].ParameterType;
                    StackPushTypes[0] = StackPushTypes[0].MakeByRefType();
                    return;
            }
        }
    }
}