using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;

namespace System.Linq.jvm
{
    class Math
    {

        private static readonly Type NULLABLE_TYPE = typeof(Nullable<>);

        public static object Evaluate(object a, object b, Type t, ExpressionType et)
        {
            TypeCode tc = Type.GetTypeCode(t);
            if (tc == TypeCode.Object)
            {
                if (t.GetGenericTypeDefinition() != NULLABLE_TYPE)
                {
                    throw new NotImplementedException(
                        string.Format(
                        "Expression with Node type {0} for type {1}", 
                        t.FullName, 
                        tc));
                    
                }
                return EvaluateNullable(a, b, Type.GetTypeCode(t.GetGenericArguments()[0]), et); 
            }    
            return Evaluate(a, b, tc, et);
        }

        public static object EvaluateNullable(object a, object b, TypeCode tc, ExpressionType et)
        {
            object o = null;
            if (a == null || b == null)
            {
                if (tc != TypeCode.Boolean)
                {
                    return null;
                }
                switch (et)
                {
                    case ExpressionType.And:
                        o = And(a, b);
                        break;
                    case ExpressionType.Or:
                        o = Or(a, b);
                        break;
                    case ExpressionType.ExclusiveOr:
                        o = ExclusiveOr(a, b);
                        break;
                }
            }
            else
            {
                o = Evaluate(a, b, tc, et);
            }
            return Convert2Nullable(o, tc);

        }

        private static object ExclusiveOr(object a, object b)
        {
            if (a == null || b == null)
            {
                return null;
            }
            return (bool)a ^ (bool)b;
        }

        public static object Or(object a, object b)
        {
            if (a == null)
            {
                if (b == null || !((bool)b))
                {
                    return null;
                }
                return true;
            }

            if (b == null)
            {
                if (a == null || !((bool)a))
                {
                    return null;
                }
                return true;
            }

            return (bool)a || (bool)b;
        }

        public static object And(object a, object b)
        {
            if (a == null)
            {
                if (b == null || (bool)b)
                {
                    return null;
                }
                return false;
            }

            if (b == null)
            {
                if (a == null || (bool)a)
                {
                    return null;
                }
                return false;
            }

            return (bool)a && (bool)b;
        }

        private static object Convert2Nullable(object o, TypeCode tc)
        {
            if (o == null)
            {
                return null;
            }
            switch (tc)
            {
                case TypeCode.Char:
                    return new Nullable<Char>((Char)o);
                case TypeCode.Byte:
                    return new Nullable<Byte>((Byte)o);
                case TypeCode.Decimal:
                    return new Nullable<Decimal>((Decimal)o);
                case TypeCode.Double:
                    return new Nullable<Double>((Double)o);
                case TypeCode.Int16:
                    return new Nullable<Int16>((Int16)o);
                case TypeCode.Int32:
                    return new Nullable<Int32>((Int32)o);
                case TypeCode.Int64:
                    return new Nullable<Int64>((Int64)o);
                case TypeCode.UInt16:
                    return new Nullable<UInt16>((UInt16)o);
                case TypeCode.UInt32:
                    return new Nullable<UInt32>((UInt32)o);
                case TypeCode.SByte:
                    return new Nullable<SByte>((SByte)o);
                case TypeCode.Single:
                    return new Nullable<Single>((Single)o);
                case TypeCode.Boolean:
                    return new Nullable<Boolean>((Boolean)o);
            }

            throw new NotImplementedException(
                string.Format("No Convert2Nullable defined for type {0} ", tc));
        }

        public static object Evaluate(object a, object b, TypeCode tc, ExpressionType et)
        {
            switch (tc)
            {
                case TypeCode.Boolean:
                    return Evaluate(Convert.ToBoolean(a), Convert.ToBoolean(b), et);
                case TypeCode.Char:
                    return Evaluate(Convert.ToChar(a), Convert.ToChar(b), et);
                case TypeCode.Byte:
                    return unchecked((Byte)Evaluate(Convert.ToByte(a), Convert.ToByte(b), et));
                case TypeCode.Decimal:
                    return Evaluate(Convert.ToDecimal(a), Convert.ToDecimal(b), et);
                case TypeCode.Double:
                    return Evaluate(Convert.ToDouble(a), Convert.ToDouble(b), et);
                case TypeCode.Int16:
                    return unchecked((Int16)Evaluate(Convert.ToInt16(a), Convert.ToInt16(b), et));
                case TypeCode.Int32:
                    return Evaluate(Convert.ToInt32(a), Convert.ToInt32(b), et);
                case TypeCode.Int64:
                    return Evaluate(Convert.ToInt64(a), Convert.ToInt64(b), et);
                case TypeCode.UInt16:
                    return unchecked((UInt16)Evaluate(Convert.ToUInt16(a), Convert.ToUInt16(b), et));
                case TypeCode.UInt32:
                    return Evaluate(Convert.ToUInt32(a), Convert.ToUInt32(b), et);
                case TypeCode.UInt64:
                    return Evaluate(Convert.ToUInt64(a), Convert.ToUInt64(b), et);
                case TypeCode.SByte:
                    return unchecked((SByte)Evaluate(Convert.ToSByte(a), Convert.ToSByte(b), et));
                case TypeCode.Single:
                    return Evaluate(Convert.ToSingle(a), Convert.ToSingle(b), et);

            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0} for type {1}", et, tc));
        }    

        public static object NegeteChecked(object a, TypeCode tc)
        {
            switch (tc)
            {
                case TypeCode.Char:
                    return checked(-Convert.ToChar(a));
                case TypeCode.Byte:
                    return checked(-Convert.ToByte(a));
                case TypeCode.Decimal:
                    return checked(-Convert.ToDecimal(a));
                case TypeCode.Double:
                    return checked(-Convert.ToDouble(a));
                case TypeCode.Int16:
                    return checked(-Convert.ToInt16(a));
                case TypeCode.Int32:
                    return checked(-Convert.ToInt32(a));
                case TypeCode.Int64:
                    return checked(-Convert.ToInt64(a));
                case TypeCode.UInt16:
                    return checked(-Convert.ToUInt16(a));
                case TypeCode.UInt32:
                    return checked(-Convert.ToUInt32(a));
                case TypeCode.SByte:
                    return checked(-Convert.ToSByte(a));
                case TypeCode.Single:
                    return checked(-Convert.ToSingle(a));
            }

            throw new NotImplementedException(
                string.Format("No NegeteChecked defined for type {0} ", tc));

        }

        public static object ConvertToTypeChecked(object a, Type fromType, Type toType)
        {
			if (Expression.IsNullable (toType) && Expression.GetNotNullableOf (toType) == fromType)
				return a == null ? a : Activator.CreateInstance (toType, a);

			if (a == null) {
				if (!toType.IsValueType)
					return a;
				if (Expression.IsNullable (fromType))
					throw new InvalidOperationException ("Nullable object must have a value");
			}
			
            if (IsType(toType, a)){
                return a;
            }
     
			if (Expression.IsPrimitiveConversion(fromType, toType))
				return Convert.ChangeType (a, toType);
			
			throw new NotImplementedException (
							string.Format ("No Convert defined for type {0} ", toType));
        }

		public static object ConvertToTypeUnchecked (object a, Type fromType, Type toType)
		{
			if (Expression.IsNullable (toType) && Expression.GetNotNullableOf (toType) == fromType)
				return a == null ? a : Activator.CreateInstance (toType, a);

			if (a == null) { 
				if (!toType.IsValueType)
					return a;
				if (Expression.IsNullable (fromType))
					throw new InvalidOperationException ("Nullable object must have a value");
			}
								
			if (IsType (toType, a)) {
				return a;
			}

			if (Expression.IsPrimitiveConversion (fromType, toType))
				return Conversion.ConvertPrimitiveUnChecked (fromType, toType, a);

			throw new NotImplementedException (
							string.Format ("No Convert defined for type {0} ", toType));
		}		

        public static bool IsType(Type t, Object o)
        {
            return t.IsInstanceOfType(o);

        }        

        public static object Negete(object a, TypeCode tc)
        {
            switch (tc)
            {
                case TypeCode.Char:
                    return unchecked(-Convert.ToChar(a));
                case TypeCode.Byte:
                    return unchecked(-Convert.ToByte(a));
                case TypeCode.Decimal:
                    return unchecked(-Convert.ToDecimal(a));
                case TypeCode.Double:
                    return unchecked(-Convert.ToDouble(a));
                case TypeCode.Int16:
                    return unchecked(-Convert.ToInt16(a));
                case TypeCode.Int32:
                    return unchecked(-Convert.ToInt32(a));
                case TypeCode.Int64:
                    return unchecked(-Convert.ToInt64(a));
                case TypeCode.UInt16:
                    return unchecked(-Convert.ToUInt16(a));
                case TypeCode.UInt32:
                    return unchecked(-Convert.ToUInt32(a));
                case TypeCode.SByte:
                    return unchecked(-Convert.ToSByte(a));
                case TypeCode.Single:
                    return unchecked(-Convert.ToSingle(a));
            }

            throw new NotImplementedException(
                string.Format("No Negete defined for type {0} ", tc));

        }

        public static object RightShift(object a, int n, TypeCode tc)
        {
            switch (tc)
            {
                case TypeCode.Int16:
                     return Convert.ToInt16(a) >> n;
                case TypeCode.Int32:
                    return Convert.ToInt32(a) >> n;
                case TypeCode.Int64:
                    return  Convert.ToInt64(a) >> n;
                case TypeCode.UInt16:
                    return Convert.ToUInt16(a) >> n;
                case TypeCode.UInt32:
                    return Convert.ToUInt32(a) >> n;
                case TypeCode.UInt64:
                    return Convert.ToUInt64(a) >> n;
            }
            throw new NotImplementedException(
                string.Format("No right shift defined for type {0} ", tc));
        }

        public static object LeftShift(object a, int n, TypeCode tc)
        {
            switch (tc)
            {
                case TypeCode.Int16:
                    return Convert.ToInt16(a) << n;
                case TypeCode.Int32:
                    return Convert.ToInt32(a) << n;
                case TypeCode.Int64:
                    return Convert.ToInt64(a) << n;
                case TypeCode.UInt16:
                    return Convert.ToUInt16(a) << n;
                case TypeCode.UInt32:
                    return Convert.ToUInt32(a) << n;
                case TypeCode.UInt64:
                    return Convert.ToUInt64(a) << n;
            }
            throw new NotImplementedException(
                string.Format("No right shift defined for type {0} ", tc));
        }

        private static Decimal Evaluate(Decimal a, Decimal b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return  unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
                
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }

        private static Double Evaluate(Double a, Double b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
                case ExpressionType.Power:
                    return System.Math.Pow(a, b);
            }

            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
            
        }

        private static Int32 Evaluate(Int16 a, Int16 b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return  a % b;
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                        string.Format("Expression with Node type {0}", et));  
        }

        private static Int32 Evaluate(Int32 a, Int32 b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }

        private static Int64 Evaluate(Int64 a, Int64 b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }

        private static Int32 Evaluate(UInt16 a, UInt16 b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked((UInt16)(a - b));
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }

        private static UInt32 Evaluate(UInt32 a, UInt32 b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }

        private static UInt64 Evaluate(UInt64 a, UInt64 b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }

        private static object Evaluate(Char a, Char b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));

        }

        private static Int32 Evaluate(SByte a, SByte b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }

        private static Int32 Evaluate(Byte a, Byte b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }

        private static Single Evaluate(Single a, Single b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.Add:
                    return unchecked(a + b);
                case ExpressionType.AddChecked:
                    return checked(a + b);
                case ExpressionType.Subtract:
                    return unchecked(a - b);
                case ExpressionType.SubtractChecked:
                    return checked(a - b);
                case ExpressionType.Multiply:
                    return unchecked(a * b);
                case ExpressionType.MultiplyChecked:
                    return checked(a * b);
                case ExpressionType.Divide:
                    return a / b;
                case ExpressionType.Modulo:
                    return a % b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }

        private static bool Evaluate(bool a, bool b, ExpressionType et)
        {
            switch (et)
            {
                case ExpressionType.ExclusiveOr:
                    return a ^ b;
                case ExpressionType.And:
                    return a & b;
                case ExpressionType.Or:
                    return a | b;
            }
            throw new NotImplementedException(
                string.Format("Expression with Node type {0}", et));
        }
    }
}