using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.Reflection.Emit;

namespace Bowin.Common.Utility
{
    public static class WebExtensions
    {
        public static T ParseTo<T>(this string value)
        {
            if (Parser<T>.ParseMethod != null)
                return Parser<T>.ParseMethod(value);


            throw new NotSupportedException();
        }

        public static bool TryParseTo<T>(this string value, out T result)
        {
            if (Parser<T>.TryParseMethod != null)
            {
                return Parser<T>.TryParseMethod(value, out result);
            }

            throw new NotSupportedException();
        }

        public static Nullable<T> ParseStrTo<T>(this string value) where T : struct
        {
            if (value == null) return null;

            if (Parser<T>.TryParseMethod != null)
            {
                T result;
                if (Parser<T>.TryParseMethod(value, out result))
                {
                    return result;
                }
                else
                {
                    return null;
                }
            }

            throw new NotSupportedException();
        }

        static WebExtensions()
        {
            Parser<short>.ParseMethod = short.Parse;
            Parser<int>.ParseMethod = int.Parse;
            Parser<long>.ParseMethod = long.Parse;
            Parser<byte>.ParseMethod = byte.Parse;
            Parser<ushort>.ParseMethod = ushort.Parse;
            Parser<uint>.ParseMethod = uint.Parse;
            Parser<ulong>.ParseMethod = ulong.Parse;
            Parser<sbyte>.ParseMethod = sbyte.Parse;
            Parser<float>.ParseMethod = float.Parse;
            Parser<double>.ParseMethod = double.Parse;
            Parser<decimal>.ParseMethod = decimal.Parse;
            Parser<bool>.ParseMethod = bool.Parse;
            Parser<DateTime>.ParseMethod = DateTime.Parse;
            Parser<TimeSpan>.ParseMethod = TimeSpan.Parse;
            Parser<Guid>.ParseMethod = Guid.Parse;


            Parser<short>.TryParseMethod = short.TryParse;
            Parser<int>.TryParseMethod = int.TryParse;
            Parser<long>.TryParseMethod = long.TryParse;
            Parser<byte>.TryParseMethod = byte.TryParse;
            Parser<ushort>.TryParseMethod = ushort.TryParse;
            Parser<uint>.TryParseMethod = uint.TryParse;
            Parser<ulong>.TryParseMethod = ulong.TryParse;
            Parser<sbyte>.TryParseMethod = sbyte.TryParse;
            Parser<float>.TryParseMethod = float.TryParse;
            Parser<double>.TryParseMethod = double.TryParse;
            Parser<decimal>.TryParseMethod = decimal.TryParse;
            Parser<bool>.TryParseMethod = bool.TryParse;
            Parser<DateTime>.TryParseMethod = DateTime.TryParse;
            Parser<TimeSpan>.TryParseMethod = TimeSpan.TryParse;
            Parser<Guid>.TryParseMethod = Guid.TryParse;
        }

        private class Parser<T>
        {
            public delegate T ParseMethodDelegate(string value);

            public delegate bool TryParseMethodDelegate(string value, out T result);

            private static bool noParseMethod = false;
            private static ParseMethodDelegate _parseMethod;

            public static ParseMethodDelegate ParseMethod
            {
                get
                {

                    if (_parseMethod != null)
                        return _parseMethod;

                    if (noParseMethod)
                        return null;

                    var method = typeof(T).GetMethod("Parse", new Type[] { typeof(string) });
                    if (method != null && (method.Attributes & MethodAttributes.Static) != 0)
                    {
                        DynamicMethod dynamicMethod = new DynamicMethod(typeof(T).FullName + "_Parse", typeof(T), new Type[] { typeof(string) });

                        var il = dynamicMethod.GetILGenerator();
                        il.Emit(OpCodes.Ldarg_0);
                        il.EmitCall(OpCodes.Call, method, null);
                        il.Emit(OpCodes.Ret);

                        return _parseMethod = (Parser<T>.ParseMethodDelegate)dynamicMethod.CreateDelegate(typeof(Parser<T>.ParseMethodDelegate));

                    }

                    noParseMethod = true;
                    return null;
                }
                set
                {
                    _parseMethod = value;
                }
            }

            private static bool noTryParseMethod = false;
            private static TryParseMethodDelegate _tryParseMethod;
            public static TryParseMethodDelegate TryParseMethod
            {
                get
                {

                    if (_tryParseMethod != null)
                        return _tryParseMethod;

                    if (noTryParseMethod)
                        return null;

                    MethodInfo tryParseMethod = typeof(T).GetMethod("TryParse", new Type[] { typeof(string), Type.GetType(typeof(T).FullName + "&") });

                    if (tryParseMethod != null)
                    {

                        DynamicMethod tryParseDm = new DynamicMethod("TryParse", typeof(bool),
                          new Type[] { typeof(string), Type.GetType(typeof(T).FullName + "&") },
                          typeof(Parser<T>), false);
                        ILGenerator tryParseIl = tryParseDm.GetILGenerator();
                        tryParseIl.Emit(OpCodes.Ldarg_0);
                        tryParseIl.Emit(OpCodes.Ldarg_1);
                        tryParseIl.Emit(OpCodes.Call, tryParseMethod);
                        tryParseIl.Emit(OpCodes.Ret);
                        return _tryParseMethod = (TryParseMethodDelegate)tryParseDm.CreateDelegate(typeof(TryParseMethodDelegate));

                    }

                    noTryParseMethod = true;
                    return null;
                }
                set
                {
                    _tryParseMethod = value;
                }
            }
        }
    }
}