sebastienros.jint/Jint/Native/String/StringInstance.cs

using System.Collections.Generic;
using Jint.Native.Object;
using Jint.Runtime;
using Jint.Runtime.Descriptors;

namespace Jint.Native.String
{
    public class StringInstance : ObjectInstance, IPrimitiveInstance
    {
        private const string PropertyNameLength = "length";
        private const int PropertyNameLengthLength = 6;

        private PropertyDescriptor _length;

        public StringInstance(Engine engine)
            : base(engine)
        {
        }

        public override string Class => "String";

        Types IPrimitiveInstance.Type => Types.String;

        JsValue IPrimitiveInstance.PrimitiveValue => PrimitiveValue;

        public JsValue PrimitiveValue { get; set; }

        private static bool IsInt(double d)
        {
            if (d >= long.MinValue && d <= long.MaxValue)
            {
                var l = (long) d;
                return l >= int.MinValue && l <= int.MaxValue;
            }

            return false;
        }

        public override PropertyDescriptor GetOwnProperty(string propertyName)
        {
            if (propertyName.Length == 8 && propertyName == "Infinity")
            {
                return PropertyDescriptor.Undefined;
            }

            if (propertyName.Length == PropertyNameLengthLength && propertyName == PropertyNameLength)
            {
                return _length ?? PropertyDescriptor.Undefined;
            }

            var desc = base.GetOwnProperty(propertyName);
            if (desc != PropertyDescriptor.Undefined)
            {
                return desc;
            }

            var integer = TypeConverter.ToInteger(propertyName);
            if (integer == 0 && propertyName != "0" || propertyName != System.Math.Abs(integer).ToString())
            {
                return PropertyDescriptor.Undefined;
            }

            var str = PrimitiveValue;
            var dIndex = integer;
            if (!IsInt(dIndex))
                return PropertyDescriptor.Undefined;

            var index = (int) dIndex;
            var len = str.AsString().Length;
            if (len <= index || index < 0)
            {
                return PropertyDescriptor.Undefined;
            }

            var resultStr = TypeConverter.ToString(str.AsString()[index]);
            return new PropertyDescriptor(resultStr, PropertyFlag.OnlyEnumerable);
        }

        public override IEnumerable<KeyValuePair<string, PropertyDescriptor>> GetOwnProperties()
        {
            if (_length != null)
            {
                yield return new KeyValuePair<string, PropertyDescriptor>(PropertyNameLength, _length);
            }

            foreach (var entry in base.GetOwnProperties())
            {
                yield return entry;
            }
        }

        protected internal override void SetOwnProperty(string propertyName, PropertyDescriptor desc)
        {
            if (propertyName.Length == PropertyNameLengthLength && propertyName == PropertyNameLength)
            {
                _length = desc;
            }
            else
            {
                base.SetOwnProperty(propertyName, desc);
            }
        }

        public override bool HasOwnProperty(string propertyName)
        {
            if (propertyName.Length == PropertyNameLengthLength && propertyName == PropertyNameLength)
            {
                return _length != null;
            }

            return base.HasOwnProperty(propertyName);
        }

        public override void RemoveOwnProperty(string propertyName)
        {
            if (propertyName.Length == PropertyNameLengthLength && propertyName == PropertyNameLength)
            {
                _length = null;
            }

            base.RemoveOwnProperty(propertyName);
        }
    }
}