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
    {
        internal PropertyDescriptor _length;

        public StringInstance(Engine engine)
            : base(engine, objectClass: "String")
        {
        }

        Types IPrimitiveInstance.Type => Types.String;

        JsValue IPrimitiveInstance.PrimitiveValue => PrimitiveValue;

        public JsString PrimitiveValue { get; set; }

        private static bool IsInt32(double d)
        {
            return d >= int.MinValue && d <= int.MaxValue && ((int) d) == d;
        }

        public override PropertyDescriptor GetOwnProperty(in Key propertyName)
        {
            if (propertyName == KnownKeys.Infinity)
            {
                return PropertyDescriptor.Undefined;
            }

            if (propertyName == KnownKeys.Length)
            {
                return _length ?? PropertyDescriptor.Undefined;
            }

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

            if (!TypeConverter.CanBeIndex(propertyName))
            {
                return PropertyDescriptor.Undefined;
            }

            var number = TypeConverter.ToNumber(propertyName.Name);
            if (!IsInt32(number))
            {
                return PropertyDescriptor.Undefined;
            }

            var index = (int) number;
            var str = PrimitiveValue.AsStringWithoutTypeCheck();
            if (index < 0 || str.Length <= index)
            {
                return PropertyDescriptor.Undefined;
            }

            return new PropertyDescriptor(str[index], PropertyFlag.OnlyEnumerable);
        }

        public override IEnumerable<KeyValuePair<Key, PropertyDescriptor>> GetOwnProperties()
        {
            if (_length != null)
            {
                yield return new KeyValuePair<Key, PropertyDescriptor>(KnownKeys.Length, _length);
            }

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

        protected internal override void SetOwnProperty(in Key propertyName, PropertyDescriptor desc)
        {
            if (propertyName == KnownKeys.Length)
            {
                _length = desc;
            }
            else
            {
                base.SetOwnProperty(propertyName, desc);
            }
        }

        public override bool HasOwnProperty(in Key propertyName)
        {
            if (propertyName == KnownKeys.Length)
            {
                return _length != null;
            }

            return base.HasOwnProperty(propertyName);
        }

        public override void RemoveOwnProperty(in Key propertyName)
        {
            if (propertyName == KnownKeys.Length)
            {
                _length = null;
            }

            base.RemoveOwnProperty(propertyName);
        }
    }
}