sebastienros.jint/Jint/Native/Function/FunctionPrototype.cs

#pragma warning disable CA1859 // Use concrete types when possible for improved performance -- most of prototype methods return JsValue

using Jint.Native.Array;
using Jint.Native.Object;
using Jint.Native.Symbol;
using Jint.Runtime;
using Jint.Runtime.Descriptors;
using Jint.Runtime.Descriptors.Specialized;
using Jint.Runtime.Interop;

namespace Jint.Native.Function;

/// <summary>
/// https://tc39.es/ecma262/#sec-properties-of-the-function-prototype-object
/// </summary>
internal sealed class FunctionPrototype : Function
{
    internal FunctionPrototype(
        Engine engine,
        Realm realm,
        ObjectPrototype objectPrototype)
        : base(engine, realm, JsString.Empty)
    {
        _prototype = objectPrototype;
        _length = new PropertyDescriptor(JsNumber.PositiveZero, PropertyFlag.Configurable);
    }

    protected override void Initialize()
    {
        const PropertyFlag PropertyFlags = PropertyFlag.Configurable | PropertyFlag.Writable;
        const PropertyFlag LengthFlags = PropertyFlag.Configurable;
        var properties = new PropertyDictionary(7, checkExistingKeys: false)
        {
            ["constructor"] = new LazyPropertyDescriptor<FunctionPrototype>(this, static prototype => prototype._realm.Intrinsics.Function, PropertyFlag.NonEnumerable),
            ["toString"] = new LazyPropertyDescriptor<FunctionPrototype>(this, static prototype => new ClrFunction(prototype._engine, "toString", prototype.ToString, 0, LengthFlags), PropertyFlags),
            ["apply"] = new LazyPropertyDescriptor<FunctionPrototype>(this, static prototype => new ClrFunction(prototype._engine, "apply", prototype.Apply, 2, LengthFlags), PropertyFlags),
            ["call"] = new LazyPropertyDescriptor<FunctionPrototype>(this, static prototype => new ClrFunction(prototype._engine, "call", prototype.CallImpl, 1, LengthFlags), PropertyFlags),
            ["bind"] = new LazyPropertyDescriptor<FunctionPrototype>(this, static prototype => new ClrFunction(prototype._engine, "bind", prototype.Bind, 1, LengthFlags), PropertyFlags),
            ["arguments"] = new GetSetPropertyDescriptor.ThrowerPropertyDescriptor(_engine, PropertyFlag.Configurable),
            ["caller"] = new GetSetPropertyDescriptor.ThrowerPropertyDescriptor(_engine, PropertyFlag.Configurable)
        };
        SetProperties(properties);

        var symbols = new SymbolDictionary(1)
        {
            [GlobalSymbolRegistry.HasInstance] = new PropertyDescriptor(new ClrFunction(_engine, "[Symbol.hasInstance]", HasInstance, 1, PropertyFlag.Configurable), PropertyFlag.AllForbidden)
        };
        SetSymbols(symbols);
    }

    /// <summary>
    /// https://tc39.es/ecma262/#sec-function.prototype-@@hasinstance
    /// </summary>
    private static JsValue HasInstance(JsValue thisObject, JsCallArguments arguments)
    {
        return thisObject.OrdinaryHasInstance(arguments.At(0));
    }

    /// <summary>
    /// https://tc39.es/ecma262/#sec-function.prototype.bind
    /// </summary>
    private JsValue Bind(JsValue thisObject, JsCallArguments arguments)
    {
        if (thisObject is not (ICallable and ObjectInstance oi))
        {
            ExceptionHelper.ThrowTypeError(_realm, "Bind must be called on a function");
            return default;
        }

        var thisArg = arguments.At(0);
        var f = BoundFunctionCreate(oi, thisArg, arguments.Skip(1));

        JsNumber l;
        var targetHasLength = oi.HasOwnProperty(CommonProperties.Length);
        if (targetHasLength)
        {
            var targetLen = oi.Get(CommonProperties.Length);
            if (targetLen is not JsNumber number)
            {
                l = JsNumber.PositiveZero;
            }
            else
            {
                if (number.IsPositiveInfinity())
                {
                    l = number;
                }
                else if (number.IsNegativeInfinity())
                {
                    l = JsNumber.PositiveZero;
                }
                else
                {
                    var targetLenAsInt = (long) TypeConverter.ToIntegerOrInfinity(targetLen);
                    // first argument is target
                    var argumentsLength = System.Math.Max(0, arguments.Length - 1);
                    l = JsNumber.Create((ulong) System.Math.Max(targetLenAsInt - argumentsLength, 0));
                }
            }
        }
        else
        {
            l = JsNumber.PositiveZero;
        }

        f.DefinePropertyOrThrow(CommonProperties.Length, new PropertyDescriptor(l, PropertyFlag.Configurable));

        var targetName = oi.Get(CommonProperties.Name);
        if (!targetName.IsString())
        {
            targetName = JsString.Empty;
        }

        f.SetFunctionName(targetName, "bound");

        return f;
    }

    /// <summary>
    /// https://tc39.es/ecma262/#sec-boundfunctioncreate
    /// </summary>
    private BindFunction BoundFunctionCreate(ObjectInstance targetFunction, JsValue boundThis, JsValue[] boundArgs)
    {
        var proto = targetFunction.GetPrototypeOf();
        var obj = new BindFunction(_engine, _realm, proto, targetFunction, boundThis, boundArgs);
        return obj;
    }

    /// <summary>
    /// https://tc39.es/ecma262/#sec-function.prototype.tostring
    /// </summary>
    private JsValue ToString(JsValue thisObject, JsCallArguments arguments)
    {
        if (thisObject.IsObject() && thisObject.IsCallable)
        {
            return thisObject.ToString();
        }

        ExceptionHelper.ThrowTypeError(_realm, "Function.prototype.toString requires that 'this' be a Function");
        return null;
    }

    /// <summary>
    /// https://tc39.es/ecma262/#sec-function.prototype.apply
    /// </summary>
    private JsValue Apply(JsValue thisObject, JsCallArguments arguments)
    {
        var func = thisObject as ICallable;
        if (func is null)
        {
            ExceptionHelper.ThrowTypeError(_realm);
        }
        var thisArg = arguments.At(0);
        var argArray = arguments.At(1);

        if (argArray.IsNullOrUndefined())
        {
            return func.Call(thisArg, Arguments.Empty);
        }

        var argList = CreateListFromArrayLike(_realm, argArray);

        var result = func.Call(thisArg, argList);

        return result;
    }

    /// <summary>
    /// https://tc39.es/ecma262/#sec-createlistfromarraylike
    /// </summary>
    internal static JsValue[] CreateListFromArrayLike(Realm realm, JsValue argArray, Types? elementTypes = null)
    {
        var argArrayObj = argArray as ObjectInstance;
        if (argArrayObj is null)
        {
            ExceptionHelper.ThrowTypeError(realm);
        }
        var operations = ArrayOperations.For(argArrayObj, forWrite: false);
        var argList = elementTypes is null ? operations.GetAll() : operations.GetAll(elementTypes.Value);
        return argList;
    }

    /// <summary>
    /// https://tc39.es/ecma262/#sec-function.prototype.call
    /// </summary>
    private JsValue CallImpl(JsValue thisObject, JsCallArguments arguments)
    {
        var func = thisObject as ICallable;
        if (func is null)
        {
            ExceptionHelper.ThrowTypeError(_realm);
        }
        JsValue[] values = [];
        if (arguments.Length > 1)
        {
            values = new JsValue[arguments.Length - 1];
            System.Array.Copy(arguments, 1, values, 0, arguments.Length - 1);
        }

        var result = func.Call(arguments.At(0), values);

        return result;
    }

    protected internal override JsValue Call(JsValue thisObject, JsCallArguments arguments)
    {
        return Undefined;
    }
}