Refactor array reindexing helper

src/Asynkron.JsEngine/StdLib/StandardLibrary.Array.cs

@@ -11,7 +11,7 @@
 {
     private const long MaxArrayLength = 9007199254740991L; // 2^53 - 1
 
     public static void AddArrayMethods(IJsPropertyAccessor array, RealmState? realm = null,
         JsObject? prototypeOverride = null)
     {
         // Once the shared Array prototype has been initialized, new arrays
@@ -52,7 +52,7 @@
             {
                 Value = "lastIndexOf", Writable = false, Enumerable = false, Configurable = true
             });
         lastIndexOf.DefineProperty("length",
             new PropertyDescriptor { Value = 1d, Writable = false, Enumerable = false, Configurable = true });
         var lastIndexDescriptor = new PropertyDescriptor
         {
@@ -102,7 +102,7 @@
         DefineArrayIteratorFunction("keys", (_, _) => idx => (double)idx);
 
         // values() - returns an iterator of values
         var valuesFn = DefineArrayIteratorFunction("values", (accessor, _) => idx =>
         {
             var key = idx.ToString(CultureInfo.InvariantCulture);
             return GetElementOrUndefined(accessor, key);
@@ -121,7 +121,7 @@
             return Math.Min(truncated, (double)MaxArrayLength); // 2^53 - 1
         }
 
         static object CreateArrayIterator(object? thisValue, IJsPropertyAccessor accessor,
             Func<uint, object?> projector)
         {
             var iterator = new JsObject();
@@ -141,7 +141,7 @@
                 if (exhausted)
                 {
                     var doneResult = new JsObject();
                     doneResult.SetProperty("value", Symbol.Undefined);
                     doneResult.SetProperty("done", true);
                     return doneResult;
                 }
@@ -456,7 +456,7 @@
         return InvokeDefaultObjectToString(target, realm);
     }
 
     private static object? ArrayIncludes(object? thisValue, IReadOnlyList<object?> args, RealmState? realm)
     {
         var accessor = EnsureArrayLikeReceiver(thisValue, "Array.prototype.includes", realm);
 
@@ -666,26 +666,7 @@
             firstElement = firstValue;
         }
 
-        for (long k = 1; k < length; k++)
-        {
-            var fromKey = ToIndexString(k);
-            var toKey = ToIndexString(k - 1);
-            var fromExists = TryGetExistingElement(accessor, fromKey, out var fromValue);
-            if (fromExists)
-            {
-                accessor.SetProperty(toKey, fromValue);
-            }
-            else
-            {
-                var toExists = HasProperty(accessor, toKey);
-                DeletePropertyOrThrow(objectLike, toKey, toExists, MethodName, realm);
-            }
-        }
-
-        var lastKey = ToIndexString(length - 1);
-        var lastExists = HasProperty(accessor, lastKey);
-        DeletePropertyOrThrow(objectLike, lastKey, lastExists, MethodName, realm);
-        accessor.SetProperty("length", (double)(length - 1));
+        MoveArrayRange(accessor, objectLike, MethodName, length, 1, length - 1, -1, -1, realm);
         return firstElement;
     }
 
@@ -698,34 +679,13 @@
         var length = (long)ToLengthOrZero(lengthValue);
         var argCount = args.Count;
 
-        if (length + argCount > MaxArrayLength)
-        {
-            throw ThrowTypeError("Array.prototype.unshift cannot exceed 2^53 - 1 elements", realm: realm);
-        }
-
-        for (long k = length - 1; k >= 0; k--)
-        {
-            var fromKey = ToIndexString(k);
-            var toKey = ToIndexString(k + argCount);
-            var fromExists = TryGetExistingElement(accessor, fromKey, out var fromValue);
-            if (fromExists)
-            {
-                accessor.SetProperty(toKey, fromValue);
-            }
-            else
-            {
-                var toExists = HasProperty(accessor, toKey);
-                DeletePropertyOrThrow(objectLike, toKey, toExists, MethodName, realm);
-            }
-        }
-
+        var newLength = MoveArrayRange(accessor, objectLike, MethodName, length, 0, length, argCount, argCount, realm,
+            overflowMessage: "Array.prototype.unshift cannot exceed 2^53 - 1 elements");
         for (var j = 0; j < argCount; j++)
         {
             accessor.SetProperty(ToIndexString(j), args[j]);
         }
 
-        var newLength = length + argCount;
-        accessor.SetProperty("length", (double)newLength);
         return (double)newLength;
     }
 
@@ -772,12 +732,6 @@
             actualDeleteCount = (long)bounded;
         }
 
-        var newLength = length - actualDeleteCount + insertCount;
-        if (newLength > MaxArrayLength)
-        {
-            throw ThrowRangeError("Array length exceeds 2^53 - 1", realm: realm);
-        }
-
         var result = ArraySpeciesCreate(thisValue, actualDeleteCount, realm);
         for (long k = 0; k < actualDeleteCount; k++)
         {
@@ -786,53 +740,11 @@
 
         SetArrayLikeLength(result, actualDeleteCount);
 
-        if (insertCount < actualDeleteCount)
-        {
-            for (long k = actualStart; k < length - actualDeleteCount; k++)
-            {
-                var from = k + actualDeleteCount;
-                var to = k + insertCount;
-                var fromKey = ToIndexString(from);
-                var toKey = ToIndexString(to);
-
-                if (TryGetExistingElement(accessor, fromKey, out var fromValue))
-                {
-                    accessor.SetProperty(toKey, fromValue);
-                }
-                else
-                {
-                    var toExists = HasProperty(accessor, toKey);
-                    DeletePropertyOrThrow(objectLike, toKey, toExists, MethodName, realm);
-                }
-            }
-
-            for (long k = length; k > length - (actualDeleteCount - insertCount); k--)
-            {
-                var key = ToIndexString(k - 1);
-                var existed = HasProperty(accessor, key);
-                DeletePropertyOrThrow(objectLike, key, existed, MethodName, realm);
-            }
-        }
-        else if (insertCount > actualDeleteCount)
-        {
-            for (long k = length - actualDeleteCount; k > actualStart; k--)
-            {
-                var from = k + actualDeleteCount - 1;
-                var to = k + insertCount - 1;
-                var fromKey = ToIndexString(from);
-                var toKey = ToIndexString(to);
-
-                if (TryGetExistingElement(accessor, fromKey, out var fromValue))
-                {
-                    accessor.SetProperty(toKey, fromValue);
-                }
-                else
-                {
-                    var toExists = HasProperty(accessor, toKey);
-                    DeletePropertyOrThrow(objectLike, toKey, toExists, MethodName, realm);
-                }
-            }
-        }
+        var lengthDelta = insertCount - actualDeleteCount;
+        var tailStart = actualStart + actualDeleteCount;
+        var tailCount = Math.Max(length - tailStart, 0);
+        var newLength = MoveArrayRange(accessor, objectLike, MethodName, length, tailStart, tailCount, lengthDelta,
+            lengthDelta, realm, overflowIsRangeError: true);
 
         for (var j = 0; j < insertCount; j++)
         {
@@ -843,7 +755,7 @@
         return result;
     }
 
     private static object? ArrayConcat(object? thisValue, IReadOnlyList<object?> args, RealmState? realm)
     {
         var accessor = EnsureArrayLikeReceiver(thisValue, "Array.prototype.concat", realm);
         var result = ArraySpeciesCreate(thisValue, 0, realm);
@@ -873,7 +785,7 @@
                     var toKey = ToIndexString(resultIndex);
                     if (TryGetExistingElement(spreadAccessor, fromKey, out var value))
                     {
                         result.SetProperty(toKey, value);
                     }
                     else if (result is not null)
                     {
@@ -890,11 +802,11 @@
                     throw ThrowTypeError("Array length exceeds 2^53 - 1", realm: realm);
                 }
 
                 result.SetProperty(ToIndexString(resultIndex++), sourceValue);
             }
         }
 
         SetArrayLikeLength(result, resultIndex);
         return result;
     }
 
@@ -939,7 +851,7 @@
                 continue;
             }
 
             if (lowerExists && !upperExists)
             {
                 DeletePropertyOrThrow(objectLike, lowerKey, lowerExists, MethodName, realm);
                 accessor.SetProperty(upperKey, lowerValue);
@@ -953,7 +865,7 @@
         return accessor;
     }
 
     private static object? ArraySort(object? thisValue, IReadOnlyList<object?> args, RealmState? realm)
     {
         var accessor = EnsureArrayLikeReceiver(thisValue, "Array.prototype.sort", realm);
         var objectLike = accessor as IJsObjectLike;
@@ -986,7 +898,7 @@
                     return 0;
                 }
 
                 return d > 0 ? 1 : d < 0 ? -1 : 0;
             }
 
             var aStr = JsValueToString(a);
@@ -1204,7 +1116,7 @@
         return target;
     }
 
     private static object? ArrayToSorted(object? thisValue, IReadOnlyList<object?> args, RealmState? realm)
     {
         var accessor = EnsureArrayLikeReceiver(thisValue, "Array.prototype.toSorted", realm);
         var lengthValue = accessor.TryGetProperty("length", out var lenVal) ? lenVal : 0d;
@@ -1234,7 +1146,7 @@
                     return 0;
                 }
 
                 return d > 0 ? 1 : d < 0 ? -1 : 0;
 
             });
         }
@@ -1262,7 +1174,7 @@
             result?.Delete(key);
         }
 
         SetArrayLikeLength(result, length);
         return result;
     }
 
@@ -1455,7 +1367,7 @@
         }
 
         var asNumber = JsOps.ToNumber(lengthVal);
         if (double.IsNaN(asNumber) || !(asNumber > 0))
         {
             return 0;
         }
@@ -1501,7 +1413,7 @@
         }
     }
 
     public static HostFunction CreateArrayConstructor(RealmState realm)
     {
         JsObject? arrayPrototype = null;
 
@@ -1663,7 +1575,7 @@
         return arrayConstructor;
     }
 
     private static object? ArrayOf(HostFunction host, object? thisValue, IReadOnlyList<object?> args, RealmState? realm)
     {
         const string MethodName = "Array.of";
         var len = args.Count;
@@ -1698,7 +1610,7 @@
         }
     }
 
     private static object? ArrayFrom(HostFunction host, object? thisValue, IReadOnlyList<object?> args,
         RealmState? realm)
     {
         const string MethodName = "Array.from";
@@ -1750,7 +1662,7 @@
 
             var key = ToIndexString(k);
             var value = GetElementOrUndefined(arrayLike, key);
             var mapped = mapping && mapper is not null
                 ? InvokeArrayFromMapper(mapper, host, thisArg, value, k)
                 : value;
             CreateDataPropertyOrThrow(result, key, mapped, realm, MethodName);
@@ -1838,7 +1750,7 @@
         return promise.JsObject;
     }
 
     private static object? ArrayFromIterable(HostFunction host, object? thisValue, object? items,
         IJsCallable iteratorMethod, IJsCallable? mapper, bool mapping, object? thisArg, RealmState? realm)
     {
         const string MethodName = "Array.from";
@@ -1916,7 +1828,7 @@
         }
     }
 
     private static bool TryAwaitPromiseLike(object? candidate, RealmState? realm, Action<object?> onFulfilled,
         Action<object?> onRejected)
     {
         if (candidate is JsObject jsObject &&
@@ -2048,8 +1960,8 @@
         private bool _awaitIteratorResult;
         private IJsPropertyAccessor? _arrayLike;
 
         public ArrayFromAsyncOperation(HostFunction host, RealmState realm, JsPromise promise, IJsObjectLike result,
             bool mapping, IJsCallable? mapper, object? thisArg, string methodName)
         {
             _host = host;
             _realm = realm;
@@ -2385,7 +2297,7 @@
     private static readonly string SymbolIsConcatSpreadableKey =
         $"@@symbol:{TypedAstSymbol.For("Symbol.isConcatSpreadable").GetHashCode()}";
 
     private static IJsObjectLike ArraySpeciesCreate(object? original, long length, RealmState? realm)
     {
         length = Math.Max(length, 0);
 
@@ -2446,7 +2358,7 @@
         var proto = ResolveConstructPrototype(callable, callable, realm);
         IJsObjectLike receiver;
 
         if (callable is HostFunction hostFunction && realm?.ArrayConstructor is not null &&
             ReferenceEquals(hostFunction, realm.ArrayConstructor))
         {
             receiver = new JsArray(realm);
@@ -2498,7 +2410,7 @@
     private static IJsObjectLike CreateArrayLikeReceiverForConstructor(IJsCallable constructor, RealmState? realm,
         long length)
     {
         var proto = ResolveConstructPrototype(constructor, constructor, realm);
         IJsObjectLike receiver;
 
         if (constructor is HostFunction hostFunction && realm?.ArrayConstructor is not null &&
@@ -2522,6 +2434,73 @@
         return receiver;
     }
 
+    private static long MoveArrayRange(IJsPropertyAccessor accessor, IJsObjectLike? objectLike, string methodName,
+        long length, long sourceStart, long sourceCount, long destinationOffset, long lengthDelta, RealmState? realm,
+        bool overflowIsRangeError = false, string? overflowMessage = null, bool updateLength = true)
+    {
+        var newLength = length + lengthDelta;
+        if (newLength > MaxArrayLength)
+        {
+            var errorMessage = overflowMessage ?? "Array length exceeds 2^53 - 1";
+            if (overflowIsRangeError)
+            {
+                throw ThrowRangeError(errorMessage, realm: realm);
+            }
+
+            throw ThrowTypeError(errorMessage, realm: realm);
+        }
+
+        if (sourceCount > 0 && destinationOffset != 0)
+        {
+            if (destinationOffset > 0)
+            {
+                for (long k = sourceStart + sourceCount - 1; k >= sourceStart; k--)
+                {
+                    MoveSingleIndex(k, destinationOffset);
+                }
+            }
+            else
+            {
+                for (long k = sourceStart; k < sourceStart + sourceCount; k++)
+                {
+                    MoveSingleIndex(k, destinationOffset);
+                }
+            }
+        }
+
+        if (lengthDelta < 0)
+        {
+            for (long k = length; k > newLength; k--)
+            {
+                var key = ToIndexString(k - 1);
+                var existed = HasProperty(accessor, key);
+                DeletePropertyOrThrow(objectLike, key, existed, methodName, realm);
+            }
+        }
+
+        if (updateLength)
+        {
+            accessor.SetProperty("length", (double)newLength);
+        }
+
+        return newLength;
+
+        void MoveSingleIndex(long fromIndex, long offset)
+        {
+            var toIndex = fromIndex + offset;
+            var fromKey = ToIndexString(fromIndex);
+            var toKey = ToIndexString(toIndex);
+            if (TryGetExistingElement(accessor, fromKey, out var value))
+            {
+                accessor.SetProperty(toKey, value);
+                return;
+            }
+
+            var toExisted = HasProperty(accessor, toKey);
+            DeletePropertyOrThrow(objectLike, toKey, toExisted, methodName, realm);
+        }
+    }
+
     private static void DeletePropertyOrThrow(IJsObjectLike? objectLike, string propertyKey, bool propertyExisted,
         string methodName, RealmState? realm)
     {
@@ -2643,8 +2622,8 @@
         }
     }
 
     private static long FlattenIntoArray(IJsPropertyAccessor target, IJsPropertyAccessor source, long sourceLength,
         long targetIndex, long depth, IJsCallable? mapper, object? thisArg, RealmState? realm, string operation)
     {
         for (long k = 0; k < sourceLength; k++)
         {
@@ -2742,7 +2721,7 @@
             return 0;
         }
 
         if (double.IsInfinity(number) || number == 0)
         {
             return number;
         }
@@ -2772,7 +2751,7 @@
         return integer > length ? length : integer;
     }
 
     internal static object? ReduceLike(object? thisValue, IReadOnlyList<object?> args, RealmState? realm,
         string methodName, bool fromRight)
     {
         var accessor = EnsureArrayLikeReceiver(thisValue, methodName, realm);
@@ -2865,7 +2844,7 @@
         return accumulatorGeneric;
     }
 
     internal static object? SomeLike(object? thisValue, IReadOnlyList<object?> args, RealmState? realm,
         string methodName)
     {
         var accessor = EnsureArrayLikeReceiver(thisValue, methodName, realm);
@@ -2931,7 +2910,7 @@
         return JsOps.StrictEquals(x, y);
     }
 
     private static IJsPropertyAccessor EnsureArrayLikeReceiver(object? receiver, string methodName, RealmState? realm)
     {
         if (receiver is null || ReferenceEquals(receiver, Symbol.Undefined))
         {
@@ -2942,7 +2921,7 @@
         {
             case IJsPropertyAccessor accessor when accessor is not TypedAstSymbol:
             {
                 if (accessor is not JsObject jsObj || !jsObj.TryGetProperty("__value__", out var inner) ||
                     inner is not string sInner)
                 {
                     return accessor;
@@ -3198,7 +3177,7 @@
             objectPrototype.TryGetProperty("toString", out var toStringValue) &&
             toStringValue is IJsCallable callable)
         {
             return callable.Invoke([], target);
         }
 
         return "[object Object]";