Function createArrayIterationHandler

packages/db/src/proxy.ts:76–179

* Creates a handler for array iteration methods that ensures proxied elements * are passed to callbacks and returned from methods like find/filter.

(
  methodName: string,
  methodFn: (...args: Array<unknown>) => unknown,
  changeTracker: ChangeTracker<T>,
  memoizedCreateChangeProxy: (
    obj: Record<string | symbol, unknown>,
    parent?: {
      tracker: ChangeTracker<Record<string | symbol, unknown>>
      prop: string | symbol
    },
  ) => { proxy: Record<string | symbol, unknown> },
)

 * are passed to callbacks and returned from methods like find/filter.
 */
function createArrayIterationHandler<T extends object>(
  methodName: string,
  methodFn: (...args: Array<unknown>) => unknown,
  changeTracker: ChangeTracker<T>,
  memoizedCreateChangeProxy: (
    obj: Record<string | symbol, unknown>,
    parent?: {
      tracker: ChangeTracker<Record<string | symbol, unknown>>
      prop: string | symbol
    },
  ) => { proxy: Record<string | symbol, unknown> },
): ((...args: Array<unknown>) => unknown) | undefined {
  if (!CALLBACK_ITERATION_METHODS.has(methodName)) {
    return undefined
  }

  return function (...args: Array<unknown>) {
    const callback = args[0]
    if (typeof callback !== `function`) {
      return methodFn.apply(changeTracker.copy_, args)
    }

    // Create a helper to get proxied version of an array element
    const getProxiedElement = (element: unknown, index: number): unknown => {
      if (isProxiableObject(element)) {
        const nestedParent = {
          tracker: changeTracker as unknown as ChangeTracker<
            Record<string | symbol, unknown>
          >,
          prop: String(index),
        }
        const { proxy: elementProxy } = memoizedCreateChangeProxy(
          element,
          nestedParent,
        )
        return elementProxy
      }
      return element
    }

    // Wrap the callback to pass proxied elements
    const wrappedCallback = function (
      this: unknown,
      element: unknown,
      index: number,
      array: unknown,
    ) {
      const proxiedElement = getProxiedElement(element, index)
      return callback.call(this, proxiedElement, index, array)
    }

    // For reduce/reduceRight, the callback signature is different
    if (methodName === `reduce` || methodName === `reduceRight`) {
      const reduceCallback = function (
        this: unknown,
        accumulator: unknown,
        element: unknown,
        index: number,