Fiber (react fibers outside react) immutable version

fiber.ts

type FiberFunction<Args extends any[], Return> = (
  cell: CellFunction
) => (...args: Args) => Return;

type FiberInstance<Args extends any[], Return> = (
  ...args: Args
) => [Return, FiberInstance<Args, Return>];

type FiberFactory = <Args extends any[], Return>(
  fiber: FiberFunction<Args, Return>,
  cells: any[]
) => FiberInstance<Args, Return>;

const fiberFactory: FiberFactory = (fiberFunction, cells) => (...args) => {
  let index = 0;
  const newCells: any[] = [];
  const cell: CellFunction = callback =>
    (newCells[index] = callback(cells[index++]));
  const result = fiberFunction(cell)(...args);
  return [result, fiberFactory(fiberFunction, newCells)];
};

export const fiber = <Args extends any[], Return>(
  fiberFunction: FiberFunction<Args, Return>
) => fiberFactory(fiberFunction, []);