import { track, effect, untrack } from 'ripple';
import {
  Virtualizer,
  elementScroll,
  observeElementOffset,
  observeElementRect,
  observeWindowOffset,
  observeWindowRect,
  windowScroll,
  type PartialKeys,
  type VirtualizerOptions,
} from '@tanstack/virtual-core';

type Defaults<TScrollElement extends Element | Window, TItemElement extends Element> = Partial<VirtualizerOptions<TScrollElement, TItemElement>>;

function createVirtualizerBase<TScrollElement extends Element | Window, TItemElement extends Element>(
  userOptions: PartialKeys<VirtualizerOptions<TScrollElement, TItemElement>, 'observeElementRect' | 'observeElementOffset' | 'scrollToFn' | 'getScrollElement'>,
  defaults: Defaults<TScrollElement, TItemElement>,
) {
  const onChange = (inst: Virtualizer<TScrollElement, TItemElement>, sync: boolean) => {
    inst._willUpdate();
    @virtualItemsSignal = inst.getVirtualItems();
    @totalSizeSignal = inst.getTotalSize();
    userOptions.onChange?.(inst, sync);
  };

  const instance = new Virtualizer<TScrollElement, TItemElement>({
    ...defaults,
    ...userOptions,
    onChange,
  });

  instance._willUpdate();

  let virtualItemsSignal = track<any[]>(instance.getVirtualItems());
  let totalSizeSignal = track(instance.getTotalSize());

  effect(() => {
    return untrack(() => {
      const cleanup = instance._didMount();
      if (typeof cleanup === 'function') return cleanup;
    });
  });

  effect(() => {
    instance.setOptions(
      {
        ...defaults,
        ...userOptions,
        onChange,
      },
    );
    instance._willUpdate();
    instance.measure();
  });

  return {
    getVirtualItems: () => @virtualItemsSignal,
    getTotalSize: () => @totalSizeSignal,
    scrollToIndex(
      index: number,
      scrollOptions?: { align?: 'start' | 'center' | 'end' | 'auto'; behavior?: 'auto' | 'smooth' },
    ) {
      instance.scrollToIndex(index, scrollOptions);
    },
    measureElement(node: TItemElement | null | undefined) {
      instance.measureElement(node);
    },
  };
}

export function createVirtualizer<TScrollElement extends Element, TItemElement extends Element>(options: PartialKeys<VirtualizerOptions<TScrollElement, TItemElement>, 'observeElementRect' | 'observeElementOffset' | 'scrollToFn'>) {
  return createVirtualizerBase<TScrollElement, TItemElement>(options, {
    observeElementRect,
    observeElementOffset,
    scrollToFn: elementScroll,
  });
}

export function createWindowVirtualizer<TItemElement extends Element>(options: PartialKeys<VirtualizerOptions<Window, TItemElement>, 'getScrollElement' | 'observeElementRect' | 'observeElementOffset' | 'scrollToFn'>) {
  return createVirtualizerBase<Window, TItemElement>(options, {
    getScrollElement: () => (typeof document !== 'undefined' ? window : null),
    observeElementRect: observeWindowRect,
    observeElementOffset: observeWindowOffset,
    scrollToFn: windowScroll,
    initialOffset: () => (typeof document !== 'undefined' ? window.scrollY : 0),
  });
}