import { tryOnMounted, tryOnUnmounted } from '@vueuse/core';
import { snapdom } from '@zumer/snapdom';

export interface SnapshotOption {
  immediate?: boolean;
}

type SnapshotTspl = (total?: number) => string;
type SnapshotTemplate = (base64: string) => SnapshotTspl;

export function useSnapshot<P extends Record<string, any>>(loader: () => Promise<{ default: Component }>, props?: P, option?: SnapshotOption) {
  const snapshot = shallowRef<string>();
  const tspl = shallowRef<SnapshotTspl | void>();

  let app: ReturnType<typeof createApp> | null = null;
  let container: HTMLDivElement | null = null;

  const mounted = (component: Component, _props?: Partial<P>) => {
    if (container == null) return;
    const { promise, resolve } = Promise.withResolvers<SnapshotTemplate>();
    app = createApp(component, { ...props, ..._props, onRendered: resolve });
    app.mount(container);

    return promise;
  };

  const unmounted = () => {
    app?.unmount();
    app = null;
  };

  const capture = async (template?: SnapshotTemplate) => {
    if (container == null) return;

    const dom = await snapdom(container, { scale: 1 });
    const img = await dom.toPng({ scale: 2 });
    snapshot.value = img.src;
    tspl.value = template?.(img.src);
  };

  async function render(props?: Partial<P>, forced = false): Promise<{ snapshot: string; tspl: SnapshotTspl }> {
    if (forced) unmounted();

    if (forced || !snapshot.value) {
      const { default: component } = await loader();

      const tspl = await mounted(component, props);
      await capture(tspl);
      unmounted();
    }
    return {
      snapshot: snapshot.value!!,
      tspl: tspl.value!!,
    };
  }

  tryOnMounted(() => {
    container = document.createElement('div');
    container.style.position = 'fixed';
    container.style.left = '-99999px';
    container.style.top = '-99999px';
    container.style.zIndex = '-1';
    document.body.appendChild(container);
    if (option?.immediate) render().then();
  });
  tryOnUnmounted(() => {
    if (container) document.body.removeChild(container);
    container = null;

    unmounted();
    snapshot.value = '';
    tspl.value = void 0;
  });

  return { snapshot, tspl, render };
}