import { computed, getCurrentInstance, inject, onUnmounted, ref } from 'vue'
import type { ComponentInternalInstance, InjectionKey } from 'vue'

type ParentProvide<T> = T & {
  add(child: ComponentInternalInstance): void
  remove(child: ComponentInternalInstance): void
  internalChildren: ComponentInternalInstance[]
}

export function useInject<T>(key: InjectionKey<ParentProvide<T>>) {
  const parent = inject(key, null)

  if (parent) {
    const instance = getCurrentInstance()!
    const { add, remove, internalChildren } = parent

    add(instance)
    onUnmounted(() => remove(instance))

    const index = computed(() => internalChildren.indexOf(instance))

    return {
      parent,
      index,
    }
  }

  return {
    parent: null,
    index: ref(-1),
  }
}