import { ref, watch } from 'vue'
import { makeUseInfiniteScroll } from 'vue-use-infinite-scroll'

export default {
    setup() {
        // INTERSECTION OBSERVER

        // set the intersection options object
        // https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API
        const useInfiniteScroll = makeUseInfiniteScroll({}) // the argument is optional

        // create the template ref for the element that
        // will trigger the intersection observer
        const intersectionTrigger = ref(null) // as Ref<HTMLElement>

        // useInfiniteScroll returns a pageRef, starting from page 1,
        // which changes we should listen to fetch more data
        const pageRef = useInfiniteScroll(intersectionTrigger)

        watch(
            pageRef,
            (page) => {
                fetchItems(page)
            },
            { immediate: true }
        )

        // DATA

        const itemsRef = ref([])
        const errorMessageRef = ref('')

        async function fetchItems(page) {
            fetch(`https://jsonplaceholder.typicode.com/comments?_page=${page}&_limit=10`)
                .then((res) => res.json())
                .then((data) => itemsRef.value.push(...data))
                .catch((error) => (errorMessageRef.value = error.message))
        }

        return { intersectionTrigger, itemsRef, errorMessageRef }
    },
}