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Pagination for Firestore
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| import React, { ReactElement } from 'react' | |
| import { Link, useSearchParams } from 'react-router-dom' | |
| import { collection, getFirestore, orderBy } from 'firebase/firestore' | |
| import { usePagedSnapshot } from './firestore-paging' | |
| const comments = collection(getFirestore(), "comments") | |
| const order = orderBy("createdAt", "desc") | |
| export function CommentList(): ReactElement { | |
| const [params] = useSearchParams() | |
| const start = params.get("start") ?? undefined | |
| const until = params.get("until") ?? undefined | |
| const page = usePagedSnapshot(comments, order, { start, until, count: 10 }) | |
| return <div>{ | |
| page === undefined ? <>Loading..</> : <> | |
| <div>{ page.prev && <Link to={`?until=${page.prev}`}>Prev</Link>}</div> | |
| <div>{ page.next && <Link to={`?start=${page.next}`}>Next</Link>}</div> | |
| <ul> | |
| {page.docs.map(doc => <li>{doc.id}</li>)} | |
| </ul> | |
| </> | |
| }</div> | |
| } |
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| import { CollectionReference, DocumentData, DocumentSnapshot, Query, QueryConstraint, QueryDocumentSnapshot, QuerySnapshot, doc, endBefore, getDoc, limit, limitToLast, onSnapshot, query, startAt } from "firebase/firestore" | |
| import { useEffect, useMemo, useState } from "react" | |
| type Page = { | |
| start?: string | |
| until?: string | |
| count: number | |
| } | |
| export function usePagedSnapshot<T = DocumentData>( | |
| src: CollectionReference<T>, | |
| filter: QueryConstraint, | |
| page: Page, | |
| ): void | { docs: QueryDocumentSnapshot<T>[], next?: string, prev?: string } { | |
| const [pivot, setPivot] = useState<DocumentSnapshot<T> | null>() | |
| useEffect(() => { | |
| (async () => { | |
| const id = page.start ?? page.until | |
| setPivot(undefined) | |
| setPivot(id ? await getDoc(doc(src, id)) : null) | |
| }) () | |
| }, [src, page.start, page.until]) | |
| const n = page.count | |
| const pagedQuery = useMemo(() => { | |
| if (pivot !== undefined) { | |
| return query( | |
| src, filter, | |
| ... pivot ? page.until | |
| ? [endBefore(pivot), limitToLast(n+1)] | |
| : [startAt(pivot), limit(n+1)] : [limit(n+1)], | |
| ) | |
| } | |
| }, [pivot, filter, n]) | |
| const snapshot = useSnapshot(pagedQuery) | |
| if (snapshot !== undefined) { | |
| const { docs } = snapshot | |
| if (page.until) { | |
| return { | |
| docs: docs.slice(-n), | |
| next: page.until, | |
| prev: docs.length !== n+1 ? undefined: docs[1].id, | |
| } | |
| } else { | |
| return { | |
| docs: docs.slice(0, n), | |
| prev: page.start, | |
| next: docs.length !== n+1 ? undefined: docs[n].id, | |
| } | |
| } | |
| } | |
| } | |
| export function useSnapshot<T = DocumentData>(query?: Query<T>): void | QuerySnapshot<T> { | |
| const [result, setResult] = useState<QuerySnapshot<T>>() | |
| useEffect(() => { | |
| setResult(undefined) | |
| if (query !== undefined) { | |
| return onSnapshot(query, setResult) | |
| } | |
| }, [query]) | |
| return result | |
| } |
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