import { InfiniteData, replaceEqualDeep } from '@tanstack/react-query'
import { ApiCollection, ResourceObject } from '../types'

type Pages = InfiniteData<ApiCollection<ResourceObject>>

/** replaceEqualById
 * TanStack's default structural sharing compares arrays by index, so an insert or
 * delete gives every shifted record a new identity. Match by id instead.
 */
export function replaceEqualById(oldData: unknown, newData: unknown): unknown {
  const prev = oldData as Pages | undefined
  const next = newData as Pages
  if (!prev?.pages || !next?.pages) return replaceEqualDeep(prev, next)

  const prevById = new Map<ResourceObject['id'], ResourceObject>()
  prev.pages.forEach(page => page.data.forEach(record => prevById.set(record.id, record)))

  let changed = prev.pages.length !== next.pages.length
  const pages = next.pages.map((page, index) => {
    const prevPage = prev.pages[index]
    const data = page.data.map(record => {
      const previous = prevById.get(record.id)
      return previous ? replaceEqualDeep(previous, record) : record
    })
    const links = replaceEqualDeep(prevPage?.links, page.links)
    const meta = replaceEqualDeep(prevPage?.meta, page.meta)
    const sameRecords =
      !!prevPage &&
      data.length === prevPage.data.length &&
      data.every((record, i) => record === prevPage.data[i])

    if (prevPage && sameRecords && links === prevPage.links && meta === prevPage.meta) {
      return prevPage
    }
    changed = true
    return { ...page, data, links, meta }
  })
  const pageParams = replaceEqualDeep(prev.pageParams, next.pageParams)

  if (!changed && pageParams === prev.pageParams) return prev
  return { ...next, pages, pageParams }
}