rsnext/packages/next/lib/data.ts

import { useContext } from 'react'
import { DataManagerContext } from 'next-server/dist/lib/data-manager-context'
import { RouterContext } from 'next-server/dist/lib/router-context'
import fetch from 'unfetch'
import { stringify } from 'querystring'

type Args = string | number | Array<string | number>

function generateArgsKey(args: Args[]) {
  return args.reduce((a: string, b: Args): string => {
    if (Array.isArray(b)) {
      return a + generateArgsKey(b)
    }
    if (typeof b !== 'string' && typeof b !== 'number') {
      throw new Error('arguments can only be string or number')
    }
    return a + b.toString()
  }, '')
}

export function createHook(
  fetcher: (...args: Args[]) => Promise<any>,
  options: { key: string }
) {
  if (!options.key) {
    throw new Error('key not provided to createHook options.')
  }
  return function useData(...args: Array<string | number>) {
    const router: import('next-server/lib/router/router').default = useContext(
      RouterContext
    )
    const dataManager: import('next-server/lib/data-manager').DataManager = useContext(
      DataManagerContext
    )
    const key = `${options.key}${generateArgsKey(args)}`
    const existing = dataManager.get(key)

    if (existing) {
      if (existing.status === 'resolved') {
        return existing.result
      }
      if (existing === 'mismatched-key') {
        throw new Error(
          'matching key was missing from returned data. make sure arguments match between the client and server'
        )
      }
    }

    // @ts-ignore webpack optimization
    if (process.browser) {
      const res = fetch(router.route + '?' + stringify(router.query), {
        headers: {
          accept: 'application/amp.bind+json',
        },
      })
        .then((res: any) => res.json())
        .then((result: any) => {
          const hasKey = result.some((pair: [string, any]) => pair[0] === key)
          if (!hasKey) {
            result = [[key, 'mismatched-key']]
          }
          dataManager.overwrite(result)
        })
      throw res
    } else {
      const res = fetcher(...args).then(result => {
        dataManager.set(key, {
          status: 'resolved',
          result,
        })
      })
      throw res
    }
  }
}