api-utils.ts

import { IncomingMessage, ServerResponse } from 'http'
import { parse } from 'next/dist/compiled/content-type'
import { CookieSerializeOptions } from 'next/dist/compiled/cookie'
import getRawBody from 'raw-body'
import { PageConfig } from 'next/types'
import { Stream } from 'stream'
import { isResSent, NextApiRequest, NextApiResponse } from '../lib/utils'
import { decryptWithSecret, encryptWithSecret } from './crypto-utils'
import { interopDefault } from './load-components'
import { Params } from './router'
import { sendEtagResponse } from './send-payload'
import generateETag from 'etag'

export type NextApiRequestCookies = { [key: string]: string }
export type NextApiRequestQuery = { [key: string]: string | string[] }

export type __ApiPreviewProps = {
  previewModeId: string
  previewModeEncryptionKey: string
  previewModeSigningKey: string
}

export async function apiResolver(
  req: IncomingMessage,
  res: ServerResponse,
  query: any,
  resolverModule: any,
  apiContext: __ApiPreviewProps,
  propagateError: boolean,
  onError?: ({ err }: { err: any }) => Promise<void>
): Promise<void> {
  const apiReq = req as NextApiRequest
  const apiRes = res as NextApiResponse

  try {
    if (!resolverModule) {
      res.statusCode = 404
      res.end('Not Found')
      return
    }
    const config: PageConfig = resolverModule.config || {}
    const bodyParser = config.api?.bodyParser !== false
    const externalResolver = config.api?.externalResolver || false

    // Parsing of cookies
    setLazyProp({ req: apiReq }, 'cookies', getCookieParser(req))
    // Parsing query string
    apiReq.query = query
    // Parsing preview data
    setLazyProp({ req: apiReq }, 'previewData', () =>
      tryGetPreviewData(req, res, apiContext)
    )
    // Checking if preview mode is enabled
    setLazyProp({ req: apiReq }, 'preview', () =>
      apiReq.previewData !== false ? true : undefined
    )

    // Parsing of body
    if (bodyParser && !apiReq.body) {
      apiReq.body = await parseBody(
        apiReq,
        config.api && config.api.bodyParser && config.api.bodyParser.sizeLimit
          ? config.api.bodyParser.sizeLimit
          : '1mb'
      )
    }

    apiRes.status = (statusCode) => sendStatusCode(apiRes, statusCode)
    apiRes.send = (data) => sendData(apiReq, apiRes, data)
    apiRes.json = (data) => sendJson(apiRes, data)
    apiRes.redirect = (statusOrUrl: number | string, url?: string) =>
      redirect(apiRes, statusOrUrl, url)
    apiRes.setPreviewData = (data, options = {}) =>
      setPreviewData(apiRes, data, Object.assign({}, apiContext, options))
    apiRes.clearPreviewData = () => clearPreviewData(apiRes)

    const resolver = interopDefault(resolverModule)
    let wasPiped = false

    if (process.env.NODE_ENV !== 'production') {
      // listen for pipe event and don't show resolve warning
      res.once('pipe', () => (wasPiped = true))
    }

    // Call API route method
    await resolver(req, res)

    if (
      process.env.NODE_ENV !== 'production' &&
      !externalResolver &&
      !isResSent(res) &&
      !wasPiped
    ) {
      console.warn(
        `API resolved without sending a response for ${req.url}, this may result in stalled requests.`
      )
    }
  } catch (err) {
    if (err instanceof ApiError) {
      sendError(apiRes, err.statusCode, err.message)
    } else {
      console.error(err)
      if (onError) await onError({ err })
      if (propagateError) {
        throw err
      }
      sendError(apiRes, 500, 'Internal Server Error')
    }
  }
}

/**
 * Parse incoming message like `json` or `urlencoded`
 * @param req request object
 */
export async function parseBody(
  req: NextApiRequest,
  limit: string | number
): Promise<any> {
  const contentType = parse(req.headers['content-type'] || 'text/plain')
  const { type, parameters } = contentType
  const encoding = parameters.charset || 'utf-8'

  let buffer

  try {
    buffer = await getRawBody(req, { encoding, limit })
  } catch (e) {
    if (e.type === 'entity.too.large') {
      throw new ApiError(413, `Body exceeded ${limit} limit`)
    } else {
      throw new ApiError(400, 'Invalid body')
    }
  }

  const body = buffer.toString()

  if (type === 'application/json' || type === 'application/ld+json') {
    return parseJson(body)
  } else if (type === 'application/x-www-form-urlencoded') {
    const qs = require('querystring')
    return qs.decode(body)
  } else {
    return body
  }
}

/**
 * Parse `JSON` and handles invalid `JSON` strings
 * @param str `JSON` string
 */
function parseJson(str: string): object {
  if (str.length === 0) {
    // special-case empty json body, as it's a common client-side mistake
    return {}
  }

  try {
    return JSON.parse(str)
  } catch (e) {
    throw new ApiError(400, 'Invalid JSON')
  }
}

/**
 * Parse cookies from `req` header
 * @param req request object
 */
export function getCookieParser(
  req: IncomingMessage
): () => NextApiRequestCookies {
  return function parseCookie(): NextApiRequestCookies {
    const header: undefined | string | string[] = req.headers.cookie

    if (!header) {
      return {}
    }

    const { parse: parseCookieFn } = require('next/dist/compiled/cookie')
    return parseCookieFn(Array.isArray(header) ? header.join(';') : header)
  }
}

/**
 *
 * @param res response object
 * @param statusCode `HTTP` status code of response
 */
export function sendStatusCode(
  res: NextApiResponse,
  statusCode: number
): NextApiResponse<any> {
  res.statusCode = statusCode
  return res
}

/**
 *
 * @param res response object
 * @param [statusOrUrl] `HTTP` status code of redirect
 * @param url URL of redirect
 */
export function redirect(
  res: NextApiResponse,
  statusOrUrl: string | number,
  url?: string
): NextApiResponse<any> {
  if (typeof statusOrUrl === 'string') {
    url = statusOrUrl
    statusOrUrl = 307
  }
  if (typeof statusOrUrl !== 'number' || typeof url !== 'string') {
    throw new Error(
      `Invalid redirect arguments. Please use a single argument URL, e.g. res.redirect('/destination') or use a status code and URL, e.g. res.redirect(307, '/destination').`
    )
  }
  res.writeHead(statusOrUrl, { Location: url })
  res.write('')
  res.end()
  return res
}

/**
 * Send `any` body to response
 * @param req request object
 * @param res response object
 * @param body of response
 */
export function sendData(
  req: NextApiRequest,
  res: NextApiResponse,
  body: any
): void {
  if (body === null) {
    res.end()
    return
  }

  const contentType = res.getHeader('Content-Type')

  if (body instanceof Stream) {
    if (!contentType) {
      res.setHeader('Content-Type', 'application/octet-stream')
    }
    body.pipe(res)
    return
  }

  const isJSONLike = ['object', 'number', 'boolean'].includes(typeof body)
  const stringifiedBody = isJSONLike ? JSON.stringify(body) : body
  const etag = generateETag(stringifiedBody)
  if (sendEtagResponse(req, res, etag)) {
    return
  }

  if (Buffer.isBuffer(body)) {
    if (!contentType) {
      res.setHeader('Content-Type', 'application/octet-stream')
    }
    res.setHeader('Content-Length', body.length)
    res.end(body)
    return
  }

  if (isJSONLike) {
    res.setHeader('Content-Type', 'application/json; charset=utf-8')
  }

  res.setHeader('Content-Length', Buffer.byteLength(stringifiedBody))
  res.end(stringifiedBody)
}

/**
 * Send `JSON` object
 * @param res response object
 * @param jsonBody of data
 */
export function sendJson(res: NextApiResponse, jsonBody: any): void {
  // Set header to application/json
  res.setHeader('Content-Type', 'application/json; charset=utf-8')

  // Use send to handle request
  res.send(jsonBody)
}

const COOKIE_NAME_PRERENDER_BYPASS = `__prerender_bypass`
const COOKIE_NAME_PRERENDER_DATA = `__next_preview_data`

export const SYMBOL_PREVIEW_DATA = Symbol(COOKIE_NAME_PRERENDER_DATA)
const SYMBOL_CLEARED_COOKIES = Symbol(COOKIE_NAME_PRERENDER_BYPASS)

export function tryGetPreviewData(
  req: IncomingMessage,
  res: ServerResponse,
  options: __ApiPreviewProps
): object | string | false {
  // Read cached preview data if present
  if (SYMBOL_PREVIEW_DATA in req) {
    return (req as any)[SYMBOL_PREVIEW_DATA] as any
  }

  const getCookies = getCookieParser(req)
  let cookies: NextApiRequestCookies
  try {
    cookies = getCookies()
  } catch {
    // TODO: warn
    return false
  }

  const hasBypass = COOKIE_NAME_PRERENDER_BYPASS in cookies
  const hasData = COOKIE_NAME_PRERENDER_DATA in cookies

  // Case: neither cookie is set.
  if (!(hasBypass || hasData)) {
    return false
  }

  // Case: one cookie is set, but not the other.
  if (hasBypass !== hasData) {
    clearPreviewData(res as NextApiResponse)
    return false
  }

  // Case: preview session is for an old build.
  if (cookies[COOKIE_NAME_PRERENDER_BYPASS] !== options.previewModeId) {
    clearPreviewData(res as NextApiResponse)
    return false
  }

  const tokenPreviewData = cookies[COOKIE_NAME_PRERENDER_DATA]

  const jsonwebtoken = require('next/dist/compiled/jsonwebtoken') as typeof import('jsonwebtoken')
  let encryptedPreviewData: {
    data: string
  }
  try {
    encryptedPreviewData = jsonwebtoken.verify(
      tokenPreviewData,
      options.previewModeSigningKey
    ) as typeof encryptedPreviewData
  } catch {
    // TODO: warn
    clearPreviewData(res as NextApiResponse)
    return false
  }

  const decryptedPreviewData = decryptWithSecret(
    Buffer.from(options.previewModeEncryptionKey),
    encryptedPreviewData.data
  )

  try {
    // TODO: strict runtime type checking
    const data = JSON.parse(decryptedPreviewData)
    // Cache lookup
    Object.defineProperty(req, SYMBOL_PREVIEW_DATA, {
      value: data,
      enumerable: false,
    })
    return data
  } catch {
    return false
  }
}

function isNotValidData(str: string): boolean {
  return typeof str !== 'string' || str.length < 16
}

function setPreviewData<T>(
  res: NextApiResponse<T>,
  data: object | string, // TODO: strict runtime type checking
  options: {
    maxAge?: number
  } & __ApiPreviewProps
): NextApiResponse<T> {
  if (isNotValidData(options.previewModeId)) {
    throw new Error('invariant: invalid previewModeId')
  }
  if (isNotValidData(options.previewModeEncryptionKey)) {
    throw new Error('invariant: invalid previewModeEncryptionKey')
  }
  if (isNotValidData(options.previewModeSigningKey)) {
    throw new Error('invariant: invalid previewModeSigningKey')
  }

  const jsonwebtoken = require('next/dist/compiled/jsonwebtoken') as typeof import('jsonwebtoken')

  const payload = jsonwebtoken.sign(
    {
      data: encryptWithSecret(
        Buffer.from(options.previewModeEncryptionKey),
        JSON.stringify(data)
      ),
    },
    options.previewModeSigningKey,
    {
      algorithm: 'HS256',
      ...(options.maxAge !== undefined
        ? { expiresIn: options.maxAge }
        : undefined),
    }
  )

  // limit preview mode cookie to 2KB since we shouldn't store too much
  // data here and browsers drop cookies over 4KB
  if (payload.length > 2048) {
    throw new Error(
      `Preview data is limited to 2KB currently, reduce how much data you are storing as preview data to continue`
    )
  }

  const {
    serialize,
  } = require('next/dist/compiled/cookie') as typeof import('cookie')
  const previous = res.getHeader('Set-Cookie')
  res.setHeader(`Set-Cookie`, [
    ...(typeof previous === 'string'
      ? [previous]
      : Array.isArray(previous)
      ? previous
      : []),
    serialize(COOKIE_NAME_PRERENDER_BYPASS, options.previewModeId, {
      httpOnly: true,
      sameSite: process.env.NODE_ENV !== 'development' ? 'none' : 'lax',
      secure: process.env.NODE_ENV !== 'development',
      path: '/',
      ...(options.maxAge !== undefined
        ? ({ maxAge: options.maxAge } as CookieSerializeOptions)
        : undefined),
    }),
    serialize(COOKIE_NAME_PRERENDER_DATA, payload, {
      httpOnly: true,
      sameSite: process.env.NODE_ENV !== 'development' ? 'none' : 'lax',
      secure: process.env.NODE_ENV !== 'development',
      path: '/',
      ...(options.maxAge !== undefined
        ? ({ maxAge: options.maxAge } as CookieSerializeOptions)
        : undefined),
    }),
  ])
  return res
}

function clearPreviewData<T>(res: NextApiResponse<T>): NextApiResponse<T> {
  if (SYMBOL_CLEARED_COOKIES in res) {
    return res
  }

  const {
    serialize,
  } = require('next/dist/compiled/cookie') as typeof import('cookie')
  const previous = res.getHeader('Set-Cookie')
  res.setHeader(`Set-Cookie`, [
    ...(typeof previous === 'string'
      ? [previous]
      : Array.isArray(previous)
      ? previous
      : []),
    serialize(COOKIE_NAME_PRERENDER_BYPASS, '', {
      // To delete a cookie, set `expires` to a date in the past:
      // https://tools.ietf.org/html/rfc6265#section-4.1.1
      // `Max-Age: 0` is not valid, thus ignored, and the cookie is persisted.
      expires: new Date(0),
      httpOnly: true,
      sameSite: process.env.NODE_ENV !== 'development' ? 'none' : 'lax',
      secure: process.env.NODE_ENV !== 'development',
      path: '/',
    }),
    serialize(COOKIE_NAME_PRERENDER_DATA, '', {
      // To delete a cookie, set `expires` to a date in the past:
      // https://tools.ietf.org/html/rfc6265#section-4.1.1
      // `Max-Age: 0` is not valid, thus ignored, and the cookie is persisted.
      expires: new Date(0),
      httpOnly: true,
      sameSite: process.env.NODE_ENV !== 'development' ? 'none' : 'lax',
      secure: process.env.NODE_ENV !== 'development',
      path: '/',
    }),
  ])

  Object.defineProperty(res, SYMBOL_CLEARED_COOKIES, {
    value: true,
    enumerable: false,
  })
  return res
}

/**
 * Custom error class
 */
export class ApiError extends Error {
  readonly statusCode: number

  constructor(statusCode: number, message: string) {
    super(message)
    this.statusCode = statusCode
  }
}

/**
 * Sends error in `response`
 * @param res response object
 * @param statusCode of response
 * @param message of response
 */
export function sendError(
  res: NextApiResponse,
  statusCode: number,
  message: string
): void {
  res.statusCode = statusCode
  res.statusMessage = message
  res.end(message)
}

interface LazyProps {
  req: NextApiRequest
  params?: Params | boolean
}

/**
 * Execute getter function only if its needed
 * @param LazyProps `req` and `params` for lazyProp
 * @param prop name of property
 * @param getter function to get data
 */
export function setLazyProp<T>(
  { req, params }: LazyProps,
  prop: string,
  getter: () => T
): void {
  const opts = { configurable: true, enumerable: true }
  const optsReset = { ...opts, writable: true }

  Object.defineProperty(req, prop, {
    ...opts,
    get: () => {
      let value = getter()
      if (params && typeof params !== 'boolean') {
        value = { ...value, ...params }
      }
      // we set the property on the object to avoid recalculating it
      Object.defineProperty(req, prop, { ...optsReset, value })
      return value
    },
    set: (value) => {
      Object.defineProperty(req, prop, { ...optsReset, value })
    },
  })
}