load-custom-routes.ts

import type { NextConfig } from '../server/config'
import type { Token } from 'next/dist/compiled/path-to-regexp'

import { bold, yellow } from './picocolors'
import { escapeStringRegexp } from '../shared/lib/escape-regexp'
import { tryToParsePath } from './try-to-parse-path'
import { allowedStatusCodes } from './redirect-status'
import { isFullStringUrl } from './url'

export type RouteHas =
  | {
      type: string
      key: string
      value?: string
    }
  | {
      type: 'host'
      key?: undefined
      value: string
    }

export type Rewrite = {
  source: string
  destination: string
  basePath?: false
  locale?: false
  has?: RouteHas[]
  missing?: RouteHas[]

  /**
   * @internal - used internally for routing
   */
  internal?: boolean
}

export type Header = {
  source: string
  basePath?: false
  locale?: false
  headers: Array<{ key: string; value: string }>
  has?: RouteHas[]
  missing?: RouteHas[]

  /**
   * @internal - used internally for routing
   */
  internal?: boolean
}

// internal type used for validation (not user facing)
export type Redirect = {
  source: string
  destination: string
  basePath?: false
  locale?: false
  has?: RouteHas[]
  missing?: RouteHas[]

  /**
   * @internal - used internally for routing
   */
  internal?: boolean
} & (
  | {
      statusCode?: never
      permanent: boolean
    }
  | {
      statusCode: number
      permanent?: never
    }
)

export type Middleware = {
  source: string
  locale?: false
  has?: RouteHas[]
  missing?: RouteHas[]
}

const allowedHasTypes = new Set(['header', 'cookie', 'query', 'host'])
const namedGroupsRegex = /\(\?<([a-zA-Z][a-zA-Z0-9]*)>/g

export function normalizeRouteRegex(regex: string) {
  // clean up un-necessary escaping from regex.source which turns / into \\/
  return regex.replace(/\\\//g, '/')
}

function checkRedirect(route: Redirect): {
  invalidParts: string[]
  hadInvalidStatus: boolean
} {
  const invalidParts: string[] = []
  let hadInvalidStatus: boolean = false

  if (route.statusCode && !allowedStatusCodes.has(route['statusCode'])) {
    hadInvalidStatus = true
    invalidParts.push(`\`statusCode\` is not undefined or valid statusCode`)
  }
  if (typeof route.permanent !== 'boolean' && !route['statusCode']) {
    invalidParts.push(`\`permanent\` is not set to \`true\` or \`false\``)
  }

  return {
    invalidParts,
    hadInvalidStatus,
  }
}

function checkHeader(route: Header): string[] {
  const invalidParts: string[] = []

  if (!Array.isArray(route.headers)) {
    invalidParts.push('`headers` field must be an array')
  } else if (route.headers.length === 0) {
    invalidParts.push('`headers` field cannot be empty')
  } else {
    for (const header of route.headers) {
      if (!header || typeof header !== 'object') {
        invalidParts.push(
          "`headers` items must be object with { key: '', value: '' }"
        )
        break
      }
      if (typeof header.key !== 'string') {
        invalidParts.push('`key` in header item must be string')
        break
      }
      if (typeof header.value !== 'string') {
        invalidParts.push('`value` in header item must be string')
        break
      }
    }
  }
  return invalidParts
}

export type RouteType = 'rewrite' | 'redirect' | 'header'

export function checkCustomRoutes(
  routes: Redirect[] | Header[] | Rewrite[] | Middleware[],
  type: RouteType | 'middleware'
): void {
  if (!Array.isArray(routes)) {
    console.error(
      `Error: ${type}s must return an array, received ${typeof routes}.\n` +
        `See here for more info: https://nextjs.org/docs/messages/routes-must-be-array`
    )
    process.exit(1)
  }

  let numInvalidRoutes = 0
  let hadInvalidStatus = false
  let hadInvalidHas = false
  let hadInvalidMissing = false

  const allowedKeys = new Set<string>(['source', 'locale', 'has', 'missing'])

  if (type === 'rewrite') {
    allowedKeys.add('basePath')
    allowedKeys.add('destination')
  }
  if (type === 'redirect') {
    allowedKeys.add('basePath')
    allowedKeys.add('statusCode')
    allowedKeys.add('permanent')
    allowedKeys.add('destination')
  }
  if (type === 'header') {
    allowedKeys.add('basePath')
    allowedKeys.add('headers')
  }

  for (const route of routes) {
    if (!route || typeof route !== 'object') {
      console.error(
        `The route ${JSON.stringify(
          route
        )} is not a valid object with \`source\`${
          type !== 'middleware'
            ? ` and \`${type === 'header' ? 'headers' : 'destination'}\``
            : ''
        }`
      )
      numInvalidRoutes++
      continue
    }

    if (
      type === 'rewrite' &&
      (route as Rewrite).basePath === false &&
      !(
        (route as Rewrite).destination.startsWith('http://') ||
        (route as Rewrite).destination.startsWith('https://')
      )
    ) {
      console.error(
        `The route ${
          (route as Rewrite).source
        } rewrites urls outside of the basePath. Please use a destination that starts with \`http://\` or \`https://\` https://nextjs.org/docs/messages/invalid-external-rewrite`
      )
      numInvalidRoutes++
      continue
    }

    const keys = Object.keys(route)
    const invalidKeys = keys.filter((key) => !allowedKeys.has(key))
    const invalidParts: string[] = []

    if (
      'basePath' in route &&
      typeof route.basePath !== 'undefined' &&
      route.basePath !== false
    ) {
      invalidParts.push('`basePath` must be undefined or false')
    }

    if (typeof route.locale !== 'undefined' && route.locale !== false) {
      invalidParts.push('`locale` must be undefined or false')
    }

    const checkInvalidHasMissing = (
      items: any,
      fieldName: 'has' | 'missing'
    ) => {
      let hadInvalidItem = false

      if (typeof items !== 'undefined' && !Array.isArray(items)) {
        invalidParts.push(
          `\`${fieldName}\` must be undefined or valid has object`
        )
        hadInvalidItem = true
      } else if (items) {
        const invalidHasItems = []

        for (const hasItem of items) {
          let invalidHasParts = []

          if (!allowedHasTypes.has(hasItem.type)) {
            invalidHasParts.push(`invalid type "${hasItem.type}"`)
          }
          if (typeof hasItem.key !== 'string' && hasItem.type !== 'host') {
            invalidHasParts.push(`invalid key "${hasItem.key}"`)
          }
          if (
            typeof hasItem.value !== 'undefined' &&
            typeof hasItem.value !== 'string'
          ) {
            invalidHasParts.push(`invalid value "${hasItem.value}"`)
          }
          if (typeof hasItem.value === 'undefined' && hasItem.type === 'host') {
            invalidHasParts.push(`value is required for "host" type`)
          }

          if (invalidHasParts.length > 0) {
            invalidHasItems.push(
              `${invalidHasParts.join(', ')} for ${JSON.stringify(hasItem)}`
            )
          }
        }

        if (invalidHasItems.length > 0) {
          hadInvalidItem = true
          const itemStr = `item${invalidHasItems.length === 1 ? '' : 's'}`

          console.error(
            `Invalid \`${fieldName}\` ${itemStr}:\n` +
              invalidHasItems.join('\n')
          )
          console.error()
          invalidParts.push(`invalid \`${fieldName}\` ${itemStr} found`)
        }
      }
      return hadInvalidItem
    }
    if (checkInvalidHasMissing(route.has, 'has')) {
      hadInvalidHas = true
    }
    if (checkInvalidHasMissing(route.missing, 'missing')) {
      hadInvalidMissing = true
    }

    if (!route.source) {
      invalidParts.push('`source` is missing')
    } else if (typeof route.source !== 'string') {
      invalidParts.push('`source` is not a string')
    } else if (!route.source.startsWith('/')) {
      invalidParts.push('`source` does not start with /')
    }

    if (type === 'header') {
      invalidParts.push(...checkHeader(route as Header))
    } else if (type !== 'middleware') {
      let _route = route as Rewrite | Redirect
      if (!_route.destination) {
        invalidParts.push('`destination` is missing')
      } else if (typeof _route.destination !== 'string') {
        invalidParts.push('`destination` is not a string')
      } else if (
        type === 'rewrite' &&
        !_route.destination.match(/^(\/|https:\/\/|http:\/\/)/)
      ) {
        invalidParts.push(
          '`destination` does not start with `/`, `http://`, or `https://`'
        )
      }
    }

    if (type === 'redirect') {
      const result = checkRedirect(route as Redirect)
      hadInvalidStatus = hadInvalidStatus || result.hadInvalidStatus
      invalidParts.push(...result.invalidParts)
    }

    let sourceTokens: Token[] | undefined

    if (typeof route.source === 'string' && route.source.startsWith('/')) {
      // only show parse error if we didn't already show error
      // for not being a string
      const { tokens, error, regexStr } = tryToParsePath(route.source)

      if (error) {
        invalidParts.push('`source` parse failed')
      }

      if (regexStr && regexStr.length > 4096) {
        invalidParts.push('`source` exceeds max built length of 4096')
      }

      sourceTokens = tokens
    }
    const hasSegments = new Set<string>()

    if (route.has) {
      for (const hasItem of route.has) {
        if (!hasItem.value && hasItem.key) {
          hasSegments.add(hasItem.key)
        }

        if (hasItem.value) {
          for (const match of hasItem.value.matchAll(namedGroupsRegex)) {
            if (match[1]) {
              hasSegments.add(match[1])
            }
          }

          if (hasItem.type === 'host') {
            hasSegments.add('host')
          }
        }
      }
    }

    // make sure no unnamed patterns are attempted to be used in the
    // destination as this can cause confusion and is not allowed
    if (typeof (route as Rewrite).destination === 'string') {
      if (
        (route as Rewrite).destination.startsWith('/') &&
        Array.isArray(sourceTokens)
      ) {
        const unnamedInDest = new Set()

        for (const token of sourceTokens) {
          if (typeof token === 'object' && typeof token.name === 'number') {
            const unnamedIndex = new RegExp(`:${token.name}(?!\\d)`)
            if ((route as Rewrite).destination.match(unnamedIndex)) {
              unnamedInDest.add(`:${token.name}`)
            }
          }
        }

        if (unnamedInDest.size > 0) {
          invalidParts.push(
            `\`destination\` has unnamed params ${[...unnamedInDest].join(
              ', '
            )}`
          )
        } else {
          const {
            tokens: destTokens,
            regexStr: destRegexStr,
            error: destinationParseFailed,
          } = tryToParsePath((route as Rewrite).destination, {
            handleUrl: true,
          })

          if (destRegexStr && destRegexStr.length > 4096) {
            invalidParts.push('`destination` exceeds max built length of 4096')
          }

          if (destinationParseFailed) {
            invalidParts.push('`destination` parse failed')
          } else {
            const sourceSegments = new Set(
              sourceTokens
                .map((item) => typeof item === 'object' && item.name)
                .filter(Boolean)
            )
            const invalidDestSegments = new Set()

            for (const token of destTokens!) {
              if (
                typeof token === 'object' &&
                !sourceSegments.has(token.name) &&
                !hasSegments.has(token.name as string)
              ) {
                invalidDestSegments.add(token.name)
              }
            }

            if (invalidDestSegments.size) {
              invalidParts.push(
                `\`destination\` has segments not in \`source\` or \`has\` (${[
                  ...invalidDestSegments,
                ].join(', ')})`
              )
            }
          }
        }
      }
    }

    const hasInvalidKeys = invalidKeys.length > 0
    const hasInvalidParts = invalidParts.length > 0

    if (hasInvalidKeys || hasInvalidParts) {
      console.error(
        `${invalidParts.join(', ')}${
          invalidKeys.length
            ? (hasInvalidParts ? ',' : '') +
              ` invalid field${invalidKeys.length === 1 ? '' : 's'}: ` +
              invalidKeys.join(',')
            : ''
        } for route ${JSON.stringify(route)}`
      )
      console.error()
      numInvalidRoutes++
    }
  }

  if (numInvalidRoutes > 0) {
    if (hadInvalidStatus) {
      console.error(
        `\nValid redirect statusCode values are ${[...allowedStatusCodes].join(
          ', '
        )}`
      )
    }
    if (hadInvalidHas) {
      console.error(
        `\nValid \`has\` object shape is ${JSON.stringify(
          {
            type: [...allowedHasTypes].join(', '),
            key: 'the key to check for',
            value: 'undefined or a value string to match against',
          },
          null,
          2
        )}`
      )
    }
    if (hadInvalidMissing) {
      console.error(
        `\nValid \`missing\` object shape is ${JSON.stringify(
          {
            type: [...allowedHasTypes].join(', '),
            key: 'the key to check for',
            value: 'undefined or a value string to match against',
          },
          null,
          2
        )}`
      )
    }
    console.error()
    console.error(
      `Error: Invalid ${type}${numInvalidRoutes === 1 ? '' : 's'} found`
    )
    process.exit(1)
  }
}

export interface CustomRoutes {
  headers: Header[]
  rewrites: {
    fallback: Rewrite[]
    afterFiles: Rewrite[]
    beforeFiles: Rewrite[]
  }
  redirects: Redirect[]
}

function processRoutes<T>(
  routes: T,
  config: NextConfig,
  type: 'redirect' | 'rewrite' | 'header'
): T {
  const _routes = routes as any as Array<{
    source: string
    locale?: false
    basePath?: false
    destination?: string
  }>
  const newRoutes: typeof _routes = []
  const defaultLocales: Array<{
    locale: string
    base: string
  }> = []

  if (config.i18n && type === 'redirect') {
    for (const item of config.i18n?.domains || []) {
      defaultLocales.push({
        locale: item.defaultLocale,
        base: `http${item.http ? '' : 's'}://${item.domain}`,
      })
    }

    defaultLocales.push({
      locale: config.i18n.defaultLocale,
      base: '',
    })
  }

  for (const r of _routes) {
    const srcBasePath =
      config.basePath && r.basePath !== false ? config.basePath : ''
    const isExternal = !r.destination?.startsWith('/')
    const destBasePath = srcBasePath && !isExternal ? srcBasePath : ''

    if (config.i18n && r.locale !== false) {
      if (!isExternal) {
        defaultLocales.forEach((item) => {
          let destination

          if (r.destination) {
            destination = item.base
              ? `${item.base}${destBasePath}${r.destination}`
              : `${destBasePath}${r.destination}`
          }

          newRoutes.push({
            ...r,
            destination,
            source: `${srcBasePath}/${item.locale}${
              r.source === '/' && !config.trailingSlash ? '' : r.source
            }`,
          })
        })
      }

      r.source = `/:nextInternalLocale(${config.i18n.locales
        .map((locale: string) => escapeStringRegexp(locale))
        .join('|')})${
        r.source === '/' && !config.trailingSlash ? '' : r.source
      }`

      if (r.destination && r.destination?.startsWith('/')) {
        r.destination = `/:nextInternalLocale${
          r.destination === '/' && !config.trailingSlash ? '' : r.destination
        }`
      }
    }
    r.source = `${srcBasePath}${
      r.source === '/' && srcBasePath ? '' : r.source
    }`

    if (r.destination) {
      r.destination = `${destBasePath}${
        r.destination === '/' && destBasePath ? '' : r.destination
      }`
    }
    newRoutes.push(r)
  }
  return newRoutes as any as T
}

async function loadRedirects(config: NextConfig) {
  if (typeof config.redirects !== 'function') {
    return []
  }
  let redirects = await config.redirects()
  // check before we process the routes and after to ensure
  // they are still valid
  checkCustomRoutes(redirects, 'redirect')

  // save original redirects before transforms
  if (Array.isArray(redirects)) {
    config._originalRedirects = redirects.map((r) => ({ ...r }))
  }
  redirects = processRoutes(redirects, config, 'redirect')
  checkCustomRoutes(redirects, 'redirect')
  return redirects
}

async function loadRewrites(config: NextConfig) {
  // If assetPrefix is set, add a rewrite for `/${assetPrefix}/_next/*`
  // requests so that they are handled in any of dev, start, or deploy
  // automatically without the user having to configure this.
  // If the assetPrefix is an absolute URL, we still consider the path for automatic rewrite.
  // but hostname routing must be handled by the user
  let maybeAssetPrefixRewrite: Rewrite[] = []
  if (config.assetPrefix) {
    let prefix = config.assetPrefix
    if (
      isFullStringUrl(config.assetPrefix) &&
      URL.canParse(config.assetPrefix)
    ) {
      prefix = new URL(config.assetPrefix).pathname
    }

    if (prefix && prefix !== '/') {
      const assetPrefix = prefix.startsWith('/') ? prefix : `/${prefix}`
      const basePath = config.basePath || ''
      // If these are the same, then this would result in an infinite rewrite.
      if (assetPrefix !== basePath) {
        maybeAssetPrefixRewrite.push({
          source: `${assetPrefix}/_next/:path+`,
          destination: `${basePath}/_next/:path+`,
        })
      }
    }
  }

  if (typeof config.rewrites !== 'function') {
    return {
      beforeFiles: [...maybeAssetPrefixRewrite],
      afterFiles: [],
      fallback: [],
    }
  }
  const _rewrites = await config.rewrites()
  let beforeFiles: Rewrite[] = []
  let afterFiles: Rewrite[] = []
  let fallback: Rewrite[] = []

  if (
    !Array.isArray(_rewrites) &&
    typeof _rewrites === 'object' &&
    Object.keys(_rewrites).every(
      (key) =>
        key === 'beforeFiles' || key === 'afterFiles' || key === 'fallback'
    )
  ) {
    beforeFiles = _rewrites.beforeFiles || []
    afterFiles = _rewrites.afterFiles || []
    fallback = _rewrites.fallback || []
  } else {
    afterFiles = _rewrites as any
  }
  // check before we process the routes and after to ensure
  // they are still valid
  checkCustomRoutes(beforeFiles, 'rewrite')
  checkCustomRoutes(afterFiles, 'rewrite')
  checkCustomRoutes(fallback, 'rewrite')

  // save original rewrites before transforms
  config._originalRewrites = {
    beforeFiles: beforeFiles.map((r) => ({ ...r })),
    afterFiles: afterFiles.map((r) => ({ ...r })),
    fallback: fallback.map((r) => ({ ...r })),
  }

  beforeFiles = [
    ...maybeAssetPrefixRewrite,
    ...processRoutes(beforeFiles, config, 'rewrite'),
  ]
  afterFiles = processRoutes(afterFiles, config, 'rewrite')
  fallback = processRoutes(fallback, config, 'rewrite')

  checkCustomRoutes(beforeFiles, 'rewrite')
  checkCustomRoutes(afterFiles, 'rewrite')
  checkCustomRoutes(fallback, 'rewrite')

  return {
    beforeFiles,
    afterFiles,
    fallback,
  }
}

async function loadHeaders(config: NextConfig) {
  if (typeof config.headers !== 'function') {
    return []
  }
  let headers = await config.headers()
  // check before we process the routes and after to ensure
  // they are still valid
  checkCustomRoutes(headers, 'header')

  headers = processRoutes(headers, config, 'header')
  checkCustomRoutes(headers, 'header')
  return headers
}

export default async function loadCustomRoutes(
  config: NextConfig
): Promise<CustomRoutes> {
  const [headers, rewrites, redirects] = await Promise.all([
    loadHeaders(config),
    loadRewrites(config),
    loadRedirects(config),
  ])

  const totalRewrites =
    rewrites.beforeFiles.length +
    rewrites.afterFiles.length +
    rewrites.fallback.length

  const totalRoutes = headers.length + redirects.length + totalRewrites

  if (totalRoutes > 1000) {
    console.warn(
      bold(yellow(`Warning: `)) +
        `total number of custom routes exceeds 1000, this can reduce performance. Route counts:\n` +
        `headers: ${headers.length}\n` +
        `rewrites: ${totalRewrites}\n` +
        `redirects: ${redirects.length}\n` +
        `See more info: https://nextjs.org/docs/messages/max-custom-routes-reached`
    )
  }

  if (!config.skipTrailingSlashRedirect) {
    if (config.trailingSlash) {
      redirects.unshift(
        {
          source: '/:file((?!\\.well-known(?:/.*)?)(?:[^/]+/)*[^/]+\\.\\w+)/',
          destination: '/:file',
          permanent: true,
          locale: config.i18n ? false : undefined,
          internal: true,
          // don't run this redirect for _next/data requests
          missing: [
            {
              type: 'header',
              key: 'x-nextjs-data',
            },
          ],
        },
        {
          source: '/:notfile((?!\\.well-known(?:/.*)?)(?:[^/]+/)*[^/\\.]+)',
          destination: '/:notfile/',
          permanent: true,
          locale: config.i18n ? false : undefined,
          internal: true,
        }
      )
      if (config.basePath) {
        redirects.unshift({
          source: config.basePath,
          destination: config.basePath + '/',
          permanent: true,
          basePath: false,
          locale: config.i18n ? false : undefined,
          internal: true,
        })
      }
    } else {
      redirects.unshift({
        source: '/:path+/',
        destination: '/:path+',
        permanent: true,
        locale: config.i18n ? false : undefined,
        internal: true,
      })
      if (config.basePath) {
        redirects.unshift({
          source: config.basePath + '/',
          destination: config.basePath,
          permanent: true,
          basePath: false,
          locale: config.i18n ? false : undefined,
          internal: true,
        })
      }
    }
  }

  return {
    headers,
    rewrites,
    redirects,
  }
}