util.ts

/**
 * Normalize a data URL into a route path.
 * @see https://github.com/vercel/next.js/blob/25e0988e7c9033cb1503cbe0c62ba5de2e97849c/packages/next/src/shared/lib/router/utils/get-next-pathname-info.ts#L69-L76
 */
export function normalizeDataUrl(urlPath: string) {
  if (urlPath.startsWith('/_next/data/') && urlPath.includes('.json')) {
    const paths = urlPath
      .replace(/^\/_next\/data\//, '')
      .replace(/\.json/, '')
      .split('/')

    urlPath = paths[1] !== 'index' ? `/${paths.slice(1).join('/')}` : '/'
  }

  return urlPath
}

export const removeBasePath = (path: string, basePath?: string) => {
  if (basePath && path.startsWith(basePath)) {
    return path.replace(basePath, '')
  }
  return path
}

export const addBasePath = (path: string, basePath?: string) => {
  if (basePath && !path.startsWith(basePath)) {
    return `${basePath}${path}`
  }
  return path
}

// add locale prefix if not present, allowing for locale fallbacks
export const addLocale = (path: string, locale?: string) => {
  if (
    locale &&
    path.toLowerCase() !== `/${locale.toLowerCase()}` &&
    !path.toLowerCase().startsWith(`/${locale.toLowerCase()}/`) &&
    !path.startsWith(`/api/`) &&
    !path.startsWith(`/_next/`)
  ) {
    return `/${locale}${path}`
  }
  return path
}

// https://github.com/vercel/next.js/blob/canary/packages/next/src/shared/lib/i18n/normalize-locale-path.ts

export interface PathLocale {
  detectedLocale?: string
  pathname: string
}

/**
 * For a pathname that may include a locale from a list of locales, it
 * removes the locale from the pathname returning it alongside with the
 * detected locale.
 *
 * @param pathname A pathname that may include a locale.
 * @param locales A list of locales.
 * @returns The detected locale and pathname without locale
 */
export function normalizeLocalePath(pathname: string, locales?: string[]): PathLocale {
  let detectedLocale: string | undefined
  // first item will be empty string from splitting at first char
  const pathnameParts = pathname.split('/')

  ;(locales || []).some((locale) => {
    if (pathnameParts[1] && pathnameParts[1].toLowerCase() === locale.toLowerCase()) {
      detectedLocale = locale
      pathnameParts.splice(1, 1)
      pathname = pathnameParts.join('/')
      return true
    }
    return false
  })
  return {
    pathname,
    detectedLocale,
  }
}

/**
 * This is how Next handles rewritten URLs.
 */
export function relativizeURL(url: string | string, base: string | URL) {
  const baseURL = typeof base === 'string' ? new URL(base) : base
  const relative = new URL(url, base)
  const origin = `${baseURL.protocol}//${baseURL.host}`
  return `${relative.protocol}//${relative.host}` === origin
    ? relative.toString().replace(origin, '')
    : relative.toString()
}

export const normalizeIndex = (path: string) => (path === '/' ? '/index' : path)

export const normalizeTrailingSlash = (path: string, trailingSlash?: boolean) =>
  trailingSlash ? addTrailingSlash(path) : stripTrailingSlash(path)

export const stripTrailingSlash = (path: string) =>
  path !== '/' && path.endsWith('/') ? path.slice(0, -1) : path

export const addTrailingSlash = (path: string) => (path.endsWith('/') ? path : `${path}/`)

/**
 * Modify a data url to point to a new page route.
 */
export function rewriteDataPath({
  dataUrl,
  newRoute,
  basePath,
}: {
  dataUrl: string
  newRoute: string
  basePath?: string
}) {
  const normalizedDataUrl = normalizeDataUrl(removeBasePath(dataUrl, basePath))

  return addBasePath(
    dataUrl.replace(
      normalizeIndex(normalizedDataUrl),
      stripTrailingSlash(normalizeIndex(newRoute)),
    ),
    basePath,
  )
}