Function denormalizeNextDataUrl

packages/next-routing/src/next-data.ts:36–59

(
  url: URL,
  basePath: string,
  buildId: string
)

 * ${basePath}/$path -> ${basePath}/_next/data/$buildId/$path.json
 */
export function denormalizeNextDataUrl(
  url: URL,
  basePath: string,
  buildId: string
): URL {
  const newUrl = new URL(url.toString())
  let pathname = newUrl.pathname

  // Only denormalize if it's not already a data URL
  const dataPrefix = `${basePath}/_next/data/${buildId}/`
  if (!pathname.startsWith(dataPrefix)) {
    // Remove basePath if present
    let pathWithoutBase = pathname
    if (basePath && pathname.startsWith(basePath)) {
      pathWithoutBase = pathname.slice(basePath.length)
    }

    // Add the /_next/data/${buildId}/ prefix and .json extension
    pathname = `${basePath}/_next/data/${buildId}${pathWithoutBase}.json`
    newUrl.pathname = pathname
  }

  return newUrl
}