const EVENT_UUID_PATTERN = /^[0-9a-f]{8}(?:-[0-9a-f]{4}){3}-[0-9a-f]{12}$/i
const EVENT_SLUG_PATTERN = /^[a-z0-9]+(?:-[a-z0-9]+)*$/

// Keep application-route words and UUID-shaped values out of public slugs.
// UUIDs are still accepted by `/e/[slug]` as private/legacy identifiers, but
// are never considered canonical SEO URLs.
export const RESERVED_EVENT_SLUGS = new Set(['new'])

export const isEventUuid = (value: string) => EVENT_UUID_PATTERN.test(value)

export const isPublicEventSlug = (value: string) =>
  EVENT_SLUG_PATTERN.test(value) && !isEventUuid(value) && !RESERVED_EVENT_SLUGS.has(value)

const getSingleSegment = (pathname: string, prefix: string) => {
  const match = new RegExp(`^/${prefix}/([^/]+)/?$`).exec(pathname)

  if (!match?.[1]) return null

  try {
    return decodeURIComponent(match[1])
  } catch {
    return null
  }
}

export const isCanonicalEventLandingRoute = (pathname: string) => {
  const segment = getSingleSegment(pathname, 'e')

  return segment ? isPublicEventSlug(segment) : false
}

export const isLegacyEventDetailRoute = (pathname: string) => {
  const segment = getSingleSegment(pathname, 'events')

  return segment ? isEventUuid(segment) : false
}

export const isLegacyEventLandingRoute = (pathname: string) => {
  const segment = getSingleSegment(pathname, 'events')

  return segment ? isPublicEventSlug(segment) : false
}