// The route report (D-33): at server start the layer posts its static
// routes and the static paths it serves noindex (#seo-routes, built from
// the pages) to the SEO plugin's POST /_seo/api/v1/registry/routes with the
// route-report token, so the CMS's page registry knows every frontend page
// and its sitemaps leave the noindex ones out (G1). Pure helpers for the
// Nitro plugin server/plugins/seo-route-report.ts, so `node --test` drives
// them.

/** The plugin's limits: at most 2000 paths of at most 2048 bytes each, per list. */
export const ROUTE_REPORT_MAX_ROUTES = 2000
export const ROUTE_REPORT_MAX_BYTES = 2048
/**
 * The most body a plugin built before the `noindex` key reads
 * (sm-seo-plugin's maxRouteReportBody: MaxReportedRoutes*(MaxRouteBytes+8)+1024,
 * 4,113,024 bytes); the serialised JSON body never exceeds it.
 */
export const ROUTE_REPORT_MAX_BODY = ROUTE_REPORT_MAX_ROUTES * (ROUTE_REPORT_MAX_BYTES + 8) + 1024
/** The one retry after a failed report waits this long. */
export const ROUTE_REPORT_RETRY_MS = 60_000

export interface RouteReportBody {
  routes: string[]
  noindex: string[]
}

const withinLimits = (paths: readonly string[]) =>
  paths.filter((p) => typeof p === 'string' && p.startsWith('/') && Buffer.byteLength(p, 'utf8') <= ROUTE_REPORT_MAX_BYTES).slice(0, ROUTE_REPORT_MAX_ROUTES)

/** The longest prefix of `paths` whose JSON array entries fit into `room` bytes (commas included). */
function fitting(paths: readonly string[], room: number): string[] {
  let used = 0
  let n = 0
  for (const p of paths) {
    const size = Buffer.byteLength(JSON.stringify(p), 'utf8') + (n > 0 ? 1 : 0)
    if (used + size > room) break
    used += size
    n++
  }
  return paths.slice(0, n)
}

/**
 * The request body: both lists filtered to paths starting with / of at most
 * 2048 bytes and cut to 2000 entries; a path in `routes` is never repeated in
 * `noindex`. `noindex` is always sent (also []), so the plugin's set follows
 * each build. The serialised body stays at or under ROUTE_REPORT_MAX_BODY:
 * `noindex` entries are dropped from the end first, then `routes` entries.
 */
export function routeReportBody(paths: readonly string[], noindexPaths: readonly string[] = []): RouteReportBody {
  const routes = withinLimits(paths)
  const listed = new Set(routes)
  let noindex = withinLimits(noindexPaths.filter((p) => !listed.has(p)))
  const routesSize = Buffer.byteLength(JSON.stringify({ routes, noindex: [] }), 'utf8')
  if (routesSize > ROUTE_REPORT_MAX_BODY) {
    // Every noindex entry is gone and the body is still too large: cut routes.
    const empty = Buffer.byteLength(JSON.stringify({ routes: [], noindex: [] }), 'utf8')
    return { routes: fitting(routes, ROUTE_REPORT_MAX_BODY - empty), noindex: [] }
  }
  noindex = fitting(noindex, ROUTE_REPORT_MAX_BODY - routesSize)
  return { routes, noindex }
}

/**
 * What an answer means: sent (2xx), absent (404: a backend without the
 * page registry, or with both tokens empty; never retried), refused (401 or
 * 403: the token is wrong; never retried) or retry (no answer, or any other
 * status: tried once more after ROUTE_REPORT_RETRY_MS).
 */
export function routeReportOutcome(status: number | null): 'sent' | 'absent' | 'refused' | 'retry' {
  if (status !== null && status >= 200 && status < 300) return 'sent'
  if (status === 404) return 'absent'
  if (status === 401 || status === 403) return 'refused'
  return 'retry'
}