// The routes the layer tells the CMS about (D-33) and compares with it at
// server start (D-20c). Built at build time from the resolved pages, whose
// meta carries requiresAuth and seo (the module adds both to Nuxt's page
// meta extraction keys), and written into the server template #seo-routes
// for the route report and the drift check. Pure TypeScript, so
// `node --test` drives it.

import { flattenPages, isNoindex, pagePattern, type GuardPage } from './guard.ts'

export interface RoutePage extends GuardPage {
  name?: string
  meta?: Record<string, unknown>
  children?: RoutePage[]
}

export interface RoutePattern {
  /** A route-rule style pattern: '/blog/:slug', '/docs/**', '/'. */
  pattern: string
  /** True when the route ends in a catch-all ('[...slug]'). */
  catchAll: boolean
}

/** True when a robots value keeps the page out of the index. */
export const robotsNoindex = (robots: unknown) => typeof robots === 'string' && /(^|[\s,])(noindex|none)($|[\s,])/i.test(robots)

/**
 * The robots value a page asks for through its meta: seo.robots when set,
 * else 'noindex, nofollow' for a page with requiresAuth: true (a signed-in
 * or auth page, D-23), else null (the CMS decides).
 */
export function pageMetaRobots(meta: Record<string, unknown> | undefined | null): string | null {
  if (!meta || typeof meta !== 'object') return null
  const seo = meta.seo
  if (seo && typeof seo === 'object') {
    const robots = (seo as { robots?: unknown }).robots
    if (typeof robots === 'string' && robots.trim() !== '') return robots.trim()
  }
  if (meta.requiresAuth === true) return 'noindex, nofollow'
  return null
}

/** The layer's own HTML sitemap pages, which the CMS knows already. */
const isLayerPage = (name: unknown) => typeof name === 'string' && name.startsWith('seo-sitemap-')

/**
 * The paths without parameters that may be indexed, sorted: no page whose
 * meta keeps it out of the index (requiresAuth, a noindex seo.robots), none
 * under seo.noindexRoutes, none of the layer's HTML sitemap pages and no
 * client-only page.
 */
export function staticRoutes(pages: readonly RoutePage[], noindexRoutes: readonly string[]): string[] {
  const out = new Set<string>()
  for (const page of flattenPages(pages) as Array<RoutePage & { fullPath: string }>) {
    // A parent with children renders through one of them.
    if (Array.isArray(page.children) && page.children.some((c) => c.path === '')) continue
    const path = page.fullPath
    if (path.includes(':') || path.includes('*')) continue
    if (page.mode === 'client' || isLayerPage(page.name)) continue
    if (robotsNoindex(pageMetaRobots(page.meta))) continue
    if (isNoindex(path, noindexRoutes)) continue
    out.add(path)
  }
  return [...out].sort()
}

/** Every page's route pattern ('/posts/:slug', '/**' for a catch-all), sorted. */
export function routePatterns(pages: readonly RoutePage[]): RoutePattern[] {
  const seen = new Map<string, RoutePattern>()
  for (const page of flattenPages(pages)) {
    const pattern = pagePattern(page.fullPath)
    if (!seen.has(pattern)) seen.set(pattern, { pattern, catchAll: pattern.endsWith('/**') })
  }
  return [...seen.values()].sort((a, b) => a.pattern.localeCompare(b.pattern))
}

/** The body of the server template #seo-routes. */
export function routesTemplate(staticPaths: readonly string[], patterns: readonly RoutePattern[]): string {
  return [
    '// Generated by vue-seo-layer (lib/routes.ts) from the resolved pages.',
    `export const staticRoutes = ${JSON.stringify(staticPaths)}`,
    `export const routePatterns = ${JSON.stringify(patterns)}`,
    '',
  ].join('\n')
}