import {
  DEV_STYLES_ATTR,
  buildDevStylesUrl,
  rootRouteId,
} from '@tanstack/router-core'
import type { AnyRoute, ServerManifestRoute } from '@tanstack/router-core'
import type { StartManifestWithClientEntry } from './transformAssetUrls'

// Pre-computed constant for dev styles URL basepath.
// Defaults to vite `base` (set via TSS_DEV_SSR_STYLES_BASEPATH in the plugin),
// aligning dev styles with how other CSS/JS assets are served.
const DEV_SSR_STYLES_BASEPATH = process.env.TSS_DEV_SSR_STYLES_BASEPATH || '/'
/**
 * @description Returns the router manifest data that should be sent to the client.
 * This includes only the assets and preloads for the current route and any
 * special assets that are needed for the client. It does not include relationships
 * between routes or any other data that is not needed for the client.
 *
 * The client entry URL is returned separately so that it can be transformed
 * (e.g. for CDN rewriting) before being embedded into the `<script>` tag.
 *
 * @param matchedRoutes - In dev mode, the matched routes are used to build
 * the dev styles URL for route-scoped CSS collection.
 */
export async function getStartManifest(
  matchedRoutes?: ReadonlyArray<AnyRoute>,
): Promise<StartManifestWithClientEntry> {
  const { tsrStartManifest } = await import('tanstack-start-manifest:v')
  const startManifest = tsrStartManifest()
  let routes = startManifest.routes
  let rootRoute = routes[rootRouteId]

  const updateRootRoute = (nextRootRoute: ServerManifestRoute) => {
    rootRoute = nextRootRoute
    routes = {
      ...routes,
      [rootRouteId]: rootRoute,
    }
  }

  // Inject dev styles link in dev mode (when SSR styles are enabled)
  if (
    process.env.TSS_DEV_SERVER === 'true' &&
    process.env.TSS_DEV_SSR_STYLES_ENABLED !== 'false' &&
    matchedRoutes
  ) {
    const matchedRouteIds = matchedRoutes.map((route) => route.id)
    updateRootRoute({
      ...rootRoute,
      css: [
        ...(rootRoute?.css ?? []),
        {
          href: buildDevStylesUrl(DEV_SSR_STYLES_BASEPATH, matchedRouteIds),
          [DEV_STYLES_ATTR]: true,
        },
      ],
    })
  }

  const manifestRoutes: Record<string, ServerManifestRoute> = {}

  for (const k in routes) {
    const v = routes[k]!
    const result = {} as ServerManifestRoute

    if (v.preloads && v.preloads.length > 0) {
      result.preloads = v.preloads
    }
    if (v.scripts && v.scripts.length > 0) {
      result.scripts = v.scripts
    }
    if (v.css?.length) {
      result.css = v.css
    }
    if (result.preloads || result.scripts || result.css) {
      manifestRoutes[k] = result
    }
  }

  const manifest = {
    ...(startManifest.scriptFormat
      ? { scriptFormat: startManifest.scriptFormat }
      : {}),
    ...(startManifest.inlineCss ? { inlineCss: startManifest.inlineCss } : {}),
    routes: manifestRoutes,
  }

  return {
    manifest: manifest as StartManifestWithClientEntry['manifest'],
    clientEntry: startManifest.clientEntry,
  }
}