import type { IncomingHttpHeaders, IncomingMessage } from 'node:http'

/** Paths Vite itself serves (HMR client, source modules, deps). */
export const isViteOwned = (url: string) =>
  /^\/(@|src\/|node_modules\/|__|mock\/|test\/)/.test(url)

/** A navigation to a page we should fetch + inject, as opposed to an asset/API call. */
export function isPageRequest(req: IncomingMessage): boolean {
  const url = req.url ?? '/'
  if (req.method !== 'GET' || isViteOwned(url)) return false
  if (/^\/(api|editor|assets|js|css|fonts|static)(\/|$)/.test(url)) return false
  if (/\.[a-z0-9]{2,5}($|\?)/i.test(url.split('?')[0])) return false // has a file extension
  return String(req.headers.accept ?? '').includes('text/html')
}

export interface Auth {
  token?: string
  apiKey?: string
  cookie?: string
}

const hasPreviewCookie = (cookie?: string) => /(?:^|;\s*)cms_preview=1/.test(cookie ?? '')

/** Headers for an upstream request: browser cookies + configured credentials + preview flag. */
export function upstreamHeaders(
  incoming: IncomingHttpHeaders,
  auth: Auth,
  opts: { identity?: boolean } = {},
): Record<string, string> {
  const h: Record<string, string> = {}
  if (incoming.accept) h.accept = String(incoming.accept)
  if (incoming['accept-language']) h['accept-language'] = String(incoming['accept-language'])
  if (opts.identity) h['accept-encoding'] = 'identity'
  const cookie = [incoming.cookie, auth.cookie].filter(Boolean).join('; ')
  if (cookie) h.cookie = cookie
  // The edge routes on the cookie OR this header; send both so a proxy hop can't lose it.
  if (hasPreviewCookie(cookie)) h['x-cms-preview'] = '1'
  if (auth.token) h.authorization = `Bearer ${auth.token}`
  else if (incoming.authorization) h.authorization = String(incoming.authorization)
  if (auth.apiKey) h['x-api-key'] = auth.apiKey
  return h
}

/** Put the dev entry in front of </body> (or at the end). */
export function injectDevEntry(html: string): string {
  const tag = '<script type="module" src="/src/dev.ts"></script>'
  return /<\/body>/i.test(html) ? html.replace(/<\/body>/i, `${tag}</body>`) : html + tag
}