// Browser revalidation of route-cached pages. Nitro's route cache answers
// 200 with `cache-control: s-maxage=<n>, stale-while-revalidate`, which
// gives browsers no max-age, so they apply heuristic freshness from
// Last-Modified; a conditional request it answers 304 with
// `public, max-age=<n>, s-maxage=<n>`, so after one revalidation a browser
// could reuse its copy for the whole TTL, past any site cache purge.
//
// This plugin passes every cache-control value a response sets through
// privateRevalidate: values with s-maxage get max-age=0, so browsers ask on
// each view (a cheap 304 while the page is unchanged) and shared caches keep
// s-maxage. The 304 path ends the response before any beforeResponse hook
// runs, so the rewrite wraps the request's res.setHeader instead. Static
// assets carry no s-maxage and are untouched.

import { privateRevalidate } from '../../app/utils/siteCache.ts'

export default defineNitroPlugin((nitroApp) => {
  nitroApp.hooks.hook('request', (event) => {
    const res = event.node.res
    const setHeader = res.setHeader
    res.setHeader = function (name, value) {
      if (typeof name === 'string' && name.toLowerCase() === 'cache-control') {
        if (typeof value === 'string') value = privateRevalidate(value)
        else if (Array.isArray(value)) value = value.map((v) => privateRevalidate(String(v)))
      }
      return setHeader.call(this, name, value)
    } as typeof res.setHeader
  })
})