package controllers.caching

import play.api.mvc.Results.NotModified
import play.api.mvc.{Request, Result}

import scala.concurrent.{ExecutionContext, Future}

trait Etagable[A]:
  extension (a: A) def etag: String


trait CheckFresh {
  protected def checkFreshAsync[A, E: Etagable](entity: E)(onStale: => Future[Result])(using request: Request[A], ec: ExecutionContext): Future[Result] = {
    compareEtag(request, entity).fold(onStale)(
      etag => Future.successful(NotModified.withHeaders("ETag" -> etag))
    )
  }

  protected def checkFresh[A, E: Etagable](entity: E)(onStale: => Result)(using request: Request[A]): Result = {
    compareEtag(request, entity).fold(onStale)(
      etag => NotModified.withHeaders("ETag" -> etag)
    )
  }

  private def compareEtag[A, E: Etagable](request: Request[A], entity: E) = request.headers.get("If-None-Match").filter(e => e == entity.etag)
}