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


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

  def checkFresh(entity: E)(onStale: => Result): Result = {
    compareEtag(entity).fold(onStale)(
      etag => NotModified.withHeaders("ETag" -> etag)
    )
  }

  private def compareEtag(entity: E) = request.headers.get("If-None-Match").filter(e => e == entity.etag)
}