package controllers

import play.api.mvc._

import java.security.MessageDigest

/*

 * Application sets a cookie in plain ASCII on the

 * clients browser recording the visits of a page.

 *

 * The cookie data is hashed and stored in the format:

 *

 * visits_counter/hashed_value 

 */

object Application extends Controller {

  //hash functions: SHA-1, SHA-256, etc

  def mk_hash(s: String) : String = {

    val hash_fun = MessageDigest.getInstance("SHA-1")

    hash_fun.digest(s.getBytes).map{ "%02x".format(_) }.mkString

  }

  //extracting from the string .../... the visits

  //value and hash

  def gt_cookie(c: Cookie) : Int = c.value.split("/") match {

    case Array(s, h) if (s.forall(_.isDigit) && mk_hash(s) == h) => s.toInt 

    case _ => 0

  }

  def mk_cookie(i: Int) : Cookie = {

    val hash = mk_hash(i.toString)

    Cookie("visits", s"$i/$hash")

  }

  def index = Action { request =>

    val visits_cookie = request.cookies.get("visits")

    val visits = visits_cookie.map(gt_cookie).getOrElse(0)

    val msg = 

      if (visits >= 10)

        s"You are a valued customer who has visited this site $visits times."               

      else s"You have visited this site $visits times."

    Ok(msg).withCookies(mk_cookie(visits + 1))

  }     

}