Play Framework/Scala example source code file (EventSource.scala)

This example Play Framework source code file (EventSource.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Play Framework (and Scala) source code examples by using tags.

All credit for the original source code belongs to Play Framework; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Play Framework tags/keywords

a, api, e, event, eventdataextractor, eventidextractor, eventnameextractor, json, lib, library, lowpriorityeventencoder, lowpriorityeventnameextractor, option, play, play framework, string

The EventSource.scala Play Framework example source code

/*
 * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
 */
package play.api.libs

import play.api.mvc._
import play.api.libs.iteratee._

import play.core.Execution.Implicits.internalContext
import play.api.libs.json.{ Json, JsValue }

object EventSource {

  case class EventDataExtractor[A](eventData: A => String)

  trait LowPriorityEventEncoder {

    implicit val stringEvents: EventDataExtractor[String] = EventDataExtractor(identity)

    implicit val jsonEvents: EventDataExtractor[JsValue] = EventDataExtractor(Json.stringify)

  }

  object EventDataExtractor extends LowPriorityEventEncoder

  case class EventNameExtractor[E](eventName: E => Option[String])

  case class EventIdExtractor[E](eventId: E => Option[String])

  trait LowPriorityEventNameExtractor {

    implicit def non[E]: EventNameExtractor[E] = EventNameExtractor[E](_ => None)

  }

  trait LowPriorityEventIdExtractor {

    implicit def non[E]: EventIdExtractor[E] = EventIdExtractor[E](_ => None)

  }

  object EventNameExtractor extends LowPriorityEventNameExtractor {

    implicit def pair[E]: EventNameExtractor[(String, E)] = EventNameExtractor[(String, E)](p => Some(p._1))

  }

  object EventIdExtractor extends LowPriorityEventIdExtractor

  def apply[E: EventDataExtractor: EventNameExtractor: EventIdExtractor]() =
    Enumeratee.map[E] { e => Event(e).formatted }

  case class Event(data: String, id: Option[String], name: Option[String]) {
    /**
     * This event, formatted according to the EventSource protocol.
     */
    lazy val formatted = {
      val sb = new StringBuilder
      name.foreach(sb.append("event: ").append(_).append('\n'))
      id.foreach(sb.append("id: ").append(_).append('\n'))
      for (line <- data.split("(\r?\n)|\r")) {
        sb.append("data: ").append(line).append('\n')
      }
      sb.append('\n')
      sb.toString()
    }
  }

  object Event {
    def apply[A](a: A)(implicit dataExtractor: EventDataExtractor[A], nameExtractor: EventNameExtractor[A], idExtractor: EventIdExtractor[A]): Event =
      Event(dataExtractor.eventData(a), idExtractor.eventId(a), nameExtractor.eventName(a))
  }

}