Mongo M101J : Week2#Exercise2

mongom101j-week2-exercise2.scala

import play.api._
import play.api.libs.json._
import play.api.mvc._

import play.api.Logger
import play.api.Play.current
import play.modules.reactivemongo._
import play.modules.reactivemongo.ReactiveMongoPlugin

import org.joda.time.DateTime

import reactivemongo.bson._
import reactivemongo.bson.handlers.DefaultBSONHandlers.DefaultBSONDocumentWriter
import reactivemongo.bson.handlers.DefaultBSONHandlers.DefaultBSONReaderHandler

import reactivemongo.bson._
import reactivemongo.bson.handlers._

import scala.concurrent.{ExecutionContext, Future}
import ExecutionContext.Implicits.global


case class Grade(id: Option[BSONObjectID], typeHomework: String, studentId: Int, score: Double)

object GradeBSON {

  implicit object GradeBSONReader extends BSONReader[Grade] {
    def fromBSON(document: BSONDocument): Grade = {
      val doc = document.toTraversable
      val page = Grade(
        doc.getAs[BSONObjectID]("_id"),
        doc.getAs[BSONString]("type").get.value,
        doc.getAs[BSONInteger]("student_id").get.value,
        doc.getAs[BSONDouble]("score").get.value)
      page
    }
  }

}

object MongoCourse extends Controller with MongoController {

  def db = ReactiveMongoPlugin.db

  def collection = db("grades")

  def findAnswer = Action {
    Async {
      implicit val reader = GradeBSON.GradeBSONReader
      val selector = BSONDocument(
        "$orderby" -> BSONDocument(
          "student_id" -> BSONInteger(1), "score" -> BSONInteger(1)
        ),
        "$query" -> BSONDocument(
          "type" -> BSONString("homework")
        )
      )
      val query = collection.find(selector)
      query.toList().map {
        grades => {
          println("grades " + grades.size)
          deleteStudentsLowerScore(grades)
          Ok
        }
      }
    }
  }

  def deleteStudentsLowerScore(grades: List[Grade]) {
    val groups = grades.groupBy(_.studentId)
    val ids = groups.map(g => g._2.head.id.get)

    ids.foreach(id => {
      val query = BSONDocument("_id" -> id)
      collection.remove(query)
    })
  }

}