package com.weEat.migrations

import org.mongodb.scala.MongoDatabase
import scala.concurrent.{ExecutionContext,Future}
import scala.util.{Success,Failure}
import scala.io.Source
import com.weEat.models._

trait Migration {
  def execute(db: MongoDatabase): Future[Any]
}

object Migration {
  implicit val ec: ExecutionContext = ExecutionContext.global

  val migrations = Seq(
    InitDb,
    SeedNutrition,
    RestoreFromFile(Source.fromResource("db-seeds/nutrients.json"), Nutrient)
    //RestoreFromFile(Source.fromResource("db-seeds/usda-foods.json"), FoodNode),
  )

  def executeAll(db: MongoDatabase) = executeFutures(db, migrations)

  def updateToLatest(db: MongoDatabase) = {
    val collection = db.getCollection[Metadata](Metadata.collectionName)
    collection.find().first().headOption().map({
      case Some(Metadata(last)) =>
        executeFutures(db, migrations.slice(last + 1, migrations.size))
      case None => executeAll(db)
    }).flatten
  }

  private def executeFutures(db: MongoDatabase, seq: Seq[Migration]): Future[Any] =
    seq match {
      case head::tail => head.execute(db).transformWith({
        case Success(_) => executeFutures(db, tail)
        case Failure(e) => db.getCollection[Metadata](Metadata.collectionName)
            .insertOne(Metadata(migrations.size - seq.size)).head()
            .transform(_ => Failure(e))
      })
      case Nil => db.getCollection[Metadata](Metadata.collectionName)
          .insertOne(Metadata(migrations.size)).head()
    }
}