[WIP] Add toTSV method (close #97)

build.sbt

@@ -39,7 +39,9 @@ lazy val root = project.in(file("."))
       Dependencies.circeParser,
       Dependencies.circeGeneric,
       // Scala (test only)
-      Dependencies.specs2
+      Dependencies.specs2,
+      Dependencies.specs2Scalacheck,
+      Dependencies.scalacheck
     )
   )
 

project/Dependencies.scala

@@ -20,6 +20,7 @@ object Dependencies {
     val circe          = "0.13.0"
     // Scala (test only)
     val specs2         = "4.8.0"
+    val scalaCheck     = "1.14.3"
   }
 
   val igluCore         = "com.snowplowanalytics"      %% "iglu-core-circe"      % V.igluCore
@@ -28,4 +29,6 @@ object Dependencies {
   val circeGeneric     = "io.circe"                   %% "circe-generic"        % V.circe
   // Scala (test only)
   val specs2           = "org.specs2"                 %% "specs2-core"          % V.specs2     % Test
+  val specs2Scalacheck = "org.specs2"                 %% "specs2-scalacheck"    % V.specs2     % Test
+  val scalacheck       = "org.scalacheck"             %% "scalacheck"           % V.scalaCheck % Test
 }

src/main/scala/com.snowplowanalytics.snowplow.analytics.scalasdk/Event.scala

@@ -15,6 +15,7 @@ package com.snowplowanalytics.snowplow.analytics.scalasdk
 // java
 import java.time.Instant
 import java.util.UUID
+import java.time.format.DateTimeFormatter
 
 // circe
 import io.circe.{Encoder, Json, JsonObject, Decoder}
@@ -28,8 +29,10 @@ import com.snowplowanalytics.iglu.core.circe.implicits._
 
 // This library
 import com.snowplowanalytics.snowplow.analytics.scalasdk.decode.{Parser, DecodeResult}
+import com.snowplowanalytics.snowplow.analytics.scalasdk.encode.TsvEncoder._
 import com.snowplowanalytics.snowplow.analytics.scalasdk.SnowplowEvent.{Contexts, UnstructEvent}
 import com.snowplowanalytics.snowplow.analytics.scalasdk.SnowplowEvent._
+import com.snowplowanalytics.snowplow.analytics.scalasdk.encode.TsvEncoder
 
 /**
   * Case class representing a canonical Snowplow event.
@@ -228,6 +231,9 @@ case class Event(app_id:                   Option[String],
       this.asJson
     }
 
+  /** Create the TSV representation of this event. */
+  def toTSV: String = TsvEncoder.encode(this)
+
   /**
     * This event as a map of keys to Circe JSON values
     */

src/main/scala/com.snowplowanalytics.snowplow.analytics.scalasdk/encode/TsvEncoder.scala

@@ -0,0 +1,89 @@
+package com.snowplowanalytics.snowplow.analytics.scalasdk.encode
+
+import java.time.format.DateTimeFormatter
+import java.time.Instant
+import java.util.UUID
+
+import io.circe.syntax._
+
+import shapeless._
+import shapeless.labelled._
+import shapeless.ops.hlist._
+import shapeless.ops.record._
+
+import com.snowplowanalytics.snowplow.analytics.scalasdk.SnowplowEvent._
+
+trait TsvEncoder[A] {
+  def encode(value: A): List[String]
+}
+
+object TsvEncoder {
+  def apply[A](implicit enc: TsvEncoder[A]): TsvEncoder[A] = enc
+
+  def instance[A](func: A => List[String]): TsvEncoder[A] = new TsvEncoder[A] {
+    def encode(value: A): List[String] =
+      func(value)
+  }
+
+  def createEncoder[A](func: A => List[String]): TsvEncoder[A] =
+    new TsvEncoder[A] {
+      def encode(value: A): List[String] = func(value)
+    }
+
+  implicit val stringEncoder: TsvEncoder[String] =
+    createEncoder(s => List(s))
+  implicit val optStringEncoder: TsvEncoder[Option[String]] =
+    createEncoder(optS => List(optS.getOrElse("")))
+  implicit val instantEncoder: TsvEncoder[Instant] =
+    createEncoder(i =>  List(TsvEncoder.formatInstant(i)))
+  implicit val optInstantEncoder: TsvEncoder[Option[Instant]] =
+    createEncoder(optI => List(optI.map(TsvEncoder.formatInstant).getOrElse("")))
+  implicit val uuidEncoder: TsvEncoder[UUID] =
+    createEncoder(u => List(u.toString()))
+  implicit val optIntEncoder: TsvEncoder[Option[Int]] =
+    createEncoder(optI => List(optI.map(_.toString).getOrElse("")))
+  implicit val optDoubleEncoder: TsvEncoder[Option[Double]] =
+    createEncoder(optD => List(optD.map(_.toString).getOrElse("")))
+  implicit val contextsEncoder: TsvEncoder[Contexts] =
+    createEncoder(c => List(c.asJson.noSpaces))
+  implicit val unstructEncoder: TsvEncoder[UnstructEvent] =
+    createEncoder(u => List(u.asJson.noSpaces))
+  implicit val optBooleanEncoder: TsvEncoder[Option[Boolean]] =
+    createEncoder(b => List(b.map(bb => if (bb) "1" else "0").getOrElse("")))
+  implicit val hnilEncoder: TsvEncoder[HNil] =
+    createEncoder(hnil => Nil)
+  implicit def hlistEncoder[H, T <: HList](
+    implicit hEncoder: TsvEncoder[H],
+    tEncoder: TsvEncoder[T]
+  ): TsvEncoder[H :: T] =
+    createEncoder {
+      case h :: t => hEncoder.encode(h) ++ tEncoder.encode(t)
+    }
+
+  implicit def genericEncoder[A, R](
+    implicit gen: Generic.Aux[A, R],
+    enc: TsvEncoder[R]
+  ): TsvEncoder[A] =
+    createEncoder(a => enc.encode(gen.to(a)))
+
+  def encode[A, H <: HList, I <: HList, J <: HList](value: A)(
+    implicit enc: TsvEncoder[A],
+    gen: LabelledGeneric.Aux[A, H],
+    keys: Keys.Aux[H, I],
+    mapper: Mapper.Aux[Symboler.type, I, J],
+    toTraversable: ToTraversable.Aux[J, List, String]
+  ): String =
+    enc.encode(value).mkString("\t")
+
+  /** Create timesteamp string with this format: '1978-03-13 20:57:30.661198953', like the output of enrich. */
+  def formatInstant(instant: Instant): String =
+    DateTimeFormatter.ISO_INSTANT
+      .format(instant)
+      .replace("T", " ")
+      .dropRight(1) // remove trailing 'Z'
+}
+
+object Symboler extends Poly1 {
+  implicit def default[A <: Symbol](implicit witness: Witness.Aux[A]) =
+    at[A](_ => witness.value.name)
+}