Add BsonWriter typeclass weakteam#12

build.sbt

@@ -106,7 +106,7 @@ lazy val core = project
   .settings(commonSettings: _*)
   .settings(
     libraryDependencies ++=
-        Seq(Dependencies.Libs.cats) ++
+        Seq(Dependencies.Libs.cats, Dependencies.Libs.simulacrum) ++
             Dependencies.Plugins.plugins ++
             Dependencies.TestLibraries.testLibraries.map(_ % Test)
   )

core/src/main/scala/io/github/weakteam/mongo/AllInstances.scala

@@ -0,0 +1,3 @@
+package io.github.weakteam.mongo
+
+trait AllInstances

core/src/main/scala/io/github/weakteam/mongo/AllSyntax.scala

@@ -0,0 +1,5 @@
+package io.github.weakteam.mongo
+
+import io.github.weakteam.mongo.bson.BsonWriter
+
+trait AllSyntax extends BsonWriter.ToBsonWriterOps

core/src/main/scala/io/github/weakteam/bson/BsonSubtype.scala → core/src/main/scala/io/github/weakteam/mongo/bson/BsonSubtype.scala

@@ -1,4 +1,4 @@
-package io.github.weakteam.bson
+package io.github.weakteam.mongo.bson
 
 import cats.Show
 

core/src/main/scala/io/github/weakteam/bson/BsonValue.scala → core/src/main/scala/io/github/weakteam/mongo/bson/BsonValue.scala

@@ -1,4 +1,4 @@
-package io.github.weakteam.bson
+package io.github.weakteam.mongo.bson
 
 import cats.Show
 import cats.syntax.show._

core/src/main/scala/io/github/weakteam/mongo/bson/BsonWriter.scala

@@ -0,0 +1,19 @@
+package io.github.weakteam.mongo.bson
+
+import cats.Contravariant
+import simulacrum.typeclass
+
+@typeclass
+trait BsonWriter[-T] { self =>
+  def writeBson(arg: T): BsonValue
+}
+
+object BsonWriter {
+  def instance[A](f: A => BsonValue): BsonWriter[A] = f(_)
+
+  implicit val bsonWriterContravariantInstance: Contravariant[BsonWriter] = new Contravariant[BsonWriter] {
+    def contramap[A, B](fa: BsonWriter[A])(f: B => A): BsonWriter[B] = { arg =>
+      fa.writeBson(f(arg))
+    }
+  }
+}

core/src/main/scala/io/github/weakteam/mongo/implicits.scala

@@ -0,0 +1,3 @@
+package io.github.weakteam.mongo
+
+object implicits extends AllSyntax with AllInstances

core/src/test/scala/io/github/weakteam/bson/BsonSubtypeSpec.scala → core/src/test/scala/io/github/weakteam/mongo/bson/BsonSubtypeSpec.scala

@@ -1,9 +1,9 @@
-package io.github.weakteam.bson
+package io.github.weakteam.mongo.bson
 
 import org.scalatest.matchers.must.Matchers
 import org.scalatest.wordspec.AnyWordSpec
 import cats.syntax.show._
-import io.github.weakteam.bson.BsonSubtype._
+import BsonSubtype._
 
 class BsonSubtypeSpec extends AnyWordSpec with Matchers {
   "BsonSubtypeShow" should {

core/src/test/scala/io/github/weakteam/bson/BsonValueSpec.scala → core/src/test/scala/io/github/weakteam/mongo/bson/BsonValueSpec.scala

@@ -1,9 +1,9 @@
-package io.github.weakteam.bson
+package io.github.weakteam.mongo.bson
 
 import org.scalatest.matchers.must.Matchers
 import org.scalatest.wordspec.AnyWordSpec
 import cats.syntax.show._
-import io.github.weakteam.bson.BsonValue._
+import BsonValue._
 
 class BsonValueSpec extends AnyWordSpec with Matchers {
   "BsonValueShow" should {

core/src/test/scala/io/github/weakteam/mongo/bson/BsonWriterSpec.scala

@@ -0,0 +1,29 @@
+package io.github.weakteam.mongo.bson
+
+import io.github.weakteam.mongo.bson.BsonValue.BsonInt
+import org.scalatest.matchers.must.Matchers
+import org.scalatest.wordspec.AnyWordSpec
+import io.github.weakteam.mongo.implicits._
+import cats.syntax.contravariant._
+
+class BsonWriterSpec extends AnyWordSpec with Matchers {
+  "BsonWriter" should {
+    "return right value" in {
+      implicit val intBsonWriter: BsonWriter[Int] = BsonInt(_)
+
+      1.writeBson mustBe BsonInt(1)
+    }
+
+    "return right value with contramap" in {
+      implicit val intBsonWriter: BsonWriter[Int] = BsonInt(_)
+      implicit val anyBsonWriter: BsonWriter[Any] = intBsonWriter.contramap {
+        case i: Int => i
+        case _      => 0
+      }
+
+      1.writeBson mustBe BsonInt(1)
+      "".writeBson mustBe BsonInt(0)
+      1L.writeBson mustBe BsonInt(0)
+    }
+  }
+}

project/Dependencies.scala

@@ -17,7 +17,8 @@ object Dependencies {
   }
 
   object Libs {
-    val cats = "org.typelevel" %% "cats-core" % Versions.cats
+    val cats       = "org.typelevel" %% "cats-core"  % Versions.cats
+    val simulacrum = "org.typelevel" %% "simulacrum" % Versions.simulacrum
   }
 
   object TestLibraries {
@@ -31,7 +32,6 @@ object Dependencies {
   object Plugins {
 
     val macroParadise       = "org.scalamacros" % "paradise"            % Versions.macroParadise cross CrossVersion.patch
-    val simulacrum          = "org.typelevel"   %% "simulacrum"         % Versions.simulacrum
     val bm4Plugin           = "com.olegpy"      %% "better-monadic-for" % Versions.bm4
     val kindProjectorPlugin = "org.typelevel"   % "kind-projector"      % Versions.kindProjector cross CrossVersion.patch
     val silencerPlugin      = "com.github.ghik" %% "silencer-plugin"    % Versions.silencer cross CrossVersion.full