Merge pull request #456 from disneystreaming/dfrancoeur/cors-example

Add a guide module - show case CORS middleware

build.sbt

@@ -1,3 +1,4 @@
+import sbt.internal.IvyConsole
 import org.scalajs.jsenv.nodejs.NodeJSEnv
 
 import java.io.File
@@ -67,6 +68,7 @@ lazy val allModules = Seq(
   `codegen-cli`,
   dynamic,
   testUtils,
+  guides,
   complianceTests
 ).flatMap(_.projectRefs)
 
@@ -761,6 +763,24 @@ lazy val example = projectMatrix
   .jvmPlatform(List(Scala213), jvmDimSettings)
   .settings(Smithy4sPlugin.doNotPublishArtifact)
 
+lazy val guides = projectMatrix
+  .in(file("modules/guides"))
+  .dependsOn(http4s)
+  .settings(
+    Compile / allowedNamespaces := Seq("smithy4s.guides.hello"),
+    smithySpecs := Seq(
+      (ThisBuild / baseDirectory).value / "modules" / "guides" / "smithy" / "hello.smithy"
+    ),
+    (Compile / sourceGenerators) := Seq(genSmithyScala(Compile).taskValue),
+    isCE3 := true,
+    libraryDependencies ++= Seq(
+      Dependencies.Http4s.emberServer.value,
+      Dependencies.Weaver.cats.value % Test
+    )
+  )
+  .jvmPlatform(Seq(Scala3), jvmDimSettings)
+  .settings(Smithy4sPlugin.doNotPublishArtifact)
+
 /**
  * Pretty primitive benchmarks to test that we're not doing anything drastically
  * slow.

modules/docs/src/03-protocols/02-simple-rest-json/01-overview.md

@@ -77,3 +77,18 @@ The `SimpleRestJson` protocol supports 3 different union encodings :
 * discriminated
 
 See the section about [unions](../../04-codegen/02-unions.md) for a detailed description.
+
+## Supported traits
+
+Here is the list of traits supported by `SimpleRestJson`
+
+```scala mdoc:passthrough
+smithy4s.api.SimpleRestJson.hints
+  .get[smithy.api.ProtocolDefinition]
+  .getOrElse(sys.error("Unable to grab protocol defition information."))
+  .traits.toList.flatten.map(_.value)
+  .map(id => s"- `$id`")
+  .foreach(println)
+```
+
+Currently, `@cors` is not supported. This is because the `@cors` annotation is too restrictive. You can still use it in your model and configure your API using the information found in the generated code. See the [`Cors.scala`](https://github.com/disneystreaming/smithy4s/tree/main/modules/guides/src/smithy4s/guides/Cors.scala) file in the `guides` module for an example.

modules/guides/smithy/hello.smithy

@@ -0,0 +1,24 @@
+$version: "2"
+
+namespace smithy4s.guides.hello
+
+use smithy4s.api#simpleRestJson
+
+@simpleRestJson
+@cors(origin: "http://mysite.com", additionalAllowedHeaders: ["Authorization"], additionalExposedHeaders: ["X-Smithy4s"])
+service HelloWorldService {
+  version: "1.0.0",
+  operations: [SayWorld]
+}
+
+
+@readonly
+@http(method: "GET", uri: "/hello", code: 200)
+operation SayWorld {
+  output: World
+}
+
+structure World {
+  message: String = "World !"
+}
+

modules/guides/src/smithy4s/guides/Cors.scala

@@ -0,0 +1,108 @@
+/*
+ *  Copyright 2021-2022 Disney Streaming
+ *
+ *  Licensed under the Tomorrow Open Source Technology License, Version 1.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *     https://disneystreaming.github.io/TOST-1.0.txt
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+package smithy4s.guides
+
+import smithy4s.guides.hello._
+import cats.effect.*
+import cats.implicits.*
+import org.http4s.implicits.*
+import org.http4s.ember.server.*
+import org.http4s.*
+import com.comcast.ip4s.*
+import smithy4s.http4s.SimpleRestJsonBuilder
+import org.http4s.server.Middleware
+import org.http4s.headers.Origin
+import org.typelevel.ci.CIString.apply
+import org.typelevel.ci.CIString
+import scala.concurrent.duration.Duration
+
+object HelloWorldImpl extends HelloWorldService[IO] {
+  def sayWorld(): IO[World] = World().pure[IO]
+}
+
+/**
+  * This is an example of how you can configure CORS on a http4s router. The
+  * source of truth for the configuration is the Smithy annotation on the
+  * service. There is currently no support for CORS in Smithy4s because
+  * the `@cors` annotation is a too restrictive.
+  *
+  * See: https://github.com/awslabs/smithy/issues/1396
+  */
+object Routes {
+  import org.http4s.server.middleware.*
+
+  val noMiddleware = (routes: HttpRoutes[IO]) => routes
+
+  /**
+    * We build a http4s CORS policy from the trait values.
+    * In this example, we set a few fields like the `origin`, the `maxAge`, etc
+    * but there is more information available in `smithy.api.Cors`.
+    *
+    * @param corsConfig instance of the trait with values from the specification
+    */
+  def buildHttp4sCors(corsConfig: smithy.api.Cors): CORSPolicy = {
+    val configuredOrigin = Origin.parse(corsConfig.origin.value)
+    configuredOrigin.swap.foreach { err =>
+      // There are better approach for error handling than a println but
+      // this will do for an example.
+      println(
+        s"Could not configure cors origin: ${err.getMessage()}"
+      )
+    }
+    val configuredExposedHeaders =
+      corsConfig.additionalExposedHeaders.toList.flatten
+        .map(_.value)
+        .toSet
+        .map(CIString(_))
+    val configuredAge =
+      Duration(corsConfig.maxAge, scala.concurrent.duration.SECONDS)
+    CORS.policy
+      .withAllowOriginHeader {
+        case Origin.Null => false
+        case o =>
+          configuredOrigin.toOption.exists { co => co == o }
+      }
+      .withExposeHeadersIn(configuredExposedHeaders)
+      .withAllowCredentials(false)
+      .withMaxAge(configuredAge)
+  }
+
+  // We use Smithy4s api to retrieve the trait (called `Hint` in Smithy4s)
+  // We get an `Option` because service are not required to have this trait
+  val corsTrait = HelloWorldServiceGen.hints.get[smithy.api.Cors]
+  val corsMiddleWare = corsTrait
+    .map { corsConfig => buildHttp4sCors(corsConfig).apply(_: HttpRoutes[IO]) }
+    .getOrElse(noMiddleware)
+
+  private val helloRoutes: Resource[IO, HttpRoutes[IO]] =
+    SimpleRestJsonBuilder.routes(HelloWorldImpl).resource
+
+  val all: Resource[IO, HttpRoutes[IO]] =
+    helloRoutes.map(r => corsMiddleWare(r))
+}
+
+object Main extends IOApp.Simple {
+  val run = Routes.all.flatMap { routes =>
+    EmberServerBuilder
+      .default[IO]
+      .withPort(port"9000")
+      .withHost(host"localhost")
+      .withHttpApp(routes.orNotFound)
+      .build
+  }.useForever
+
+}