feat: type discriminator field in the search API response (#24)

modules/search-api/src/main/scala/io/renku/search/api/HttpApplication.scala

@@ -21,7 +21,6 @@ package io.renku.search.api
 import cats.effect.{Async, Resource}
 import cats.syntax.all.*
 import fs2.io.net.Network
-import io.renku.search.api.Project.given
 import io.renku.search.http.borer.TapirBorerJson
 import io.renku.solr.client.SolrConfig
 import org.http4s.dsl.Http4sDsl
@@ -60,13 +59,14 @@ class HttpApplication[F[_]: Async](searchApi: SearchApi[F])
       searchEndpoint.serverLogic(searchApi.find)
     )
 
-  private lazy val searchEndpoint: PublicEndpoint[String, String, List[Project], Any] =
+  private lazy val searchEndpoint
+      : PublicEndpoint[String, String, List[SearchEntity], Any] =
     val query =
       path[String].name("user query").description("User defined query e.g. renku~")
     endpoint.get
       .in(query)
       .errorOut(borerJsonBody[String])
-      .out(borerJsonBody[List[Project]])
+      .out(borerJsonBody[List[SearchEntity]])
       .description("Search API for searching Renku entities")
 
   private lazy val swaggerEndpoints =

modules/search-api/src/main/scala/io/renku/search/api/SearchApi.scala

@@ -24,7 +24,7 @@ import io.renku.search.solr.client.SearchSolrClient
 import io.renku.solr.client.SolrConfig
 
 trait SearchApi[F[_]]:
-  def find(phrase: String): F[Either[String, List[Project]]]
+  def find(phrase: String): F[Either[String, List[SearchEntity]]]
 
 object SearchApi:
   def apply[F[_]: Async: Network](

modules/search-api/src/main/scala/io/renku/search/api/SearchApiImpl.scala

@@ -31,12 +31,13 @@ private class SearchApiImpl[F[_]: Async](solrClient: SearchSolrClient[F])
 
   private given Scribe[F] = scribe.cats[F]
 
-  override def find(phrase: String): F[Either[String, List[Project]]] =
+  override def find(phrase: String): F[Either[String, List[SearchEntity]]] =
     solrClient
       .findProjects(phrase)
       .map(toApiModel)
       .map(_.asRight[String])
       .handleErrorWith(errorResponse(phrase))
+      .widen
 
   private def errorResponse(
       phrase: String

modules/search-api/src/main/scala/io/renku/search/api/SearchEntity.scala

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2024 Swiss Data Science Center (SDSC)
+ * A partnership between École Polytechnique Fédérale de Lausanne (EPFL) and
+ * Eidgenössische Technische Hochschule Zürich (ETHZ).
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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 io.renku.search.api
+
+import io.bullet.borer.derivation.MapBasedCodecs.{deriveAllCodecs, deriveCodec}
+import io.bullet.borer.{AdtEncodingStrategy, Codec, Decoder, Encoder}
+import io.renku.search.model.*
+import sttp.tapir.Schema.SName
+import sttp.tapir.SchemaType.{SDateTime, SProductField}
+import sttp.tapir.generic.Configuration
+import sttp.tapir.{FieldName, Schema, SchemaType}
+
+sealed trait SearchEntity
+
+final case class Project(
+    id: projects.Id,
+    name: projects.Name,
+    slug: projects.Slug,
+    repositories: Seq[projects.Repository],
+    visibility: projects.Visibility,
+    description: Option[projects.Description] = None,
+    createdBy: User,
+    creationDate: projects.CreationDate,
+    members: Seq[User]
+) extends SearchEntity
+
+object Project:
+  private given Schema[projects.Id] = Schema.string[projects.Id]
+  private given Schema[projects.Name] = Schema.string[projects.Name]
+  private given Schema[projects.Slug] = Schema.string[projects.Slug]
+  private given Schema[projects.Repository] = Schema.string[projects.Repository]
+  private given Schema[projects.Visibility] =
+    Schema.derivedEnumeration[projects.Visibility].defaultStringBased
+  private given Schema[projects.Description] = Schema.string[projects.Description]
+  private given Schema[projects.CreationDate] = Schema(SDateTime())
+  given Schema[Project] = Schema.derived[Project]
+
+final case class User(
+    id: users.Id
+)
+
+object User:
+  given Codec[User] = deriveCodec[User]
+
+  private given Schema[users.Id] = Schema.string[users.Id]
+  given Schema[User] = Schema.derived[User]
+
+object SearchEntity:
+
+  private val discriminatorField = "type"
+  given AdtEncodingStrategy = AdtEncodingStrategy.flat(discriminatorField)
+  given Codec[SearchEntity] = deriveAllCodecs[SearchEntity]
+
+  given Schema[SearchEntity] = {
+    val derived = Schema.derived[SearchEntity]
+    derived.schemaType match {
+      case s: SchemaType.SCoproduct[_] =>
+        derived.copy(schemaType =
+          s.addDiscriminatorField(
+            FieldName(discriminatorField),
+            Schema.string,
+            List(
+              implicitly[Schema[Project]].name.map(SchemaType.SRef(_)).map("Project" -> _)
+            ).flatten.toMap
+          )
+        )
+      case s => derived
+    }
+  }