chore(model-server): revert previously introduced openapi gradle subproject

Author: nkoester

api/build.gradle.kts

@@ -81,7 +81,6 @@ ktor-serialization-json = { group = "io.ktor", name = "ktor-serialization-kotlin
 keycloak-authz-client = { group = "org.keycloak", name = "keycloak-authz-client", version = "23.0.3" }
 guava = { group = "com.google.guava", name = "guava", version = "32.1.3-jre" }
 org-json = { group = "org.json", name = "json", version = "20231013" }
-google-gson = { group = "com.google.code.gson", name = "gson", version = "2.10.1" }
 google-oauth-client = { group = "com.google.oauth-client", name = "google-oauth-client", version = "1.34.1" }
 google-oauth-clientjetty = { group = "com.google.oauth-client", name = "google-oauth-client-jetty", version = "1.34.1" }
 

gradle/libs.versions.toml

@@ -1,5 +1,6 @@
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 import com.github.jengelman.gradle.plugins.shadow.transformers.PropertiesFileTransformer
+import org.openapitools.generator.gradle.plugin.tasks.GenerateTask
 
 plugins {
     application
@@ -9,6 +10,7 @@ plugins {
     alias(libs.plugins.shadow)
     kotlin("jvm")
     kotlin("plugin.serialization")
+    alias(libs.plugins.openapi.generator)
 }
 
 description = "Model Server offering access to model storage"
@@ -28,7 +30,6 @@ dependencies {
     implementation(libs.kotlin.serialization.json)
     implementation(libs.kotlin.coroutines.core)
 
-    implementation(project(":api"))
     implementation(project(":model-api"))
     implementation(project(":model-server-api"))
     implementation(project(":model-client", configuration = "jvmRuntimeElements"))
@@ -123,7 +124,7 @@ val cucumber = task("cucumber") {
 // copies the openAPI specifications from the api folder into a resource
 // folder so that they are packaged and deployed with the model-server
 tasks.register<Copy>("copyApis") {
-    from(project(":api").layout.projectDirectory.dir("openapi/specifications"))
+    from(project.layout.projectDirectory.dir("../model-server-openapi/specifications"))
     include("*.yaml")
     into(project.layout.buildDirectory.dir("openapi/src/main/resources/api"))
     sourceSets["main"].resources.srcDir(project.layout.buildDirectory.dir("openapi/src/main/resources/"))
@@ -214,3 +215,86 @@ spotless {
                 '\n'*/
     }
 }
+
+// OpenAPI integration
+val basePackage = project.group.toString()
+val openAPIgenerationPath = "${project.layout.buildDirectory.get()}/generated/openapi"
+
+// Pairs of the different OpenAPI files we use. Each pair must have its own 'category' as first argument as these
+// are used to generate corresponding packages
+val openApiFiles = listOf(
+    "public" to "model-server",
+    "operative" to "model-server-operative",
+    "light" to "model-server-light",
+    "html" to "model-server-html",
+    "deprecated" to "model-server-deprecated",
+)
+
+// generate tasks for each OpenAPI file
+openApiFiles.forEach {
+    val targetTaskName = "openApiGenerate-${it.second}"
+    val targetPackageName = "$basePackage.api.${it.first}"
+    val outputPath = "$openAPIgenerationPath/${it.first}"
+    tasks.register<GenerateTask>(targetTaskName) {
+        // we let the Gradle OpenAPI generator plugin build data classes and API interfaces based on the provided
+        // OpenAPI specification. That way, the code is forced to stay in sync with the API specification.
+        generatorName.set("kotlin-server")
+        inputSpec.set(layout.projectDirectory.dir("../model-server-openapi/specifications").file("${it.second}.yaml").toString())
+        outputDir.set(outputPath)
+        packageName.set(targetPackageName)
+        apiPackage.set(targetPackageName)
+        modelPackage.set(targetPackageName)
+        // We use patched mustache so that only the necessary parts (i.e. resources and models)
+        // are generated. additionally we patch the used serialization framework as the `ktor` plugin
+        // uses a different one than we do in the model-server. The templates are based on
+        // https://github.com/OpenAPITools/openapi-generator/tree/809b3331a95b3c3b7bcf025d16ae09dc0682cd69/modules/openapi-generator/src/main/resources/kotlin-server
+        templateDir.set("${layout.projectDirectory.dir("src/main/resources/openapi/templates")}")
+        configOptions.set(
+            mapOf(
+                // we use the ktor generator to generate server side resources and model (i.e. data classes)
+                "library" to "ktor",
+                // the generated artifacts are not built independently, thus no dedicated build files have to be generated
+                "omitGradleWrapper" to "true",
+                // the path to resource generation we need
+                "featureResources" to "true",
+                // disable features we do not use
+                "featureAutoHead" to "false",
+                "featureCompression" to "false",
+                "featureHSTS" to "false",
+                "featureMetrics" to "false",
+            ),
+        )
+        // generate only Paths and Models - only this set will produce the intended Paths.kt as well as the models
+        // the openapi generator is generally very picky and configuring it is rather complex
+        globalProperties.putAll(
+            mapOf(
+                "models" to "",
+                "apis" to "",
+                "supportingFiles" to "Paths.kt",
+            ),
+        )
+    }
+
+    // Ensure that the OpenAPI generator runs before starting to compile
+    tasks.named("processResources") {
+        dependsOn(targetTaskName)
+    }
+    tasks.named("compileKotlin") {
+        dependsOn(targetTaskName)
+    }
+    tasks.named("runKtlintCheckOverMainSourceSet") {
+        dependsOn(targetTaskName)
+    }
+
+    // do not apply ktlint on the generated files
+    ktlint {
+        filter {
+            exclude {
+                it.file.toPath().toAbsolutePath().startsWith(outputPath)
+            }
+        }
+    }
+
+    // add openAPI generated artifacts to the sourceSets
+    sourceSets["main"].kotlin.srcDir("$outputPath/src/main/kotlin")
+}