build: rewrite build.gradle files to Kotlin DSL

build.gradle.kts

@@ -0,0 +1,47 @@
+import com.android.build.gradle.internal.tasks.factory.dependsOn
+import java.io.File
+import java.net.URI
+
+plugins {
+    id("com.android.application") version "8.5.0" apply false
+    id("org.jetbrains.kotlin.android") version "2.0.0" apply false
+    id("org.hidetake.swagger.generator") version "2.19.2"
+}
+
+fun download(url: String, filename: String) {
+    URI(url).toURL().openConnection().let { conn ->
+        File(filename).outputStream().use { out ->
+            conn.inputStream.use { inp ->
+                inp.copyTo(out)
+            }
+        }
+    }
+}
+
+tasks.register("downloadSpec") {
+    val gotifyVersion = "master"
+    val url = "https://raw.githubusercontent.com/gotify/server/$gotifyVersion/docs/spec.json"
+    val buildDir = project.layout.buildDirectory.get()
+    val specLocation = buildDir.file("gotify.spec.json").asFile.absolutePath
+    doFirst {
+        buildDir.asFile.mkdirs()
+        download(url, specLocation)
+    }
+}
+
+swaggerSources {
+    create("swagger") {
+        setInputFile(file("$projectDir/build/gotify.spec.json"))
+        code.apply {
+            language = "java"
+            configFile = file("$projectDir/swagger.config.json")
+            outputDir = file("$projectDir/client")
+        }
+    }
+}
+
+dependencies {
+    "swaggerCodegen"("io.swagger.codegen.v3:swagger-codegen-cli:3.0.63")
+}
+
+tasks.named("generateSwaggerCode").dependsOn("downloadSpec")