Build Protobuf Files for App

The following PR makes sure, that the proto file which is put inside
the app/src/main/proto folder correctly generates the corresponding
services.

app/build.gradle.kts

@@ -17,6 +17,7 @@
 plugins {
     alias(libs.plugins.android.application)
     alias(libs.plugins.kotlin.android)
+    alias(libs.plugins.protobuf)
 }
 
 android {
@@ -51,9 +52,53 @@ android {
     }
 }
 
+protobuf {
+    protoc {
+        artifact = libs.protoc.asProvider().get().toString()
+    }
+    plugins {
+        create("java") {
+            artifact = libs.protoc.gen.grpc.java.get().toString()
+        }
+        create("grpc") {
+            artifact = libs.protoc.gen.grpc.java.get().toString()
+        }
+        create("grpckt") {
+            artifact = libs.protoc.gen.grpc.kotlin.get().toString() + ":jdk8@jar"
+        }
+    }
+    generateProtoTasks {
+        all().forEach {
+            it.builtins {
+                create("java") {
+                    option("lite")
+                }
+                create("kotlin") {
+                    option("lite")
+                }
+            }
+            it.plugins {
+                create("grpc") {
+                    option("lite")
+                }
+                create("grpckt") {
+                    option("lite")
+                }
+            }
+        }
+    }
+}
+
 dependencies {
     implementation(project(":sdk"))
 
+    implementation(libs.grpc.okhttp)
+    implementation(libs.grpc.protobuf.lite)
+    implementation(libs.grpc.stub)
+    implementation(libs.grpc.kotlin.stub)
+
+    implementation(libs.protobuf.kotlin.lite)
+
     implementation(libs.androidx.fragment.ktx)
 
     implementation(libs.androidx.car.app)

app/src/main/java/com/example/service/CarService.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2024 Contributors to the Eclipse Foundation
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License, Version 2.0 which is available at
+ * https://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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.example.service
+
+interface CarService {
+    fun lockDoor(): Boolean
+    fun unlockDoor(): Boolean
+}

app/src/main/java/com/example/service/GrpcCarService.kt

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2024 Contributors to the Eclipse Foundation
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License, Version 2.0 which is available at
+ * https://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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.example.service
+
+import android.util.Log
+import door.DoorGrpc
+import door.DoorGrpc.DoorFutureStub
+import door.DoorService
+import io.grpc.Grpc
+import io.grpc.InsecureChannelCredentials
+
+private const val TAG = "SampleServiceImpl"
+
+class GrpcCarService(
+    host: String,
+    port: Int,
+) : CarService {
+
+    private val doorService: DoorFutureStub
+
+    init {
+        Log.i(TAG, "Connecting to gRPC service at $host:$port")
+
+        val channelCredentials = InsecureChannelCredentials.create()
+        val channel = Grpc.newChannelBuilderForAddress(host, port, channelCredentials).build()
+
+        doorService = DoorGrpc.newFutureStub(channel)
+    }
+
+    // Door service
+    override fun lockDoor(): Boolean {
+        val request = DoorService.LockRequest.newBuilder().build()
+        val response = doorService.lock(request).get() // blocking call
+        Log.i(TAG, "lockDoor: Got response: " + response.getCode())
+        return response.getCode() == DoorService.BCMReturnCode.BCM_RETURN_CODE_SUCCESS
+    }
+
+    override fun unlockDoor(): Boolean {
+        val request = DoorService.UnlockRequest.newBuilder().build()
+        val response = doorService.unlock(request).get() // blocking call
+        Log.i(TAG, "unlockDoor: Got response: " + response.getCode())
+        return response.getCode() == DoorService.BCMReturnCode.BCM_RETURN_CODE_SUCCESS
+    }
+}

app/src/proto/door.proto → app/src/main/proto/door.proto

@@ -2,7 +2,11 @@
  * Provides door control and status service, one atomic service for each door.
  */
 syntax = "proto3";
+
 package door;
+
+option java_outer_classname = "DoorService";
+
 service Door {
   /* Unlock the door. */
   rpc Unlock(UnlockRequest) returns (UnlockResponse);