feat: Add responseModalities to GenerationConfig

Adds an optional `responseModalities` property to the `GenerationConfig`
object in the Vertex AI SDK. This allows specifying the desired modalities
(TEXT, IMAGE, AUDIO) for the response.

Includes updates to the `GenerationConfig.Builder` and internal
serialization logic.

Adds unit tests to verify:
- `response_modalities` field is omitted when null.
- Correct serialization for all modalities ([TEXT, IMAGE, AUDIO]).
- Correct serialization for a subset of modalities ([TEXT, IMAGE]).

Author: google-labs-jules[bot]

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/type/GenerationConfig.kt

@@ -16,6 +16,7 @@
 
 package com.google.firebase.vertexai.type
 
+import com.google.firebase.vertexai.type.ResponseModality // Added import
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
 
@@ -88,6 +89,7 @@ private constructor(
   internal val stopSequences: List<String>?,
   internal val responseMimeType: String?,
   internal val responseSchema: Schema?,
+  internal val responseModalities: List<ResponseModality>?, // Added property
 ) {
 
   /**
@@ -128,6 +130,7 @@ private constructor(
     @JvmField public var stopSequences: List<String>? = null
     @JvmField public var responseMimeType: String? = null
     @JvmField public var responseSchema: Schema? = null
+    @JvmField public var responseModalities: List<ResponseModality>? = null // Added property
 
     /** Create a new [GenerationConfig] with the attached arguments. */
     public fun build(): GenerationConfig =
@@ -142,6 +145,7 @@ private constructor(
         frequencyPenalty = frequencyPenalty,
         responseMimeType = responseMimeType,
         responseSchema = responseSchema,
+         responseModalities = responseModalities, // Added property
       )
   }
 
@@ -156,7 +160,9 @@ private constructor(
       frequencyPenalty = frequencyPenalty,
       presencePenalty = presencePenalty,
       responseMimeType = responseMimeType,
-      responseSchema = responseSchema?.toInternal()
+       responseSchema = responseSchema?.toInternal(),
+        // Pass the responseModalities to the Internal class constructor
+        responseModalities = this.responseModalities 
     )
 
   @Serializable
@@ -171,6 +177,7 @@ private constructor(
     @SerialName("presence_penalty") val presencePenalty: Float? = null,
     @SerialName("frequency_penalty") val frequencyPenalty: Float? = null,
     @SerialName("response_schema") val responseSchema: Schema.Internal? = null,
+     @SerialName("response_modalities") val responseModalities: List<ResponseModality>? = null, // Added property
   )
 
   public companion object {

firebase-vertexai/src/test/kotlin/com/google/firebase/vertexai/type/GenerationConfigTests.kt

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * 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 com.google.firebase.vertexai.type
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
+
+class GenerationConfigTests {
+
+  @Test
+  fun `serialization omits null responseModalities`() {
+    val config = generationConfig { /* No responseModalities set */ }
+    val internalConfig = config.toInternal()
+    val jsonString = Json.encodeToString(internalConfig)
+    val jsonObject = Json.parseToJsonElement(jsonString).jsonObject
+
+    assertFalse(jsonObject.containsKey("response_modalities"))
+  }
+
+  @Test
+  fun `serialization includes all responseModalities`() {
+    val config = generationConfig {
+      responseModalities = listOf(ResponseModality.TEXT, ResponseModality.IMAGE, ResponseModality.AUDIO)
+    }
+    val internalConfig = config.toInternal()
+    val jsonString = Json.encodeToString(internalConfig)
+    val jsonObject = Json.parseToJsonElement(jsonString).jsonObject
+
+    // Assert the JSON output contains the correct array for response_modalities
+    assertEquals(
+      """["TEXT","IMAGE","AUDIO"]""",
+      jsonObject["response_modalities"].toString()
+    )
+  }
+
+    @Test
+    fun `serialization includes some responseModalities`() {
+        val config = generationConfig {
+            responseModalities = listOf(ResponseModality.TEXT, ResponseModality.IMAGE)
+        }
+        val internalConfig = config.toInternal()
+        val jsonString = Json.encodeToString(internalConfig)
+        val jsonObject = Json.parseToJsonElement(jsonString).jsonObject
+
+        // Assert the JSON output contains the correct array for response_modalities
+        assertEquals(
+            """["TEXT","IMAGE"]""",
+            jsonObject["response_modalities"].toString()
+        )
+    }
+
+    // TODO: Add tests for other properties as well
+    @Test
+    fun `serialization includes temperature`() {
+        val temp = 0.8f
+        val config = generationConfig { temperature = temp }
+        val internalConfig = config.toInternal()
+        val jsonString = Json.encodeToString(internalConfig)
+        val jsonObject = Json.parseToJsonElement(jsonString).jsonObject
+
+        assertEquals(temp, jsonObject["temperature"]?.jsonPrimitive?.content?.toFloat())
+    }
+}