Function calling (common only) (#97)

Based on work from
https://github.com/google/generative-ai-android/tree/davidmotson.auto_function_split

---------

Co-authored-by: David Motsonashvili <davidmotson@google.com>
Co-authored-by: David Motsonashvili <davidmotson@gmail.com>

common/src/main/kotlin/com/google/ai/client/generativeai/common/Request.kt

@@ -17,6 +17,7 @@
 package com.google.ai.client.generativeai.common
 
 import com.google.ai.client.generativeai.common.client.GenerationConfig
+import com.google.ai.client.generativeai.common.client.Tool
 import com.google.ai.client.generativeai.common.shared.Content
 import com.google.ai.client.generativeai.common.shared.SafetySetting
 import kotlinx.serialization.SerialName
@@ -30,6 +31,7 @@ data class GenerateContentRequest(
   val contents: List<Content>,
   @SerialName("safety_settings") val safetySettings: List<SafetySetting>? = null,
   @SerialName("generation_config") val generationConfig: GenerationConfig? = null,
+  val tools: List<Tool>? = null,
 ) : Request
 
 @Serializable

common/src/main/kotlin/com/google/ai/client/generativeai/common/RequestOptions.kt

@@ -31,16 +31,16 @@ import kotlin.time.toDuration
 class RequestOptions(
   val timeout: Duration,
   val apiVersion: String = "v1",
-  val endpoint: String = "https://generativelanguage.googleapis.com"
+  val endpoint: String = "https://generativelanguage.googleapis.com",
 ) {
   @JvmOverloads
   constructor(
     timeout: Long? = HttpTimeout.INFINITE_TIMEOUT_MS,
     apiVersion: String = "v1",
-    endpoint: String = "https://generativelanguage.googleapis.com"
+    endpoint: String = "https://generativelanguage.googleapis.com",
   ) : this(
     (timeout ?: HttpTimeout.INFINITE_TIMEOUT_MS).toDuration(DurationUnit.MILLISECONDS),
     apiVersion,
-    endpoint
+    endpoint,
   )
 }

common/src/main/kotlin/com/google/ai/client/generativeai/common/client/Types.kt

@@ -26,5 +26,25 @@ data class GenerationConfig(
   @SerialName("top_k") val topK: Int?,
   @SerialName("candidate_count") val candidateCount: Int?,
   @SerialName("max_output_tokens") val maxOutputTokens: Int?,
-  @SerialName("stop_sequences") val stopSequences: List<String>?
+  @SerialName("stop_sequences") val stopSequences: List<String>?,
+)
+
+@Serializable data class Tool(val functionDeclarations: List<FunctionDeclaration>)
+
+@Serializable
+data class FunctionDeclaration(
+  val name: String,
+  val description: String,
+  val parameters: Schema,
+)
+
+@Serializable
+data class Schema(
+  val type: String,
+  val description: String? = null,
+  val format: String? = null,
+  val enum: List<String>? = null,
+  val properties: Map<String, Schema>? = null,
+  val required: List<String>? = null,
+  val items: Schema? = null,
 )

common/src/main/kotlin/com/google/ai/client/generativeai/common/shared/Types.kt

@@ -26,6 +26,7 @@ import kotlinx.serialization.Serializable
 import kotlinx.serialization.SerializationException
 import kotlinx.serialization.json.JsonContentPolymorphicSerializer
 import kotlinx.serialization.json.JsonElement
+import kotlinx.serialization.json.JsonObject
 import kotlinx.serialization.json.jsonObject
 
 object HarmCategorySerializer :
@@ -52,6 +53,14 @@ data class Content(@EncodeDefault val role: String? = "user", val parts: List<Pa
 
 @Serializable data class BlobPart(@SerialName("inline_data") val inlineData: Blob) : Part
 
+@Serializable data class FunctionCallPart(val functionCall: FunctionCall) : Part
+
+@Serializable data class FunctionResponsePart(val functionResponse: FunctionResponse) : Part
+
+@Serializable data class FunctionResponse(val name: String, val response: JsonObject)
+
+@Serializable data class FunctionCall(val name: String, val args: Map<String, String>)
+
 @Serializable data class FileDataPart(@SerialName("file_data") val fileData: FileData) : Part
 
 @Serializable
@@ -83,6 +92,8 @@ object PartSerializer : JsonContentPolymorphicSerializer<Part>(Part::class) {
     val jsonObject = element.jsonObject
     return when {
       "text" in jsonObject -> TextPart.serializer()
+      "functionCall" in jsonObject -> FunctionCallPart.serializer()
+      "functionResponse" in jsonObject -> FunctionResponsePart.serializer()
       "inline_data" in jsonObject -> BlobPart.serializer()
       "file_data" in jsonObject -> FileDataPart.serializer()
       else -> throw SerializationException("Unknown Part type")