Add function calling support (google-gemini#116)

Author: andrewheard

Sources/GoogleAI/Chat.swift

@@ -30,11 +30,7 @@ public class Chat {
   /// model. This will be provided to the model for each message sent as context for the discussion.
   public var history: [ModelContent]
 
-  /// Sends a message using the existing history of this chat as context. If successful, the message
-  /// and response will be added to the history. If unsuccessful, history will remain unchanged.
-  /// - Parameter parts: The new content to send as a single chat message.
-  /// - Returns: The model's response if no error occurred.
-  /// - Throws: A ``GenerateContentError`` if an error occurred.
+  /// See ``sendMessage(_:)-3ify5``.
   public func sendMessage(_ parts: any ThrowingPartsRepresentable...) async throws
     -> GenerateContentResponse {
     return try await sendMessage([ModelContent(parts: parts)])
@@ -102,10 +98,7 @@ public class Chat {
     return try await sendMessage([functionResponseContent])
   }
 
-  /// Sends a message using the existing history of this chat as context. If successful, the message
-  /// and response will be added to the history. If unsuccessful, history will remain unchanged.
-  /// - Parameter parts: The new content to send as a single chat message.
-  /// - Returns: A stream containing the model's response or an error if an error occurred.
+  /// See ``sendMessageStream(_:)-4abs3``.
   @available(macOS 12.0, *)
   public func sendMessageStream(_ parts: any ThrowingPartsRepresentable...)
     -> AsyncThrowingStream<GenerateContentResponse, Error> {
@@ -182,7 +175,7 @@ public class Chat {
         case let .text(str):
           combinedText += str
 
-        case .data, .fileData, .functionCall, .functionResponse:
+        case .data, .functionCall, .functionResponse:
           // Don't combine it, just add to the content. If there's any text pending, add that as
           // a part.
           if !combinedText.isEmpty {