[Vertex AI] Replace ModelContent.Part enum with protocol/structs

Author: andrewheard

FirebaseVertexAI/Sample/FunctionCallingSample/ViewModels/FunctionCallingViewModel.swift

@@ -144,14 +144,14 @@ class FunctionCallingViewModel: ObservableObject {
 
     for part in candidate.content.parts {
       switch part {
-      case let .text(text):
+      case let text as TextPart:
         // replace pending message with backend response
-        messages[messages.count - 1].message += text
+        messages[messages.count - 1].message += text.textValue
         messages[messages.count - 1].pending = false
-      case let .functionCall(functionCall):
+      case let functionCall as FunctionCall:
         messages.insert(functionCall.chatMessage(), at: messages.count - 1)
         functionCalls.append(functionCall)
-      case .inlineData, .fileData, .functionResponse:
+      default:
         fatalError("Unsupported response content.")
       }
     }
@@ -250,10 +250,6 @@ private extension FunctionResponse {
 
 private extension [FunctionResponse] {
   func modelContent() -> [ModelContent] {
-    return self.map { ModelContent(
-      role: "function",
-      parts: [ModelContent.Part.functionResponse($0)]
-    )
-    }
+    return self.map { ModelContent(role: "function", parts: [$0]) }
   }
 }

FirebaseVertexAI/Sources/Chat.swift

@@ -146,20 +146,20 @@ public class Chat {
   }
 
   private func aggregatedChunks(_ chunks: [ModelContent]) -> ModelContent {
-    var parts: [ModelContent.Part] = []
+    var parts: [any ModelContent.Part] = []
     var combinedText = ""
     for aggregate in chunks {
       // Loop through all the parts, aggregating the text and adding the images.
       for part in aggregate.parts {
         switch part {
-        case let .text(str):
-          combinedText += str
+        case let textPart as TextPart:
+          combinedText += textPart.textValue
 
-        case .inlineData, .fileData, .functionCall, .functionResponse:
+        default:
           // Don't combine it, just add to the content. If there's any text pending, add that as
           // a part.
           if !combinedText.isEmpty {
-            parts.append(.text(combinedText))
+            parts.append(TextPart(text: combinedText))
             combinedText = ""
           }
 
@@ -169,7 +169,7 @@ public class Chat {
     }
 
     if !combinedText.isEmpty {
-      parts.append(.text(combinedText))
+      parts.append(TextPart(text: combinedText))
     }
 
     return ModelContent(role: "model", parts: parts)

FirebaseVertexAI/Sources/GenerateContentResponse.swift

@@ -49,10 +49,10 @@ public struct GenerateContentResponse: Sendable {
       return nil
     }
     let textValues: [String] = candidate.content.parts.compactMap { part in
-      guard case let .text(text) = part else {
+      guard let textPart = part as? TextPart else {
         return nil
       }
-      return text
+      return textPart.textValue
     }
     guard textValues.count > 0 else {
       VertexLog.error(
@@ -70,7 +70,7 @@ public struct GenerateContentResponse: Sendable {
       return []
     }
     return candidate.content.parts.compactMap { part in
-      guard case let .functionCall(functionCall) = part else {
+      guard let functionCall = part as? FunctionCall else {
         return nil
       }
       return functionCall