improvements(ai): Improve AI streaming UI/UX interactions + better separation of AI provider responsibilities (#2039)

* Start refactor

* Interface updates

* Rework Assistant, Provider, and tests for better domain boundaries

* Consolidate and simplify OpenAI provider and provider concepts

* Clean up assistant streaming

* Improve assistant message orchestration logic

* Clean up "thinking" UI interactions

* Remove stale class

* Regenerate VCR test responses

test/models/assistant_test.rb

@@ -1,5 +1,4 @@
 require "test_helper"
-require "ostruct"
 
 class AssistantTest < ActiveSupport::TestCase
   include ProviderTestHelper
@@ -8,74 +7,109 @@ class AssistantTest < ActiveSupport::TestCase
     @chat = chats(:two)
     @message = @chat.messages.create!(
       type: "UserMessage",
-      content: "Help me with my finances",
+      content: "What is my net worth?",
       ai_model: "gpt-4o"
     )
     @assistant = Assistant.for_chat(@chat)
     @provider = mock
-    @assistant.expects(:get_model_provider).with("gpt-4o").returns(@provider)
   end
 
-  test "responds to basic prompt" do
-    text_chunk = OpenStruct.new(type: "output_text", data: "Hello from assistant")
-    response_chunk = OpenStruct.new(
-    type: "response",
-    data: OpenStruct.new(
-      id: "1",
-      model: "gpt-4o",
-      messages: [
-        OpenStruct.new(
-          id: "1",
-          content: "Hello from assistant",
-        )
-      ],
-      functions: []
-    )
-  )
+  test "errors get added to chat" do
+    @assistant.expects(:get_model_provider).with("gpt-4o").returns(@provider)
 
-    @provider.expects(:chat_response).with do |message, **options|
-      options[:streamer].call(text_chunk)
-      options[:streamer].call(response_chunk)
-      true
-    end
+    error = StandardError.new("test error")
+    @provider.expects(:chat_response).returns(provider_error_response(error))
 
-    assert_difference "AssistantMessage.count", 1 do
+    @chat.expects(:add_error).with(error).once
+
+    assert_no_difference "AssistantMessage.count"  do
       @assistant.respond_to(@message)
     end
   end
 
-  test "responds with tool function calls" do
-    function_request_chunk = OpenStruct.new(type: "function_request", data: "get_net_worth")
-    text_chunk = OpenStruct.new(type: "output_text", data: "Your net worth is $124,200")
-    response_chunk = OpenStruct.new(
-      type: "response",
-      data: OpenStruct.new(
-        id: "1",
-        model: "gpt-4o",
-        messages: [
-          OpenStruct.new(
-            id: "1",
-            content: "Your net worth is $124,200",
-          )
-        ],
-        functions: [
-          OpenStruct.new(
-            id: "1",
-            call_id: "1",
-            name: "get_net_worth",
-            arguments: "{}",
-            result: "$124,200"
-          )
-        ]
-      )
+  test "responds to basic prompt" do
+    @assistant.expects(:get_model_provider).with("gpt-4o").returns(@provider)
+
+    text_chunks = [
+      provider_text_chunk("I do not "),
+      provider_text_chunk("have the information "),
+      provider_text_chunk("to answer that question")
+    ]
+
+    response_chunk = provider_response_chunk(
+      id: "1",
+      model: "gpt-4o",
+      messages: [ provider_message(id: "1", text: text_chunks.join) ],
+      function_requests: []
     )
 
+    response = provider_success_response(response_chunk.data)
+
     @provider.expects(:chat_response).with do |message, **options|
-      options[:streamer].call(function_request_chunk)
-      options[:streamer].call(text_chunk)
+      text_chunks.each do |text_chunk|
+        options[:streamer].call(text_chunk)
+      end
+
       options[:streamer].call(response_chunk)
       true
+    end.returns(response)
+
+    assert_difference "AssistantMessage.count", 1 do
+      @assistant.respond_to(@message)
+      message = @chat.messages.ordered.where(type: "AssistantMessage").last
+      assert_equal "I do not have the information to answer that question", message.content
+      assert_equal 0, message.tool_calls.size
     end
+  end
+
+  test "responds with tool function calls" do
+    @assistant.expects(:get_model_provider).with("gpt-4o").returns(@provider).once
+
+    # Only first provider call executes function
+    Assistant::Function::GetAccounts.any_instance.stubs(:call).returns("test value").once
+
+    # Call #1: Function requests
+    call1_response_chunk = provider_response_chunk(
+      id: "1",
+      model: "gpt-4o",
+      messages: [],
+      function_requests: [
+        provider_function_request(id: "1", call_id: "1", function_name: "get_accounts", function_args: "{}")
+      ]
+    )
+
+    call1_response = provider_success_response(call1_response_chunk.data)
+
+    # Call #2: Text response (that uses function results)
+    call2_text_chunks = [
+      provider_text_chunk("Your net worth is "),
+      provider_text_chunk("$124,200")
+    ]
+
+    call2_response_chunk = provider_response_chunk(
+      id: "2",
+      model: "gpt-4o",
+      messages: [ provider_message(id: "1", text: call2_text_chunks.join) ],
+      function_requests: []
+    )
+
+    call2_response = provider_success_response(call2_response_chunk.data)
+
+    sequence = sequence("provider_chat_response")
+
+    @provider.expects(:chat_response).with do |message, **options|
+      call2_text_chunks.each do |text_chunk|
+        options[:streamer].call(text_chunk)
+      end
+
+      options[:streamer].call(call2_response_chunk)
+      true
+    end.returns(call2_response).once.in_sequence(sequence)
+
+    @provider.expects(:chat_response).with do |message, **options|
+      options[:streamer].call(call1_response_chunk)
+      true
+    end.returns(call1_response).once.in_sequence(sequence)
 
     assert_difference "AssistantMessage.count", 1 do
       @assistant.respond_to(@message)
@@ -83,4 +117,34 @@ class AssistantTest < ActiveSupport::TestCase
       assert_equal 1, message.tool_calls.size
     end
   end
+
+  private
+    def provider_function_request(id:, call_id:, function_name:, function_args:)
+      Provider::LlmConcept::ChatFunctionRequest.new(
+        id: id,
+        call_id: call_id,
+        function_name: function_name,
+        function_args: function_args
+      )
+    end
+
+    def provider_message(id:, text:)
+      Provider::LlmConcept::ChatMessage.new(id: id, output_text: text)
+    end
+
+    def provider_text_chunk(text)
+      Provider::LlmConcept::ChatStreamChunk.new(type: "output_text", data: text)
+    end
+
+    def provider_response_chunk(id:, model:, messages:, function_requests:)
+      Provider::LlmConcept::ChatStreamChunk.new(
+        type: "response",
+        data: Provider::LlmConcept::ChatResponse.new(
+          id: id,
+          model: model,
+          messages: messages,
+          function_requests: function_requests
+        )
+      )
+    end
 end