feat(chat): Implement real-time SSE streaming with reasoning steps and improved UI indicators.

frontend/src/services/chat.test.ts

@@ -0,0 +1,67 @@
+import { describe, it, expect, vi } from "vitest"
+import { ChatService, type ChatEvent } from "./chat"
+
+describe("ChatService SSE Parsing", () => {
+  it("should correctly parse a text stream chunk", () => {
+    const rawChunk = `data: {"type": "on_chat_model_stream", "name": "summarizer", "data": {"chunk": "Hello"}}\n\n`
+    const events = ChatService.parseSSEChunk(rawChunk)
+    
+    expect(events).toHaveLength(1)
+    expect(events[0]).toEqual({
+      type: "on_chat_model_stream",
+      name: "summarizer",
+      data: { chunk: "Hello" }
+    })
+  })
+
+  it("should handle multiple events in one chunk", () => {
+    const rawChunk = 
+      `data: {"type": "on_chat_model_stream", "name": "summarizer", "data": {"chunk": "Hello"}}\n\n` +
+      `data: {"type": "on_chat_model_stream", "name": "summarizer", "data": {"chunk": " World"}}\n\n`
+    
+    const events = ChatService.parseSSEChunk(rawChunk)
+    
+    expect(events).toHaveLength(2)
+    expect(events[1].data.chunk).toBe(" World")
+  })
+
+  it("should parse encoded plots from executor node", () => {
+    const rawChunk = `data: {"type": "on_chain_end", "name": "executor", "data": {"encoded_plots": ["base64data"]}}\n\n`
+    const events = ChatService.parseSSEChunk(rawChunk)
+    
+    expect(events[0].data.encoded_plots).toEqual(["base64data"])
+  })
+
+  it("should identify the done event", () => {
+    const rawChunk = `data: {"type": "done"}\n\n`
+    const events = ChatService.parseSSEChunk(rawChunk)
+    
+    expect(events[0].type).toBe("done")
+  })
+})
+
+describe("ChatService Message State Management", () => {
+  it("should append text chunks to the last message content", () => {
+    const messages = [{ id: "1", role: "assistant", content: "Initial", created_at: new Date().toISOString() }]
+    const event: ChatEvent = {
+      type: "on_chat_model_stream",
+      node: "summarizer",
+      data: { chunk: { content: " text" } }
+    }
+    
+    const updatedMessages = ChatService.updateMessagesWithEvent(messages as any, event)
+    expect(updatedMessages[0].content).toBe("Initial text")
+  })
+
+  it("should add plots to the message state", () => {
+    const messages = [{ id: "1", role: "assistant", content: "Analysis", created_at: new Date().toISOString(), plots: [] }]
+    const event: ChatEvent = {
+      type: "on_chain_end",
+      name: "executor",
+      data: { encoded_plots: ["plot1"] }
+    }
+    
+    const updatedMessages = ChatService.updateMessagesWithEvent(messages as any, event)
+    expect(updatedMessages[0].plots).toEqual(["plot1"])
+  })
+})