feat(chat): Implement real-time SSE streaming with reasoning steps and improved UI indicators.
This commit is contained in:
Yunxiao Xu
263
frontend/src/services/chat.ts
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263
frontend/src/services/chat.ts
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import api from "./api"
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export interface MessageResponse {
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id: string
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role: "user" | "assistant"
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content: string
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created_at: string
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plots?: string[] // base64 encoded plots
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steps?: string[] // reasoning steps
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}
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export interface ChatEvent {
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type: string
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name?: string
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node?: string
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data?: any
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}
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export interface StreamCallbacks {
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onMessageUpdate: (messages: MessageResponse[]) => void
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onDone?: () => void
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onError?: (error: string) => void
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}
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export const ChatService = {
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/**
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* Parse a raw SSE chunk into one or more ChatEvent objects.
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* Handles partial lines by returning the processed events and any remaining buffer.
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*/
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parseSSEBuffer(buffer: string): { events: ChatEvent[], remaining: string } {
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const events: ChatEvent[] = []
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const lines = buffer.split("\n")
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// The last element might be a partial line if it doesn't end with \n
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const remaining = buffer.endsWith("\n") ? "" : lines.pop() || ""
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for (const line of lines) {
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if (line.startsWith("data: ")) {
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const dataStr = line.slice(6).trim()
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if (!dataStr) continue
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try {
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const event = JSON.parse(dataStr)
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events.push(event)
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} catch (err) {
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console.error("Failed to parse SSE event JSON:", err, dataStr)
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}
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}
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}
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return { events, remaining }
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},
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/**
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* Legacy method for backward compatibility in tests
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*/
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parseSSEChunk(chunk: string): ChatEvent[] {
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return this.parseSSEBuffer(chunk).events
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},
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/**
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* Update a list of messages based on a new ChatEvent.
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* This is a pure function designed for use with React state updates.
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*/
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updateMessagesWithEvent(messages: MessageResponse[], event: ChatEvent): MessageResponse[] {
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const { type, name, node, data } = event
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// 1. Handle incremental LLM chunks for terminal nodes
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if (type === "on_chat_model_stream" && (node === "summarizer" || node === "researcher" || node === "clarification")) {
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const chunk = data?.chunk?.content || ""
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if (!chunk) return messages
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const newMessages = [...messages]
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const lastMsgIndex = newMessages.length - 1
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const lastMsg = { ...newMessages[lastMsgIndex] }
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if (lastMsg && lastMsg.role === "assistant") {
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lastMsg.content = (lastMsg.content || "") + chunk
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newMessages[lastMsgIndex] = lastMsg
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}
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return newMessages
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}
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// 2. Handle final node outputs
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if (type === "on_chain_end") {
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const newMessages = [...messages]
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const lastMsgIndex = newMessages.length - 1
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const lastMsg = { ...newMessages[lastMsgIndex] }
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if (!lastMsg || lastMsg.role !== "assistant") return messages
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// Terminal nodes final text
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if (name === "summarizer" || name === "researcher" || name === "clarification") {
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const messages_list = data?.output?.messages
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const msg = messages_list ? messages_list[messages_list.length - 1]?.content : null
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if (msg) {
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lastMsg.content = msg
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newMessages[lastMsgIndex] = lastMsg
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return newMessages
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}
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}
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// Plots from executor
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if (name === "executor" && data?.encoded_plots) {
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lastMsg.plots = [...(lastMsg.plots || []), ...data.encoded_plots]
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// Filter out the 'active' step and replace with 'complete'
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const filteredSteps = (lastMsg.steps || []).filter(s => s !== "Performing data analysis...");
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lastMsg.steps = [...filteredSteps, "Data analysis and visualization complete."]
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newMessages[lastMsgIndex] = lastMsg
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return newMessages
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}
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// Status for intermediate nodes (completion)
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const statusMap: Record<string, string> = {
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"query_analyzer": "Query analysis complete.",
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"planner": "Strategic plan generated.",
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"coder": "Analysis code generated."
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}
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if (name && statusMap[name]) {
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// Find and replace the active status if it exists
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const activeStatus = name === "query_analyzer" ? "Analyzing query..." :
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name === "planner" ? "Generating strategic plan..." :
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name === "coder" ? "Writing analysis code..." : null;
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let filteredSteps = lastMsg.steps || [];
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if (activeStatus) {
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filteredSteps = filteredSteps.filter(s => s !== activeStatus);
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}
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lastMsg.steps = [...filteredSteps, statusMap[name]]
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newMessages[lastMsgIndex] = lastMsg
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return newMessages
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}
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}
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// 3. Handle node start events for progress feedback
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if (type === "on_chain_start") {
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const startStatusMap: Record<string, string> = {
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"query_analyzer": "Analyzing query...",
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"planner": "Generating strategic plan...",
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"coder": "Writing analysis code...",
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"executor": "Performing data analysis..."
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}
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if (name && startStatusMap[name]) {
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const newMessages = [...messages]
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const lastMsgIndex = newMessages.length - 1
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const lastMsg = { ...newMessages[lastMsgIndex] }
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if (lastMsg && lastMsg.role === "assistant") {
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// Avoid duplicate start messages
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if (!(lastMsg.steps || []).includes(startStatusMap[name])) {
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lastMsg.steps = [...(lastMsg.steps || []), startStatusMap[name]]
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newMessages[lastMsgIndex] = lastMsg
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return newMessages
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}
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}
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}
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}
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return messages
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},
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/**
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* Stream agent execution events via SSE.
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* Uses fetch + ReadableStream because backend uses POST.
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*/
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async streamChat(
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message: string,
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threadId: string,
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currentMessages: MessageResponse[],
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callbacks: StreamCallbacks
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) {
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const { onMessageUpdate, onDone, onError } = callbacks
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// Add user message and a placeholder assistant message
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let activeMessages: MessageResponse[] = [
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...currentMessages,
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{
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id: `user-${Date.now()}`,
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role: "user",
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content: message,
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created_at: new Date().toISOString()
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},
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{
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id: `assistant-${Date.now()}`,
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role: "assistant",
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content: "",
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created_at: new Date().toISOString(),
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plots: []
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}
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]
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onMessageUpdate(activeMessages)
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let buffer = ""
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try {
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const API_URL = import.meta.env.VITE_API_URL || ""
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const response = await fetch(`${API_URL}/api/v1/chat/stream`, {
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method: "POST",
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headers: {
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"Content-Type": "application/json",
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},
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body: JSON.stringify({
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message,
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thread_id: threadId
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}),
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credentials: "include"
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})
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if (!response.ok) {
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throw new Error(`Streaming failed: ${response.statusText}`)
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}
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const reader = response.body?.getReader()
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if (!reader) throw new Error("No readable stream in response body")
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const decoder = new TextDecoder()
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while (true) {
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const { done, value } = await reader.read()
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if (done) break
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buffer += decoder.decode(value, { stream: true })
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const { events, remaining } = this.parseSSEBuffer(buffer)
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buffer = remaining
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for (const event of events) {
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if (event.type === "done") {
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if (onDone) onDone()
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continue
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}
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if (event.type === "error") {
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if (onError) onError(event.data?.message || "Unknown error")
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continue
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}
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activeMessages = this.updateMessagesWithEvent(activeMessages, event)
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onMessageUpdate(activeMessages)
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}
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}
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} catch (err: any) {
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console.error("Streaming error:", err)
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if (onError) onError(err.message || "Connection failed")
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}
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},
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async listConversations() {
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const response = await api.get("/conversations")
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return response.data
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},
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async createConversation(name: string = "New Conversation") {
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const response = await api.post("/conversations", { name })
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return response.data
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},
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async getMessages(conversationId: string) {
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const response = await api.get(`/conversations/${conversationId}/messages`)
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return response.data
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}
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}
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