feat: 实现发送消息前余额检测

- creditsService.ts: 新增余额缓存和检测服务
- apiClient.ts: 新增 getCreditBalance() API 调用
- dialogService.ts: SSE credit_update 事件更新余额缓存
- messageHandler.ts: 发送消息前检测余额，低于5点阻止发送

src/services/apiClient.ts

@@ -224,3 +224,22 @@ export async function getUserInfo(): Promise<UserInfoResponse> {
     method: 'GET'
   });
 }
+
+/** 余额查询响应 */
+export interface CreditBalanceResponse {
+  success: boolean;
+  balance?: number;
+  error?: string;
+}
+
+/**
+ * 查询用户资源点余额
+ * GET /api/dialog/balance?userId=xxx
+ */
+export async function getCreditBalance(userId: string): Promise<CreditBalanceResponse> {
+  console.log('[API] 查询余额: userId=', userId);
+  return request<CreditBalanceResponse>(`/api/dialog/balance?userId=${userId}`, {
+    method: 'GET',
+    timeout: 5000
+  });
+}

src/services/creditsService.ts

@@ -0,0 +1,121 @@
+/**
+ * 资源点余额管理服务
+ * 负责缓存余额、主动查询、发送前检测
+ */
+
+import { getCreditBalance } from './apiClient';
+import { getCachedUserInfo } from './userService';
+
+/** 低余额阈值 */
+const LOW_CREDIT_THRESHOLD = 5;
+
+/** 缓存的余额 */
+let cachedBalance: number | null = null;
+
+/** 最后更新时间 */
+let lastUpdateTime: number = 0;
+
+/** 缓存有效期（5分钟） */
+const CACHE_TTL_MS = 5 * 60 * 1000;
+
+/**
+ * 更新缓存的余额（从 SSE credit_update 事件调用）
+ */
+export function updateCachedBalance(balance: number): void {
+  cachedBalance = balance;
+  lastUpdateTime = Date.now();
+  console.log('[CreditsService] 余额已更新:', balance);
+}
+
+/**
+ * 获取缓存的余额
+ */
+export function getCachedBalance(): number | null {
+  return cachedBalance;
+}
+
+/**
+ * 检查缓存是否有效
+ */
+function isCacheValid(): boolean {
+  if (cachedBalance === null) return false;
+  return Date.now() - lastUpdateTime < CACHE_TTL_MS;
+}
+
+/**
+ * 主动查询余额
+ */
+export async function fetchBalance(): Promise<number | null> {
+  const userInfo = getCachedUserInfo();
+  if (!userInfo?.userId) {
+    console.warn('[CreditsService] 无法查询余额：未登录');
+    return null;
+  }
+
+  try {
+    const response = await getCreditBalance(userInfo.userId);
+    if (response.success && response.balance !== undefined) {
+      updateCachedBalance(response.balance);
+      return response.balance;
+    } else {
+      console.warn('[CreditsService] 查询余额失败:', response.error);
+      return null;
+    }
+  } catch (error) {
+    console.error('[CreditsService] 查询余额异常:', error);
+    return null;
+  }
+}
+
+/**
+ * 获取当前余额（优先使用缓存，过期则主动查询）
+ */
+export async function getBalance(): Promise<number | null> {
+  if (isCacheValid()) {
+    return cachedBalance;
+  }
+  return await fetchBalance();
+}
+
+/**
+ * 检查余额是否足够发送消息
+ * @returns { allowed: boolean, balance: number | null, message?: string }
+ */
+export async function checkBalanceBeforeSend(): Promise<{
+  allowed: boolean;
+  balance: number | null;
+  message?: string;
+}> {
+  const userInfo = getCachedUserInfo();
+  if (!userInfo) {
+    // 未登录，允许发送（后端会处理）
+    return { allowed: true, balance: null };
+  }
+
+  const balance = await getBalance();
+
+  if (balance === null) {
+    // 无法获取余额，允许发送（后端会处理）
+    console.warn('[CreditsService] 无法获取余额，允许发送');
+    return { allowed: true, balance: null };
+  }
+
+  if (balance < LOW_CREDIT_THRESHOLD) {
+    return {
+      allowed: false,
+      balance,
+      message: `资源点余额不足！当前余额 ${balance.toFixed(2)} 点，低于最低要求 ${LOW_CREDIT_THRESHOLD} 点。请充值后再试。`
+    };
+  }
+
+  return { allowed: true, balance };
+}
+
+/**
+ * 清除缓存（登出时调用）
+ */
+export function clearBalanceCache(): void {
+  cachedBalance = null;
+  lastUpdateTime = 0;
+  console.log('[CreditsService] 余额缓存已清除');
+}

src/services/dialogService.ts

@@ -13,6 +13,7 @@ import type { DialogRequest, ToolCallRequest, AskUserEvent, RunMode, ServiceTier
 import { submitToolConfirm, submitAnswer, stopDialog } from './apiClient';
 import { ChatHistoryManager } from '../utils/chatHistoryManager';
 import { getUserIdFromToken } from '../utils/jwtUtils';
+import { updateCachedBalance } from './creditsService';
 
 /**
  * 消息段落类型
@@ -791,6 +792,8 @@ export class DialogSession {
 
       onCreditUpdate: (data) => {
         console.log('[DialogSession] onCreditUpdate: 扣除', data.deductedCredits, '剩余', data.remainingCredits);
+        // 更新余额缓存
+        updateCachedBalance(data.remainingCredits);
         // 资源点余额低于阈值时弹窗提醒
         const LOW_CREDIT_THRESHOLD = 5;
         if (data.remainingCredits < LOW_CREDIT_THRESHOLD) {

src/utils/messageHandler.ts

@@ -18,6 +18,7 @@ import { ChatHistoryManager } from "./chatHistoryManager";
 import { dialogManager, DialogSession } from "../services/dialogService";
 import { userInteractionManager } from "../services/userInteraction";
 import { healthCheck } from "../services/apiClient";
+import { checkBalanceBeforeSend } from "../services/creditsService";
 
 import type { RunMode, ServiceTier } from "../types/api";
 
@@ -90,6 +91,27 @@ export async function handleUserMessage(
     return;
   }
 
+  // 发送前检测余额
+  const balanceCheck = await checkBalanceBeforeSend();
+  if (!balanceCheck.allowed) {
+    console.warn("[MessageHandler] 余额不足，阻止发送:", balanceCheck.message);
+    // 显示错误提示
+    const selection = await vscode.window.showWarningMessage(
+      balanceCheck.message || "资源点余额不足",
+      "去充值"
+    );
+    if (selection === "去充值") {
+      vscode.env.openExternal(vscode.Uri.parse("https://iccoder.com/recharge"));
+    }
+    // 恢复输入状态
+    panel.webview.postMessage({
+      command: "updateSegments",
+      segments: [],
+      isComplete: true,
+    });
+    return;
+  }
+
   // 尝试使用后端服务
   if (useBackendService && extensionPath) {
     try {