refactor: 后端代码优化 11 项（codestable/refactors/2026-04-25-backend-cleanup）

- 提取 getWKFromContext 辅助函数，消除 handler 中 5 处重复代码
- 提取 retryCode 函数，消除 Login/performStudy 中验证码重试重复
- 提取 removeSession 内部方法，消除 Del/ClearAll/ClearExpired 中 3 处重复
- 提取 WK.UserKey() 方法，消除 4 处 userKey 手动拼接
- SessionManager.Get() 改用 RLock 优化读性能
- GetRecords 递归分页改为迭代，避免栈溢出
- prepareRequestClient 添加配置缓存，仅在 debug 设置变化时重建
- 修正 schedule.go 时区为 Asia/Shanghai + cron "0 6 * * *"
- 修正 typo "以达到" → "已达到"
- 删除未使用的 QAList struct
- 修复 bufferHub.append 切片内存泄漏

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/ckwk/api.go

@@ -43,6 +43,11 @@ type WK struct {
 	authMu         sync.Mutex
 	sessionID      string
 	sessionManager *SessionManager
+
+	// 缓存上次应用到的 debug 配置，仅在配置变化时重建
+	lastDebugEnabled       bool
+	lastDebugProxy         string
+	lastDebugSkipSSLVerify bool
 }
 
 func NewWK(username, password, host string, cookies []*http.Cookie) *WK {
@@ -86,25 +91,45 @@ func (wk *WK) bindSession(sm *SessionManager, sessionID string) {
 	wk.sessionID = sessionID
 }
 
+// UserKey 返回 "host:username" 格式的用户标识，用于 SessionManager 的 userToSession 索引
+func (wk *WK) UserKey() string {
+	return wk.Host + ":" + wk.Username
+}
+
 func (wk *WK) prepareRequestClient() {
 	if wk == nil || wk.Req == nil {
 		return
 	}
 
+	debugEnabled := conf.IsRuntimeDebugEnabled()
+	debugProxy := conf.DebugProxy
+	debugSkipSSLVerify := conf.DebugSkipSSLVerify
+
+	// 仅在 debug 配置变化时重建
+	if wk.lastDebugEnabled == debugEnabled &&
+		wk.lastDebugProxy == debugProxy &&
+		wk.lastDebugSkipSSLVerify == debugSkipSSLVerify {
+		return
+	}
+
 	cfg := &request.Config{
 		UserAgent: request.DefaultUserAgent,
 		VerifySSL: true,
-		Debug:     conf.IsRuntimeDebugEnabled(),
+		Debug:     debugEnabled,
 	}
-	if conf.IsRuntimeDebugEnabled() {
-		cfg.Proxy = conf.DebugProxy
-		cfg.VerifySSL = !conf.DebugSkipSSLVerify
+	if debugEnabled {
+		cfg.Proxy = debugProxy
+		cfg.VerifySSL = !debugSkipSSLVerify
 	}
 
 	request.ApplyConfig(wk.Req, cfg)
 	if len(wk.Cookies) > 0 {
 		wk.Req.SetCookies(wk.Cookies)
 	}
+
+	wk.lastDebugEnabled = debugEnabled
+	wk.lastDebugProxy = debugProxy
+	wk.lastDebugSkipSSLVerify = debugSkipSSLVerify
 }
 
 func (wk *WK) newRequest() *resty.Request {
@@ -154,18 +179,23 @@ func (wk *WK) Code() (string, error) {
 	return result.Data, nil
 }
 
-// Login: Login WebSite
-func (wk *WK) Login() (bool, error) {
-	yzm := ""
-	for i := 1; i <= 3; i++ {
-		yzm, _ = wk.Code()
+// retryCode 重试获取验证码，最多 maxRetries 次
+func retryCode(wk *WK, maxRetries int) (string, error) {
+	for i := 1; i <= maxRetries; i++ {
+		yzm, _ := wk.Code()
 		if yzm != "" {
-			break
+			return yzm, nil
 		}
 		log.Warnf("第 %d 次获取验证码失败, 正在重试...\n", i)
 	}
-	if yzm == "" {
-		return false, fmt.Errorf("以达到最大重试次数，验证码获取失败，登录终止。")
+	return "", fmt.Errorf("已达到最大重试次数，验证码获取失败")
+}
+
+// Login: Login WebSite
+func (wk *WK) Login() (bool, error) {
+	yzm, err := retryCode(wk, 3)
+	if err != nil {
+		return false, err
 	}
 
 	resp, err := wk.newRequest().
@@ -415,7 +445,7 @@ func (wk *WK) performStudy(nodeID, studyID, studyTime string, status StudyStatus
 			log.Warnf("第 %d 次获取验证码失败, 正在重试...\n", i)
 		}
 		if yzm == "" {
-			return nil, fmt.Errorf("以达到最大重试次数，验证码获取失败，登录终止。")
+			return nil, fmt.Errorf("已达到最大重试次数，验证码获取失败，登录终止。")
 		}
 		data = map[string]string{
 			"nodeId":    nodeID,

internal/ckwk/session_manager.go

@@ -29,12 +29,23 @@ func NewSessionManager() *SessionManager {
 	}
 }
 
+// removeSession 取消 context、删除双 map 条目、记日志
+func (m *SessionManager) removeSession(sessionID string, item SessionItem) {
+	if item.cancel != nil {
+		item.cancel()
+	}
+	userKey := item.Instance.UserKey()
+	delete(m.userToSession, userKey)
+	delete(m.sessions, sessionID)
+	log.Info("删除 Session", zap.String("id", sessionID))
+}
+
 // Store: 保存 session 并返回 session id
 func (m *SessionManager) Store(wk *WK) string {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
-	userKey := wk.Host + ":" + wk.Username
+	userKey := wk.UserKey()
 	if oldID, exists := m.userToSession[userKey]; exists {
 		item := m.sessions[oldID]
 		if item.cancel != nil {
@@ -78,16 +89,20 @@ func (m *SessionManager) Store(wk *WK) string {
 
 // Get: 获取指定 session id 的 wk
 func (m *SessionManager) Get(sessionID string) (*WK, bool) {
-	m.mu.Lock()
-	defer m.mu.Unlock()
-
+	m.mu.RLock()
 	item, ok := m.sessions[sessionID]
-	if ok {
-		item.LastValue = time.Now()
-		m.sessions[sessionID] = item
-		return item.Instance, true
+	if !ok {
+		m.mu.RUnlock()
+		return nil, false
 	}
-	return nil, false
+	m.mu.RUnlock()
+
+	m.mu.Lock()
+	item.LastValue = time.Now()
+	m.sessions[sessionID] = item
+	m.mu.Unlock()
+
+	return item.Instance, true
 }
 
 func (m *SessionManager) Del(sessionID string) {
@@ -95,16 +110,7 @@ func (m *SessionManager) Del(sessionID string) {
 	defer m.mu.Unlock()
 
 	if item, ok := m.sessions[sessionID]; ok {
-		userKey := item.Instance.Host + ":" + item.Instance.Username
-
-		if item.cancel != nil {
-			item.cancel()
-		}
-
-		delete(m.userToSession, userKey)
-		delete(m.sessions, sessionID)
-
-		log.Info("删除 Session", zap.String("id", sessionID))
+		m.removeSession(sessionID, item)
 	}
 }
 
@@ -141,16 +147,7 @@ func (m *SessionManager) ClearAll() {
 	defer m.mu.Unlock()
 
 	for sessionID, item := range m.sessions {
-		// 停止 KeepAlive
-		if item.cancel != nil {
-			item.cancel()
-		}
-
-		userKey := item.Instance.Host + ":" + item.Instance.Username
-		delete(m.userToSession, userKey)
-		delete(m.sessions, sessionID)
-
-		log.Info("清理 Session", zap.String("id", sessionID))
+		m.removeSession(sessionID, item)
 	}
 
 	log.Info("所有 Session 已清空")
@@ -164,15 +161,7 @@ func (m *SessionManager) ClearExpired(d time.Duration) {
 
 	for sessionID, item := range m.sessions {
 		if now.Sub(item.LastValue) > d {
-			if item.cancel != nil {
-				item.cancel()
-			}
-
-			userKey := item.Instance.Host + ":" + item.Instance.Username
-			delete(m.userToSession, userKey)
-			delete(m.sessions, sessionID)
-
-			log.Info("清理过期 Session", zap.String("id", sessionID))
+			m.removeSession(sessionID, item)
 		}
 	}
 }

internal/ckwk/types.go

@@ -25,7 +25,7 @@ const (
 
 	StudyStart StudyStatus = 1 // 开始学习
 	Study      StudyStatus = 2 // 学习中
-	StudyOver  StudyStatus = 3 // 学习介绍
+	StudyOver  StudyStatus = 3 // 学习结束
 )
 
 // User: 用户
@@ -49,11 +49,36 @@ type Course struct {
 	Type      string  `json:"type"`
 }
 
-type QAList struct {
-}
-
+// GetRecords 分页获取记录（迭代实现）
 func GetRecords[T any](wk *WK, rType RecordType, courseID, page string) (*AllRecordResp[T], error) {
 	log.Debug("获取记录信息", zap.String("host", wk.Host), zap.String("type", string(rType)))
+
+	result, err := fetchRecordPage[T](wk, rType, courseID, page)
+	if err != nil {
+		return nil, err
+	}
+	if !result.Status {
+		return &result, fmt.Errorf("接口报错: %s", result.Msg)
+	}
+
+	for result.PageInfo.Page < result.PageInfo.PageCount {
+		nextPage := fmt.Sprint(result.PageInfo.Page + 1)
+		nextResult, err := fetchRecordPage[T](wk, rType, courseID, nextPage)
+		if err != nil {
+			return nil, err
+		}
+
+		result.List = append(result.List, nextResult.List...)
+		log.Debug("Page", zap.Int("currentPage", result.PageInfo.Page), zap.Int("nextPage", nextResult.PageInfo.Page))
+		result.PageInfo = nextResult.PageInfo
+	}
+
+	return &result, nil
+}
+
+// fetchRecordPage 获取单页记录
+func fetchRecordPage[T any](wk *WK, rType RecordType, courseID, page string) (AllRecordResp[T], error) {
+	var result AllRecordResp[T]
 	resp, err := wk.newRequest().
 		SetQueryParams(map[string]string{
 			"courseId": courseID,
@@ -62,32 +87,13 @@ func GetRecords[T any](wk *WK, rType RecordType, courseID, page string) (*AllRec
 		}).
 		Get(fmt.Sprintf("https://%s/user/study_record%s.json", wk.Host, rType))
 	if err != nil {
-		return nil, err
+		return result, err
 	}
 
-	var result AllRecordResp[T]
 	if err := json.Unmarshal(resp.Bytes(), &result); err != nil {
 		log.Error("JSON解析失败", zap.Error(err))
-		return nil, err
+		return result, err
 	}
 
-	if !result.Status {
-		return &result, fmt.Errorf("接口报错: %s", result.Msg)
-	}
-	currentPage := result.PageInfo.Page
-	totalPages := result.PageInfo.PageCount
-
-	for currentPage < totalPages {
-		nextPage := fmt.Sprint(currentPage + 1)
-		nextResult, err := GetRecords[T](wk, rType, courseID, nextPage)
-		if err != nil {
-			return nil, err
-		}
-
-		result.List = append(result.List, nextResult.List...)
-		log.Debug("Page", zap.Int("currentPage", currentPage), zap.Int("Page", nextResult.PageInfo.Page))
-		currentPage = nextResult.PageInfo.Page
-	}
-
-	return &result, nil
+	return result, nil
 }

internal/handler/ckwk.go

@@ -22,6 +22,16 @@ func NewWKHandler() *WKHandler {
 	}
 }
 
+// getWKFromContext 从 gin.Context 中提取 wk_instance，不存在时自动返回错误响应
+func getWKFromContext(ctx *gin.Context) (*ckwk.WK, bool) {
+	val, ok := ctx.Get("wk_instance")
+	if !ok {
+		ctx.JSON(200, dto.Error(-1, "登录已过期"))
+		return nil, false
+	}
+	return val.(*ckwk.WK), true
+}
+
 func (h *WKHandler) Login(ctx *gin.Context) {
 	var req dto.LoginReq
 	if err := ctx.ShouldBindJSON(&req); err != nil {
@@ -65,12 +75,10 @@ func (h *WKHandler) Login(ctx *gin.Context) {
 }
 
 func (h *WKHandler) Online(ctx *gin.Context) {
-	val, ok := ctx.Get("wk_instance")
+	wk, ok := getWKFromContext(ctx)
 	if !ok {
-		ctx.JSON(http.StatusOK, dto.Error(-1, "登录已过期"))
 		return
 	}
-	wk := val.(*ckwk.WK)
 
 	flag, err := wk.Online()
 	if err != nil {
@@ -96,12 +104,10 @@ func (h *WKHandler) Logout(ctx *gin.Context) {
 }
 
 func (h *WKHandler) UserInfo(ctx *gin.Context) {
-	val, ok := ctx.Get("wk_instance")
+	wk, ok := getWKFromContext(ctx)
 	if !ok {
-		ctx.JSON(200, dto.Error(-1, "登录已过期"))
 		return
 	}
-	wk := val.(*ckwk.WK)
 
 	userinfo, err := wk.UserInfoGet()
 	if err != nil {
@@ -121,12 +127,10 @@ func (h *WKHandler) Course(ctx *gin.Context) {
 		return
 	}
 
-	val, ok := ctx.Get("wk_instance")
+	wk, ok := getWKFromContext(ctx)
 	if !ok {
-		ctx.JSON(200, dto.Error(-1, "登录已过期"))
 		return
 	}
-	wk := val.(*ckwk.WK)
 
 	courses, err := wk.CourseGet(req.Status)
 	if err != nil {
@@ -140,12 +144,10 @@ func (h *WKHandler) Course(ctx *gin.Context) {
 }
 
 func (h *WKHandler) Study(ctx *gin.Context) {
-	val, ok := ctx.Get("wk_instance")
+	wk, ok := getWKFromContext(ctx)
 	if !ok {
-		ctx.JSON(200, dto.Error(-1, "登录已过期"))
 		return
 	}
-	wk := val.(*ckwk.WK)
 
 	var req dto.StudyReq
 	if err := ctx.ShouldBindJSON(&req); err != nil {
@@ -167,12 +169,10 @@ func (h *WKHandler) Study(ctx *gin.Context) {
 }
 
 func (h *WKHandler) AllRecord(ctx *gin.Context) {
-	val, ok := ctx.Get("wk_instance")
+	wk, ok := getWKFromContext(ctx)
 	if !ok {
-		ctx.JSON(200, dto.Error(-1, "登录已过期"))
 		return
 	}
-	wk := val.(*ckwk.WK)
 
 	var req dto.AllRecordReq
 	if err := ctx.ShouldBindJSON(&req); err != nil {

internal/schedule/schedule.go

@@ -11,14 +11,14 @@ import (
 )
 
 func StartCron(m *ckwk.SessionManager) {
-	loc, _ := time.LoadLocation("Asia/Singapore")
+	loc, _ := time.LoadLocation("Asia/Shanghai")
 
 	c := cron.New(
 		cron.WithLocation(loc),
 	)
 
 	// 每天 6 点执行
-	_, err := c.AddFunc("0 2 * * *", func() {
+	_, err := c.AddFunc("0 6 * * *", func() {
 		log.Info("开始定时清理 Session")
 		m.ClearAll()
 	})