refactor(channels): consolidate media handling and improve resource cleanup

Extract common file download and audio detection logic to utils package,
implement consistent temp file cleanup with defer, add allowlist checks
before downloading attachments, and improve context management across
Discord, Slack, and Telegram channels. Replace logging with structured
logger and prevent context leaks in transcription and thinking animations.

pkg/channels/slack.go

@@ -3,10 +3,7 @@ package channels
 import (
 	"context"
 	"fmt"
-	"io"
-	"net/http"
 	"os"
-	"path/filepath"
 	"strings"
 	"sync"
 	"time"
@@ -18,6 +15,7 @@ import (
 	"github.com/sipeed/picoclaw/pkg/bus"
 	"github.com/sipeed/picoclaw/pkg/config"
 	"github.com/sipeed/picoclaw/pkg/logger"
+	"github.com/sipeed/picoclaw/pkg/utils"
 	"github.com/sipeed/picoclaw/pkg/voice"
 )
 
@@ -186,10 +184,6 @@ func (c *SlackChannel) handleEventsAPI(event socketmode.Event) {
 		c.handleMessageEvent(ev)
 	case *slackevents.AppMentionEvent:
 		c.handleAppMention(ev)
-	case *slackevents.ReactionAddedEvent:
-		c.handleReactionAdded(ev)
-	case *slackevents.ReactionRemovedEvent:
-		c.handleReactionRemoved(ev)
 	}
 }
 
@@ -204,6 +198,14 @@ func (c *SlackChannel) handleMessageEvent(ev *slackevents.MessageEvent) {
 		return
 	}
 
+	// 检查白名单，避免为被拒绝的用户下载附件
+	if !c.IsAllowed(ev.User) {
+		logger.DebugCF("slack", "Message rejected by allowlist", map[string]interface{}{
+			"user_id": ev.User,
+		})
+		return
+	}
+
 	senderID := ev.User
 	channelID := ev.Channel
 	threadTS := ev.ThreadTimeStamp
@@ -228,6 +230,19 @@ func (c *SlackChannel) handleMessageEvent(ev *slackevents.MessageEvent) {
 	content = c.stripBotMention(content)
 
 	var mediaPaths []string
+	localFiles := []string{} // 跟踪需要清理的本地文件
+
+	// 确保临时文件在函数返回时被清理
+	defer func() {
+		for _, file := range localFiles {
+			if err := os.Remove(file); err != nil {
+				logger.DebugCF("slack", "Failed to cleanup temp file", map[string]interface{}{
+					"file":  file,
+					"error": err.Error(),
+				})
+			}
+		}
+	}()
 
 	if ev.Message != nil && len(ev.Message.Files) > 0 {
 		for _, file := range ev.Message.Files {
@@ -235,12 +250,13 @@ func (c *SlackChannel) handleMessageEvent(ev *slackevents.MessageEvent) {
 			if localPath == "" {
 				continue
 			}
+			localFiles = append(localFiles, localPath)
 			mediaPaths = append(mediaPaths, localPath)
 
-			if isAudioFile(file.Name, file.Mimetype) && c.transcriber != nil && c.transcriber.IsAvailable() {
-				ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+			if utils.IsAudioFile(file.Name, file.Mimetype) && c.transcriber != nil && c.transcriber.IsAvailable() {
+				ctx, cancel := context.WithTimeout(c.ctx, 30*time.Second)
+				defer cancel()
 				result, err := c.transcriber.Transcribe(ctx, localPath)
-				cancel()
 
 				if err != nil {
 					logger.ErrorCF("slack", "Voice transcription failed", map[string]interface{}{"error": err.Error()})
@@ -266,9 +282,9 @@ func (c *SlackChannel) handleMessageEvent(ev *slackevents.MessageEvent) {
 	}
 
 	logger.DebugCF("slack", "Received message", map[string]interface{}{
-		"sender_id":  senderID,
-		"chat_id":    chatID,
-		"preview":    truncateStringSlack(content, 50),
+		"sender_id": senderID,
+		"chat_id":   chatID,
+		"preview":   utils.Truncate(content, 50),
 		"has_thread": threadTS != "",
 	})
 
@@ -348,35 +364,13 @@ func (c *SlackChannel) handleSlashCommand(event socketmode.Event) {
 	logger.DebugCF("slack", "Slash command received", map[string]interface{}{
 		"sender_id": senderID,
 		"command":   cmd.Command,
-		"text":      truncateStringSlack(content, 50),
+		"text":      utils.Truncate(content, 50),
 	})
 
 	c.HandleMessage(senderID, chatID, content, nil, metadata)
 }
 
-func (c *SlackChannel) handleReactionAdded(ev *slackevents.ReactionAddedEvent) {
-	logger.DebugCF("slack", "Reaction added", map[string]interface{}{
-		"reaction": ev.Reaction,
-		"user":     ev.User,
-		"item_ts":  ev.Item.Timestamp,
-	})
-}
-
-func (c *SlackChannel) handleReactionRemoved(ev *slackevents.ReactionRemovedEvent) {
-	logger.DebugCF("slack", "Reaction removed", map[string]interface{}{
-		"reaction": ev.Reaction,
-		"user":     ev.User,
-		"item_ts":  ev.Item.Timestamp,
-	})
-}
-
 func (c *SlackChannel) downloadSlackFile(file slack.File) string {
-	mediaDir := filepath.Join(os.TempDir(), "picoclaw_media")
-	if err := os.MkdirAll(mediaDir, 0755); err != nil {
-		logger.ErrorCF("slack", "Failed to create media directory", map[string]interface{}{"error": err.Error()})
-		return ""
-	}
-
 	downloadURL := file.URLPrivateDownload
 	if downloadURL == "" {
 		downloadURL = file.URLPrivate
@@ -386,41 +380,12 @@ func (c *SlackChannel) downloadSlackFile(file slack.File) string {
 		return ""
 	}
 
-	localPath := filepath.Join(mediaDir, file.Name)
-
-	req, err := http.NewRequest("GET", downloadURL, nil)
-	if err != nil {
-		logger.ErrorCF("slack", "Failed to create download request", map[string]interface{}{"error": err.Error()})
-		return ""
-	}
-	req.Header.Set("Authorization", "Bearer "+c.config.BotToken)
-
-	resp, err := http.DefaultClient.Do(req)
-	if err != nil {
-		logger.ErrorCF("slack", "Failed to download file", map[string]interface{}{"error": err.Error()})
-		return ""
-	}
-	defer resp.Body.Close()
-
-	if resp.StatusCode != http.StatusOK {
-		logger.ErrorCF("slack", "File download returned non-200 status", map[string]interface{}{"status": resp.StatusCode})
-		return ""
-	}
-
-	out, err := os.Create(localPath)
-	if err != nil {
-		logger.ErrorCF("slack", "Failed to create local file", map[string]interface{}{"error": err.Error()})
-		return ""
-	}
-	defer out.Close()
-
-	if _, err := io.Copy(out, resp.Body); err != nil {
-		logger.ErrorCF("slack", "Failed to write file", map[string]interface{}{"error": err.Error()})
-		return ""
-	}
-
-	logger.DebugCF("slack", "File downloaded", map[string]interface{}{"path": localPath, "name": file.Name})
-	return localPath
+	return utils.DownloadFile(downloadURL, file.Name, utils.DownloadOptions{
+		LoggerPrefix: "slack",
+		ExtraHeaders: map[string]string{
+			"Authorization": "Bearer " + c.config.BotToken,
+		},
+	})
 }
 
 func (c *SlackChannel) stripBotMention(text string) string {
@@ -437,10 +402,3 @@ func parseSlackChatID(chatID string) (channelID, threadTS string) {
 	}
 	return
 }
-
-func truncateStringSlack(s string, maxLen int) string {
-	if len(s) <= maxLen {
-		return s
-	}
-	return s[:maxLen]
-}