fix: 解决钉钉图片问题

platform/dingtalk/dingtalk.go

@@ -261,12 +261,12 @@ func (p *Platform) onMessage(data *chatbot.BotCallbackDataModel, richText *richT
 			return
 		}
 
-		// Download images from pictureDownloadCode
+		// Download images from downloadCode
 		var images []core.ImageAttachment
 		for _, code := range imageCodes {
 			imgData, mimeType, err := p.downloadImageByCode(code)
 			if err != nil {
-				slog.Error("dingtalk: failed to download richText image", "error", err, "code", code)
+				slog.Error("dingtalk: failed to download richText image", "error", err)
 				continue
 			}
 			images = append(images, core.ImageAttachment{
@@ -331,8 +331,9 @@ func (p *Platform) onMessage(data *chatbot.BotCallbackDataModel, richText *richT
 }
 
 // extractRichText extracts plain text and image download codes from a DingTalk richText content payload.
-// The expected structure is: {"richText": [{"text": "..."}, {"pictureDownloadCode": "..."}, ...]}
+// The expected structure is: {"richText": [{"text": "..."}, {"downloadCode": "...", "pictureDownloadCode": "...", "type": "picture"}, ...]}
 // Returns text and a list of download codes for images found in the rich text.
+// Prefers "downloadCode" over "pictureDownloadCode" (the former is used by the messageFiles/download API).
 func extractRichText(content interface{}) (string, []string) {
 	m, ok := content.(map[string]interface{})
 	if !ok {
@@ -352,7 +353,13 @@ func extractRichText(content interface{}) (string, []string) {
 		if text, ok := item["text"].(string); ok {
 			b.WriteString(text)
 		}
-		if code, ok := item["pictureDownloadCode"].(string); ok && code != "" {
+		// Prefer downloadCode (used by handleImageMessage and messageFiles/download API).
+		// Fall back to pictureDownloadCode if downloadCode is not present.
+		code, _ := item["downloadCode"].(string)
+		if code == "" {
+			code, _ = item["pictureDownloadCode"].(string)
+		}
+		if code != "" {
 			imageCodes = append(imageCodes, code)
 		}
 	}
@@ -505,7 +512,7 @@ func (p *Platform) handleImageMessage(data *chatbot.BotCallbackDataModel, sessio
 	p.handler(p, msg)
 }
 
-// downloadImageByCode downloads an image using a pictureDownloadCode from richText messages.
+// downloadImageByCode downloads an image using a downloadCode from richText messages.
 func (p *Platform) downloadImageByCode(downloadCode string) ([]byte, string, error) {
 	downloadURL, err := p.getDownloadURL(downloadCode)
 	if err != nil {
@@ -605,7 +612,8 @@ func (p *Platform) getDownloadURL(downloadCode string) (string, error) {
 	defer resp.Body.Close()
 
 	if resp.StatusCode != http.StatusOK {
-		return "", fmt.Errorf("api returned status %d", resp.StatusCode)
+		respBody, _ := io.ReadAll(resp.Body)
+		return "", fmt.Errorf("api returned status %d: %s", resp.StatusCode, string(respBody))
 	}
 
 	var result downloadResponse