Fix: perform two-step xlsx->pdf->jpg conversion to preserve gridlines for thumbnails

backend/workers/thumbnails.go

@@ -154,81 +154,120 @@ func generateOfficeThumbnail(filePath, destPath string, cfg *config.Config) erro
 		ext = "docx"
 	}
 
-	payload := map[string]interface{}{
-		"async":      false,
-		"filetype":   ext,
-		"key":        fmt.Sprintf("thumb_%d", time.Now().UnixNano()),
-		"outputtype": "jpg",
-		"title":      "preview.jpg",
-		"url":        fileUrl,
-		"thumbnail": map[string]interface{}{
-			"aspect": 1,
-			"first":  true,
-			"width":  1024,
-			"height": 1024,
-		},
-	}
-
-	if ext == "xlsx" {
-		payload["spreadsheetLayout"] = map[string]interface{}{
-			"ignorePrintArea": true,
-			"printGridlines":  true,
-			"printHeadings":   true,
-			"fitToWidth":      1,
+	callConvert := func(payload map[string]interface{}) (string, error) {
+		payloadBytes, err := json.Marshal(payload)
+		if err != nil {
+			return "", err
 		}
-	}
 
-	payloadBytes, err := json.Marshal(payload)
-	if err != nil {
-		return err
-	}
-
-	req, err := http.NewRequest("POST", "https://office.elijahkuntz.com/ConvertService.ashx", bytes.NewBuffer(payloadBytes))
-	if err != nil {
-		return err
-	}
-	req.Header.Set("Content-Type", "application/json")
-	req.Header.Set("Accept", "application/json")
-
-	// Sign the payload with the OnlyOffice JWT
-	if cfg.OnlyOfficeJWT != "" {
-		jwtToken := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims(payload))
-		signedToken, err := jwtToken.SignedString([]byte(cfg.OnlyOfficeJWT))
-		if err == nil {
-			req.Header.Set("Authorization", "Bearer "+signedToken)
+		req, err := http.NewRequest("POST", "https://office.elijahkuntz.com/ConvertService.ashx", bytes.NewBuffer(payloadBytes))
+		if err != nil {
+			return "", err
 		}
+		req.Header.Set("Content-Type", "application/json")
+		req.Header.Set("Accept", "application/json")
+
+		if cfg.OnlyOfficeJWT != "" {
+			jwtToken := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims(payload))
+			signedToken, err := jwtToken.SignedString([]byte(cfg.OnlyOfficeJWT))
+			if err == nil {
+				req.Header.Set("Authorization", "Bearer "+signedToken)
+			}
+		}
+
+		client := &http.Client{Timeout: 30 * time.Second}
+		resp, err := client.Do(req)
+		if err != nil {
+			return "", fmt.Errorf("conversion request failed: %w", err)
+		}
+		defer resp.Body.Close()
+
+		if resp.StatusCode != http.StatusOK {
+			return "", fmt.Errorf("conversion request returned status: %d", resp.StatusCode)
+		}
+
+		var result struct {
+			Error   *int   `json:"error,omitempty"`
+			FileUrl string `json:"fileUrl,omitempty"`
+		}
+		if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+			return "", fmt.Errorf("failed to decode conversion response: %w", err)
+		}
+
+		if result.Error != nil && *result.Error != 0 {
+			return "", fmt.Errorf("conversion service returned error code: %d", *result.Error)
+		}
+
+		if result.FileUrl == "" {
+			return "", fmt.Errorf("no fileUrl in conversion response")
+		}
+		return result.FileUrl, nil
 	}
 
-	client := &http.Client{Timeout: 30 * time.Second}
-	resp, err := client.Do(req)
-	if err != nil {
-		return fmt.Errorf("conversion request failed: %w", err)
-	}
-	defer resp.Body.Close()
+	var finalImgUrl string
 
-	if resp.StatusCode != http.StatusOK {
-		return fmt.Errorf("conversion request returned status: %d", resp.StatusCode)
-	}
+	if ext == "xlsx" || ext == "xls" {
+		pdfPayload := map[string]interface{}{
+			"async":      false,
+			"filetype":   ext,
+			"key":        fmt.Sprintf("thumb_pdf_%d", time.Now().UnixNano()),
+			"outputtype": "pdf",
+			"title":      "preview.pdf",
+			"url":        fileUrl,
+			"spreadsheetLayout": map[string]interface{}{
+				"ignorePrintArea": true,
+				"printGridlines":  true,
+				"printHeadings":   true,
+				"fitToWidth":      1,
+			},
+		}
+		pdfUrl, err := callConvert(pdfPayload)
+		if err != nil {
+			return fmt.Errorf("failed to convert xlsx to pdf: %w", err)
+		}
 		
-	var result struct {
-		Error   *int   `json:"error,omitempty"`
-		FileUrl string `json:"fileUrl,omitempty"`
-	}
-	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
-		return fmt.Errorf("failed to decode conversion response: %w", err)
-	}
-
-	// Wait, the API might return error 0 for success
-	if result.Error != nil && *result.Error != 0 {
-		return fmt.Errorf("conversion service returned error code: %d", *result.Error)
-	}
-
-	if result.FileUrl == "" {
-		return fmt.Errorf("no fileUrl in conversion response")
+		jpgPayload := map[string]interface{}{
+			"async":      false,
+			"filetype":   "pdf",
+			"key":        fmt.Sprintf("thumb_jpg_%d", time.Now().UnixNano()),
+			"outputtype": "jpg",
+			"title":      "preview.jpg",
+			"url":        pdfUrl,
+			"thumbnail": map[string]interface{}{
+				"aspect": 1,
+				"first":  true,
+				"width":  1024,
+				"height": 1024,
+			},
+		}
+		finalImgUrl, err = callConvert(jpgPayload)
+		if err != nil {
+			return fmt.Errorf("failed to convert pdf to jpg: %w", err)
+		}
+	} else {
+		payload := map[string]interface{}{
+			"async":      false,
+			"filetype":   ext,
+			"key":        fmt.Sprintf("thumb_%d", time.Now().UnixNano()),
+			"outputtype": "jpg",
+			"title":      "preview.jpg",
+			"url":        fileUrl,
+			"thumbnail": map[string]interface{}{
+				"aspect": 1,
+				"first":  true,
+				"width":  1024,
+				"height": 1024,
+			},
+		}
+		var err error
+		finalImgUrl, err = callConvert(payload)
+		if err != nil {
+			return err
+		}
 	}
 
 	// Download the resulting image
-	imgResp, err := http.Get(result.FileUrl)
+	imgResp, err := http.Get(finalImgUrl)
 	if err != nil {
 		return fmt.Errorf("failed to download converted image: %w", err)
 	}