generate thumbnails

backend/Dockerfile

@@ -11,14 +11,14 @@ RUN CGO_ENABLED=0 GOOS=linux go build -o /bin/server ./cmd/server
 
 FROM alpine:3.21
 
-RUN apk add --no-cache ca-certificates curl
+RUN apk add --no-cache ca-certificates curl libreoffice-core poppler-utils
 
 WORKDIR /app
 
 COPY --from=builder /bin/server .
 COPY internal/db/migrations ./internal/db/migrations
 
-RUN mkdir -p /app/uploads /data
+RUN mkdir -p /app/uploads /app/uploads/thumbnails /data
 
 EXPOSE 8080
 

backend/cmd/server/main.go

@@ -32,6 +32,7 @@ func main() {
 
 	fileSvc := service.NewFileService(queries, cfg)
 	ocrSvc := service.NewOCRService(cfg, fileSvc)
+	conversionSvc := service.NewConversionService(queries, cfg)
 	urlSvc := service.NewURLService(cfg.HMACSecret, cfg.ServerHost)
 	authSvc, err := auth.NewAuthService(queries, cfg)
 	if err != nil {
@@ -41,7 +42,10 @@ func main() {
 	ocrSvc.Start()
 	defer ocrSvc.Stop()
 
-	h := handler.New(fileSvc, ocrSvc, urlSvc, auth.NewAuthHandler(authSvc))
+	conversionSvc.Start()
+	defer conversionSvc.Stop()
+
+	h := handler.New(fileSvc, ocrSvc, urlSvc, auth.NewAuthHandler(authSvc), conversionSvc)
 
 	r := gin.Default()
 	handler.SetupRoutes(r, h, authSvc)

backend/internal/config/config.go

@@ -10,6 +10,9 @@ type Config struct {
 	HMACSecret      string
 	ServerHost      string
 	PASETOKey       string
+	LibreOfficePath string
+	PdftoppmPath    string
+	ThumbnailDir    string
 }
 
 func Load() *Config {
@@ -21,6 +24,9 @@ func Load() *Config {
 		HMACSecret:      envOr("HMAC_SECRET", "thisismyrandomstring"),
 		ServerHost:      envOr("SERVER_HOST", "http://192.168.1.17:8080"),
 		PASETOKey:       envOr("PASETO_KEY", "01234567890123456789012345678901234567890123456789012345678901234"),
+		LibreOfficePath: envOr("LIBREOFFICE_PATH", "/usr/bin/libreoffice"),
+		PdftoppmPath:    envOr("PDFTOPPM_PATH", "/usr/bin/pdftoppm"),
+		ThumbnailDir:    envOr("THUMBNAIL_DIR", "./uploads/thumbnails"),
 	}
 }
 

backend/internal/db/migrations/011_thumbnails.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS thumbnails;

backend/internal/db/migrations/011_thumbnails.up.sql

@@ -0,0 +1,14 @@
+CREATE TABLE thumbnails (
+    id               TEXT PRIMARY KEY DEFAULT gen_random_uuid(),
+    file_id          TEXT NOT NULL REFERENCES files(id) ON DELETE CASCADE,
+    page_number      INTEGER NOT NULL,
+    resolution_label TEXT NOT NULL,
+    width            INTEGER NOT NULL,
+    height           INTEGER NOT NULL,
+    storage_key      TEXT NOT NULL,
+    mime_type        TEXT NOT NULL DEFAULT 'image/jpeg',
+    created_at       TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE INDEX idx_thumbnails_file_id ON thumbnails(file_id);
+CREATE UNIQUE INDEX idx_thumbnails_unique ON thumbnails(file_id, page_number, resolution_label);

backend/internal/db/models.go

@@ -47,6 +47,18 @@ type Tag struct {
 	UpdatedAt   time.Time      `json:"updated_at"`
 }
 
+type Thumbnail struct {
+	ID              string    `json:"id"`
+	FileID          string    `json:"file_id"`
+	PageNumber      int32     `json:"page_number"`
+	ResolutionLabel string    `json:"resolution_label"`
+	Width           int32     `json:"width"`
+	Height          int32     `json:"height"`
+	StorageKey      string    `json:"storage_key"`
+	MimeType        string    `json:"mime_type"`
+	CreatedAt       time.Time `json:"created_at"`
+}
+
 type User struct {
 	ID           string    `json:"id"`
 	Username     string    `json:"username"`

backend/internal/db/queries/thumbnails.sql

@@ -0,0 +1,21 @@
+-- name: CreateThumbnail :one
+INSERT INTO thumbnails (file_id, page_number, resolution_label, width, height, storage_key, mime_type)
+VALUES ($1, $2, $3, $4, $5, $6, $7)
+RETURNING *;
+
+-- name: GetThumbnailsByFileID :many
+SELECT * FROM thumbnails
+WHERE file_id = $1
+ORDER BY page_number ASC, resolution_label ASC;
+
+-- name: GetThumbnailByID :one
+SELECT * FROM thumbnails
+WHERE id = $1 LIMIT 1;
+
+-- name: DeleteThumbnailsByFileID :exec
+DELETE FROM thumbnails WHERE file_id = $1;
+
+-- name: GetThumbnailByFilePageResolution :one
+SELECT * FROM thumbnails
+WHERE file_id = $1 AND page_number = $2 AND resolution_label = $3
+LIMIT 1;

backend/internal/db/thumbnails.sql.go

@@ -0,0 +1,150 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+// source: thumbnails.sql
+
+package db
+
+import (
+	"context"
+)
+
+const createThumbnail = `-- name: CreateThumbnail :one
+INSERT INTO thumbnails (file_id, page_number, resolution_label, width, height, storage_key, mime_type)
+VALUES ($1, $2, $3, $4, $5, $6, $7)
+RETURNING id, file_id, page_number, resolution_label, width, height, storage_key, mime_type, created_at
+`
+
+type CreateThumbnailParams struct {
+	FileID          string `json:"file_id"`
+	PageNumber      int32  `json:"page_number"`
+	ResolutionLabel string `json:"resolution_label"`
+	Width           int32  `json:"width"`
+	Height          int32  `json:"height"`
+	StorageKey      string `json:"storage_key"`
+	MimeType        string `json:"mime_type"`
+}
+
+func (q *Queries) CreateThumbnail(ctx context.Context, arg CreateThumbnailParams) (Thumbnail, error) {
+	row := q.db.QueryRowContext(ctx, createThumbnail,
+		arg.FileID,
+		arg.PageNumber,
+		arg.ResolutionLabel,
+		arg.Width,
+		arg.Height,
+		arg.StorageKey,
+		arg.MimeType,
+	)
+	var i Thumbnail
+	err := row.Scan(
+		&i.ID,
+		&i.FileID,
+		&i.PageNumber,
+		&i.ResolutionLabel,
+		&i.Width,
+		&i.Height,
+		&i.StorageKey,
+		&i.MimeType,
+		&i.CreatedAt,
+	)
+	return i, err
+}
+
+const deleteThumbnailsByFileID = `-- name: DeleteThumbnailsByFileID :exec
+DELETE FROM thumbnails WHERE file_id = $1
+`
+
+func (q *Queries) DeleteThumbnailsByFileID(ctx context.Context, fileID string) error {
+	_, err := q.db.ExecContext(ctx, deleteThumbnailsByFileID, fileID)
+	return err
+}
+
+const getThumbnailByFilePageResolution = `-- name: GetThumbnailByFilePageResolution :one
+SELECT id, file_id, page_number, resolution_label, width, height, storage_key, mime_type, created_at FROM thumbnails
+WHERE file_id = $1 AND page_number = $2 AND resolution_label = $3
+LIMIT 1
+`
+
+type GetThumbnailByFilePageResolutionParams struct {
+	FileID          string `json:"file_id"`
+	PageNumber      int32  `json:"page_number"`
+	ResolutionLabel string `json:"resolution_label"`
+}
+
+func (q *Queries) GetThumbnailByFilePageResolution(ctx context.Context, arg GetThumbnailByFilePageResolutionParams) (Thumbnail, error) {
+	row := q.db.QueryRowContext(ctx, getThumbnailByFilePageResolution, arg.FileID, arg.PageNumber, arg.ResolutionLabel)
+	var i Thumbnail
+	err := row.Scan(
+		&i.ID,
+		&i.FileID,
+		&i.PageNumber,
+		&i.ResolutionLabel,
+		&i.Width,
+		&i.Height,
+		&i.StorageKey,
+		&i.MimeType,
+		&i.CreatedAt,
+	)
+	return i, err
+}
+
+const getThumbnailByID = `-- name: GetThumbnailByID :one
+SELECT id, file_id, page_number, resolution_label, width, height, storage_key, mime_type, created_at FROM thumbnails
+WHERE id = $1 LIMIT 1
+`
+
+func (q *Queries) GetThumbnailByID(ctx context.Context, id string) (Thumbnail, error) {
+	row := q.db.QueryRowContext(ctx, getThumbnailByID, id)
+	var i Thumbnail
+	err := row.Scan(
+		&i.ID,
+		&i.FileID,
+		&i.PageNumber,
+		&i.ResolutionLabel,
+		&i.Width,
+		&i.Height,
+		&i.StorageKey,
+		&i.MimeType,
+		&i.CreatedAt,
+	)
+	return i, err
+}
+
+const getThumbnailsByFileID = `-- name: GetThumbnailsByFileID :many
+SELECT id, file_id, page_number, resolution_label, width, height, storage_key, mime_type, created_at FROM thumbnails
+WHERE file_id = $1
+ORDER BY page_number ASC, resolution_label ASC
+`
+
+func (q *Queries) GetThumbnailsByFileID(ctx context.Context, fileID string) ([]Thumbnail, error) {
+	rows, err := q.db.QueryContext(ctx, getThumbnailsByFileID, fileID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []Thumbnail
+	for rows.Next() {
+		var i Thumbnail
+		if err := rows.Scan(
+			&i.ID,
+			&i.FileID,
+			&i.PageNumber,
+			&i.ResolutionLabel,
+			&i.Width,
+			&i.Height,
+			&i.StorageKey,
+			&i.MimeType,
+			&i.CreatedAt,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}

backend/internal/handler/files.go

@@ -15,6 +15,7 @@ type FileHandler struct {
 	files      *service.FileService
 	urls       *service.URLService
 	ocr        *service.OCRService
+	conversion *service.ConversionService
 }
 
 func (h *FileHandler) Upload(c *gin.Context) {
@@ -40,6 +41,10 @@ func (h *FileHandler) Upload(c *gin.Context) {
 
 		h.ocr.Enqueue(result.ID, result.Path)
 
+		if service.IsConvertible(result.MimeType) {
+			h.conversion.Enqueue(result.ID, result.Path, result.MimeType)
+		}
+
 		results = append(results, gin.H{
 			"id":   result.ID,
 			"name": result.Name,
@@ -252,3 +257,56 @@ func (h *FileHandler) ListFilesByParent(c *gin.Context) {
 	}
 	api.Success(c, files)
 }
+
+func (h *FileHandler) GetThumbnails(c *gin.Context) {
+	id := c.Param("id")
+	thumbnails, err := h.files.GetThumbnailsByFileID(id)
+	if err != nil {
+		api.Error(c, http.StatusInternalServerError, "DB_ERROR", "Failed to fetch thumbnails")
+		return
+	}
+
+	type thumbnailResponse struct {
+		ID              string `json:"id"`
+		PageNumber      int    `json:"pageNumber"`
+		ResolutionLabel string `json:"resolutionLabel"`
+		Width           int    `json:"width"`
+		Height          int    `json:"height"`
+		URL             string `json:"url"`
+		MimeType        string `json:"mimeType"`
+	}
+
+	resp := make([]thumbnailResponse, len(thumbnails))
+	for i, t := range thumbnails {
+		resp[i] = thumbnailResponse{
+			ID:              t.ID,
+			PageNumber:      t.PageNumber,
+			ResolutionLabel: t.ResolutionLabel,
+			Width:           t.Width,
+			Height:          t.Height,
+			URL:             h.urls.GenerateThumbnailURL(t.ID),
+			MimeType:        t.MimeType,
+		}
+	}
+
+	api.Success(c, resp)
+}
+
+func (h *FileHandler) ServeThumbnail(c *gin.Context) {
+	id := c.Param("id")
+	exp, _ := strconv.ParseInt(c.Query("expires"), 10, 64)
+	sig := c.Query("sig")
+
+	if !h.urls.Validate(id, sig, exp) {
+		api.Error(c, http.StatusForbidden, "FORBIDDEN", "Invalid or expired link")
+		return
+	}
+
+	storagePath, err := h.files.GetThumbnailStoragePath(id)
+	if err != nil {
+		api.Error(c, http.StatusNotFound, "THUMBNAIL_NOT_FOUND", "Thumbnail not found")
+		return
+	}
+
+	c.File(path.Clean(storagePath))
+}

backend/internal/handler/handler.go

@@ -12,9 +12,9 @@ type Handler struct {
 	Auth   *auth.AuthHandler
 }
 
-func New(fileSvc *service.FileService, ocrSvc *service.OCRService, urlSvc *service.URLService, authHandler *auth.AuthHandler) *Handler {
+func New(fileSvc *service.FileService, ocrSvc *service.OCRService, urlSvc *service.URLService, authHandler *auth.AuthHandler, conversionSvc *service.ConversionService) *Handler {
 	return &Handler{
-		File:   &FileHandler{files: fileSvc, urls: urlSvc, ocr: ocrSvc},
+		File:   &FileHandler{files: fileSvc, urls: urlSvc, ocr: ocrSvc, conversion: conversionSvc},
 		OCR:    &OCRHandler{ocr: ocrSvc, files: fileSvc},
 		Health: &HealthHandler{ocr: ocrSvc},
 		Auth:   authHandler,

backend/internal/handler/router.go

@@ -34,4 +34,8 @@ func SetupRoutes(r *gin.Engine, h *Handler, authMiddleware *auth.AuthService) {
 
 	protected.POST("/ocr/jobs", h.OCR.CreateJob)
 	protected.GET("/ocr/jobs/:id", h.OCR.GetJobStatus)
+
+	protected.GET("/files/:id/thumbnails", h.File.GetThumbnails)
+
+	api.GET("/thumbnails/:id", h.File.ServeThumbnail)
 }

backend/internal/model/file.go

@@ -25,4 +25,5 @@ type UploadResult struct {
 	ID       string `json:"id"`
 	Name     string `json:"name"`
 	Path     string `json:"path"`
+	MimeType string `json:"mimeType"`
 }

backend/internal/model/thumbnail.go

@@ -0,0 +1,13 @@
+package model
+
+type Thumbnail struct {
+	ID              string `json:"id"`
+	FileID          string `json:"fileId"`
+	PageNumber      int    `json:"pageNumber"`
+	ResolutionLabel string `json:"resolutionLabel"`
+	Width           int    `json:"width"`
+	Height          int    `json:"height"`
+	StorageKey      string `json:"-"`
+	MimeType        string `json:"mimeType"`
+	CreatedAt       string `json:"createdAt"`
+}

backend/internal/service/conversion.go

@@ -0,0 +1,251 @@
+package service
+
+import (
+	"context"
+	"fmt"
+	"image"
+	_ "image/jpeg"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/google/uuid"
+	"github.com/vaultdrop/backend/internal/config"
+	"github.com/vaultdrop/backend/internal/db"
+)
+
+type ConversionJob struct {
+	FileID   string
+	FilePath string
+	MimeType string
+}
+
+type ConversionService struct {
+	queries *db.Queries
+	cfg     *config.Config
+	jobs    chan ConversionJob
+}
+
+func NewConversionService(queries *db.Queries, cfg *config.Config) *ConversionService {
+	return &ConversionService{
+		queries: queries,
+		cfg:     cfg,
+		jobs:    make(chan ConversionJob, 100),
+	}
+}
+
+func (s *ConversionService) Start() {
+	go s.worker()
+	log.Println("[Conversion] Worker started")
+}
+
+func (s *ConversionService) Stop() {
+	close(s.jobs)
+	log.Println("[Conversion] Worker stopped")
+}
+
+func (s *ConversionService) Enqueue(fileID, filePath, mimeType string) {
+	s.jobs <- ConversionJob{FileID: fileID, FilePath: filePath, MimeType: mimeType}
+	log.Printf("[Conversion] Enqueued file %s", fileID)
+}
+
+func (s *ConversionService) worker() {
+	for job := range s.jobs {
+		s.process(job)
+	}
+}
+
+func (s *ConversionService) process(job ConversionJob) {
+	log.Printf("[Conversion] Processing file %s (mime: %s)", job.FileID, job.MimeType)
+
+	pdfPath := job.FilePath
+	tmpDir := ""
+
+	if isOfficeDocument(job.MimeType) {
+		var err error
+		pdfPath, tmpDir, err = s.convertToPDF(job.FilePath)
+		if err != nil {
+			log.Printf("[Conversion] Failed to convert file %s to PDF: %v", job.FileID, err)
+			return
+		}
+		defer os.RemoveAll(tmpDir)
+	} else if !isPDF(job.MimeType) {
+		log.Printf("[Conversion] Skipping file %s: unsupported mime type %s", job.FileID, job.MimeType)
+		return
+	}
+
+	thumbDir := filepath.Join(s.cfg.ThumbnailDir, job.FileID)
+	if err := os.MkdirAll(thumbDir, 0o755); err != nil {
+		log.Printf("[Conversion] Failed to create thumbnail dir for %s: %v", job.FileID, err)
+		return
+	}
+
+	resolutions := []struct {
+		label string
+		dpi   int
+	}{
+		{"thumbnail", 21},
+		{"full", 200},
+	}
+
+	for _, res := range resolutions {
+		pages, err := s.convertPDFToImages(pdfPath, thumbDir, res.dpi)
+		if err != nil {
+			log.Printf("[Conversion] Failed to convert file %s to images (res=%s): %v", job.FileID, res.label, err)
+			continue
+		}
+
+		for _, page := range pages {
+			width, height, err := getImageDimensions(page.path)
+			if err != nil {
+				log.Printf("[Conversion] Failed to get dimensions for %s: %v", page.path, err)
+				width, height = 0, 0
+			}
+
+			thumbUUID := uuid.New().String()
+			dstPath := filepath.Join(thumbDir, thumbUUID+".jpg")
+			if err := os.Rename(page.path, dstPath); err != nil {
+				log.Printf("[Conversion] Failed to move %s to %s: %v", page.path, dstPath, err)
+				continue
+			}
+
+			_, err = s.queries.CreateThumbnail(context.Background(), db.CreateThumbnailParams{
+				FileID:          job.FileID,
+				PageNumber:      int32(page.number),
+				ResolutionLabel: res.label,
+				Width:           int32(width),
+				Height:          int32(height),
+				StorageKey:      dstPath,
+				MimeType:        "image/jpeg",
+			})
+			if err != nil {
+				log.Printf("[Conversion] Failed to create thumbnail record for file %s page %d: %v", job.FileID, page.number, err)
+				continue
+			}
+		}
+
+		log.Printf("[Conversion] Generated %d %s images for file %s", len(pages), res.label, job.FileID)
+	}
+
+	log.Printf("[Conversion] Completed file %s", job.FileID)
+}
+
+func (s *ConversionService) convertToPDF(inputPath string) (string, string, error) {
+	tmpDir, err := os.MkdirTemp("", "conversion-*")
+	if err != nil {
+		return "", "", fmt.Errorf("create temp dir: %w", err)
+	}
+
+	cmd := exec.Command(s.cfg.LibreOfficePath,
+		"--headless",
+		"--convert-to", "pdf",
+		"--outdir", tmpDir,
+		inputPath,
+	)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		os.RemoveAll(tmpDir)
+		return "", "", fmt.Errorf("libreoffice conversion failed: %s: %w", string(output), err)
+	}
+
+	baseName := filepath.Base(inputPath)
+	pdfName := strings.TrimSuffix(baseName, filepath.Ext(baseName)) + ".pdf"
+	pdfPath := filepath.Join(tmpDir, pdfName)
+
+	if _, err := os.Stat(pdfPath); os.IsNotExist(err) {
+		os.RemoveAll(tmpDir)
+		return "", "", fmt.Errorf("PDF not found at %s", pdfPath)
+	}
+
+	return pdfPath, tmpDir, nil
+}
+
+type imagePage struct {
+	number int
+	path   string
+}
+
+func (s *ConversionService) convertPDFToImages(pdfPath, outputDir string, dpi int) ([]imagePage, error) {
+	prefix := filepath.Join(outputDir, fmt.Sprintf("tmp_%d_", dpi))
+
+	cmd := exec.Command(s.cfg.PdftoppmPath,
+		"-jpeg",
+		"-r", fmt.Sprintf("%d", dpi),
+		pdfPath,
+		prefix,
+	)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		return nil, fmt.Errorf("pdftoppm failed: %s: %w", string(output), err)
+	}
+
+	entries, err := os.ReadDir(outputDir)
+	if err != nil {
+		return nil, fmt.Errorf("read output dir: %w", err)
+	}
+
+	var pages []imagePage
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+		name := entry.Name()
+		if !strings.HasPrefix(name, fmt.Sprintf("tmp_%d_", dpi)) || !strings.HasSuffix(name, ".jpg") {
+			continue
+		}
+		var num int
+		if _, err := fmt.Sscanf(strings.TrimPrefix(name, fmt.Sprintf("tmp_%d_", dpi)), "%d", &num); err != nil {
+			continue
+		}
+		pages = append(pages, imagePage{
+			number: num,
+			path:   filepath.Join(outputDir, name),
+		})
+	}
+
+	return pages, nil
+}
+
+func isPDF(mimeType string) bool {
+	return strings.Contains(mimeType, "pdf")
+}
+
+func isOfficeDocument(mimeType string) bool {
+	officeTypes := []string{
+		"application/vnd.openxmlformats-officedocument",
+		"application/vnd.ms-excel",
+		"application/msword",
+		"application/vnd.ms-powerpoint",
+		"application/vnd.oasis.opendocument",
+		"application/x-doc",
+		"application/x-xls",
+		"application/x-ppt",
+	}
+	for _, t := range officeTypes {
+		if strings.Contains(mimeType, t) {
+			return true
+		}
+	}
+	return false
+}
+
+func IsConvertible(mimeType string) bool {
+	return isPDF(mimeType) || isOfficeDocument(mimeType)
+}
+
+func getImageDimensions(path string) (int, int, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return 0, 0, err
+	}
+	defer f.Close()
+
+	cfg, _, err := image.DecodeConfig(f)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	return cfg.Width, cfg.Height, nil
+}

backend/internal/service/file.go

@@ -62,6 +62,7 @@ func (s *FileService) Upload(file *multipart.FileHeader) (*model.UploadResult, e
 		ID:       dbFile.ID,
 		Name:     dbFile.Name,
 		Path:     dst,
+		MimeType: dbFile.MimeType,
 	}, nil
 }
 
@@ -206,6 +207,37 @@ func (s *FileService) ListFilesByParentID(parentID string) ([]model.File, error)
 	return files, nil
 }
 
+func (s *FileService) GetThumbnailsByFileID(fileID string) ([]model.Thumbnail, error) {
+	dbThumbnails, err := s.queries.GetThumbnailsByFileID(context.Background(), fileID)
+	if err != nil {
+		return nil, fmt.Errorf("get thumbnails: %w", err)
+	}
+
+	thumbnails := make([]model.Thumbnail, len(dbThumbnails))
+	for i, t := range dbThumbnails {
+		thumbnails[i] = model.Thumbnail{
+			ID:              t.ID,
+			FileID:          t.FileID,
+			PageNumber:      int(t.PageNumber),
+			ResolutionLabel: t.ResolutionLabel,
+			Width:           int(t.Width),
+			Height:          int(t.Height),
+			StorageKey:      t.StorageKey,
+			MimeType:        t.MimeType,
+			CreatedAt:       t.CreatedAt.String(),
+		}
+	}
+	return thumbnails, nil
+}
+
+func (s *FileService) GetThumbnailStoragePath(id string) (string, error) {
+	t, err := s.queries.GetThumbnailByID(context.Background(), id)
+	if err != nil {
+		return "", fmt.Errorf("get thumbnail: %w", err)
+	}
+	return t.StorageKey, nil
+}
+
 func dbToModel(f db.File, dbTags []db.Tag) model.File {
 	tags := make([]model.Tag, len(dbTags))
 	for i, t := range dbTags {

backend/internal/service/url.go

@@ -37,6 +37,19 @@ func (s *URLService) GenerateDownloadURL(fileUUID string) string {
 	)
 }
 
+func (s *URLService) GenerateThumbnailURL(thumbUUID string) string {
+	expires := time.Now().Add(10 * time.Minute).Unix()
+	sig := s.sign(thumbUUID, expires)
+
+	return fmt.Sprintf(
+		"%s/api/v1/thumbnails/%s?expires=%d&sig=%s",
+		s.serverHost,
+		thumbUUID,
+		expires,
+		sig,
+	)
+}
+
 func (s *URLService) Validate(fileID, sig string, expires int64) bool {
 	if time.Now().Unix() > expires {
 		return false