Save signatures to server (#5080)

# Description of Changes

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Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)
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---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Co-authored-by: Anthony Stirling <[email protected]>

app/common/src/main/java/stirling/software/common/service/PersonalSignatureServiceInterface.java

@@ -0,0 +1,21 @@
+package stirling.software.common.service;
+
+import java.io.IOException;
+
+/**
+ * Interface for personal signature access (proprietary feature). Implemented only in proprietary
+ * module to provide authenticated users access to their personal signatures.
+ */
+public interface PersonalSignatureServiceInterface {
+
+    /**
+     * Get a personal signature from the user's folder. Only checks personal folder, not shared
+     * folder.
+     *
+     * @param username Username of the signature owner
+     * @param fileName Signature filename
+     * @return Personal signature image bytes
+     * @throws IOException If file not found or read error
+     */
+    byte[] getPersonalSignatureBytes(String username, String fileName) throws IOException;
+}

app/core/src/main/java/stirling/software/SPDF/controller/api/UIDataController.java

@@ -26,7 +26,7 @@ import lombok.extern.slf4j.Slf4j;
 
 import stirling.software.SPDF.model.Dependency;
 import stirling.software.SPDF.model.SignatureFile;
-import stirling.software.SPDF.service.SignatureService;
+import stirling.software.SPDF.service.SharedSignatureService;
 import stirling.software.common.annotations.api.UiDataApi;
 import stirling.software.common.configuration.InstallationPathConfig;
 import stirling.software.common.configuration.RuntimePathConfig;
@@ -40,14 +40,14 @@ import stirling.software.common.util.GeneralUtils;
 public class UIDataController {
 
     private final ApplicationProperties applicationProperties;
-    private final SignatureService signatureService;
+    private final SharedSignatureService signatureService;
     private final UserServiceInterface userService;
     private final ResourceLoader resourceLoader;
     private final RuntimePathConfig runtimePathConfig;
 
     public UIDataController(
             ApplicationProperties applicationProperties,
-            SignatureService signatureService,
+            SharedSignatureService signatureService,
             @Autowired(required = false) UserServiceInterface userService,
             ResourceLoader resourceLoader,
             RuntimePathConfig runtimePathConfig) {

app/core/src/main/java/stirling/software/SPDF/controller/web/GeneralWebController.java

@@ -25,7 +25,7 @@ import lombok.Setter;
 import lombok.extern.slf4j.Slf4j;
 
 import stirling.software.SPDF.model.SignatureFile;
-import stirling.software.SPDF.service.SignatureService;
+import stirling.software.SPDF.service.SharedSignatureService;
 import stirling.software.common.configuration.InstallationPathConfig;
 import stirling.software.common.configuration.RuntimePathConfig;
 import stirling.software.common.service.UserServiceInterface;
@@ -37,13 +37,13 @@ import stirling.software.common.util.GeneralUtils;
 @Slf4j
 public class GeneralWebController {
 
-    private final SignatureService signatureService;
+    private final SharedSignatureService signatureService;
     private final UserServiceInterface userService;
     private final ResourceLoader resourceLoader;
     private final RuntimePathConfig runtimePathConfig;
 
     public GeneralWebController(
-            SignatureService signatureService,
+            SharedSignatureService signatureService,
             @Autowired(required = false) UserServiceInterface userService,
             ResourceLoader resourceLoader,
             RuntimePathConfig runtimePathConfig) {

app/core/src/main/java/stirling/software/SPDF/controller/web/SignatureController.java

@@ -1,48 +0,0 @@
-package stirling.software.SPDF.controller.web;
-
-import java.io.IOException;
-
-import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.http.HttpStatus;
-import org.springframework.http.MediaType;
-import org.springframework.http.ResponseEntity;
-import org.springframework.web.bind.annotation.GetMapping;
-import org.springframework.web.bind.annotation.PathVariable;
-import org.springframework.web.bind.annotation.RequestMapping;
-
-import stirling.software.SPDF.service.SignatureService;
-import stirling.software.common.service.UserServiceInterface;
-
-// @Controller // Disabled - Backend-only mode, no Thymeleaf UI
-@RequestMapping("/api/v1/general")
-public class SignatureController {
-
-    private final SignatureService signatureService;
-
-    private final UserServiceInterface userService;
-
-    public SignatureController(
-            SignatureService signatureService,
-            @Autowired(required = false) UserServiceInterface userService) {
-        this.signatureService = signatureService;
-        this.userService = userService;
-    }
-
-    @GetMapping("/sign/{fileName}")
-    public ResponseEntity<byte[]> getSignature(@PathVariable(name = "fileName") String fileName)
-            throws IOException {
-        String username = "NON_SECURITY_USER";
-        if (userService != null) {
-            username = userService.getCurrentUsername();
-        }
-        // Verify access permission
-        if (!signatureService.hasAccessToFile(username, fileName)) {
-            return ResponseEntity.status(HttpStatus.FORBIDDEN).build();
-        }
-        byte[] imageBytes = signatureService.getSignatureBytes(username, fileName);
-        return ResponseEntity.ok()
-                .contentType( // Adjust based on file type
-                        MediaType.IMAGE_JPEG)
-                .body(imageBytes);
-    }
-}

app/core/src/main/java/stirling/software/SPDF/controller/web/SignatureImageController.java

@@ -0,0 +1,84 @@
+package stirling.software.SPDF.controller.web;
+
+import java.io.IOException;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import lombok.extern.slf4j.Slf4j;
+
+import stirling.software.SPDF.service.SharedSignatureService;
+import stirling.software.common.service.PersonalSignatureServiceInterface;
+import stirling.software.common.service.UserServiceInterface;
+
+/**
+ * Unified signature image controller that works for both authenticated and unauthenticated users.
+ * Uses composition pattern: - Core SharedSignatureService (always available): reads shared signatures -
+ * PersonalSignatureService (proprietary, optional): reads personal signatures For authenticated
+ * signature management (save/delete), see proprietary SignatureController.
+ */
+@Slf4j
+@RestController
+@RequestMapping("/api/v1/general")
+public class SignatureImageController {
+
+    private final SharedSignatureService sharedSignatureService;
+    private final PersonalSignatureServiceInterface personalSignatureService;
+    private final UserServiceInterface userService;
+
+    public SignatureImageController(
+            SharedSignatureService sharedSignatureService,
+            @Autowired(required = false) PersonalSignatureServiceInterface personalSignatureService,
+            @Autowired(required = false) UserServiceInterface userService) {
+        this.sharedSignatureService = sharedSignatureService;
+        this.personalSignatureService = personalSignatureService;
+        this.userService = userService;
+    }
+
+    /**
+     * Get a signature image (works for both authenticated and unauthenticated users). -
+     * Authenticated with proprietary: tries personal first, then shared - Unauthenticated or
+     * community: tries shared only
+     */
+    @GetMapping("/signatures/{fileName}")
+    public ResponseEntity<byte[]> getSignature(@PathVariable(name = "fileName") String fileName) {
+        try {
+            byte[] imageBytes = null;
+
+            // If proprietary service available and user authenticated, try personal folder first
+            if (personalSignatureService != null && userService != null) {
+                try {
+                    String username = userService.getCurrentUsername();
+                    imageBytes =
+                            personalSignatureService.getPersonalSignatureBytes(username, fileName);
+                } catch (Exception e) {
+                    // Not found in personal folder or not authenticated, will try shared
+                    log.debug("Personal signature not found, trying shared: {}", e.getMessage());
+                }
+            }
+
+            // If not found in personal (or no personal service), try shared
+            if (imageBytes == null) {
+                imageBytes = sharedSignatureService.getSharedSignatureBytes(fileName);
+            }
+
+            // Determine content type from file extension
+            MediaType contentType = MediaType.IMAGE_PNG; // Default
+            String lowerFileName = fileName.toLowerCase();
+            if (lowerFileName.endsWith(".jpg") || lowerFileName.endsWith(".jpeg")) {
+                contentType = MediaType.IMAGE_JPEG;
+            }
+
+            return ResponseEntity.ok().contentType(contentType).body(imageBytes);
+        } catch (IOException e) {
+            log.debug("Signature not found: {}", fileName);
+            return ResponseEntity.status(HttpStatus.NOT_FOUND).build();
+        }
+    }
+}

app/core/src/main/java/stirling/software/SPDF/model/api/signature/SavedSignatureRequest.java

@@ -0,0 +1,18 @@
+package stirling.software.SPDF.model.api.signature;
+
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@NoArgsConstructor
+public class SavedSignatureRequest {
+    private String id;
+    private String label;
+    private String type; // "canvas", "image", "text"
+    private String scope; // "personal", "shared"
+    private String dataUrl; // For canvas and image types
+    private String signerName; // For text type
+    private String fontFamily; // For text type
+    private Integer fontSize; // For text type
+    private String textColor; // For text type
+}

app/core/src/main/java/stirling/software/SPDF/model/api/signature/SavedSignatureResponse.java

@@ -0,0 +1,22 @@
+package stirling.software.SPDF.model.api.signature;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class SavedSignatureResponse {
+    private String id;
+    private String label;
+    private String type; // "canvas", "image", "text"
+    private String scope; // "personal", "shared"
+    private String dataUrl; // For canvas and image types (or URL to fetch image)
+    private String signerName; // For text type
+    private String fontFamily; // For text type
+    private Integer fontSize; // For text type
+    private String textColor; // For text type
+    private Long createdAt;
+    private Long updatedAt;
+}

app/core/src/main/java/stirling/software/SPDF/service/SharedSignatureService.java

@@ -0,0 +1,308 @@
+package stirling.software.SPDF.service;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+import java.util.ArrayList;
+import java.util.Base64;
+import java.util.List;
+import java.util.stream.Stream;
+
+import org.springframework.stereotype.Service;
+import org.springframework.util.StringUtils;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import lombok.extern.slf4j.Slf4j;
+
+import stirling.software.SPDF.model.SignatureFile;
+import stirling.software.SPDF.model.api.signature.SavedSignatureRequest;
+import stirling.software.SPDF.model.api.signature.SavedSignatureResponse;
+import stirling.software.common.configuration.InstallationPathConfig;
+
+@Service
+@Slf4j
+public class SharedSignatureService {
+
+    private final String SIGNATURE_BASE_PATH;
+    private final String ALL_USERS_FOLDER = "ALL_USERS";
+    private final ObjectMapper objectMapper;
+
+    public SharedSignatureService() {
+        SIGNATURE_BASE_PATH = InstallationPathConfig.getSignaturesPath();
+        this.objectMapper = new ObjectMapper();
+    }
+
+    public boolean hasAccessToFile(String username, String fileName) throws IOException {
+        validateFileName(fileName);
+        // Check if file exists in user's personal folder or ALL_USERS folder
+        Path userPath = Paths.get(SIGNATURE_BASE_PATH, username, fileName);
+        Path allUsersPath = Paths.get(SIGNATURE_BASE_PATH, ALL_USERS_FOLDER, fileName);
+
+        return Files.exists(userPath) || Files.exists(allUsersPath);
+    }
+
+    public List<SignatureFile> getAvailableSignatures(String username) {
+        List<SignatureFile> signatures = new ArrayList<>();
+
+        // Get signatures from user's personal folder
+        if (StringUtils.hasText(username)) {
+            Path userFolder = Paths.get(SIGNATURE_BASE_PATH, username);
+            if (Files.exists(userFolder)) {
+                try {
+                    signatures.addAll(getSignaturesFromFolder(userFolder, "Personal"));
+                } catch (IOException e) {
+                    log.error("Error reading user signatures folder", e);
+                }
+            }
+        }
+
+        // Get signatures from ALL_USERS folder
+        Path allUsersFolder = Paths.get(SIGNATURE_BASE_PATH, ALL_USERS_FOLDER);
+        if (Files.exists(allUsersFolder)) {
+            try {
+                signatures.addAll(getSignaturesFromFolder(allUsersFolder, "Shared"));
+            } catch (IOException e) {
+                log.error("Error reading shared signatures folder", e);
+            }
+        }
+
+        return signatures;
+    }
+
+    private List<SignatureFile> getSignaturesFromFolder(Path folder, String category)
+            throws IOException {
+        try (Stream<Path> stream = Files.list(folder)) {
+            return stream.filter(this::isImageFile)
+                    .map(path -> new SignatureFile(path.getFileName().toString(), category))
+                    .toList();
+        }
+    }
+
+    /**
+     * Get a signature from the shared (ALL_USERS) folder. This is always available for both
+     * authenticated and unauthenticated users.
+     */
+    public byte[] getSharedSignatureBytes(String fileName) throws IOException {
+        validateFileName(fileName);
+        Path allUsersPath = Paths.get(SIGNATURE_BASE_PATH, ALL_USERS_FOLDER, fileName);
+        if (!Files.exists(allUsersPath)) {
+            throw new FileNotFoundException("Shared signature file not found");
+        }
+        return Files.readAllBytes(allUsersPath);
+    }
+
+    private boolean isImageFile(Path path) {
+        String fileName = path.getFileName().toString().toLowerCase();
+        return fileName.endsWith(".jpg") || fileName.endsWith(".jpeg") || fileName.endsWith(".png");
+    }
+
+    private void validateFileName(String fileName) {
+        if (fileName.contains("..") || fileName.contains("/") || fileName.contains("\\")) {
+            throw new IllegalArgumentException("Invalid filename");
+        }
+        // Only allow alphanumeric, hyphen, underscore, and dot (for extensions)
+        if (!fileName.matches("^[a-zA-Z0-9_.-]+$")) {
+            throw new IllegalArgumentException("Filename contains invalid characters");
+        }
+    }
+
+    private String validateAndNormalizeExtension(String extension) {
+        String normalized = extension.toLowerCase().trim();
+        // Whitelist only safe image extensions
+        if (normalized.equals("png") || normalized.equals("jpg") || normalized.equals("jpeg")) {
+            return normalized;
+        }
+        throw new IllegalArgumentException("Unsupported image extension: " + extension);
+    }
+
+    private void verifyPathWithinDirectory(Path resolvedPath, Path targetDirectory)
+            throws IOException {
+        Path canonicalTarget = targetDirectory.toAbsolutePath().normalize();
+        Path canonicalResolved = resolvedPath.toAbsolutePath().normalize();
+        if (!canonicalResolved.startsWith(canonicalTarget)) {
+            throw new IOException("Resolved path is outside the target directory");
+        }
+    }
+
+    /** Save a signature as image file */
+    public SavedSignatureResponse saveSignature(String username, SavedSignatureRequest request)
+            throws IOException {
+        validateFileName(request.getId());
+
+        // Determine folder based on scope
+        String scope = request.getScope();
+        if (scope == null || scope.isEmpty()) {
+            scope = "personal"; // Default to personal
+        }
+
+        String folderName = "shared".equals(scope) ? ALL_USERS_FOLDER : username;
+        Path targetFolder = Paths.get(SIGNATURE_BASE_PATH, folderName);
+        Files.createDirectories(targetFolder);
+
+        long timestamp = System.currentTimeMillis();
+
+        SavedSignatureResponse response = new SavedSignatureResponse();
+        response.setId(request.getId());
+        response.setLabel(request.getLabel());
+        response.setType(request.getType());
+        response.setScope(scope);
+        response.setCreatedAt(timestamp);
+        response.setUpdatedAt(timestamp);
+
+        // Extract and save image data
+        String dataUrl = request.getDataUrl();
+        if (dataUrl != null && dataUrl.startsWith("data:image/")) {
+            // Extract base64 data
+            String base64Data = dataUrl.substring(dataUrl.indexOf(",") + 1);
+            byte[] imageBytes = Base64.getDecoder().decode(base64Data);
+
+            // Determine and validate file extension from data URL
+            String mimeType = dataUrl.substring(dataUrl.indexOf(":") + 1, dataUrl.indexOf(";"));
+            String rawExtension = mimeType.substring(mimeType.indexOf("/") + 1);
+            String extension = validateAndNormalizeExtension(rawExtension);
+
+            // Save image file only
+            String imageFileName = request.getId() + "." + extension;
+            Path imagePath = targetFolder.resolve(imageFileName);
+
+            // Verify path is within target directory
+            verifyPathWithinDirectory(imagePath, targetFolder);
+
+            Files.write(
+                    imagePath,
+                    imageBytes,
+                    StandardOpenOption.CREATE,
+                    StandardOpenOption.TRUNCATE_EXISTING);
+
+            // Store reference to image file
+            response.setDataUrl("/api/v1/general/sign/" + imageFileName);
+        }
+
+        log.info("Saved signature {} for user {}", request.getId(), username);
+        return response;
+    }
+
+    /** Get all saved signatures for a user */
+    public List<SavedSignatureResponse> getSavedSignatures(String username) throws IOException {
+        List<SavedSignatureResponse> signatures = new ArrayList<>();
+
+        // Load personal signatures
+        Path personalFolder = Paths.get(SIGNATURE_BASE_PATH, username);
+        if (Files.exists(personalFolder)) {
+            try (Stream<Path> stream = Files.list(personalFolder)) {
+                stream.filter(this::isImageFile)
+                        .forEach(
+                                path -> {
+                                    try {
+                                        String fileName = path.getFileName().toString();
+                                        String id =
+                                                fileName.substring(0, fileName.lastIndexOf('.'));
+
+                                        SavedSignatureResponse sig = new SavedSignatureResponse();
+                                        sig.setId(id);
+                                        sig.setLabel(id); // Use ID as label
+                                        sig.setType("image"); // Default type
+                                        sig.setScope("personal");
+                                        sig.setDataUrl("/api/v1/general/sign/" + fileName);
+                                        sig.setCreatedAt(
+                                                Files.getLastModifiedTime(path).toMillis());
+                                        sig.setUpdatedAt(
+                                                Files.getLastModifiedTime(path).toMillis());
+
+                                        signatures.add(sig);
+                                    } catch (IOException e) {
+                                        log.error("Error reading signature file: " + path, e);
+                                    }
+                                });
+            }
+        }
+
+        // Load shared signatures
+        Path sharedFolder = Paths.get(SIGNATURE_BASE_PATH, ALL_USERS_FOLDER);
+        if (Files.exists(sharedFolder)) {
+            try (Stream<Path> stream = Files.list(sharedFolder)) {
+                stream.filter(this::isImageFile)
+                        .forEach(
+                                path -> {
+                                    try {
+                                        String fileName = path.getFileName().toString();
+                                        String id =
+                                                fileName.substring(0, fileName.lastIndexOf('.'));
+
+                                        SavedSignatureResponse sig = new SavedSignatureResponse();
+                                        sig.setId(id);
+                                        sig.setLabel(id); // Use ID as label
+                                        sig.setType("image"); // Default type
+                                        sig.setScope("shared");
+                                        sig.setDataUrl("/api/v1/general/sign/" + fileName);
+                                        sig.setCreatedAt(
+                                                Files.getLastModifiedTime(path).toMillis());
+                                        sig.setUpdatedAt(
+                                                Files.getLastModifiedTime(path).toMillis());
+
+                                        signatures.add(sig);
+                                    } catch (IOException e) {
+                                        log.error("Error reading signature file: " + path, e);
+                                    }
+                                });
+            }
+        }
+
+        return signatures;
+    }
+
+    /** Delete a saved signature */
+    public void deleteSignature(String username, String signatureId) throws IOException {
+        validateFileName(signatureId);
+
+        // Try to find and delete image file in personal folder
+        Path personalFolder = Paths.get(SIGNATURE_BASE_PATH, username);
+        boolean deleted = false;
+
+        if (Files.exists(personalFolder)) {
+            try (Stream<Path> stream = Files.list(personalFolder)) {
+                List<Path> matchingFiles =
+                        stream.filter(
+                                        path ->
+                                                path.getFileName()
+                                                        .toString()
+                                                        .startsWith(signatureId + "."))
+                                .toList();
+                for (Path file : matchingFiles) {
+                    Files.delete(file);
+                    deleted = true;
+                }
+            }
+        }
+
+        // Try shared folder if not found in personal
+        if (!deleted) {
+            Path sharedFolder = Paths.get(SIGNATURE_BASE_PATH, ALL_USERS_FOLDER);
+            if (Files.exists(sharedFolder)) {
+                try (Stream<Path> stream = Files.list(sharedFolder)) {
+                    List<Path> matchingFiles =
+                            stream.filter(
+                                            path ->
+                                                    path.getFileName()
+                                                            .toString()
+                                                            .startsWith(signatureId + "."))
+                                    .toList();
+                    for (Path file : matchingFiles) {
+                        Files.delete(file);
+                        deleted = true;
+                    }
+                }
+            }
+        }
+
+        if (!deleted) {
+            throw new FileNotFoundException("Signature not found");
+        }
+
+        log.info("Deleted signature {} for user {}", signatureId, username);
+    }
+}

app/core/src/main/java/stirling/software/SPDF/service/SignatureService.java

@@ -1,107 +0,0 @@
-package stirling.software.SPDF.service;
-
-import java.io.FileNotFoundException;
-import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.Paths;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.stream.Stream;
-
-import org.springframework.stereotype.Service;
-import org.springframework.util.StringUtils;
-
-import lombok.extern.slf4j.Slf4j;
-
-import stirling.software.SPDF.model.SignatureFile;
-import stirling.software.common.configuration.InstallationPathConfig;
-
-@Service
-@Slf4j
-public class SignatureService {
-
-    private final String SIGNATURE_BASE_PATH;
-    private final String ALL_USERS_FOLDER = "ALL_USERS";
-
-    public SignatureService() {
-        SIGNATURE_BASE_PATH = InstallationPathConfig.getSignaturesPath();
-    }
-
-    public boolean hasAccessToFile(String username, String fileName) throws IOException {
-        validateFileName(fileName);
-        // Check if file exists in user's personal folder or ALL_USERS folder
-        Path userPath = Paths.get(SIGNATURE_BASE_PATH, username, fileName);
-        Path allUsersPath = Paths.get(SIGNATURE_BASE_PATH, ALL_USERS_FOLDER, fileName);
-
-        return Files.exists(userPath) || Files.exists(allUsersPath);
-    }
-
-    public List<SignatureFile> getAvailableSignatures(String username) {
-        List<SignatureFile> signatures = new ArrayList<>();
-
-        // Get signatures from user's personal folder
-        if (StringUtils.hasText(username)) {
-            Path userFolder = Paths.get(SIGNATURE_BASE_PATH, username);
-            if (Files.exists(userFolder)) {
-                try {
-                    signatures.addAll(getSignaturesFromFolder(userFolder, "Personal"));
-                } catch (IOException e) {
-                    log.error("Error reading user signatures folder", e);
-                }
-            }
-        }
-
-        // Get signatures from ALL_USERS folder
-        Path allUsersFolder = Paths.get(SIGNATURE_BASE_PATH, ALL_USERS_FOLDER);
-        if (Files.exists(allUsersFolder)) {
-            try {
-                signatures.addAll(getSignaturesFromFolder(allUsersFolder, "Shared"));
-            } catch (IOException e) {
-                log.error("Error reading shared signatures folder", e);
-            }
-        }
-
-        return signatures;
-    }
-
-    private List<SignatureFile> getSignaturesFromFolder(Path folder, String category)
-            throws IOException {
-        try (Stream<Path> stream = Files.list(folder)) {
-            return stream.filter(this::isImageFile)
-                    .map(path -> new SignatureFile(path.getFileName().toString(), category))
-                    .toList();
-        }
-    }
-
-    public byte[] getSignatureBytes(String username, String fileName) throws IOException {
-        validateFileName(fileName);
-        // First try user's personal folder
-        Path userPath = Paths.get(SIGNATURE_BASE_PATH, username, fileName);
-        if (Files.exists(userPath)) {
-            return Files.readAllBytes(userPath);
-        }
-
-        // Then try ALL_USERS folder
-        Path allUsersPath = Paths.get(SIGNATURE_BASE_PATH, ALL_USERS_FOLDER, fileName);
-        if (Files.exists(allUsersPath)) {
-            return Files.readAllBytes(allUsersPath);
-        }
-
-        throw new FileNotFoundException("Signature file not found");
-    }
-
-    private boolean isImageFile(Path path) {
-        String fileName = path.getFileName().toString().toLowerCase();
-        return fileName.endsWith(".jpg")
-                || fileName.endsWith(".jpeg")
-                || fileName.endsWith(".png")
-                || fileName.endsWith(".gif");
-    }
-
-    private void validateFileName(String fileName) {
-        if (fileName.contains("..") || fileName.contains("/") || fileName.contains("\\")) {
-            throw new IllegalArgumentException("Invalid filename");
-        }
-    }
-}

app/core/src/test/java/stirling/software/SPDF/service/SignatureServiceTest.java

@@ -23,7 +23,7 @@ import stirling.software.common.configuration.InstallationPathConfig;
 class SignatureServiceTest {
 
     @TempDir Path tempDir;
-    private SignatureService signatureService;
+    private SharedSignatureService signatureService;
     private Path personalSignatureFolder;
     private Path sharedSignatureFolder;
     private final String ALL_USERS_FOLDER = "ALL_USERS";
@@ -53,7 +53,7 @@ class SignatureServiceTest {
                     .thenReturn(tempDir.toString());
 
             // Initialize the service with our temp directory
-            signatureService = new SignatureService();
+            signatureService = new SharedSignatureService();
         }
     }
 
@@ -165,7 +165,7 @@ class SignatureServiceTest {
     }
 
     @Test
-    void testGetSignatureBytes_PersonalFile() throws IOException {
+    void testGetSharedSignatureBytes_SharedFile() throws IOException {
         // Mock static method for each test
         try (MockedStatic<InstallationPathConfig> mockedConfig =
                 mockStatic(InstallationPathConfig.class)) {
@@ -173,28 +173,8 @@ class SignatureServiceTest {
                     .when(InstallationPathConfig::getSignaturesPath)
                     .thenReturn(tempDir.toString());
 
-            // Test
+            // Test - core service only reads shared signatures
-            byte[] bytes = signatureService.getSignatureBytes(TEST_USER, "personal.png");
+            byte[] bytes = signatureService.getSharedSignatureBytes("shared.jpg");
-
-            // Verify
-            assertEquals(
-                    "personal signature content",
-                    new String(bytes),
-                    "Should return the correct content for personal file");
-        }
-    }
-
-    @Test
-    void testGetSignatureBytes_SharedFile() throws IOException {
-        // Mock static method for each test
-        try (MockedStatic<InstallationPathConfig> mockedConfig =
-                mockStatic(InstallationPathConfig.class)) {
-            mockedConfig
-                    .when(InstallationPathConfig::getSignaturesPath)
-                    .thenReturn(tempDir.toString());
-
-            // Test
-            byte[] bytes = signatureService.getSignatureBytes(TEST_USER, "shared.jpg");
 
             // Verify
             assertEquals(
@@ -205,7 +185,7 @@ class SignatureServiceTest {
     }
 
     @Test
-    void testGetSignatureBytes_FileNotFound() {
+    void testGetSharedSignatureBytes_FileNotFound() {
         // Mock static method for each test
         try (MockedStatic<InstallationPathConfig> mockedConfig =
                 mockStatic(InstallationPathConfig.class)) {
@@ -216,13 +196,13 @@ class SignatureServiceTest {
             // Test and verify
             assertThrows(
                     FileNotFoundException.class,
-                    () -> signatureService.getSignatureBytes(TEST_USER, "nonexistent.png"),
+                    () -> signatureService.getSharedSignatureBytes("nonexistent.png"),
                     "Should throw exception for non-existent files");
         }
     }
 
     @Test
-    void testGetSignatureBytes_InvalidFileName() {
+    void testGetSharedSignatureBytes_InvalidFileName() {
         // Mock static method for each test
         try (MockedStatic<InstallationPathConfig> mockedConfig =
                 mockStatic(InstallationPathConfig.class)) {
@@ -233,11 +213,28 @@ class SignatureServiceTest {
             // Test and verify
             assertThrows(
                     IllegalArgumentException.class,
-                    () -> signatureService.getSignatureBytes(TEST_USER, "../invalid.png"),
+                    () -> signatureService.getSharedSignatureBytes("../invalid.png"),
                     "Should throw exception for file names with directory traversal");
         }
     }
 
+    @Test
+    void testGetSharedSignatureBytes_CannotAccessPersonalFiles() {
+        // Mock static method for each test
+        try (MockedStatic<InstallationPathConfig> mockedConfig =
+                mockStatic(InstallationPathConfig.class)) {
+            mockedConfig
+                    .when(InstallationPathConfig::getSignaturesPath)
+                    .thenReturn(tempDir.toString());
+
+            // Test and verify - core service should NOT be able to read personal files
+            assertThrows(
+                    FileNotFoundException.class,
+                    () -> signatureService.getSharedSignatureBytes("personal.png"),
+                    "Core service should not have access to personal signatures");
+        }
+    }
+
     @Test
     void testGetAvailableSignatures_EmptyUsername() throws IOException {
         // Mock static method for each test

app/proprietary/src/main/java/stirling/software/proprietary/controller/api/SignatureController.java

@@ -0,0 +1,102 @@
+package stirling.software.proprietary.controller.api;
+
+import java.io.IOException;
+import java.util.List;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.access.prepost.PreAuthorize;
+import org.springframework.web.bind.annotation.DeleteMapping;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+import stirling.software.common.annotations.api.UserApi;
+import stirling.software.proprietary.model.api.signature.SavedSignatureRequest;
+import stirling.software.proprietary.model.api.signature.SavedSignatureResponse;
+import stirling.software.proprietary.security.service.UserService;
+import stirling.software.proprietary.service.SignatureService;
+
+/**
+ * Controller for managing user signatures in proprietary/authenticated mode only. Requires user
+ * authentication and enforces per-user storage limits. All endpoints require authentication
+ * via @PreAuthorize("isAuthenticated()").
+ */
+@UserApi
+@Slf4j
+@RestController
+@RequestMapping("/api/v1/proprietary/signatures")
+@RequiredArgsConstructor
+@PreAuthorize("isAuthenticated()")
+public class SignatureController {
+
+    private final SignatureService signatureService;
+    private final UserService userService;
+
+    /**
+     * Save a new signature for the authenticated user. Enforces storage limits and authentication
+     * requirements.
+     */
+    @PostMapping
+    public ResponseEntity<SavedSignatureResponse> saveSignature(
+            @RequestBody SavedSignatureRequest request) {
+        try {
+            String username = userService.getCurrentUsername();
+
+            // Validate request
+            if (request.getDataUrl() == null || request.getDataUrl().isEmpty()) {
+                log.warn("User {} attempted to save signature without dataUrl", username);
+                return ResponseEntity.badRequest().build();
+            }
+
+            SavedSignatureResponse response = signatureService.saveSignature(username, request);
+            log.info("User {} saved signature {}", username, request.getId());
+            return ResponseEntity.ok(response);
+        } catch (IllegalArgumentException e) {
+            log.warn("Invalid signature save request: {}", e.getMessage());
+            return ResponseEntity.badRequest().build();
+        } catch (IOException e) {
+            log.error("Failed to save signature", e);
+            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
+        }
+    }
+
+    /**
+     * List all signatures accessible to the authenticated user. Includes both personal and shared
+     * signatures.
+     */
+    @GetMapping
+    public ResponseEntity<List<SavedSignatureResponse>> listSignatures() {
+        try {
+            String username = userService.getCurrentUsername();
+            List<SavedSignatureResponse> signatures = signatureService.getSavedSignatures(username);
+            return ResponseEntity.ok(signatures);
+        } catch (IOException e) {
+            log.error("Failed to list signatures for user", e);
+            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
+        }
+    }
+
+    /**
+     * Delete a signature owned by the authenticated user. Users can only delete their own personal
+     * signatures, not shared ones.
+     */
+    @DeleteMapping("/{signatureId}")
+    public ResponseEntity<Void> deleteSignature(@PathVariable String signatureId) {
+        try {
+            String username = userService.getCurrentUsername();
+            signatureService.deleteSignature(username, signatureId);
+            log.info("User {} deleted signature {}", username, signatureId);
+            return ResponseEntity.noContent().build();
+        } catch (IOException e) {
+            log.warn("Failed to delete signature {} for user: {}", signatureId, e.getMessage());
+            return ResponseEntity.status(HttpStatus.NOT_FOUND).build();
+        }
+    }
+}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/signature/SavedSignatureRequest.java

@@ -0,0 +1,18 @@
+package stirling.software.proprietary.model.api.signature;
+
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@NoArgsConstructor
+public class SavedSignatureRequest {
+    private String id;
+    private String label;
+    private String type; // "canvas", "image", "text"
+    private String scope; // "personal", "shared"
+    private String dataUrl; // For canvas and image types
+    private String signerName; // For text type
+    private String fontFamily; // For text type
+    private Integer fontSize; // For text type
+    private String textColor; // For text type
+}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/signature/SavedSignatureResponse.java

@@ -0,0 +1,22 @@
+package stirling.software.proprietary.model.api.signature;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class SavedSignatureResponse {
+    private String id;
+    private String label;
+    private String type; // "canvas", "image", "text"
+    private String scope; // "personal", "shared"
+    private String dataUrl; // For canvas and image types (or URL to fetch image)
+    private String signerName; // For text type
+    private String fontFamily; // For text type
+    private Integer fontSize; // For text type
+    private String textColor; // For text type
+    private Long createdAt;
+    private Long updatedAt;
+}

app/proprietary/src/main/java/stirling/software/proprietary/service/SignatureService.java

@@ -0,0 +1,299 @@
+package stirling.software.proprietary.service;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+import java.util.ArrayList;
+import java.util.Base64;
+import java.util.List;
+import java.util.stream.Stream;
+
+import org.springframework.stereotype.Service;
+
+import lombok.extern.slf4j.Slf4j;
+
+import stirling.software.common.configuration.InstallationPathConfig;
+import stirling.software.common.service.PersonalSignatureServiceInterface;
+import stirling.software.proprietary.model.api.signature.SavedSignatureRequest;
+import stirling.software.proprietary.model.api.signature.SavedSignatureResponse;
+
+/**
+ * Service for managing user signatures with authentication and storage limits. This proprietary
+ * version enforces per-user quotas and requires authentication. Provides access to personal
+ * signatures only (shared signatures handled by core service).
+ */
+@Service
+@Slf4j
+public class SignatureService implements PersonalSignatureServiceInterface {
+
+    private final String SIGNATURE_BASE_PATH;
+    private final String ALL_USERS_FOLDER = "ALL_USERS";
+
+    // Storage limits per user
+    private static final int MAX_SIGNATURES_PER_USER = 20;
+    private static final long MAX_SIGNATURE_SIZE_BYTES = 2_000_000; // 2MB per signature
+    private static final long MAX_TOTAL_USER_STORAGE_BYTES = 20_000_000; // 20MB total per user
+
+    public SignatureService() {
+        SIGNATURE_BASE_PATH = InstallationPathConfig.getSignaturesPath();
+    }
+
+    /**
+     * Get a personal signature from the user's folder only. Does NOT check shared folder (that's
+     * handled by core service).
+     */
+    @Override
+    public byte[] getPersonalSignatureBytes(String username, String fileName) throws IOException {
+        validateFileName(fileName);
+        Path userPath = Paths.get(SIGNATURE_BASE_PATH, username, fileName);
+
+        if (!Files.exists(userPath)) {
+            throw new FileNotFoundException("Personal signature not found");
+        }
+
+        return Files.readAllBytes(userPath);
+    }
+
+    /** Save a signature with storage limits enforced. */
+    public SavedSignatureResponse saveSignature(String username, SavedSignatureRequest request)
+            throws IOException {
+        validateFileName(request.getId());
+
+        // Determine folder based on scope
+        String scope = request.getScope();
+        if (scope == null || scope.isEmpty()) {
+            scope = "personal"; // Default to personal
+        }
+
+        String folderName = "shared".equals(scope) ? ALL_USERS_FOLDER : username;
+        Path targetFolder = Paths.get(SIGNATURE_BASE_PATH, folderName);
+
+        // Only enforce limits for personal signatures (not shared)
+        if ("personal".equals(scope)) {
+            enforceStorageLimits(username, request.getDataUrl());
+        }
+
+        Files.createDirectories(targetFolder);
+
+        long timestamp = System.currentTimeMillis();
+
+        SavedSignatureResponse response = new SavedSignatureResponse();
+        response.setId(request.getId());
+        response.setLabel(request.getLabel());
+        response.setType(request.getType());
+        response.setScope(scope);
+        response.setCreatedAt(timestamp);
+        response.setUpdatedAt(timestamp);
+
+        // Extract and save image data
+        String dataUrl = request.getDataUrl();
+        if (dataUrl != null && dataUrl.startsWith("data:image/")) {
+            // Validate dataUrl size before decoding
+            if (dataUrl.length() > MAX_SIGNATURE_SIZE_BYTES * 2) {
+                throw new IllegalArgumentException(
+                        "Signature data too large (max "
+                                + (MAX_SIGNATURE_SIZE_BYTES / 1024)
+                                + "KB)");
+            }
+
+            // Extract base64 data
+            String base64Data = dataUrl.substring(dataUrl.indexOf(",") + 1);
+            byte[] imageBytes = Base64.getDecoder().decode(base64Data);
+
+            // Validate decoded size
+            if (imageBytes.length > MAX_SIGNATURE_SIZE_BYTES) {
+                throw new IllegalArgumentException(
+                        "Signature image too large (max "
+                                + (MAX_SIGNATURE_SIZE_BYTES / 1024)
+                                + "KB)");
+            }
+
+            // Determine and validate file extension from data URL
+            String mimeType = dataUrl.substring(dataUrl.indexOf(":") + 1, dataUrl.indexOf(";"));
+            String rawExtension = mimeType.substring(mimeType.indexOf("/") + 1);
+            String extension = validateAndNormalizeExtension(rawExtension);
+
+            // Save image file
+            String imageFileName = request.getId() + "." + extension;
+            Path imagePath = targetFolder.resolve(imageFileName);
+
+            // Verify path is within target directory
+            verifyPathWithinDirectory(imagePath, targetFolder);
+
+            Files.write(
+                    imagePath,
+                    imageBytes,
+                    StandardOpenOption.CREATE,
+                    StandardOpenOption.TRUNCATE_EXISTING);
+
+            // Store reference to image file (unified endpoint for all signatures)
+            response.setDataUrl("/api/v1/general/signatures/" + imageFileName);
+        }
+
+        log.info("Saved signature {} for user {} (scope: {})", request.getId(), username, scope);
+        return response;
+    }
+
+    /** Get all saved signatures for a user (personal + shared). */
+    public List<SavedSignatureResponse> getSavedSignatures(String username) throws IOException {
+        List<SavedSignatureResponse> signatures = new ArrayList<>();
+
+        // Load personal signatures
+        Path personalFolder = Paths.get(SIGNATURE_BASE_PATH, username);
+        if (Files.exists(personalFolder)) {
+            signatures.addAll(loadSignaturesFromFolder(personalFolder, "personal", true));
+        }
+
+        // Load shared signatures
+        Path sharedFolder = Paths.get(SIGNATURE_BASE_PATH, ALL_USERS_FOLDER);
+        if (Files.exists(sharedFolder)) {
+            signatures.addAll(loadSignaturesFromFolder(sharedFolder, "shared", false));
+        }
+
+        return signatures;
+    }
+
+    /** Delete a signature from user's personal folder. Cannot delete shared signatures. */
+    public void deleteSignature(String username, String signatureId) throws IOException {
+        validateFileName(signatureId);
+
+        // Only allow deletion from personal folder
+        Path personalFolder = Paths.get(SIGNATURE_BASE_PATH, username);
+        boolean deleted = false;
+
+        if (Files.exists(personalFolder)) {
+            try (Stream<Path> stream = Files.list(personalFolder)) {
+                List<Path> matchingFiles =
+                        stream.filter(
+                                        path ->
+                                                path.getFileName()
+                                                        .toString()
+                                                        .startsWith(signatureId + "."))
+                                .toList();
+                for (Path file : matchingFiles) {
+                    Files.delete(file);
+                    deleted = true;
+                    log.info("Deleted signature file: {}", file);
+                }
+            }
+        }
+
+        if (!deleted) {
+            throw new FileNotFoundException("Signature not found or cannot be deleted");
+        }
+    }
+
+    // Private helper methods
+
+    private void enforceStorageLimits(String username, String dataUrlToAdd) throws IOException {
+        Path userFolder = Paths.get(SIGNATURE_BASE_PATH, username);
+
+        if (!Files.exists(userFolder)) {
+            return; // First signature, no limits to check
+        }
+
+        // Count existing signatures
+        long signatureCount;
+        try (Stream<Path> stream = Files.list(userFolder)) {
+            signatureCount = stream.filter(this::isImageFile).count();
+        }
+
+        if (signatureCount >= MAX_SIGNATURES_PER_USER) {
+            throw new IllegalArgumentException(
+                    "Maximum signatures limit reached (" + MAX_SIGNATURES_PER_USER + ")");
+        }
+
+        // Calculate total storage used
+        long totalSize = 0;
+        try (Stream<Path> stream = Files.list(userFolder)) {
+            totalSize =
+                    stream.filter(this::isImageFile)
+                            .mapToLong(
+                                    path -> {
+                                        try {
+                                            return Files.size(path);
+                                        } catch (IOException e) {
+                                            return 0;
+                                        }
+                                    })
+                            .sum();
+        }
+
+        // Estimate new signature size (base64 decodes to ~75% of original)
+        long estimatedNewSize = (long) (dataUrlToAdd.length() * 0.75);
+
+        if (totalSize + estimatedNewSize > MAX_TOTAL_USER_STORAGE_BYTES) {
+            throw new IllegalArgumentException(
+                    "Storage quota exceeded (max "
+                            + (MAX_TOTAL_USER_STORAGE_BYTES / 1_000_000)
+                            + "MB)");
+        }
+    }
+
+    private List<SavedSignatureResponse> loadSignaturesFromFolder(
+            Path folder, String scope, boolean isPersonal) throws IOException {
+        List<SavedSignatureResponse> signatures = new ArrayList<>();
+
+        try (Stream<Path> stream = Files.list(folder)) {
+            stream.filter(this::isImageFile)
+                    .forEach(
+                            path -> {
+                                try {
+                                    String fileName = path.getFileName().toString();
+                                    String id = fileName.substring(0, fileName.lastIndexOf('.'));
+
+                                    SavedSignatureResponse sig = new SavedSignatureResponse();
+                                    sig.setId(id);
+                                    sig.setLabel(id);
+                                    sig.setType("image");
+                                    sig.setScope(scope);
+                                    sig.setCreatedAt(Files.getLastModifiedTime(path).toMillis());
+                                    sig.setUpdatedAt(Files.getLastModifiedTime(path).toMillis());
+
+                                    // Set unified URL path (works for both personal and shared)
+                                    sig.setDataUrl("/api/v1/general/signatures/" + fileName);
+
+                                    signatures.add(sig);
+                                } catch (IOException e) {
+                                    log.error("Error reading signature file: " + path, e);
+                                }
+                            });
+        }
+
+        return signatures;
+    }
+
+    private boolean isImageFile(Path path) {
+        String fileName = path.getFileName().toString().toLowerCase();
+        return fileName.endsWith(".jpg") || fileName.endsWith(".jpeg") || fileName.endsWith(".png");
+    }
+
+    private void validateFileName(String fileName) {
+        if (fileName.contains("..") || fileName.contains("/") || fileName.contains("\\")) {
+            throw new IllegalArgumentException("Invalid filename");
+        }
+        if (!fileName.matches("^[a-zA-Z0-9_.-]+$")) {
+            throw new IllegalArgumentException("Filename contains invalid characters");
+        }
+    }
+
+    private String validateAndNormalizeExtension(String extension) {
+        String normalized = extension.toLowerCase().trim();
+        if (normalized.equals("png") || normalized.equals("jpg") || normalized.equals("jpeg")) {
+            return normalized;
+        }
+        throw new IllegalArgumentException("Unsupported image extension: " + extension);
+    }
+
+    private void verifyPathWithinDirectory(Path resolvedPath, Path targetDirectory)
+            throws IOException {
+        Path canonicalTarget = targetDirectory.toAbsolutePath().normalize();
+        Path canonicalResolved = resolvedPath.toAbsolutePath().normalize();
+        if (!canonicalResolved.startsWith(canonicalTarget)) {
+            throw new IOException("Resolved path is outside the target directory");
+        }
+    }
+}

frontend/public/locales/en-GB/translation.toml

@@ -2267,8 +2267,16 @@ defaultCanvasLabel = "Drawing signature"
 defaultImageLabel = "Uploaded signature"
 defaultTextLabel = "Typed signature"
 saveButton = "Save signature"
+savePersonal = "Save Personal"
+saveShared = "Save Shared"
 saveUnavailable = "Create a signature first to save it."
 noChanges = "Current signature is already saved."
+tempStorageTitle = "Temporary browser storage"
+tempStorageDescription = "Signatures are stored in your browser only. They will be lost if you clear browser data or switch browsers."
+personalHeading = "Personal Signatures"
+sharedHeading = "Shared Signatures"
+personalDescription = "Only you can see these signatures."
+sharedDescription = "All users can see and use these signatures."
 
 [sign.saved.type]
 canvas = "Drawing"

frontend/src/core/components/tools/sign/SavedSignaturesSection.tsx

@@ -1,13 +1,15 @@
-import { useCallback, useEffect, useRef, useState } from 'react';
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import { useTranslation } from 'react-i18next';
 import { ActionIcon, Alert, Badge, Box, Card, Group, Stack, Text, TextInput, Tooltip } from '@mantine/core';
 import { LocalIcon } from '@app/components/shared/LocalIcon';
 import { MAX_SAVED_SIGNATURES, SavedSignature, SavedSignatureType } from '@app/hooks/tools/sign/useSavedSignatures';
+import type { StorageType } from '@app/services/signatureStorageService';
 
 interface SavedSignaturesSectionProps {
   signatures: SavedSignature[];
   disabled?: boolean;
   isAtCapacity: boolean;
+  storageType?: StorageType | null;
   onUseSignature: (signature: SavedSignature) => void;
   onDeleteSignature: (signature: SavedSignature) => void;
   onRenameSignature: (id: string, label: string) => void;
@@ -24,6 +26,7 @@ export const SavedSignaturesSection = ({
   signatures,
   disabled = false,
   isAtCapacity,
+  storageType: _storageType,
   onUseSignature,
   onDeleteSignature,
   onRenameSignature,
@@ -36,20 +39,30 @@ export const SavedSignaturesSection = ({
     [t, translationScope]
   );
   const [labelDrafts, setLabelDrafts] = useState<Record<string, string>>({});
-  const [activeIndex, setActiveIndex] = useState(0);
+
-  const activeSignature = signatures[activeIndex];
+  // Group signatures by scope
-  const activeSignatureRef = useRef<SavedSignature | null>(activeSignature ?? null);
+  const groupedSignatures = useMemo(() => {
-  const appliedSignatureIdRef = useRef<string | null>(null);
+    const personal = signatures.filter(sig => sig.scope === 'personal');
+    const shared = signatures.filter(sig => sig.scope === 'shared');
+    const localStorage = signatures.filter(sig => sig.scope === 'localStorage');
+    return { personal, shared, localStorage };
+  }, [signatures]);
+
+  // Separate carousel state for each category
+  const [activePersonalIndex, setActivePersonalIndex] = useState(0);
+  const [activeSharedIndex, setActiveSharedIndex] = useState(0);
+  const [activeLocalStorageIndex, setActiveLocalStorageIndex] = useState(0);
+
+  const activePersonalSignature = groupedSignatures.personal[activePersonalIndex];
+  const activeSharedSignature = groupedSignatures.shared[activeSharedIndex];
+  const activeLocalStorageSignature = groupedSignatures.localStorage[activeLocalStorageIndex];
+
   const onUseSignatureRef = useRef(onUseSignature);
 
   useEffect(() => {
     onUseSignatureRef.current = onUseSignature;
   }, [onUseSignature]);
 
-  useEffect(() => {
-    activeSignatureRef.current = activeSignature ?? null;
-  }, [activeSignature]);
-
   useEffect(() => {
     setLabelDrafts(prev => {
       const nextDrafts: Record<string, string> = {};
@@ -60,25 +73,18 @@ export const SavedSignaturesSection = ({
     });
   }, [signatures]);
 
+  // Reset carousel indices when categories change
   useEffect(() => {
-    if (signatures.length === 0) {
+    setActivePersonalIndex(prev => Math.min(prev, Math.max(groupedSignatures.personal.length - 1, 0)));
-      setActiveIndex(0);
+  }, [groupedSignatures.personal.length]);
-      return;
-    }
-    setActiveIndex(prev => Math.min(prev, Math.max(signatures.length - 1, 0)));
-  }, [signatures.length]);
 
-  const handleNavigate = useCallback(
+  useEffect(() => {
-    (direction: 'prev' | 'next') => {
+    setActiveSharedIndex(prev => Math.min(prev, Math.max(groupedSignatures.shared.length - 1, 0)));
-      setActiveIndex(prev => {
+  }, [groupedSignatures.shared.length]);
-        if (direction === 'prev') {
+
-          return Math.max(0, prev - 1);
+  useEffect(() => {
-        }
+    setActiveLocalStorageIndex(prev => Math.min(prev, Math.max(groupedSignatures.localStorage.length - 1, 0)));
-        return Math.min(signatures.length - 1, prev + 1);
+  }, [groupedSignatures.localStorage.length]);
-      });
-    },
-    [signatures.length]
-  );
 
   const renderPreview = (signature: SavedSignature) => {
     if (signature.type === 'text') {
@@ -193,21 +199,6 @@ export const SavedSignaturesSection = ({
     }
   };
 
-  useEffect(() => {
-    const signature = activeSignatureRef.current;
-    if (!signature || disabled) {
-      appliedSignatureIdRef.current = null;
-      return;
-    }
-
-    if (appliedSignatureIdRef.current === signature.id) {
-      return;
-    }
-
-    appliedSignatureIdRef.current = signature.id;
-    onUseSignatureRef.current(signature);
-  }, [activeSignature?.id, disabled]);
-
   return (
     <Stack gap="sm">
       <Group justify="space-between" align="flex-start">
@@ -234,67 +225,253 @@ export const SavedSignaturesSection = ({
       {signatures.length === 0 ? (
         emptyState
       ) : (
-        <Stack gap="xs">
+        <Stack gap="md">
-          <Group justify="space-between" align="center">
+          {/* Personal Signatures */}
-            <Text size="sm" c="dimmed">
+          {groupedSignatures.personal.length > 0 && activePersonalSignature && (
-              {translate('saved.carouselPosition', '{{current}} of {{total}}', {
+            <Stack gap="xs">
-                current: activeIndex + 1,
+              <Group gap="xs">
-                total: signatures.length,
+                <LocalIcon icon="material-symbols:person-rounded" width={18} height={18} />
-              })}
+                <Text fw={600} size="sm">
-            </Text>
+                  {translate('saved.personalHeading', 'Personal Signatures')}
-            <Group gap={4}>
+                </Text>
-              <ActionIcon
+              </Group>
-                variant="light"
+              <Text size="xs" c="dimmed">
-                aria-label={translate('saved.prev', 'Previous')}
+                {translate('saved.personalDescription', 'Only you can see these signatures.')}
-                onClick={() => handleNavigate('prev')}
+              </Text>
-                disabled={disabled || activeIndex === 0}
-              >
-                <LocalIcon icon="material-symbols:chevron-left-rounded" width={18} height={18} />
-              </ActionIcon>
-              <ActionIcon
-                variant="light"
-                aria-label={translate('saved.next', 'Next')}
-                onClick={() => handleNavigate('next')}
-                disabled={disabled || activeIndex >= signatures.length - 1}
-              >
-                <LocalIcon icon="material-symbols:chevron-right-rounded" width={18} height={18} />
-              </ActionIcon>
-            </Group>
-          </Group>
 
-          {activeSignature && (
+              <Group justify="space-between" align="center">
-            <Card withBorder padding="sm" key={activeSignature.id}>
+                <Text size="sm" c="dimmed">
-              <Stack gap="sm">
+                  {translate('saved.carouselPosition', '{{current}} of {{total}}', {
-                <Group justify="space-between" align="center">
+                    current: activePersonalIndex + 1,
-                  <Badge color={typeBadgeColor[activeSignature.type]} variant="light">
+                    total: groupedSignatures.personal.length,
-                    {typeLabel(activeSignature.type)}
+                  })}
-                  </Badge>
+                </Text>
-                  <Tooltip label={translate('saved.delete', 'Remove')}>
+                <Group gap={4}>
-                    <ActionIcon
+                  <ActionIcon
-                      variant="subtle"
+                    variant="light"
-                      color="red"
+                    aria-label={translate('saved.prev', 'Previous')}
-                      aria-label={translate('saved.delete', 'Remove')}
+                    onClick={() => setActivePersonalIndex(prev => Math.max(0, prev - 1))}
-                      onClick={() => onDeleteSignature(activeSignature)}
+                    disabled={disabled || activePersonalIndex === 0}
-                      disabled={disabled}
+                  >
-                    >
+                    <LocalIcon icon="material-symbols:chevron-left-rounded" width={18} height={18} />
-                      <LocalIcon icon="material-symbols:delete-outline-rounded" width={18} height={18} />
+                  </ActionIcon>
-                    </ActionIcon>
+                  <ActionIcon
-                  </Tooltip>
+                    variant="light"
+                    aria-label={translate('saved.next', 'Next')}
+                    onClick={() => setActivePersonalIndex(prev => Math.min(groupedSignatures.personal.length - 1, prev + 1))}
+                    disabled={disabled || activePersonalIndex >= groupedSignatures.personal.length - 1}
+                  >
+                    <LocalIcon icon="material-symbols:chevron-right-rounded" width={18} height={18} />
+                  </ActionIcon>
                 </Group>
+              </Group>
 
-                {renderPreview(activeSignature)}
+              <Card withBorder padding="sm">
+                <Stack gap="sm">
+                  <Group justify="space-between" align="center">
+                    <Badge color={typeBadgeColor[activePersonalSignature.type]} variant="light">
+                      {typeLabel(activePersonalSignature.type)}
+                    </Badge>
+                    <Group gap="xs">
+                      <ActionIcon
+                        variant="subtle"
+                        color="blue"
+                        aria-label="Use signature"
+                        onClick={() => onUseSignature(activePersonalSignature)}
+                        disabled={disabled}
+                      >
+                        <LocalIcon icon="material-symbols:check-circle-outline-rounded" width={18} height={18} />
+                      </ActionIcon>
+                      <Tooltip label={translate('saved.delete', 'Remove')}>
+                        <ActionIcon
+                          variant="subtle"
+                          color="red"
+                          aria-label={translate('saved.delete', 'Remove')}
+                          onClick={() => onDeleteSignature(activePersonalSignature)}
+                          disabled={disabled}
+                        >
+                          <LocalIcon icon="material-symbols:delete-outline-rounded" width={18} height={18} />
+                        </ActionIcon>
+                      </Tooltip>
+                    </Group>
+                  </Group>
+                  {renderPreview(activePersonalSignature)}
+                  <TextInput
+                    label={translate('saved.label', 'Label')}
+                    value={labelDrafts[activePersonalSignature.id] ?? activePersonalSignature.label}
+                    onChange={event => handleLabelChange(event, activePersonalSignature)}
+                    onBlur={() => handleLabelBlur(activePersonalSignature)}
+                    onKeyDown={event => handleLabelKeyDown(event, activePersonalSignature)}
+                    disabled={disabled}
+                  />
+                </Stack>
+              </Card>
+            </Stack>
+          )}
 
-                <TextInput
+          {/* Shared Signatures */}
-                  label={translate('saved.label', 'Label')}
+          {groupedSignatures.shared.length > 0 && activeSharedSignature && (
-                  value={labelDrafts[activeSignature.id] ?? activeSignature.label}
+            <Stack gap="xs">
-                  onChange={event => handleLabelChange(event, activeSignature)}
+              <Group gap="xs">
-                  onBlur={() => handleLabelBlur(activeSignature)}
+                <LocalIcon icon="material-symbols:groups-rounded" width={18} height={18} />
-                  onKeyDown={event => handleLabelKeyDown(event, activeSignature)}
+                <Text fw={600} size="sm">
-                  disabled={disabled}
+                  {translate('saved.sharedHeading', 'Shared Signatures')}
-                />
+                </Text>
+              </Group>
+              <Text size="xs" c="dimmed">
+                {translate('saved.sharedDescription', 'All users can see and use these signatures.')}
+              </Text>
 
-              </Stack>
+              <Group justify="space-between" align="center">
-            </Card>
+                <Text size="sm" c="dimmed">
+                  {translate('saved.carouselPosition', '{{current}} of {{total}}', {
+                    current: activeSharedIndex + 1,
+                    total: groupedSignatures.shared.length,
+                  })}
+                </Text>
+                <Group gap={4}>
+                  <ActionIcon
+                    variant="light"
+                    aria-label={translate('saved.prev', 'Previous')}
+                    onClick={() => setActiveSharedIndex(prev => Math.max(0, prev - 1))}
+                    disabled={disabled || activeSharedIndex === 0}
+                  >
+                    <LocalIcon icon="material-symbols:chevron-left-rounded" width={18} height={18} />
+                  </ActionIcon>
+                  <ActionIcon
+                    variant="light"
+                    aria-label={translate('saved.next', 'Next')}
+                    onClick={() => setActiveSharedIndex(prev => Math.min(groupedSignatures.shared.length - 1, prev + 1))}
+                    disabled={disabled || activeSharedIndex >= groupedSignatures.shared.length - 1}
+                  >
+                    <LocalIcon icon="material-symbols:chevron-right-rounded" width={18} height={18} />
+                  </ActionIcon>
+                </Group>
+              </Group>
+
+              <Card withBorder padding="sm">
+                <Stack gap="sm">
+                  <Group justify="space-between" align="center">
+                    <Badge color={typeBadgeColor[activeSharedSignature.type]} variant="light">
+                      {typeLabel(activeSharedSignature.type)}
+                    </Badge>
+                    <Group gap="xs">
+                      <ActionIcon
+                        variant="subtle"
+                        color="blue"
+                        aria-label="Use signature"
+                        onClick={() => onUseSignature(activeSharedSignature)}
+                        disabled={disabled}
+                      >
+                        <LocalIcon icon="material-symbols:check-circle-outline-rounded" width={18} height={18} />
+                      </ActionIcon>
+                      <Tooltip label={translate('saved.delete', 'Remove')}>
+                        <ActionIcon
+                          variant="subtle"
+                          color="red"
+                          aria-label={translate('saved.delete', 'Remove')}
+                          onClick={() => onDeleteSignature(activeSharedSignature)}
+                          disabled={disabled}
+                        >
+                          <LocalIcon icon="material-symbols:delete-outline-rounded" width={18} height={18} />
+                        </ActionIcon>
+                      </Tooltip>
+                    </Group>
+                  </Group>
+                  {renderPreview(activeSharedSignature)}
+                  <TextInput
+                    label={translate('saved.label', 'Label')}
+                    value={labelDrafts[activeSharedSignature.id] ?? activeSharedSignature.label}
+                    onChange={event => handleLabelChange(event, activeSharedSignature)}
+                    onBlur={() => handleLabelBlur(activeSharedSignature)}
+                    onKeyDown={event => handleLabelKeyDown(event, activeSharedSignature)}
+                    disabled={disabled}
+                  />
+                </Stack>
+              </Card>
+            </Stack>
+          )}
+
+          {/* Browser Storage (localStorage) - Temporary */}
+          {groupedSignatures.localStorage.length > 0 && activeLocalStorageSignature && (
+            <Stack gap="xs">
+              <Alert color="blue" title={translate('saved.tempStorageTitle', 'Temporary browser storage')}>
+                <Text size="xs">
+                  {translate(
+                    'saved.tempStorageDescription',
+                    'Signatures are stored in your browser only. They will be lost if you clear browser data or switch browsers.'
+                  )}
+                </Text>
+              </Alert>
+
+              <Group justify="space-between" align="center">
+                <Text size="sm" c="dimmed">
+                  {translate('saved.carouselPosition', '{{current}} of {{total}}', {
+                    current: activeLocalStorageIndex + 1,
+                    total: groupedSignatures.localStorage.length,
+                  })}
+                </Text>
+                <Group gap={4}>
+                  <ActionIcon
+                    variant="light"
+                    aria-label={translate('saved.prev', 'Previous')}
+                    onClick={() => setActiveLocalStorageIndex(prev => Math.max(0, prev - 1))}
+                    disabled={disabled || activeLocalStorageIndex === 0}
+                  >
+                    <LocalIcon icon="material-symbols:chevron-left-rounded" width={18} height={18} />
+                  </ActionIcon>
+                  <ActionIcon
+                    variant="light"
+                    aria-label={translate('saved.next', 'Next')}
+                    onClick={() => setActiveLocalStorageIndex(prev => Math.min(groupedSignatures.localStorage.length - 1, prev + 1))}
+                    disabled={disabled || activeLocalStorageIndex >= groupedSignatures.localStorage.length - 1}
+                  >
+                    <LocalIcon icon="material-symbols:chevron-right-rounded" width={18} height={18} />
+                  </ActionIcon>
+                </Group>
+              </Group>
+
+              <Card withBorder padding="sm">
+                <Stack gap="sm">
+                  <Group justify="space-between" align="center">
+                    <Badge color={typeBadgeColor[activeLocalStorageSignature.type]} variant="light">
+                      {typeLabel(activeLocalStorageSignature.type)}
+                    </Badge>
+                    <Group gap="xs">
+                      <ActionIcon
+                        variant="subtle"
+                        color="blue"
+                        aria-label="Use signature"
+                        onClick={() => onUseSignature(activeLocalStorageSignature)}
+                        disabled={disabled}
+                      >
+                        <LocalIcon icon="material-symbols:check-circle-outline-rounded" width={18} height={18} />
+                      </ActionIcon>
+                      <Tooltip label={translate('saved.delete', 'Remove')}>
+                        <ActionIcon
+                          variant="subtle"
+                          color="red"
+                          aria-label={translate('saved.delete', 'Remove')}
+                          onClick={() => onDeleteSignature(activeLocalStorageSignature)}
+                          disabled={disabled}
+                        >
+                          <LocalIcon icon="material-symbols:delete-outline-rounded" width={18} height={18} />
+                        </ActionIcon>
+                      </Tooltip>
+                    </Group>
+                  </Group>
+                  {renderPreview(activeLocalStorageSignature)}
+                  <TextInput
+                    label={translate('saved.label', 'Label')}
+                    value={labelDrafts[activeLocalStorageSignature.id] ?? activeLocalStorageSignature.label}
+                    onChange={event => handleLabelChange(event, activeLocalStorageSignature)}
+                    onBlur={() => handleLabelBlur(activeLocalStorageSignature)}
+                    onKeyDown={event => handleLabelKeyDown(event, activeLocalStorageSignature)}
+                    disabled={disabled}
+                  />
+                </Stack>
+              </Card>
+            </Stack>
           )}
         </Stack>
       )}

frontend/src/core/components/tools/sign/SignSettings.tsx

@@ -16,6 +16,7 @@ import { ColorPicker } from "@app/components/annotation/shared/ColorPicker";
 import { LocalIcon } from "@app/components/shared/LocalIcon";
 import { useSavedSignatures, SavedSignature, SavedSignaturePayload, SavedSignatureType, MAX_SAVED_SIGNATURES, AddSignatureResult } from '@app/hooks/tools/sign/useSavedSignatures';
 import { SavedSignaturesSection } from '@app/components/tools/sign/SavedSignaturesSection';
+import { buildSignaturePreview } from '@app/utils/signaturePreview';
 
 type SignatureDrafts = {
   canvas?: string;
@@ -99,6 +100,7 @@ const SignSettings = ({
     removeSignature,
     updateSignatureLabel,
     byTypeCounts,
+    storageType,
   } = useSavedSignatures();
   const [signatureSource, setSignatureSource] = useState<SignatureSource>(() => {
     const paramSource = parameters.signatureType as SignatureSource;
@@ -157,11 +159,11 @@ const SignSettings = ({
   }, [canvasSignatureData, imageSignatureData, buildTextSignatureKey, parameters.signerName, parameters.fontSize, parameters.fontFamily, parameters.textColor]);
 
   const saveSignatureToLibrary = useCallback(
-    (payload: SavedSignaturePayload, type: SavedSignatureType): AddSignatureResult => {
+    async (payload: SavedSignaturePayload, type: SavedSignatureType, scope: 'personal' | 'shared'): Promise<AddSignatureResult> => {
       if (isSavedSignatureLimitReached) {
         return { success: false, reason: 'limit' };
       }
-      return addSignature(payload, getDefaultSavedLabel(type));
+      return await addSignature(payload, getDefaultSavedLabel(type), scope);
     },
     [addSignature, getDefaultSavedLabel, isSavedSignatureLimitReached]
   );
@@ -176,40 +178,57 @@ const SignSettings = ({
     [signatureKeysByType]
   );
 
-  const handleSaveCanvasSignature = useCallback(() => {
+  const handleSaveCanvasSignature = useCallback(async (scope: 'personal' | 'shared') => {
     if (!canvasSignatureData) {
       return;
     }
-    const result = saveSignatureToLibrary({ type: 'canvas', dataUrl: canvasSignatureData }, 'canvas');
+    const result = await saveSignatureToLibrary({ type: 'canvas', dataUrl: canvasSignatureData }, 'canvas', scope);
     if (result.success) {
       setLastSavedKeyForType('canvas');
     }
   }, [canvasSignatureData, saveSignatureToLibrary, setLastSavedKeyForType]);
 
-  const handleSaveImageSignature = useCallback(() => {
+  const handleSaveImageSignature = useCallback(async (scope: 'personal' | 'shared') => {
     if (!imageSignatureData) {
       return;
     }
-    const result = saveSignatureToLibrary({ type: 'image', dataUrl: imageSignatureData }, 'image');
+    const result = await saveSignatureToLibrary({ type: 'image', dataUrl: imageSignatureData }, 'image', scope);
     if (result.success) {
       setLastSavedKeyForType('image');
     }
   }, [imageSignatureData, saveSignatureToLibrary, setLastSavedKeyForType]);
 
-  const handleSaveTextSignature = useCallback(() => {
+  const handleSaveTextSignature = useCallback(async (scope: 'personal' | 'shared') => {
     const signerName = (parameters.signerName ?? '').trim();
     if (!signerName) {
       return;
     }
-    const result = saveSignatureToLibrary(
+
+    // Generate image from text signature
+    const preview = await buildSignaturePreview({
+      signatureType: 'text',
+      signerName,
+      fontFamily: parameters.fontFamily ?? 'Helvetica',
+      fontSize: parameters.fontSize ?? 16,
+      textColor: parameters.textColor ?? '#000000',
+    });
+
+    if (!preview?.dataUrl) {
+      console.error('Failed to generate text signature preview');
+      return;
+    }
+
+    const result = await saveSignatureToLibrary(
       {
         type: 'text',
+        dataUrl: preview.dataUrl,
         signerName,
         fontFamily: parameters.fontFamily ?? 'Helvetica',
         fontSize: parameters.fontSize ?? 16,
         textColor: parameters.textColor ?? '#000000',
       },
-      'text'
+      'text',
+      scope
     );
     if (result.success) {
       setLastSavedKeyForType('text');
@@ -286,16 +305,21 @@ const SignSettings = ({
     [updateSignatureLabel]
   );
 
-  const renderSaveButton = (type: SavedSignatureType, isReady: boolean, onClick: () => void) => {
+  const renderSaveButton = (type: SavedSignatureType, isReady: boolean, onClick: (scope: 'personal' | 'shared') => void, scope: 'personal' | 'shared', icon: string, label: string) => {
     if (!canUseSavedLibrary) {
       return null;
     }
-    const label = translate('saved.saveButton', 'Save signature');
     const currentKey = signatureKeysByType[type];
     const lastSavedKey = lastSavedSignatureKeys[type];
     const hasChanges = Boolean(currentKey && currentKey !== lastSavedKey);
     const isSaved = isReady && !hasChanges;
 
+    // Only show backend storage buttons when backend is available
+    const showButton = storageType === 'backend' || storageType === null;
+    if (!showButton) {
+      return null;
+    }
+
     let tooltipMessage: string | undefined;
     if (!isReady) {
       tooltipMessage = translate('saved.saveUnavailable', 'Create a signature first to save it.');
@@ -312,11 +336,11 @@ const SignSettings = ({
         size="xs"
         variant="outline"
         color={isSaved ? 'green' : undefined}
-        onClick={onClick}
+        onClick={() => onClick(scope)}
         disabled={!isReady || disabled || isSavedSignatureLimitReached || !hasChanges}
-        leftSection={<LocalIcon icon="material-symbols:save-rounded" width={16} height={16} />}
+        leftSection={<LocalIcon icon={icon} width={16} height={16} />}
       >
-        {isSaved ? translate('saved.status.saved', 'Saved') : label}
+        {label}
       </Button>
     );
 
@@ -331,15 +355,38 @@ const SignSettings = ({
     return button;
   };
 
-  const renderSaveButtonRow = (type: SavedSignatureType, isReady: boolean, onClick: () => void) => {
+  const renderSaveButtonRow = (type: SavedSignatureType, isReady: boolean, onClick: (scope: 'personal' | 'shared') => void) => {
-    const button = renderSaveButton(type, isReady, onClick);
+    if (!canUseSavedLibrary) {
-    if (!button) {
       return null;
     }
+
+    const personalButton = renderSaveButton(
+      type,
+      isReady,
+      onClick,
+      'personal',
+      'material-symbols:person-rounded',
+      translate('saved.savePersonal', 'Save Personal')
+    );
+
+    const sharedButton = renderSaveButton(
+      type,
+      isReady,
+      onClick,
+      'shared',
+      'material-symbols:groups-rounded',
+      translate('saved.saveShared', 'Save Shared')
+    );
+
+    if (!personalButton && !sharedButton) {
+      return null;
+    }
+
     return (
-      <Box style={{ alignSelf: 'flex-start', marginTop: '0.4rem' }}>
+      <Group gap="xs" style={{ alignSelf: 'flex-start', marginTop: '0.4rem' }}>
-        {button}
+        {personalButton}
-      </Box>
+        {sharedButton}
+      </Group>
     );
   };
 
@@ -744,6 +791,7 @@ const SignSettings = ({
           signatures={savedSignatures}
           disabled={disabled}
           isAtCapacity={isSavedSignatureLimitReached}
+          storageType={storageType}
           onUseSignature={handleUseSavedSignature}
           onDeleteSignature={handleDeleteSavedSignature}
           onRenameSignature={handleRenameSavedSignature}

frontend/src/core/hooks/tools/sign/useSavedSignatures.ts

@@ -1,9 +1,10 @@
 import { useCallback, useEffect, useMemo, useState } from 'react';
+import { signatureStorageService, type StorageType } from '@app/services/signatureStorageService';
 
-const STORAGE_KEY = 'stirling:saved-signatures:v1';
 export const MAX_SAVED_SIGNATURES = 10;
 
 export type SavedSignatureType = 'canvas' | 'image' | 'text';
+export type SignatureScope = 'personal' | 'shared' | 'localStorage';
 
 export type SavedSignaturePayload =
   | {
@@ -16,6 +17,7 @@ export type SavedSignaturePayload =
     }
   | {
       type: 'text';
+      dataUrl: string;
       signerName: string;
       fontFamily: string;
       fontSize: number;
@@ -25,6 +27,7 @@ export type SavedSignaturePayload =
 export type SavedSignature = SavedSignaturePayload & {
   id: string;
   label: string;
+  scope: SignatureScope;
   createdAt: number;
   updatedAt: number;
 };
@@ -35,68 +38,6 @@ export type AddSignatureResult =
 
 const isSupportedEnvironment = () => typeof window !== 'undefined' && typeof window.localStorage !== 'undefined';
 
-const safeParse = (raw: string | null): SavedSignature[] => {
-  if (!raw) {
-    return [];
-  }
-
-  try {
-    const parsed = JSON.parse(raw);
-    if (!Array.isArray(parsed)) {
-      return [];
-    }
-
-    return parsed.filter((entry: any): entry is SavedSignature => {
-      if (!entry || typeof entry !== 'object') {
-        return false;
-      }
-      if (typeof entry.id !== 'string' || typeof entry.label !== 'string') {
-        return false;
-      }
-      if (typeof entry.type !== 'string') {
-        return false;
-      }
-
-      if (entry.type === 'text') {
-        return (
-          typeof entry.signerName === 'string' &&
-          typeof entry.fontFamily === 'string' &&
-          typeof entry.fontSize === 'number' &&
-          typeof entry.textColor === 'string'
-        );
-      }
-
-      return typeof entry.dataUrl === 'string';
-    });
-  } catch {
-    return [];
-  }
-};
-
-const readFromStorage = (): SavedSignature[] => {
-  if (!isSupportedEnvironment()) {
-    return [];
-  }
-
-  try {
-    return safeParse(window.localStorage.getItem(STORAGE_KEY));
-  } catch {
-    return [];
-  }
-};
-
-const writeToStorage = (entries: SavedSignature[]) => {
-  if (!isSupportedEnvironment()) {
-    return;
-  }
-
-  try {
-    window.localStorage.setItem(STORAGE_KEY, JSON.stringify(entries));
-  } catch {
-    // Swallow storage errors silently; we still keep state in memory.
-  }
-};
-
 const generateId = () => {
   if (typeof crypto !== 'undefined' && typeof crypto.randomUUID === 'function') {
     return crypto.randomUUID();
@@ -105,29 +46,61 @@ const generateId = () => {
 };
 
 export const useSavedSignatures = () => {
-  const [savedSignatures, setSavedSignatures] = useState<SavedSignature[]>(() => readFromStorage());
+  const [savedSignatures, setSavedSignatures] = useState<SavedSignature[]>([]);
+  const [storageType, setStorageType] = useState<StorageType | null>(null);
+  const [isLoading, setIsLoading] = useState(true);
 
+  // Load signatures and detect storage type on mount
   useEffect(() => {
-    if (!isSupportedEnvironment()) {
+    const loadSignatures = async () => {
+      try {
+        const [signatures, type] = await Promise.all([
+          signatureStorageService.loadSignatures(),
+          signatureStorageService.getStorageType(),
+        ]);
+        setSavedSignatures(signatures);
+        setStorageType(type);
+      } catch (error) {
+        console.error('[useSavedSignatures] Failed to load signatures:', error);
+      } finally {
+        setIsLoading(false);
+      }
+    };
+
+    loadSignatures();
+  }, []);
+
+  // Attempt migration from localStorage to backend when backend becomes available
+  useEffect(() => {
+    if (storageType === 'backend' && !isLoading) {
+      signatureStorageService.migrateToBackend().then(result => {
+        if (result.migrated > 0) {
+          console.log(`[useSavedSignatures] Migrated ${result.migrated} signatures to backend`);
+          // Reload after migration
+          signatureStorageService.loadSignatures().then(setSavedSignatures);
+        }
+      });
+    }
+  }, [storageType, isLoading]);
+
+  // Listen for storage events (for localStorage only)
+  useEffect(() => {
+    if (!isSupportedEnvironment() || storageType !== 'localStorage') {
       return;
     }
 
     const syncFromStorage = () => {
-      setSavedSignatures(readFromStorage());
+      signatureStorageService.loadSignatures().then(setSavedSignatures);
     };
 
     window.addEventListener('storage', syncFromStorage);
     return () => window.removeEventListener('storage', syncFromStorage);
-  }, []);
+  }, [storageType]);
-
-  useEffect(() => {
-    writeToStorage(savedSignatures);
-  }, [savedSignatures]);
 
   const isAtCapacity = savedSignatures.length >= MAX_SAVED_SIGNATURES;
 
   const addSignature = useCallback(
-    (payload: SavedSignaturePayload, label?: string): AddSignatureResult => {
+    async (payload: SavedSignaturePayload, label?: string, scope?: SignatureScope): Promise<AddSignatureResult> => {
       if (
         (payload.type === 'text' && !payload.signerName.trim()) ||
         ((payload.type === 'canvas' || payload.type === 'image') && !payload.dataUrl)
@@ -135,62 +108,85 @@ export const useSavedSignatures = () => {
         return { success: false, reason: 'invalid' };
       }
 
-      let createdSignature: SavedSignature | null = null;
+      if (savedSignatures.length >= MAX_SAVED_SIGNATURES) {
-      setSavedSignatures(prev => {
+        return { success: false, reason: 'limit' };
-        if (prev.length >= MAX_SAVED_SIGNATURES) {
+      }
-          return prev;
-        }
 
-        const timestamp = Date.now();
+      const timestamp = Date.now();
-        const nextEntry: SavedSignature = {
+      const newSignature: SavedSignature = {
-          ...payload,
+        ...payload,
-          id: generateId(),
+        id: generateId(),
-          label: (label || 'Signature').trim() || 'Signature',
+        label: (label || 'Signature').trim() || 'Signature',
-          createdAt: timestamp,
+        scope: scope || (storageType === 'backend' ? 'personal' : 'localStorage'),
-          updatedAt: timestamp,
+        createdAt: timestamp,
-        };
+        updatedAt: timestamp,
-        createdSignature = nextEntry;
+      };
-        return [nextEntry, ...prev];
-      });
 
-      return createdSignature
+      try {
-        ? { success: true, signature: createdSignature }
+        await signatureStorageService.saveSignature(newSignature);
-        : { success: false, reason: 'limit' };
+        setSavedSignatures(prev => [newSignature, ...prev]);
+        return { success: true, signature: newSignature };
+      } catch (error) {
+        console.error('[useSavedSignatures] Failed to save signature:', error);
+        return { success: false, reason: 'invalid' };
+      }
     },
-    []
+    [savedSignatures.length, storageType]
   );
 
-  const removeSignature = useCallback((id: string) => {
+  const removeSignature = useCallback(async (id: string) => {
-    setSavedSignatures(prev => prev.filter(entry => entry.id !== id));
+    try {
+      await signatureStorageService.deleteSignature(id);
+      setSavedSignatures(prev => prev.filter(entry => entry.id !== id));
+    } catch (error) {
+      console.error('[useSavedSignatures] Failed to delete signature:', error);
+    }
   }, []);
 
-  const updateSignatureLabel = useCallback((id: string, nextLabel: string) => {
+  const updateSignatureLabel = useCallback(async (id: string, nextLabel: string) => {
-    setSavedSignatures(prev =>
+    try {
-      prev.map(entry =>
+      await signatureStorageService.updateSignatureLabel(id, nextLabel);
-        entry.id === id
+      setSavedSignatures(prev =>
-          ? { ...entry, label: nextLabel.trim() || entry.label || 'Signature', updatedAt: Date.now() }
+        prev.map(entry =>
-          : entry
+          entry.id === id
-      )
+            ? { ...entry, label: nextLabel.trim() || entry.label || 'Signature', updatedAt: Date.now() }
-    );
+            : entry
+        )
+      );
+    } catch (error) {
+      console.error('[useSavedSignatures] Failed to update signature label:', error);
+    }
   }, []);
 
-  const replaceSignature = useCallback((id: string, payload: SavedSignaturePayload) => {
+  const replaceSignature = useCallback(
-    setSavedSignatures(prev =>
+    async (id: string, payload: SavedSignaturePayload) => {
-      prev.map(entry =>
+      const existing = savedSignatures.find(s => s.id === id);
-        entry.id === id
+      if (!existing) return;
-          ? {
-              ...entry,
-              ...payload,
-              updatedAt: Date.now(),
-            }
-          : entry
-      )
-    );
-  }, []);
 
-  const clearSignatures = useCallback(() => {
+      const updated: SavedSignature = {
-    setSavedSignatures([]);
+        ...existing,
-  }, []);
+        ...payload,
+        updatedAt: Date.now(),
+      };
+
+      try {
+        await signatureStorageService.saveSignature(updated);
+        setSavedSignatures(prev => prev.map(entry => (entry.id === id ? updated : entry)));
+      } catch (error) {
+        console.error('[useSavedSignatures] Failed to replace signature:', error);
+      }
+    },
+    [savedSignatures]
+  );
+
+  const clearSignatures = useCallback(async () => {
+    try {
+      await Promise.all(savedSignatures.map(sig => signatureStorageService.deleteSignature(sig.id)));
+      setSavedSignatures([]);
+    } catch (error) {
+      console.error('[useSavedSignatures] Failed to clear signatures:', error);
+    }
+  }, [savedSignatures]);
 
   const byTypeCounts = useMemo(() => {
     return savedSignatures.reduce<Record<SavedSignatureType, number>>(
@@ -211,6 +207,8 @@ export const useSavedSignatures = () => {
     replaceSignature,
     clearSignatures,
     byTypeCounts,
+    storageType,
+    isLoading,
   };
 };
 

frontend/src/core/services/signatureStorageService.ts

@@ -0,0 +1,282 @@
+import apiClient from '@app/services/apiClient';
+import type { SavedSignature } from '@app/hooks/tools/sign/useSavedSignatures';
+
+export type StorageType = 'backend' | 'localStorage';
+
+interface SignatureStorageCapabilities {
+  supportsBackend: boolean;
+  storageType: StorageType;
+}
+
+/**
+ * Service to handle signature storage with adaptive backend/localStorage fallback
+ */
+class SignatureStorageService {
+  private capabilities: SignatureStorageCapabilities | null = null;
+  private detectionPromise: Promise<SignatureStorageCapabilities> | null = null;
+  private blobUrls: Set<string> = new Set();
+
+  /**
+   * Detect if backend supports signature storage API
+   */
+  async detectCapabilities(): Promise<SignatureStorageCapabilities> {
+    // Return cached result if already detected
+    if (this.capabilities) {
+      return this.capabilities;
+    }
+
+    // Return in-flight detection if already running
+    if (this.detectionPromise) {
+      return this.detectionPromise;
+    }
+
+    // Start new detection
+    this.detectionPromise = this._performDetection();
+    this.capabilities = await this.detectionPromise;
+    this.detectionPromise = null;
+
+    return this.capabilities;
+  }
+
+  private async _performDetection(): Promise<SignatureStorageCapabilities> {
+    try {
+      // Probe the proprietary signatures endpoint (requires authentication)
+      await apiClient.get('/api/v1/proprietary/signatures', {
+        timeout: 3000,
+      });
+
+      // 200 = Backend available and accessible (authenticated)
+      console.log('[SignatureStorage] Backend signature API detected and accessible (authenticated)');
+      return {
+        supportsBackend: true,
+        storageType: 'backend',
+      };
+    } catch (error: any) {
+      // Check if it's an HTTP error with status code
+      if (error?.response?.status === 401 || error?.response?.status === 403) {
+        // Backend exists but needs auth - gracefully fall back to localStorage
+        console.log('[SignatureStorage] Backend signature API requires authentication, using localStorage');
+      } else if (error?.response?.status === 404) {
+        // Endpoint doesn't exist (not running proprietary mode)
+        console.log('[SignatureStorage] Backend signature API not available (not in proprietary mode), using localStorage');
+      } else {
+        // Network error, timeout, or other error
+        console.log('[SignatureStorage] Backend signature API not available, using localStorage');
+      }
+
+      return {
+        supportsBackend: false,
+        storageType: 'localStorage',
+      };
+    }
+  }
+
+  /**
+   * Get current storage type
+   */
+  async getStorageType(): Promise<StorageType> {
+    const capabilities = await this.detectCapabilities();
+    return capabilities.storageType;
+  }
+
+  /**
+   * Load all signatures
+   */
+  async loadSignatures(): Promise<SavedSignature[]> {
+    // Clean up old blob URLs before loading new ones
+    this.cleanup();
+
+    const capabilities = await this.detectCapabilities();
+
+    if (capabilities.supportsBackend) {
+      return this._loadFromBackend();
+    } else {
+      return this._loadFromLocalStorage();
+    }
+  }
+
+  /**
+   * Save a signature
+   */
+  async saveSignature(signature: SavedSignature): Promise<void> {
+    const capabilities = await this.detectCapabilities();
+
+    if (capabilities.supportsBackend && signature.scope !== 'localStorage') {
+      await this._saveToBackend(signature);
+    } else {
+      // Force scope to localStorage for browser storage
+      signature.scope = 'localStorage';
+      this._saveToLocalStorage(signature);
+    }
+  }
+
+  /**
+   * Delete a signature
+   */
+  async deleteSignature(id: string): Promise<void> {
+    const capabilities = await this.detectCapabilities();
+
+    if (capabilities.supportsBackend) {
+      await this._deleteFromBackend(id);
+    } else {
+      this._deleteFromLocalStorage(id);
+    }
+  }
+
+  /**
+   * Update signature label
+   */
+  async updateSignatureLabel(id: string, label: string): Promise<void> {
+    const capabilities = await this.detectCapabilities();
+
+    if (capabilities.supportsBackend) {
+      // Backend only stores images - labels not supported for backend signatures
+      console.log('[SignatureStorage] Label updates not supported for backend signatures');
+      return;
+    } else {
+      this._updateLabelInLocalStorage(id, label);
+    }
+  }
+
+  // Backend methods
+  private async _loadFromBackend(): Promise<SavedSignature[]> {
+    try {
+      const response = await apiClient.get<SavedSignature[]>('/api/v1/proprietary/signatures');
+      const signatures = response.data;
+
+      // Fetch image data for each signature and convert to blob URLs
+      const signaturePromises = signatures.map(async (sig) => {
+        if (sig.dataUrl && sig.dataUrl.startsWith('/api/v1/general/signatures/')) {
+          try {
+            // Fetch image via apiClient (unified endpoint works for both authenticated and unauthenticated)
+            const imageResponse = await apiClient.get<ArrayBuffer>(sig.dataUrl, {
+              responseType: 'arraybuffer',
+            });
+
+            // Convert to blob URL
+            const blob = new Blob([imageResponse.data], {
+              type: imageResponse.headers['content-type'] || 'image/png',
+            });
+            const blobUrl = URL.createObjectURL(blob);
+            this.blobUrls.add(blobUrl);
+
+            return { ...sig, dataUrl: blobUrl };
+          } catch (error) {
+            console.error(`[SignatureStorage] Failed to load image for ${sig.id}:`, error);
+            return sig; // Return original if image fetch fails
+          }
+        }
+        return sig;
+      });
+
+      return await Promise.all(signaturePromises);
+    } catch (error) {
+      console.error('[SignatureStorage] Failed to load from backend:', error);
+      return [];
+    }
+  }
+
+  private async _saveToBackend(signature: SavedSignature): Promise<void> {
+    await apiClient.post('/api/v1/proprietary/signatures', signature);
+  }
+
+  private async _deleteFromBackend(id: string): Promise<void> {
+    await apiClient.delete(`/api/v1/proprietary/signatures/${id}`);
+  }
+
+  // LocalStorage methods
+  private readonly STORAGE_KEY = 'stirling:saved-signatures:v1';
+
+  private _loadFromLocalStorage(): SavedSignature[] {
+    try {
+      const raw = localStorage.getItem(this.STORAGE_KEY);
+      if (!raw) return [];
+      const signatures = JSON.parse(raw);
+      // Ensure all localStorage signatures have the correct scope
+      return signatures.map((sig: SavedSignature) => ({
+        ...sig,
+        scope: 'localStorage' as const,
+      }));
+    } catch {
+      return [];
+    }
+  }
+
+  private _saveToLocalStorage(signature: SavedSignature): void {
+    const signatures = this._loadFromLocalStorage();
+    const index = signatures.findIndex(s => s.id === signature.id);
+
+    if (index >= 0) {
+      signatures[index] = signature;
+    } else {
+      signatures.unshift(signature);
+    }
+
+    localStorage.setItem(this.STORAGE_KEY, JSON.stringify(signatures));
+  }
+
+  private _deleteFromLocalStorage(id: string): void {
+    const signatures = this._loadFromLocalStorage();
+    const filtered = signatures.filter(s => s.id !== id);
+    localStorage.setItem(this.STORAGE_KEY, JSON.stringify(filtered));
+  }
+
+  private _updateLabelInLocalStorage(id: string, label: string): void {
+    const signatures = this._loadFromLocalStorage();
+    const signature = signatures.find(s => s.id === id);
+    if (signature) {
+      signature.label = label;
+      signature.updatedAt = Date.now();
+      localStorage.setItem(this.STORAGE_KEY, JSON.stringify(signatures));
+    }
+  }
+
+  /**
+   * Migrate signatures from localStorage to backend
+   */
+  async migrateToBackend(): Promise<{ migrated: number; failed: number }> {
+    const capabilities = await this.detectCapabilities();
+
+    if (!capabilities.supportsBackend) {
+      return { migrated: 0, failed: 0 };
+    }
+
+    const localSignatures = this._loadFromLocalStorage();
+    if (localSignatures.length === 0) {
+      return { migrated: 0, failed: 0 };
+    }
+
+    let migrated = 0;
+    let failed = 0;
+
+    for (const signature of localSignatures) {
+      try {
+        await this._saveToBackend(signature);
+        migrated++;
+      } catch (error) {
+        console.error(`[SignatureStorage] Failed to migrate signature ${signature.id}:`, error);
+        failed++;
+      }
+    }
+
+    // Clear localStorage after successful migration
+    if (migrated > 0 && failed === 0) {
+      localStorage.removeItem(this.STORAGE_KEY);
+      console.log(`[SignatureStorage] Successfully migrated ${migrated} signatures to backend`);
+    }
+
+    return { migrated, failed };
+  }
+
+  /**
+   * Clean up blob URLs to prevent memory leaks
+   */
+  cleanup(): void {
+    this.blobUrls.forEach(url => {
+      URL.revokeObjectURL(url);
+    });
+    this.blobUrls.clear();
+  }
+}
+
+export const signatureStorageService = new SignatureStorageService();