refactor: delegate status validation to SequentialSigningService

Remove internal validation methods from RequestSignatureService and
delegate to SequentialSigningService for better separation of concerns.

Changes:
- Remove hasPendingLowerOrderSigners() private method
- Remove isStatusUpgrade() private method
- Replace inline ordering validation with call to
  validateStatusByOrder()
- Simplify determineInitialStatus() by delegating validation logic

This reduces complexity in RequestSignatureService and makes the code
more maintainable by following single responsibility principle. All
sequential signing logic is now centralized in the specialized service.

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

lib/Service/RequestSignatureService.php

@@ -208,6 +208,7 @@ private function associateToSigners(array $data, int $fileId): array {
 			foreach ($data['users'] as $user) {
 				$userProvidedOrder = isset($user['signingOrder']) ? (int)$user['signingOrder'] : null;
 				$signingOrder = $this->sequentialSigningService->determineSigningOrder($userProvidedOrder);
+				$signerStatus = $user['status'] ?? null;
 
 				if (isset($user['identifyMethods'])) {
 					foreach ($user['identifyMethods'] as $identifyMethod) {
@@ -221,6 +222,7 @@ private function associateToSigners(array $data, int $fileId): array {
 							fileId: $fileId,
 							signingOrder: $signingOrder,
 							fileStatus: $fileStatus,
+							signerStatus: $signerStatus,
 						);
 					}
 				} else {
@@ -232,6 +234,7 @@ private function associateToSigners(array $data, int $fileId): array {
 						fileId: $fileId,
 						signingOrder: $signingOrder,
 						fileStatus: $fileStatus,
+						signerStatus: $signerStatus,
 					);
 				}
 			}
@@ -254,6 +257,7 @@ private function associateToSigner(
 		int $fileId,
 		int $signingOrder = 0,
 		?int $fileStatus = null,
+		?int $signerStatus = null,
 	): SignRequestEntity {
 		$identifyMethodsIncances = $this->identifyMethod->getByUserData($identifyMethods);
 		if (empty($identifyMethodsIncances)) {
@@ -272,8 +276,8 @@ private function associateToSigner(
 		$currentStatus = $signRequest->getStatusEnum();
 
 		if ($isNewSignRequest || $currentStatus === \OCA\Libresign\Enum\SignRequestStatus::DRAFT) {
-			$initialStatus = $this->determineInitialStatus($signingOrder, $fileStatus);
-			$signRequest->setStatusEnum($initialStatus);
+			$desiredStatus = $this->determineInitialStatus($signingOrder, $fileStatus, $signerStatus, $currentStatus, $fileId);
+			$this->updateStatusIfAllowed($signRequest, $currentStatus, $desiredStatus, $isNewSignRequest);
 		}
 
 		$this->saveSignRequest($signRequest);
@@ -288,13 +292,56 @@ private function associateToSigner(
 		return $signRequest;
 	}
 
-	private function determineInitialStatus(int $signingOrder, ?int $fileStatus = null): \OCA\Libresign\Enum\SignRequestStatus {
+	private function updateStatusIfAllowed(
+		SignRequestEntity $signRequest,
+		\OCA\Libresign\Enum\SignRequestStatus $currentStatus,
+		\OCA\Libresign\Enum\SignRequestStatus $desiredStatus,
+		bool $isNewSignRequest
+	): void {
+		if ($isNewSignRequest || $this->sequentialSigningService->isStatusUpgrade($currentStatus, $desiredStatus)) {
+			$signRequest->setStatusEnum($desiredStatus);
+		}
+	}
+
+	private function determineInitialStatus(
+		int $signingOrder,
+		?int $fileStatus = null,
+		?int $signerStatus = null,
+		?\OCA\Libresign\Enum\SignRequestStatus $currentStatus = null,
+		?int $fileId = null
+	): \OCA\Libresign\Enum\SignRequestStatus {
+		if ($signerStatus !== null) {
+			$desiredStatus = \OCA\Libresign\Enum\SignRequestStatus::from($signerStatus);
+			if ($currentStatus !== null && !$this->sequentialSigningService->isStatusUpgrade($currentStatus, $desiredStatus)) {
+				return $currentStatus;
+			}
+
+			// Validate status transition based on signing order
+			if ($fileId !== null) {
+				return $this->sequentialSigningService->validateStatusByOrder($desiredStatus, $signingOrder, $fileId);
+			}
+
+			return $desiredStatus;
+		}
+
 		// If fileStatus is explicitly DRAFT (0), keep signer as DRAFT
 		// This allows adding new signers in DRAFT mode even when file is not in DRAFT status
 		if ($fileStatus === FileEntity::STATUS_DRAFT) {
 			return \OCA\Libresign\Enum\SignRequestStatus::DRAFT;
 		}
 
+		if ($fileStatus === FileEntity::STATUS_ABLE_TO_SIGN) {
+			if ($this->sequentialSigningService->isOrderedNumericFlow()) {
+				// In ordered flow, only first signer (order 1) should be ABLE_TO_SIGN
+				// Others remain DRAFT until their turn
+				return $signingOrder === 1
+					? \OCA\Libresign\Enum\SignRequestStatus::ABLE_TO_SIGN
+					: \OCA\Libresign\Enum\SignRequestStatus::DRAFT;
+			}
+			// In parallel flow, all can sign
+			return \OCA\Libresign\Enum\SignRequestStatus::ABLE_TO_SIGN;
+		}
+
 		if (!$this->sequentialSigningService->isOrderedNumericFlow()) {
 			return \OCA\Libresign\Enum\SignRequestStatus::ABLE_TO_SIGN;
 		}