fix(platform): guard approval transitions

backend/api/internal/logic/platform/audit.go

@@ -14,6 +14,8 @@ import (
 	"gorm.io/gorm"
 )
 
+var errApprovalNotProcessable = errors.New("approval is not processable")
+
 func approvalValues(status, opinion, operatorIdentity string) map[string]any {
 	return map[string]any{
 		"status":           status,
@@ -40,6 +42,10 @@ func ApproveAudit(ctx *gin.Context) {
 		infra.Response.Error(ctx, errcode.ErrInvalidArgument)
 		return
 	}
+	if request.Status != "approved" && request.Status != "rejected" {
+		infra.Response.Error(ctx, errcode.ErrInvalidArgument)
+		return
+	}
 
 	values := approvalValues(request.Status, request.Opinion, claims.Identity)
 	var approval models.AudApproval
@@ -47,6 +53,9 @@ func ApproveAudit(ctx *gin.Context) {
 		if err := transaction.Where("identity = ?", ctx.Param("identity")).First(&approval).Error; err != nil {
 			return err
 		}
+		if approval.Status != "pending" || approval.ApplicantIdentity == claims.Identity {
+			return errApprovalNotProcessable
+		}
 		before, err := json.Marshal(gin.H{
 			"status": approval.Status, "opinion": approval.Opinion,
 			"handler_identity": approval.HandlerIdentity, "handled_at": approval.HandledAt,
@@ -54,10 +63,10 @@ func ApproveAudit(ctx *gin.Context) {
 		if err != nil {
 			return err
 		}
-		if result := transaction.Model(&models.AudApproval{}).Where("identity = ?", approval.Identity).Updates(values); result.Error != nil {
+		if result := transaction.Model(&models.AudApproval{}).Where("identity = ? AND status = ?", approval.Identity, "pending").Updates(values); result.Error != nil {
 			return result.Error
 		} else if result.RowsAffected == 0 {
-			return gorm.ErrRecordNotFound
+			return errApprovalNotProcessable
 		}
 		after, err := json.Marshal(values)
 		if err != nil {
@@ -74,6 +83,10 @@ func ApproveAudit(ctx *gin.Context) {
 		}).Error
 	})
 	if err != nil {
+		if errors.Is(err, errApprovalNotProcessable) {
+			infra.Response.Error(ctx, errcode.ErrInvalidArgument)
+			return
+		}
 		if errors.Is(err, gorm.ErrRecordNotFound) {
 			infra.Response.Error(ctx, errcode.ErrRecordNotFound)
 			return