Narrow jail config types with explicit union values

frontend/src/types/config.ts

@@ -39,6 +39,10 @@ export interface BantimeEscalationUpdate {
 // Jail Configuration
 // ---------------------------------------------------------------------------
 
+export type DNSMode = "yes" | "warn" | "no" | "raw";
+export type LogEncoding = "auto" | "ascii" | "utf-8" | "UTF-8" | "latin-1";
+export type BackendType = "auto" | "polling" | "pyinotify" | "systemd" | "gamin";
+
 export interface JailConfig {
   name: string;
   ban_time: number;
@@ -48,10 +52,10 @@ export interface JailConfig {
   ignore_regex: string[];
   log_paths: string[];
   date_pattern: string | null;
-  log_encoding: string;
-  backend: string;
+  log_encoding: LogEncoding;
+  backend: BackendType;
   /** DNS look-up mode reported by fail2ban: "yes" | "warn" | "no" | "raw". */
-  use_dns: string;
+  use_dns: DNSMode;
   /** Prefix regex prepended to every failregex; empty string means disabled. */
   prefregex: string;
   actions: string[];
@@ -76,9 +80,9 @@ export interface JailConfigUpdate {
   /** Prefix regex; undefined/null = skip, "" = clear, non-empty = set. */
   prefregex?: string | null;
   date_pattern?: string | null;
-  dns_mode?: string | null;
-  backend?: string | null;
-  log_encoding?: string | null;
+  dns_mode?: DNSMode | null;
+  backend?: BackendType | null;
+  log_encoding?: LogEncoding | null;
   enabled?: boolean | null;
   bantime_escalation?: BantimeEscalationUpdate | null;
 }
@@ -454,7 +458,7 @@ export interface JailSectionConfig {
   findtime: number | null;
   bantime: number | null;
   action: string[];
-  backend: string | null;
+  backend: BackendType | null;
   extra: Record<string, string>;
 }
 
@@ -505,13 +509,13 @@ export interface InactiveJail {
   /** Failure-counting window in seconds, parsed from findtime. */
   find_time_seconds: number;
   /** Log encoding, e.g. ``"auto"`` or ``"utf-8"``. */
-  log_encoding: string;
+  log_encoding: LogEncoding;
   /** Log-monitoring backend. */
-  backend: string;
+  backend: BackendType;
   /** Date pattern for log parsing, or null for auto-detect. */
   date_pattern: string | null;
   /** DNS resolution mode. */
-  use_dns: string;
+  use_dns: DNSMode;
   /** Prefix regex prepended to every failregex. */
   prefregex: string;
   /** List of failure regex patterns. */

frontend/src/types/jail.ts

@@ -7,7 +7,7 @@
  *   - `backend/app/models/geo.py`   (GeoDetail / IpLookupResponse)
  */
 
-import type { BantimeEscalation } from "./config";
+import type { BantimeEscalation, BackendType, LogEncoding } from "./config";
 
 // ---------------------------------------------------------------------------
 // Jail statistics
@@ -48,7 +48,7 @@ export interface JailSummary {
   /** Whether the jail is in idle mode (monitoring paused). */
   idle: boolean;
   /** Backend type used for log access (e.g. `"systemd"`, `"polling"`). */
-  backend: string;
+  backend: BackendType;
   /** Observation window in seconds before a ban is triggered. */
   find_time: number;
   /** Duration of a ban in seconds (negative = permanent). */
@@ -88,7 +88,7 @@ export interface Jail {
   /** Whether the jail is in idle mode. */
   idle: boolean;
   /** Backend type (systemd, polling, etc.). */
-  backend: string;
+  backend: BackendType;
   /** Log file paths monitored by this jail. */
   log_paths: string[];
   /** Fail-regex patterns used to identify offenders. */
@@ -98,7 +98,7 @@ export interface Jail {
   /** Date-pattern used for timestamp parsing, or empty string. */
   date_pattern: string;
   /** Log file encoding (e.g. `"UTF-8"`). */
-  log_encoding: string;
+  log_encoding: LogEncoding;
   /** Action names attached to this jail. */
   actions: string[];
   /** Observation window in seconds. */