feat(desktop-client): 阶段4-6 Electron EXE 客户端（登录/课表/作业/通知/成绩/设置 + Socket.IO 实时 + IndexedDB 离线缓存与自动同步 + electron-builder 打包）

packages/desktop-client/src/main/config.ts

@@ -0,0 +1,110 @@
+import fs from 'node:fs';
+import path from 'node:path';
+import { app, safeStorage } from 'electron';
+import { DEFAULT_SERVER_URL } from '@classhelper/shared';
+import type { DesktopStoredConfig } from '../types/desktop.js';
+
+interface PersistedConfig {
+  serverUrl: string;
+  username: string;
+  /** 加密后的 token（base64）或明文（当系统不支持加密时） */
+  token: string | null;
+  tokenEncrypted: boolean;
+}
+
+const DEFAULT_CONFIG: PersistedConfig = {
+  serverUrl: DEFAULT_SERVER_URL,
+  username: '',
+  token: null,
+  tokenEncrypted: false,
+};
+
+function configFilePath(): string {
+  return path.join(app.getPath('userData'), 'config.json');
+}
+
+function encryptToken(token: string | null): { token: string | null; tokenEncrypted: boolean } {
+  if (!token) return { token: null, tokenEncrypted: false };
+  try {
+    if (safeStorage.isEncryptionAvailable()) {
+      return { token: safeStorage.encryptString(token).toString('base64'), tokenEncrypted: true };
+    }
+  } catch {
+    // 某些环境下 DPAPI 不可用，降级为明文存储（仅本地开发场景）
+  }
+  return { token, tokenEncrypted: false };
+}
+
+function decryptToken(raw: PersistedConfig): string | null {
+  if (!raw.token) return null;
+  if (!raw.tokenEncrypted) return raw.token;
+  try {
+    return safeStorage.decryptString(Buffer.from(raw.token, 'base64'));
+  } catch {
+    return null;
+  }
+}
+
+function readPersisted(): PersistedConfig {
+  try {
+    const content = fs.readFileSync(configFilePath(), 'utf8');
+    const parsed = JSON.parse(content) as Partial<PersistedConfig>;
+    return {
+      serverUrl:
+        typeof parsed.serverUrl === 'string' && parsed.serverUrl
+          ? parsed.serverUrl
+          : DEFAULT_CONFIG.serverUrl,
+      username: typeof parsed.username === 'string' ? parsed.username : '',
+      token: typeof parsed.token === 'string' ? parsed.token : null,
+      tokenEncrypted: parsed.tokenEncrypted === true,
+    };
+  } catch {
+    return { ...DEFAULT_CONFIG };
+  }
+}
+
+function writePersisted(config: PersistedConfig): void {
+  const target = configFilePath();
+  fs.mkdirSync(path.dirname(target), { recursive: true });
+  fs.writeFileSync(target, JSON.stringify(config, null, 2), 'utf8');
+}
+
+/** 读取配置（token 已解密），供渲染进程使用 */
+export function getConfig(): DesktopStoredConfig {
+  const persisted = readPersisted();
+  return {
+    serverUrl: persisted.serverUrl,
+    username: persisted.username,
+    token: decryptToken(persisted),
+  };
+}
+
+/** 局部更新配置：只覆盖传入的字段 */
+export function saveConfig(patch: Partial<DesktopStoredConfig>): DesktopStoredConfig {
+  const persisted = readPersisted();
+
+  if (typeof patch.serverUrl === 'string' && patch.serverUrl.trim()) {
+    persisted.serverUrl = patch.serverUrl.trim().replace(/\/+$/, '');
+  }
+  if (typeof patch.username === 'string') {
+    persisted.username = patch.username;
+  }
+  if (patch.token !== undefined) {
+    const encrypted = encryptToken(patch.token);
+    persisted.token = encrypted.token;
+    persisted.tokenEncrypted = encrypted.tokenEncrypted;
+  }
+
+  writePersisted(persisted);
+  return getConfig();
+}
+
+/** 清空为默认配置（退出登录 / 重置） */
+export function clearConfig(): DesktopStoredConfig {
+  writePersisted({ ...DEFAULT_CONFIG });
+  return getConfig();
+}
+
+export function getConfigPath(): string {
+  return configFilePath();
+}