1 files changed, 103 insertions, 0 deletions

diff --git a/packages/main/src/services/ConfigPersistenceService.ts b/packages/main/src/services/ConfigPersistenceService.ts
new file mode 100644
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--- /dev/null
+++ b/packages/main/src/services/ConfigPersistenceService.ts
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C)  2021-2022 Kristóf Marussy <kristof@marussy.com>
+ *
+ * This file is part of Sophie.
+ *
+ * Sophie is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { watch } from 'fs';
+import { readFile, stat, writeFile } from 'fs/promises';
+import JSON5 from 'json5';
+import { throttle } from 'lodash';
+import { IDisposer } from 'mobx-state-tree';
+import { join } from 'path';
+
+import type { ConfigSnapshotOut } from  '../stores/Config';
+
+export type ReadConfigResult = { found: true; data: unknown; } | { found: false; };
+
+export class ConfigPersistenceService {
+  readonly #userDataDir: string;
+
+  readonly #configFileName: string;
+
+  readonly #configFilePath: string;
+
+  constructor(
+    userDataDir: string,
+    configFileName: string,
+  ) {
+    this.#userDataDir = userDataDir;
+    this.#configFileName = configFileName;
+    this.#configFilePath = join(this.#userDataDir, this.#configFileName);
+  }
+
+  async readConfig(): Promise<ReadConfigResult> {
+    let configStr;
+    try {
+      configStr = await readFile(this.#configFilePath, 'utf8');
+    } catch (err) {
+      if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
+        return { found: false };
+      }
+      throw err;
+    }
+    return {
+      found: true,
+      data: JSON5.parse(configStr),
+    };
+  }
+
+  async writeConfig(configSnapshot: ConfigSnapshotOut): Promise<Date> {
+    const configJson = JSON5.stringify(configSnapshot, {
+      space: 2,
+    });
+    await writeFile(this.#configFilePath, configJson, 'utf8');
+    const { mtime } = await stat(this.#configFilePath);
+    return mtime;
+  }
+
+  watchConfig(callback: (mtime: Date) => Promise<void>, throttleMs: number): IDisposer {
+    const configChanged = throttle(async () => {
+      let mtime: Date;
+      try {
+        const stats = await stat(this.#configFilePath);
+        mtime = stats.mtime;
+      } catch (err) {
+        if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
+          return;
+        }
+        throw err;
+      }
+      return callback(mtime);
+    }, throttleMs);
+
+    const watcher = watch(this.#userDataDir, {
+      persistent: false,
+    });
+
+    watcher.on('change', (eventType, filename) => {
+      if (eventType === 'change'
+        && (filename === this.#configFileName || filename === null)) {
+        configChanged()?.catch((err) => {
+          console.log('Unhandled error while listening for config changes', err);
+        });
+      }
+    });
+
+    return () => watcher.close();
+  }
+}