feat: file / directory watcher (WIP)

packages/file-watcher/package.json

@@ -0,0 +1,5 @@
+{
+    "name": "your-project-name",
+    "version": "1.0.0",
+    "type": "module"
+}

packages/file-watcher/src/example.js

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+// @ts-check
+import { promises as fs } from 'fs'; // Assuming fs promises for async reading
+import { FileWatcher } from './file-watcher.js';
+
+(async () => {
+  const watcher = new FileWatcher(fs);
+
+  const { env } = process;
+  console.log('watching Downloads');
+  for await (const file of watcher.watchDirectory(`${env.HOME}/Downloads`)) {
+    console.log(`New file added: ${file.getName()}`);
+    console.log(await file.getContent()); // Call getContent to read the file
+  }
+})();

packages/file-watcher/src/file-watcher.js

@@ -0,0 +1,54 @@
+// @ts-check
+import path from 'node:path';
+import fs from 'node:fs/promises';
+import { Far } from '@endo/far';
+
+export class FileWatcher {
+  /**
+   * @param {Pick<typeof import('fs/promises'), 'readFile' | 'watch'>} fs
+   */
+  constructor(fs) {
+    this.fs = fs;
+  }
+
+  /**
+   * @param {string} directory
+   * @param {Parameters<import('fs/promises').watch>[1]} options
+   */
+  async *watchDirectory(directory, options = {}) {
+    const events = this.fs.watch(directory, options);
+
+    for await (const event of events) {
+      console.log('@@', event);
+      const { filename } = event;
+      // XXX Buffer not supported
+      if (typeof filename !== 'string') break;
+      const fullPath = path.join(directory, filename);
+      yield Far('File', {
+        getName: () => filename,
+        getContent: async () => {
+          const content = await this.fs.readFile(fullPath, 'utf-8');
+          return content;
+        },
+      });
+    }
+  }
+}
+
+const watcher = new FileWatcher(fs);
+
+export const make = () => {
+  return Far('FileWatcherFactory', {
+    /** @param {string} path */
+    make: path =>
+      Far('FileWatcher', {
+        watch: () => {
+          const events = watcher.watchDirectory(path);
+          return Far('FileEvents', {
+            next: () => events.next(),
+            return: () => events.return(),
+          });
+        },
+      }),
+  });
+};