smartwatch/ts/watchers/watcher.node.ts

import * as fs from 'fs';
import * as path from 'path';
import * as smartrx from '@push.rocks/smartrx';
import type { IWatcher, IWatcherOptions, IWatchEvent, TWatchEventType } from './interfaces.js';

/**
 * Node.js/Bun file watcher using native fs.watch API
 */
export class NodeWatcher implements IWatcher {
  private watchers: Map<string, fs.FSWatcher> = new Map();
  private watchedFiles: Set<string> = new Set();
  private _isWatching = false;

  // Debounce: pending emits per file path
  private pendingEmits: Map<string, NodeJS.Timeout> = new Map();

  public readonly events$ = new smartrx.rxjs.Subject<IWatchEvent>();

  constructor(private options: IWatcherOptions) {}

  /**
   * Check if a file is a temporary file created by editors
   */
  private isTemporaryFile(filePath: string): boolean {
    const basename = path.basename(filePath);
    // Editor temp files: *.tmp.*, *.swp, *.swx, *~, .#*
    if (basename.includes('.tmp.')) return true;
    if (basename.endsWith('.swp') || basename.endsWith('.swx')) return true;
    if (basename.endsWith('~')) return true;
    if (basename.startsWith('.#')) return true;
    return false;
  }

  get isWatching(): boolean {
    return this._isWatching;
  }

  async start(): Promise<void> {
    if (this._isWatching) {
      return;
    }

    try {
      // Start watching each base path
      for (const basePath of this.options.basePaths) {
        await this.watchPath(basePath, 0);
      }

      this._isWatching = true;

      // Perform initial scan to emit 'add' events for existing files
      for (const basePath of this.options.basePaths) {
        await this.scanDirectory(basePath, 0);
      }

      // Emit ready event
      this.events$.next({ type: 'ready', path: '' });
    } catch (error: any) {
      this.events$.next({ type: 'error', path: '', error });
      throw error;
    }
  }

  async stop(): Promise<void> {
    this._isWatching = false;

    // Cancel all pending debounced emits
    for (const timeout of this.pendingEmits.values()) {
      clearTimeout(timeout);
    }
    this.pendingEmits.clear();

    // Close all watchers
    for (const [, watcher] of this.watchers) {
      watcher.close();
    }
    this.watchers.clear();
    this.watchedFiles.clear();
  }

  /**
   * Start watching a path (file or directory)
   */
  private async watchPath(watchPath: string, depth: number): Promise<void> {
    if (depth > this.options.depth) {
      return;
    }

    try {
      const stats = await this.statSafe(watchPath);
      if (!stats) {
        return;
      }

      if (stats.isDirectory()) {
        // Watch the directory with recursive option (Node.js 20+ supports this on all platforms)
        const watcher = fs.watch(
          watchPath,
          { recursive: true, persistent: true },
          (eventType, filename) => {
            if (filename) {
              this.handleFsEvent(watchPath, filename, eventType);
            }
          }
        );

        watcher.on('error', (error) => {
          this.events$.next({ type: 'error', path: watchPath, error });
        });

        this.watchers.set(watchPath, watcher);
      }
    } catch (error: any) {
      this.events$.next({ type: 'error', path: watchPath, error });
    }
  }

  /**
   * Handle raw fs.watch events - debounce and normalize them
   */
  private handleFsEvent(
    basePath: string,
    filename: string,
    eventType: 'rename' | 'change' | string
  ): void {
    const fullPath = path.join(basePath, filename);

    // Skip temporary files created by editors (atomic saves)
    if (this.isTemporaryFile(fullPath)) {
      return;
    }

    // Debounce: cancel any pending emit for this file
    const existing = this.pendingEmits.get(fullPath);
    if (existing) {
      clearTimeout(existing);
    }

    // Schedule debounced emit
    const timeout = setTimeout(() => {
      this.pendingEmits.delete(fullPath);
      this.emitFileEvent(fullPath, eventType);
    }, this.options.debounceMs);

    this.pendingEmits.set(fullPath, timeout);
  }

  /**
   * Emit the actual file event after debounce
   */
  private async emitFileEvent(
    fullPath: string,
    eventType: 'rename' | 'change' | string
  ): Promise<void> {
    try {
      const stats = await this.statSafe(fullPath);

      if (eventType === 'rename') {
        // 'rename' can mean add or unlink - check if file exists
        if (stats) {
          // File exists - it's either a new file or was renamed to this location
          if (stats.isDirectory()) {
            if (!this.watchedFiles.has(fullPath)) {
              this.watchedFiles.add(fullPath);
              this.events$.next({ type: 'addDir', path: fullPath, stats });
            }
          } else {
            const wasWatched = this.watchedFiles.has(fullPath);
            this.watchedFiles.add(fullPath);
            this.events$.next({
              type: wasWatched ? 'change' : 'add',
              path: fullPath,
              stats
            });
          }
        } else {
          // File doesn't exist - it was deleted
          if (this.watchedFiles.has(fullPath)) {
            const wasDir = this.isKnownDirectory(fullPath);
            this.watchedFiles.delete(fullPath);
            this.events$.next({
              type: wasDir ? 'unlinkDir' : 'unlink',
              path: fullPath
            });
          }
        }
      } else if (eventType === 'change') {
        // File was modified
        if (stats && !stats.isDirectory()) {
          const wasWatched = this.watchedFiles.has(fullPath);
          if (!wasWatched) {
            // This is actually an 'add' - file wasn't being watched before
            this.watchedFiles.add(fullPath);
            this.events$.next({ type: 'add', path: fullPath, stats });
          } else {
            this.events$.next({ type: 'change', path: fullPath, stats });
          }
        } else if (!stats && this.watchedFiles.has(fullPath)) {
          // File was deleted
          this.watchedFiles.delete(fullPath);
          this.events$.next({ type: 'unlink', path: fullPath });
        }
      }
    } catch (error: any) {
      this.events$.next({ type: 'error', path: fullPath, error });
    }
  }

  /**
   * Scan directory and emit 'add' events for existing files
   */
  private async scanDirectory(dirPath: string, depth: number): Promise<void> {
    if (depth > this.options.depth) {
      return;
    }

    try {
      const entries = await fs.promises.readdir(dirPath, { withFileTypes: true });

      for (const entry of entries) {
        const fullPath = path.join(dirPath, entry.name);

        // Skip temp files during initial scan too
        if (this.isTemporaryFile(fullPath)) {
          continue;
        }

        const stats = await this.statSafe(fullPath);

        if (!stats) {
          continue;
        }

        if (entry.isDirectory()) {
          this.watchedFiles.add(fullPath);
          this.events$.next({ type: 'addDir', path: fullPath, stats });
          await this.scanDirectory(fullPath, depth + 1);
        } else if (entry.isFile()) {
          this.watchedFiles.add(fullPath);
          this.events$.next({ type: 'add', path: fullPath, stats });
        }
      }
    } catch (error: any) {
      if (error.code !== 'ENOENT' && error.code !== 'EACCES') {
        this.events$.next({ type: 'error', path: dirPath, error });
      }
    }
  }

  /**
   * Safely stat a path, returning null if it doesn't exist
   */
  private async statSafe(filePath: string): Promise<fs.Stats | null> {
    try {
      if (this.options.followSymlinks) {
        return await fs.promises.stat(filePath);
      } else {
        return await fs.promises.lstat(filePath);
      }
    } catch {
      return null;
    }
  }

  /**
   * Check if a path was known to be a directory (for proper unlink event type)
   */
  private isKnownDirectory(filePath: string): boolean {
    // Check if any watched files are children of this path
    for (const watched of this.watchedFiles) {
      if (watched.startsWith(filePath + path.sep)) {
        return true;
      }
    }
    return false;
  }
}