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

/**
 * Node.js/Bun file watcher using chokidar
 *
 * Chokidar handles all the edge cases:
 * - Atomic writes (temp file + rename)
 * - Inode tracking
 * - Cross-platform differences
 * - Debouncing
 * - Write stabilization
 */
export class NodeWatcher implements IWatcher {
  private watcher: chokidar.FSWatcher | null = null;
  private _isWatching = false;

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

  constructor(private options: IWatcherOptions) {}

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

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

    console.log(`[smartwatch] Starting chokidar watcher for ${this.options.basePaths.length} base path(s)...`);

    try {
      // Resolve all paths to absolute
      const absolutePaths = this.options.basePaths.map(p => path.resolve(p));

      this.watcher = chokidar.watch(absolutePaths, {
        persistent: true,
        ignoreInitial: false,
        followSymlinks: this.options.followSymlinks,
        depth: this.options.depth,
        atomic: true, // Handle atomic writes
        awaitWriteFinish: this.options.awaitWriteFinish ? {
          stabilityThreshold: this.options.stabilityThreshold || 300,
          pollInterval: this.options.pollInterval || 100,
        } : false,
      });

      // Wire up all events
      this.watcher
        .on('add', (filePath: string, stats?: fs.Stats) => {
          this.safeEmit({ type: 'add', path: filePath, stats });
        })
        .on('change', (filePath: string, stats?: fs.Stats) => {
          this.safeEmit({ type: 'change', path: filePath, stats });
        })
        .on('unlink', (filePath: string) => {
          this.safeEmit({ type: 'unlink', path: filePath });
        })
        .on('addDir', (filePath: string, stats?: fs.Stats) => {
          this.safeEmit({ type: 'addDir', path: filePath, stats });
        })
        .on('unlinkDir', (filePath: string) => {
          this.safeEmit({ type: 'unlinkDir', path: filePath });
        })
        .on('error', (error: Error) => {
          console.error('[smartwatch] Chokidar error:', error);
          this.safeEmit({ type: 'error', path: '', error });
        })
        .on('ready', () => {
          console.log('[smartwatch] Chokidar ready - initial scan complete');
          this.safeEmit({ type: 'ready', path: '' });
        });

      this._isWatching = true;
      console.log('[smartwatch] Watcher started');
    } catch (error: any) {
      console.error('[smartwatch] Failed to start watcher:', error);
      this.safeEmit({ type: 'error', path: '', error });
      throw error;
    }
  }

  async stop(): Promise<void> {
    console.log('[smartwatch] Stopping watcher...');

    if (this.watcher) {
      await this.watcher.close();
      this.watcher = null;
    }

    this._isWatching = false;
    console.log('[smartwatch] Watcher stopped');
  }

  /** Safely emit an event, isolating subscriber errors */
  private safeEmit(event: IWatchEvent): void {
    try {
      this.events$.next(event);
    } catch (error) {
      console.error('[smartwatch] Subscriber threw error (isolated):', error);
    }
  }
}