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

// Resolve the package directory for binary location
const packageDir = path.resolve(new URL('.', import.meta.url).pathname, '..', '..');

/**
 * Command map for the Rust file watcher binary
 */
type TWatcherCommands = {
  watch: {
    params: {
      paths: string[];
      depth: number;
      followSymlinks: boolean;
      debounceMs: number;
    };
    result: { watching: boolean };
  };
  stop: {
    params: Record<string, never>;
    result: { stopped: boolean };
  };
};

/**
 * Build local search paths for the Rust binary
 */
function buildLocalPaths(): string[] {
  const platform = process.platform === 'darwin' ? 'macos' : process.platform;
  const arch = process.arch === 'x64' ? 'amd64' : process.arch === 'arm64' ? 'arm64' : process.arch;
  const platformSuffix = `${platform}_${arch}`;

  return [
    path.join(packageDir, 'dist_rust', `smartwatch-rust_${platformSuffix}`),
    path.join(packageDir, 'dist_rust', 'smartwatch-rust'),
    path.join(packageDir, 'rust', 'target', 'release', 'smartwatch-rust'),
    path.join(packageDir, 'rust', 'target', 'debug', 'smartwatch-rust'),
  ];
}

/**
 * Rust-based file watcher using the notify crate via @push.rocks/smartrust
 *
 * Uses a Rust binary for native OS-level file watching (inotify/FSEvents/ReadDirectoryChangesW).
 * Works across Node.js, Deno, and Bun via smartrust's IPC bridge.
 */
export class RustWatcher implements IWatcher {
  private bridge: smartrust.RustBridge<TWatcherCommands>;
  private _isWatching = false;

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

  constructor(private options: IWatcherOptions) {
    this.bridge = new smartrust.RustBridge<TWatcherCommands>({
      binaryName: 'smartwatch-rust',
      localPaths: buildLocalPaths(),
      searchSystemPath: false,
      cliArgs: ['--management'],
      requestTimeoutMs: 30000,
      readyTimeoutMs: 10000,
    });
  }

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

  /**
   * Check if the Rust binary is available on this system
   */
  static async isAvailable(): Promise<boolean> {
    try {
      const locator = new smartrust.RustBinaryLocator({
        binaryName: 'smartwatch-rust',
        localPaths: buildLocalPaths(),
        searchSystemPath: false,
      });
      const binaryPath = await locator.findBinary();
      return binaryPath !== null;
    } catch {
      return false;
    }
  }

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

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

    // Listen for file system events from the Rust binary
    this.bridge.on('management:fsEvent', (data: { type: string; path: string }) => {
      const eventType = data.type as TWatchEventType;
      this.safeEmit({ type: eventType, path: data.path });
    });

    this.bridge.on('management:error', (data: { message: string }) => {
      console.error('[smartwatch] Rust watcher error:', data.message);
      this.safeEmit({ type: 'error', path: '', error: new Error(data.message) });
    });

    this.bridge.on('management:watchReady', () => {
      console.log('[smartwatch] Rust watcher ready - initial scan complete');
      this.safeEmit({ type: 'ready', path: '' });
    });

    // Spawn the Rust binary
    const ok = await this.bridge.spawn();
    if (!ok) {
      throw new Error('[smartwatch] Failed to spawn Rust watcher binary');
    }

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

    // Send watch command
    await this.bridge.sendCommand('watch', {
      paths: absolutePaths,
      depth: this.options.depth,
      followSymlinks: this.options.followSymlinks,
      debounceMs: this.options.debounceMs,
    });

    this._isWatching = true;
    console.log('[smartwatch] Rust watcher started');
  }

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

    if (this._isWatching) {
      try {
        await this.bridge.sendCommand('stop', {} as any);
      } catch {
        // Binary may already be gone
      }
    }

    this.bridge.kill();
    this._isWatching = false;
    console.log('[smartwatch] Rust 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);
    }
  }
}