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

// Type definitions for Deno APIs (these exist at runtime in Deno)
declare const Deno: {
  watchFs(paths: string | string[], options?: { recursive?: boolean }): AsyncIterable<{
    kind: 'create' | 'modify' | 'remove' | 'access' | 'any' | 'other';
    paths: string[];
    flag?: { rescan: boolean };
  }> & { close(): void };
  stat(path: string): Promise<{
    isFile: boolean;
    isDirectory: boolean;
    isSymlink: boolean;
    size: number;
    mtime: Date | null;
    atime: Date | null;
    birthtime: Date | null;
    mode: number | null;
    uid: number | null;
    gid: number | null;
  }>;
  lstat(path: string): Promise<{
    isFile: boolean;
    isDirectory: boolean;
    isSymlink: boolean;
    size: number;
    mtime: Date | null;
    atime: Date | null;
    birthtime: Date | null;
    mode: number | null;
    uid: number | null;
    gid: number | null;
  }>;
  readDir(path: string): AsyncIterable<{
    name: string;
    isFile: boolean;
    isDirectory: boolean;
    isSymlink: boolean;
  }>;
};

/**
 * Convert Deno stat to Node.js-like Stats object
 */
function denoStatToNodeStats(denoStat: Awaited<ReturnType<typeof Deno.stat>>): any {
  return {
    isFile: () => denoStat.isFile,
    isDirectory: () => denoStat.isDirectory,
    isSymbolicLink: () => denoStat.isSymlink,
    size: denoStat.size,
    mtime: denoStat.mtime,
    atime: denoStat.atime,
    birthtime: denoStat.birthtime,
    mode: denoStat.mode,
    uid: denoStat.uid,
    gid: denoStat.gid
  };
}

/**
 * Deno file watcher using native Deno.watchFs API
 */
export class DenoWatcher implements IWatcher {
  private watcher: ReturnType<typeof Deno.watchFs> | null = null;
  private watchedFiles: Set<string> = new Set();
  private _isWatching = false;

  // Debounce: pending emits per file path
  private pendingEmits: Map<string, ReturnType<typeof setTimeout>> = 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 = filePath.split('/').pop() || '';
    // 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 all base paths
      this.watcher = Deno.watchFs(this.options.basePaths, { recursive: true });
      this._isWatching = true;

      // Perform initial scan
      for (const basePath of this.options.basePaths) {
        await this.scanDirectory(basePath, 0);
      }

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

      // Start processing events
      this.processEvents();
    } 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 the watcher
    if (this.watcher) {
      (this.watcher as any).close();
      this.watcher = null;
    }

    this.watchedFiles.clear();
  }

  /**
   * Process events from the Deno watcher
   */
  private async processEvents(): Promise<void> {
    if (!this.watcher) {
      return;
    }

    try {
      for await (const event of this.watcher) {
        if (!this._isWatching) {
          break;
        }

        for (const filePath of event.paths) {
          this.handleDenoEvent(event.kind, filePath);
        }
      }
    } catch (error: any) {
      if (this._isWatching) {
        this.events$.next({ type: 'error', path: '', error });
      }
    }
  }

  /**
   * Handle a Deno file system event - debounce and normalize
   */
  private handleDenoEvent(
    kind: 'create' | 'modify' | 'remove' | 'access' | 'any' | 'other',
    filePath: string
  ): void {
    // Ignore 'access' events (just reading the file)
    if (kind === 'access') {
      return;
    }

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

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

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

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

  /**
   * Emit the actual file event after debounce
   */
  private async emitFileEvent(
    filePath: string,
    kind: 'create' | 'modify' | 'remove' | 'access' | 'any' | 'other'
  ): Promise<void> {
    try {
      if (kind === 'create') {
        const stats = await this.statSafe(filePath);
        if (stats) {
          this.watchedFiles.add(filePath);
          const eventType: TWatchEventType = stats.isDirectory() ? 'addDir' : 'add';
          this.events$.next({ type: eventType, path: filePath, stats });
        }
      } else if (kind === 'modify') {
        const stats = await this.statSafe(filePath);
        if (stats && !stats.isDirectory()) {
          this.events$.next({ type: 'change', path: filePath, stats });
        }
      } else if (kind === 'remove') {
        const wasDirectory = this.isKnownDirectory(filePath);
        this.watchedFiles.delete(filePath);
        this.events$.next({
          type: wasDirectory ? 'unlinkDir' : 'unlink',
          path: filePath
        });
      }
    } catch (error: any) {
      this.events$.next({ type: 'error', path: filePath, 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 {
      for await (const entry of Deno.readDir(dirPath)) {
        const fullPath = `${dirPath}/${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<any | null> {
    try {
      const statFn = this.options.followSymlinks ? Deno.stat : Deno.lstat;
      const denoStats = await statFn(filePath);
      return denoStatToNodeStats(denoStats);
    } catch {
      return null;
    }
  }

  /**
   * Check if a path was known to be a directory
   */
  private isKnownDirectory(filePath: string): boolean {
    for (const watched of this.watchedFiles) {
      if (watched.startsWith(filePath + '/')) {
        return true;
      }
    }
    return false;
  }
}