import * as plugins from './plugins.js';
import { LineScanner } from './classes.linescanner.js';
import type { IRustBridgeLogger } from './interfaces/index.js';
import type { IRustTransport } from './interfaces/transport.js';

export interface IStdioTransportOptions {
  binaryPath: string;
  cliArgs: string[];
  env?: Record<string, string>;
  maxPayloadSize: number;
  logger: IRustBridgeLogger;
}

/**
 * Transport that spawns a child process and communicates via stdin/stdout.
 * Extracted from the original RustBridge process management logic.
 */
export class StdioTransport extends plugins.events.EventEmitter implements IRustTransport {
  private options: IStdioTransportOptions;
  private childProcess: plugins.childProcess.ChildProcess | null = null;
  private lineScanner: LineScanner;
  private stderrRemainder: string = '';
  private _connected: boolean = false;

  constructor(options: IStdioTransportOptions) {
    super();
    this.options = options;
    this.lineScanner = new LineScanner(options.maxPayloadSize, options.logger);
  }

  public get connected(): boolean {
    return this._connected;
  }

  /**
   * Spawn the child process. Resolves when the process is running (not necessarily ready).
   */
  public async connect(): Promise<void> {
    const env = this.options.env
      ? { ...process.env, ...this.options.env }
      : { ...process.env };

    this.childProcess = plugins.childProcess.spawn(
      this.options.binaryPath,
      this.options.cliArgs,
      { stdio: ['pipe', 'pipe', 'pipe'], env },
    );

    // Handle stderr with cross-chunk buffering
    this.childProcess.stderr?.on('data', (data: Buffer) => {
      this.stderrRemainder += data.toString();
      const lines = this.stderrRemainder.split('\n');
      this.stderrRemainder = lines.pop()!;
      for (const line of lines) {
        const trimmed = line.trim();
        if (trimmed) {
          this.emit('stderr', trimmed);
        }
      }
    });

    // Handle stdout via LineScanner
    this.childProcess.stdout!.on('data', (chunk: Buffer) => {
      this.lineScanner.push(chunk, (line) => {
        this.emit('line', line);
      });
    });

    // Handle process exit
    this.childProcess.on('exit', (code: number | null, signal: string | null) => {
      // Flush remaining stderr
      if (this.stderrRemainder.trim()) {
        this.emit('stderr', this.stderrRemainder.trim());
      }
      this._connected = false;
      this.lineScanner.clear();
      this.stderrRemainder = '';
      this.emit('close', code, signal);
    });

    this.childProcess.on('error', (err: Error) => {
      this._connected = false;
      this.emit('error', err);
    });

    this._connected = true;
  }

  /**
   * Write data to stdin with backpressure support.
   */
  public async write(data: string): Promise<void> {
    return new Promise<void>((resolve, reject) => {
      if (!this.childProcess?.stdin) {
        reject(new Error('stdin not available'));
        return;
      }

      const canContinue = this.childProcess.stdin.write(data, 'utf8', (err) => {
        if (err) {
          reject(err);
        }
      });

      if (canContinue) {
        resolve();
      } else {
        this.childProcess.stdin.once('drain', () => {
          resolve();
        });
      }
    });
  }

  /**
   * Kill the child process. Sends SIGTERM, then SIGKILL after 5s.
   */
  public disconnect(): void {
    if (!this.childProcess) return;

    const proc = this.childProcess;
    this.childProcess = null;
    this._connected = false;
    this.lineScanner.clear();
    this.stderrRemainder = '';

    // Remove all listeners
    proc.removeAllListeners();
    proc.stdout?.removeAllListeners();
    proc.stderr?.removeAllListeners();
    proc.stdin?.removeAllListeners();

    // Kill the process
    try { proc.kill('SIGTERM'); } catch { /* already dead */ }

    // Destroy stdio pipes
    try { proc.stdin?.destroy(); } catch { /* ignore */ }
    try { proc.stdout?.destroy(); } catch { /* ignore */ }
    try { proc.stderr?.destroy(); } catch { /* ignore */ }

    // Unref so Node doesn't wait
    try { proc.unref(); } catch { /* ignore */ }

    // Force kill after 5 seconds
    setTimeout(() => {
      try { proc.kill('SIGKILL'); } catch { /* already dead */ }
    }, 5000).unref();
  }
}