import { Readable, Writable, Duplex } from 'stream';

/**
 * stream-to-push-stream - Convert Node.js streams to push-streams
 *
 * Bridges Node.js Readable/Writable/Duplex streams into the push-stream protocol
 * so they can be composed with `@push-stream-std/*` operators.
 */

class PushSource {
  constructor(readable) {
    this.readable = readable;
    this.sink = null;
    this.paused = true;
    this.ended = false;
    this._endedWithError = null;

    this._onData = this._onData.bind(this);
    this._onEnd = this._onEnd.bind(this);
    this._onError = this._onError.bind(this);
    this._onResume = this._onResume.bind(this);

    readable.on('data', this._onData);
    readable.on('end', this._onEnd);
    readable.on('error', this._onError);
  }

  pipe(sink) {
    this.sink = sink;
    sink.source = this;
    if (!sink.paused) {
      this.resume();
    }
    return sink;
  }

  resume() {
    if (this.ended) return;
    this.paused = false;
    this.readable.resume();
    this._drain();
  }

  abort(err) {
    if (this.ended) return;
    this.ended = err || new Error('Aborted');
    this._cleanup();
    if (this.sink) {
      this.sink.end(this.ended);
      this.sink.source = null;
      this.sink = null;
    }
  }

  _drain() {
    // _drain is no longer needed - _onData handles all data events
    // This method is kept for compatibility but does nothing
    // The readable stream's 'data' event handler (_onData) is already set up in constructor
  }

  _onData(data) {
    if (this.ended) return;
    if (this.sink) {
      if (this.sink.paused) {
        this.paused = true;
        this.readable.pause();
        return;
      }
      this.sink.write(data);
      this.paused = this.sink.paused;
    } else {
      this.paused = true;
      this.readable.pause();
    }
  }

  _onEnd() {
    if (this.ended) return;
    this.ended = true;
    this._cleanup();
    if (this.sink) {
      this.sink.end(this._endedWithError);
      this.sink.source = null;
      this.sink = null;
    }
  }

  _onError(err) {
    if (this.ended) return;
    this._endedWithError = err;
    this.ended = err;
    this._cleanup();
    if (this.sink) {
      this.sink.end(err);
      this.sink.source = null;
      this.sink = null;
    }
  }

  _onResume() {
    if (this.paused && !this.ended) {
      this.paused = false;
      this.readable.resume();
      this._drain();
    }
  }

  _cleanup() {
    this.readable.removeListener('data', this._onData);
    this.readable.removeListener('end', this._onEnd);
    this.readable.removeListener('error', this._onError);
  }
}

class PushSink {
  constructor(writable) {
    this.writable = writable;
    this.source = null;
    this.paused = false;
    this.ended = false;
    this._endedWithError = null;
    this._draining = false;

    this._onDrain = this._onDrain.bind(this);
    this._onError = this._onError.bind(this);

    writable.on('drain', this._onDrain);
    writable.on('error', this._onError);
  }

  pipe(sink) {
    if (sink && sink.write) {
      this.source = sink;
      sink.source = this;
    }
    return sink;
  }

  write(data) {
    if (this.ended) return;
    const ok = this.writable.write(data);
    if (!ok) {
      this.paused = true;
    }
    return ok;
  }

  end(err) {
    if (this.ended) return;
    this.ended = err || true;
    this._cleanup();
    if (this.writable.destroyed || this.writable.writableEnded) {
      return;
    }
    if (err) {
      this.writable.destroy(err);
    } else {
      this.writable.end();
    }
    if (this.source) {
      this.source.sink = null;
      this.source = null;
    }
  }

  abort(err) {
    if (this.ended) return;
    this.ended = err || new Error('Aborted');
    this._cleanup();
    if (!this.writable.destroyed) {
      this.writable.destroy(this.ended);
    }
    if (this.source) {
      this.source.abort(this.ended);
      this.source = null;
    }
  }

  _onDrain() {
    if (this.paused && !this.ended) {
      this.paused = false;
      if (this.source) {
        this.source.resume();
      }
    }
  }

  _onError(err) {
    if (this.ended) return;
    this._endedWithError = err;
    this.ended = err;
    this._cleanup();
    if (this.source) {
      this.source.abort(err);
      this.source.sink = null;
      this.source = null;
    }
  }

  _cleanup() {
    this.writable.removeListener('drain', this._onDrain);
    this.writable.removeListener('error', this._onError);
  }
}

class PushDuplex {
  constructor(duplex) {
    this.source = new PushSource(duplex);
    this.sink = new PushSink(duplex);
    this.paused = false;
    this.ended = false;

    this.sink.source = this.source;
    this.source.sink = this.sink;
  }

  pipe(sink) {
    return this.source.pipe(sink);
  }

  resume() {
    this.source.resume();
  }

  abort(err) {
    if (this.ended) return;
    this.ended = err || new Error('Aborted');
    this.source.abort(err);
    this.sink.end(err);
  }
}

/**
 * Wrap a Node.js Readable stream as a push-stream source.
 * @param {import('stream').Readable} readableStream
 * @returns {object} A push-stream source
 */
export function source(readableStream) {
  if (!(readableStream instanceof Readable)) {
    throw new Error('Expected a Node.js Readable stream');
  }
  return new PushSource(readableStream);
}

/**
 * Wrap a Node.js Writable stream as a push-stream sink.
 * @param {import('stream').Writable} writableStream
 * @returns {object} A push-stream sink
 */
export function sink(writableStream) {
  if (!(writableStream instanceof Writable)) {
    throw new Error('Expected a Node.js Writable stream');
  }
  return new PushSink(writableStream);
}

/**
 * Wrap a Node.js Duplex stream as a push-stream duplex (`{ source, sink }`).
 * @param {import('stream').Duplex} duplexStream
 * @returns {{source: object, sink: object}} Push-stream duplex
 */
export function duplex(duplexStream) {
  if (!(duplexStream instanceof Duplex)) {
    throw new Error('Expected a Node.js Duplex stream');
  }
  return new PushDuplex(duplexStream);
}