class CoinFlipProtocol {
  constructor(mesh) {
    this.mesh = mesh;
    this.state = 'IDLE';
    this.secret = null;
    this.commits = new Map();
    this.reveals = new Map();
    this.result = null;
    this.totalPeers = 0;
    this.expectedPeers = new Set();
    this.TIMEOUT_MS = 12000;
    this._commitTimer = null;
    this._revealTimer = null;

    this.onstatechange = null;
    this.onprogress = null;
    this.oncomplete = null;
    this.onerror = null;
  }

  async start() {
    if (this.state !== 'IDLE') return;
    this.state = 'STARTING';
    this.expectedPeers = new Set([this.mesh.myPeerId, ...this.mesh.getPeerIds()]);
    this.totalPeers = this.expectedPeers.size;
    this.secret = await generateSecret();
    const myCommit = await commit(this.secret);
    this.commits.set(this.mesh.myPeerId, myCommit);
    if (this.onprogress) this.onprogress('commit', 1, this.totalPeers);
    if (this.onstatechange) this.onstatechange('COMMITTING');
    this.mesh.broadcast({ type: 'protocol', phase: 'commit', data: bufToBase64(myCommit) });
    this.state = 'WAITING_FOR_COMMITS';
    if (this.onstatechange) this.onstatechange('WAITING_FOR_COMMITS');
    this._startCommitTimer();
    this._checkCommits();
  }

  handleMessage(peerId, msg) {
    if (msg.type !== 'protocol') return;

    if (msg.phase === 'commit' && (this.state === 'WAITING_FOR_COMMITS' || this.state === 'COMMITTING' || this.state === 'STARTING')) {
      if (!this.commits.has(peerId)) {
        this.commits.set(peerId, base64ToBuf(msg.data));
        if (this.onprogress) this.onprogress('commit', this.commits.size, this.totalPeers);
        this._checkCommits();
      }
    }

    if (msg.phase === 'reveal' && (this.state === 'WAITING_FOR_REVEALS' || this.state === 'REVEALING')) {
      if (!this.reveals.has(peerId)) {
        this.reveals.set(peerId, base64ToBuf(msg.data));
        if (this.onprogress) this.onprogress('reveal', this.reveals.size, this.totalPeers);
        this._checkReveals();
      }
    }
  }

  /* ─── Timeout ─── */

  _startCommitTimer() {
    this._clearCommitTimer();
    this._commitTimer = setTimeout(() => {
      if (this.commits.size >= this.totalPeers) return;
      const missing = [...this.expectedPeers].filter(p => !this.commits.has(p));
      this._abort(`Timeout auf Commits von: ${missing.map(p => p.slice(0, 8)).join(', ')}`);
    }, this.TIMEOUT_MS);
  }

  _startRevealTimer() {
    this._clearRevealTimer();
    this._revealTimer = setTimeout(() => {
      if (this.reveals.size >= this.totalPeers) return;
      const missing = [...this.expectedPeers].filter(p => !this.reveals.has(p));
      this._abort(`Timeout auf Reveals von: ${missing.map(p => p.slice(0, 8)).join(', ')}`);
    }, this.TIMEOUT_MS);
  }

  _clearCommitTimer() {
    if (this._commitTimer) {
      clearTimeout(this._commitTimer);
      this._commitTimer = null;
    }
  }

  _clearRevealTimer() {
    if (this._revealTimer) {
      clearTimeout(this._revealTimer);
      this._revealTimer = null;
    }
  }

  _abort(reason) {
    this._clearCommitTimer();
    this._clearRevealTimer();
    this.state = 'ABORTED';
    if (this.onstatechange) this.onstatechange('ABORTED');
    if (this.onerror) this.onerror(reason);
  }

  /* ─── Commit phase ─── */

  _checkCommits() {
    if (this.state !== 'WAITING_FOR_COMMITS') return;
    if (this.commits.size >= this.totalPeers) {
      this._clearCommitTimer();
      this._allCommitsReceived();
    }
  }

  async _allCommitsReceived() {
    this.state = 'REVEALING';
    if (this.onstatechange) this.onstatechange('REVEALING');
    this.mesh.broadcast({ type: 'protocol', phase: 'reveal', data: bufToBase64(this.secret) });
    this.reveals.set(this.mesh.myPeerId, this.secret);
    if (this.onprogress) this.onprogress('reveal', 1, this.totalPeers);
    this.state = 'WAITING_FOR_REVEALS';
    if (this.onstatechange) this.onstatechange('WAITING_FOR_REVEALS');
    this._startRevealTimer();
    this._checkReveals();
  }

  /* ─── Reveal phase ─── */

  _checkReveals() {
    if (this.state !== 'WAITING_FOR_REVEALS') return;
    if (this.reveals.size >= this.totalPeers) {
      this._clearRevealTimer();
      this._allRevealsReceived();
    }
  }

  async _allRevealsReceived() {
    this._clearRevealTimer();

    this.state = 'VERIFYING';
    if (this.onstatechange) this.onstatechange('VERIFYING');

    for (const [peerId, secret] of this.reveals) {
      if (peerId === this.mesh.myPeerId) continue;
      const commitment = this.commits.get(peerId);
      if (!commitment) {
        this._abort(`Fehler: Kein Commit von ${peerId.slice(0, 8)}`);
        return;
      }
      const expected = await commit(secret);
      if (!arraysEqual(expected, commitment)) {
        this._abort(`Betrug erkannt! ${peerId.slice(0, 8)} hat gefälscht.`);
        return;
      }
    }

    this.state = 'COMPLETE';
    this.result = combine(Array.from(this.reveals.values()));
    if (this.onstatechange) this.onstatechange('COMPLETE');
    if (this.oncomplete) this.oncomplete(this.result);
  }

  /* ─── Reset ─── */

  reset() {
    this._clearCommitTimer();
    this._clearRevealTimer();
    this.state = 'IDLE';
    this.secret = null;
    this.commits.clear();
    this.reveals.clear();
    this.result = null;
    this.totalPeers = 0;
    this.expectedPeers = new Set();
  }
}