import {
  CONNECTION_STATE_CONNECTED,
  DATA_CHANNEL_RECOVERY_GRACE_MS,
  DATA_CHANNEL_STATE_OPEN,
  P2P_TYPE_VOICE_STATE_REQUEST,
  PEER_DISCONNECT_GRACE_MS,
  PEER_RECONNECT_INTERVAL_MS,
  PEER_RECONNECT_MAX_ATTEMPTS
} from '../../realtime.constants';
import { shouldInitiatePeerConnection } from '../../peer-role.rules';
import {
  PeerConnectionManagerContext,
  PeerConnectionManagerState,
  RecoveryHandlers,
  RemovePeerOptions
} from '../shared';
import { clearAllPingTimers, stopPingInterval } from '../messaging/ping';
import { clearDebugNetworkPeerMetrics } from '../../logging/debug-network-metrics';

/**
 * Close and remove a peer connection, data channel, and emit a disconnect event.
 */
export function removePeer(
  context: PeerConnectionManagerContext,
  peerId: string,
  options?: RemovePeerOptions
): void {
  const { state } = context;
  const peerData = state.activePeerConnections.get(peerId);
  const preserveReconnectState = options?.preserveReconnectState === true;

  clearPeerDisconnectGraceTimer(state, peerId);
  clearDataChannelRecoveryTimer(state, peerId);

  if (!preserveReconnectState) {
    clearPeerReconnectTimer(state, peerId);
    state.disconnectedPeerTracker.delete(peerId);
    clearDebugNetworkPeerMetrics(peerId);
  }

  state.remotePeerStreams.delete(peerId);
  state.remotePeerVoiceStreams.delete(peerId);
  state.remotePeerScreenShareStreams.delete(peerId);
  state.remotePeerCameraStreams.delete(peerId);

  if (peerData) {
    if (peerData.dataChannel)
      peerData.dataChannel.close();

    peerData.connection.close();
    state.activePeerConnections.delete(peerId);
    state.peerNegotiationQueue.delete(peerId);
    removeFromConnectedPeers(state, peerId);
    stopPingInterval(state, peerId);
    state.peerLatencies.delete(peerId);
    state.pendingPings.delete(peerId);
    state.peerDisconnected$.next(peerId);
  }
}

/** Close every active peer connection and clear internal state. */
export function closeAllPeers(state: PeerConnectionManagerState): void {
  clearAllPeerReconnectTimers(state);
  clearAllPeerDisconnectGraceTimers(state);
  clearAllDataChannelRecoveryTimers(state);
  clearAllPingTimers(state);

  state.activePeerConnections.forEach((peerData) => {
    if (peerData.dataChannel)
      peerData.dataChannel.close();

    peerData.connection.close();
  });

  state.activePeerConnections.clear();
  state.remotePeerStreams.clear();
  state.remotePeerVoiceStreams.clear();
  state.remotePeerScreenShareStreams.clear();
  state.remotePeerCameraStreams.clear();
  state.peerNegotiationQueue.clear();
  state.peerLatencies.clear();
  state.pendingPings.clear();
  state.connectedPeersChanged$.next([]);
}

export function trackDisconnectedPeer(state: PeerConnectionManagerState, peerId: string): void {
  state.disconnectedPeerTracker.set(peerId, {
    lastSeenTimestamp: Date.now(),
    reconnectAttempts: 0
  });
}

export function clearPeerReconnectTimer(
  state: PeerConnectionManagerState,
  peerId: string
): void {
  const timer = state.peerReconnectTimers.get(peerId);

  if (timer) {
    clearInterval(timer);
    state.peerReconnectTimers.delete(peerId);
  }
}

export function clearPeerDisconnectGraceTimer(
  state: PeerConnectionManagerState,
  peerId: string
): void {
  const timer = state.peerDisconnectGraceTimers.get(peerId);

  if (timer) {
    clearTimeout(timer);
    state.peerDisconnectGraceTimers.delete(peerId);
  }
}

export function clearDataChannelRecoveryTimer(
  state: PeerConnectionManagerState,
  peerId: string
): void {
  const timer = state.dataChannelRecoveryTimers.get(peerId);

  if (timer) {
    clearTimeout(timer);
    state.dataChannelRecoveryTimers.delete(peerId);
  }
}

/** Cancel all pending peer reconnect timers and clear the tracker. */
export function clearAllPeerReconnectTimers(state: PeerConnectionManagerState): void {
  state.peerReconnectTimers.forEach((timer) => clearInterval(timer));
  state.peerReconnectTimers.clear();
  state.disconnectedPeerTracker.clear();
}

export function clearAllPeerDisconnectGraceTimers(state: PeerConnectionManagerState): void {
  state.peerDisconnectGraceTimers.forEach((timer) => clearTimeout(timer));
  state.peerDisconnectGraceTimers.clear();
}

export function clearAllDataChannelRecoveryTimers(state: PeerConnectionManagerState): void {
  state.dataChannelRecoveryTimers.forEach((timer) => clearTimeout(timer));
  state.dataChannelRecoveryTimers.clear();
}

export function scheduleDataChannelRecovery(
  context: PeerConnectionManagerContext,
  peerId: string,
  channel: RTCDataChannel,
  reason: string,
  handlers: RecoveryHandlers
): void {
  const { logger, state } = context;
  const peerData = state.activePeerConnections.get(peerId);

  if (!peerData || peerData.dataChannel !== channel)
    return;

  if (channel.readyState === DATA_CHANNEL_STATE_OPEN)
    return;

  if (channel.readyState === 'closed') {
    logger.warn('[data-channel] Control channel closed; reconnecting peer immediately', {
      channelLabel: channel.label,
      connectionState: peerData.connection.connectionState,
      peerId,
      reason
    });

    repairUnavailableDataChannel(context, peerId, channel, reason, handlers);
    return;
  }

  if (state.dataChannelRecoveryTimers.has(peerId))
    return;

  logger.warn('[data-channel] Control channel unavailable; waiting before reconnect', {
    channelLabel: channel.label,
    peerId,
    readyState: channel.readyState,
    reason
  });

  const timer = setTimeout(() => {
    state.dataChannelRecoveryTimers.delete(peerId);

    const latestPeerData = state.activePeerConnections.get(peerId);

    if (!latestPeerData || latestPeerData.dataChannel !== channel)
      return;

    if (latestPeerData.dataChannel?.readyState === DATA_CHANNEL_STATE_OPEN)
      return;

    logger.warn('[data-channel] Control channel did not recover; selecting repair path', {
      channelLabel: channel.label,
      connectionState: latestPeerData.connection.connectionState,
      peerId,
      readyState: latestPeerData.dataChannel?.readyState ?? null,
      reason
    });

    repairUnavailableDataChannel(context, peerId, channel, reason, handlers);
  }, DATA_CHANNEL_RECOVERY_GRACE_MS);

  state.dataChannelRecoveryTimers.set(peerId, timer);
}

/**
 * Repair a failed control channel with the least destructive option available.
 *
 * While the `RTCPeerConnection` is still connected the channel is replaced on that same
 * connection, so voice, camera, and screen share keep flowing. Only the deterministically
 * elected initiator creates the replacement; the other side adopts the incoming channel.
 * A full peer rebuild is the fallback when the connection itself is gone, when the
 * replacement cannot be created, or when the replacement never opens.
 */
function repairUnavailableDataChannel(
  context: PeerConnectionManagerContext,
  peerId: string,
  channel: RTCDataChannel,
  reason: string,
  handlers: RecoveryHandlers
): void {
  const { callbacks, logger, state } = context;
  const peerData = state.activePeerConnections.get(peerId);

  if (!peerData || peerData.dataChannel !== channel)
    return;

  if (peerData.dataChannel?.readyState === DATA_CHANNEL_STATE_OPEN)
    return;

  if (peerData.connection.connectionState !== CONNECTION_STATE_CONNECTED) {
    rebuildPeerAfterDataChannelFailure(context, peerId, reason, handlers);
    return;
  }

  const localOderId = callbacks.getIdentifyCredentialsForPeer(peerId)?.oderId ?? null;

  if (!localOderId) {
    logger.warn('[data-channel] Logical identity unknown; rebuilding peer instead of replacing channel', {
      peerId,
      reason
    });

    rebuildPeerAfterDataChannelFailure(context, peerId, reason, handlers);
    return;
  }

  if (shouldInitiatePeerConnection(localOderId, peerId)) {
    logger.warn('[data-channel] Replacing control channel on the live connection', {
      channelLabel: channel.label,
      peerId,
      reason
    });

    if (!handlers.replaceDataChannel(peerId, channel)) {
      rebuildPeerAfterDataChannelFailure(context, peerId, reason, handlers);
      return;
    }

    watchDataChannelReplacement(context, peerId, reason, handlers);
    return;
  }

  logger.info('[data-channel] Waiting for the remote replacement control channel', {
    channelLabel: channel.label,
    localOderId,
    peerId,
    reason
  });

  watchDataChannelReplacement(context, peerId, reason, handlers);
}

/** Rebuild the peer if the replacement control channel does not open within the grace period. */
function watchDataChannelReplacement(
  context: PeerConnectionManagerContext,
  peerId: string,
  reason: string,
  handlers: RecoveryHandlers
): void {
  const { logger, state } = context;

  clearDataChannelRecoveryTimer(state, peerId);

  const timer = setTimeout(() => {
    state.dataChannelRecoveryTimers.delete(peerId);

    const latestPeerData = state.activePeerConnections.get(peerId);

    if (!latestPeerData)
      return;

    if (latestPeerData.dataChannel?.readyState === DATA_CHANNEL_STATE_OPEN) {
      logger.info('[data-channel] Replacement control channel is open; peer kept alive', {
        peerId,
        reason
      });

      return;
    }

    logger.warn('[data-channel] Replacement control channel never opened; rebuilding peer', {
      connectionState: latestPeerData.connection.connectionState,
      peerId,
      readyState: latestPeerData.dataChannel?.readyState ?? null,
      reason
    });

    rebuildPeerAfterDataChannelFailure(context, peerId, reason, handlers);
  }, DATA_CHANNEL_RECOVERY_GRACE_MS);

  state.dataChannelRecoveryTimers.set(peerId, timer);
}

function rebuildPeerAfterDataChannelFailure(
  context: PeerConnectionManagerContext,
  peerId: string,
  reason: string,
  handlers: RecoveryHandlers
): void {
  const { logger, state } = context;
  const peerData = state.activePeerConnections.get(peerId);

  logger.warn('[data-channel] Recreating peer transport after control channel failure', {
    connectionState: peerData?.connection.connectionState ?? null,
    peerId,
    readyState: peerData?.dataChannel?.readyState ?? null,
    reason
  });

  trackDisconnectedPeer(state, peerId);
  handlers.removePeer(peerId, { preserveReconnectState: true });
  attemptPeerReconnect(context, peerId, handlers);
  schedulePeerReconnect(context, peerId, handlers);
}

export function schedulePeerDisconnectRecovery(
  context: PeerConnectionManagerContext,
  peerId: string,
  handlers: RecoveryHandlers
): void {
  const { logger, state } = context;

  if (state.peerDisconnectGraceTimers.has(peerId))
    return;

  logger.warn('Peer temporarily disconnected; waiting before reconnect', { peerId });

  const timer = setTimeout(() => {
    state.peerDisconnectGraceTimers.delete(peerId);

    const peerData = state.activePeerConnections.get(peerId);

    if (!peerData)
      return;

    const connectionState = peerData.connection.connectionState;

    if (connectionState === CONNECTION_STATE_CONNECTED || connectionState === 'connecting') {
      logger.info('Peer recovered before disconnect grace expired', {
        peerId,
        state: connectionState
      });

      return;
    }

    logger.warn('Peer still disconnected after grace period; recreating connection', {
      peerId,
      state: connectionState
    });

    trackDisconnectedPeer(state, peerId);
    handlers.removePeer(peerId, { preserveReconnectState: true });
    schedulePeerReconnect(context, peerId, handlers);
  }, PEER_DISCONNECT_GRACE_MS);

  state.peerDisconnectGraceTimers.set(peerId, timer);
}

export function schedulePeerReconnect(
  context: PeerConnectionManagerContext,
  peerId: string,
  handlers: RecoveryHandlers
): void {
  const { callbacks, logger, state } = context;

  if (state.peerReconnectTimers.has(peerId))
    return;

  logger.info('Scheduling P2P reconnect', { peerId });

  const timer = setInterval(() => {
    const info = state.disconnectedPeerTracker.get(peerId);

    if (!info) {
      clearPeerReconnectTimer(state, peerId);
      return;
    }

    // An attempt costs nothing while the socket is down and there is no way to send an
    // offer, so the budget must only be spent on attempts that can actually reach the peer.
    if (!callbacks.isSignalingConnected()) {
      logger.info('Deferring P2P reconnect - no signaling connection', {
        peerId,
        attemptsSpent: info.reconnectAttempts
      });

      return;
    }

    if (info.reconnectAttempts >= PEER_RECONNECT_MAX_ATTEMPTS) {
      failPeerRecovery(context, peerId, info.reconnectAttempts);
      return;
    }

    info.reconnectAttempts++;
    logger.info('P2P reconnect attempt', {
      peerId,
      attempt: info.reconnectAttempts
    });

    attemptPeerReconnect(context, peerId, handlers);
  }, PEER_RECONNECT_INTERVAL_MS);

  state.peerReconnectTimers.set(peerId, timer);
}

/**
 * Stop retrying a peer and say so. The tracker entry is kept (marked failed) so
 * `resumeStalledPeerRecovery` can re-arm it once signaling is usable again.
 */
function failPeerRecovery(
  context: PeerConnectionManagerContext,
  peerId: string,
  attempts: number
): void {
  const { logger, state } = context;
  const info = state.disconnectedPeerTracker.get(peerId);

  logger.warn('P2P reconnect gave up', { attempts, peerId });
  clearPeerReconnectTimer(state, peerId);

  if (info) {
    info.recoveryFailed = true;
  }

  state.peerRecoveryStatus$.next({ attempts, peerId, status: 'failed' });
}

/**
 * Re-arm every peer whose recovery gave up. Called when signaling reconnects, so a peer
 * that ran out of attempts during an outage is retried instead of staying dead silently.
 */
export function resumeStalledPeerRecovery(
  context: PeerConnectionManagerContext,
  handlers: RecoveryHandlers
): void {
  const { callbacks, logger, state } = context;

  if (!callbacks.isSignalingConnected())
    return;

  state.disconnectedPeerTracker.forEach((info, peerId) => {
    if (!info.recoveryFailed)
      return;

    logger.info('Re-arming P2P recovery after signaling returned', { peerId });

    info.recoveryFailed = false;
    info.reconnectAttempts = 0;
    state.peerRecoveryStatus$.next({ attempts: 0, peerId, status: 'retrying' });

    attemptPeerReconnect(context, peerId, handlers);
    schedulePeerReconnect(context, peerId, handlers);
  });
}

export function attemptPeerReconnect(
  context: PeerConnectionManagerContext,
  peerId: string,
  handlers: RecoveryHandlers
): void {
  const { callbacks, logger, state } = context;

  if (state.activePeerConnections.has(peerId)) {
    handlers.removePeer(peerId, { preserveReconnectState: true });
  }

  const localOderId = callbacks.getIdentifyCredentialsForPeer(peerId)?.oderId ?? null;

  if (!localOderId) {
    logger.info('Skipping reconnect offer until logical identity is ready', { peerId });
    handlers.createPeerConnection(peerId, false);
    return;
  }

  const shouldInitiate = shouldInitiatePeerConnection(localOderId, peerId);

  handlers.createPeerConnection(peerId, shouldInitiate);

  if (shouldInitiate) {
    void handlers.createAndSendOffer(peerId);
    return;
  }

  logger.info('Waiting for remote reconnect offer based on deterministic initiator selection', {
    localOderId,
    peerId
  });
}

export function requestVoiceStateFromPeer(
  state: PeerConnectionManagerState,
  logger: PeerConnectionManagerContext['logger'],
  peerId: string
): void {
  const peerData = state.activePeerConnections.get(peerId);

  if (peerData?.dataChannel?.readyState === DATA_CHANNEL_STATE_OPEN) {
    try {
      peerData.dataChannel.send(JSON.stringify({ type: P2P_TYPE_VOICE_STATE_REQUEST }));
    } catch (error) {
      logger.warn('Failed to request voice state', error);
    }
  }
}

/** Return a snapshot copy of the currently-connected peer IDs. */
export function getConnectedPeerIds(state: PeerConnectionManagerState): string[] {
  return [...state.connectedPeersList];
}

export function addToConnectedPeers(state: PeerConnectionManagerState, peerId: string): void {
  if (!state.connectedPeersList.includes(peerId)) {
    state.connectedPeersList = [...state.connectedPeersList, peerId];
    state.connectedPeersChanged$.next(state.connectedPeersList);
  }
}

/**
 * Remove a peer from the connected list and notify subscribers.
 */
export function removeFromConnectedPeers(
  state: PeerConnectionManagerState,
  peerId: string
): void {
  state.connectedPeersList = state.connectedPeersList.filter(
    (connectedId) => connectedId !== peerId
  );

  state.connectedPeersChanged$.next(state.connectedPeersList);
}

/** Reset the connected peers list to empty and notify subscribers. */
export function resetConnectedPeers(state: PeerConnectionManagerState): void {
  state.connectedPeersList = [];
  state.connectedPeersChanged$.next([]);
}