import {
  ConnectedSocket,
  MessageBody,
  OnGatewayConnection,
  OnGatewayDisconnect,
  SubscribeMessage,
  WebSocketGateway,
  WebSocketServer,
} from '@nestjs/websockets';
import { Logger } from '@nestjs/common';
import { Server, Socket } from 'socket.io';
import { introspectGuildToken } from '../common/center-auth.js';

type XType = 'general' | 'work' | 'report' | 'discuss' | 'triage' | 'custom' | 'dm';

/**
 * Per-recipient delivery decision for a non-rotating channel message.
 *
 *   • `wake` — push the event AND wake the recipient (model turn fires)
 *   • `observer` — push the event with wakeup=false (silent; UI displays
 *     but the openclaw plugin records-only without dispatch). Currently
 *     used for the Center admin observing triage traffic
 *   • `skip` — don't even emit the event to this recipient
 *
 * Wakeup-only channels (general/report/dm/custom) never return
 * 'observer'; the legacy behaviour is preserved end-to-end.
 *
 * Precedence for triage (the only place 'skip' / 'observer' fire):
 *   1. author never gets back their own message
 *   2. wake_mapping (on-duty) → wake
 *   3. mention → wake (NEW: was 'skip' before — see Fabric PR 'triage
 *      mention exception')
 *   4. admin (Center-scoped, at most one) → observer
 *   5. everyone else → skip (was 'deliver, wakeup=false' before)
 */
export type DeliveryDecision = 'wake' | 'observer' | 'skip';

export interface ComputeDeliveryArgs {
  xType: XType;
  recipientUserId: string;
  authorUserId: string;
  wakeUserIds: Set<string>;
  mentionUserIds?: Set<string>;
  /** Single Center-scoped admin userId, or null. */
  adminUserId?: string | null;
}

export function computeDelivery(args: ComputeDeliveryArgs): DeliveryDecision {
  const { xType, recipientUserId, authorUserId, wakeUserIds, mentionUserIds, adminUserId } = args;
  if (recipientUserId === authorUserId) return 'skip';

  switch (xType) {
    case 'triage':
      if (wakeUserIds.has(recipientUserId)) return 'wake';
      if (mentionUserIds?.has(recipientUserId)) return 'wake';
      if (adminUserId && recipientUserId === adminUserId) return 'observer';
      return 'skip';
    case 'general':
      if (mentionUserIds && mentionUserIds.size > 0) {
        return mentionUserIds.has(recipientUserId) ? 'wake' : 'observer';
      }
      return 'wake';
    case 'custom':
      // wake_mapping decides who wakes; everyone else still sees the
      // message (observer) — preserves the legacy "deliver to all, wake
      // some" contract for custom channels.
      return wakeUserIds.has(recipientUserId) ? 'wake' : 'observer';
    case 'dm':
      return 'wake';
    default:
      // report (and anything else): deliver as observer, no wake
      return 'observer';
  }
}

/**
 * @deprecated Use computeDelivery (returns 3-state). Kept for any
 * external callers; treats 'observer' and 'skip' both as `false`.
 */
export function computeWakeup(args: {
  xType: XType;
  recipientUserId: string;
  authorUserId: string;
  wakeUserIds: Set<string>;
  mentionUserIds?: Set<string>;
}): boolean {
  return computeDelivery(args) === 'wake';
}

@WebSocketGateway({
  namespace: '/realtime',
  cors: {
    origin: '*',
  },
})
export class RealtimeGateway implements OnGatewayConnection, OnGatewayDisconnect {
  @WebSocketServer()
  server!: Server;

  private readonly logger = new Logger(RealtimeGateway.name);
  private readonly onlineUsers = new Set<string>();

  private userIdFromClient(client: Socket): string {
    const authUser = client.handshake.auth?.userId;
    const headerUser = client.handshake.headers['x-user-id'];
    const userId = typeof authUser === 'string' ? authUser : Array.isArray(headerUser) ? headerUser[0] : headerUser;
    return userId && typeof userId === 'string' && userId.trim() !== '' ? userId : `anon:${client.id}`;
  }

  async handleConnection(client: Socket): Promise<void> {
    const authToken = client.handshake.auth?.token;
    const headerAuth = client.handshake.headers['authorization'];
    const bearer =
      typeof authToken === 'string'
        ? authToken
        : typeof headerAuth === 'string' && headerAuth.startsWith('Bearer ')
          ? headerAuth.slice(7)
          : '';

    if (!bearer) {
      this.logger.warn(`socket rejected (missing token): ${client.id}`);
      client.disconnect(true);
      return;
    }

    const result = await introspectGuildToken(bearer);
    if (!result.active || !result.user?.id) {
      this.logger.warn(`socket rejected: ${client.id}`);
      client.disconnect(true);
      return;
    }

    this.logger.log(`socket connected: ${client.id}`);

    const userId = result.user.id || this.userIdFromClient(client);
    client.data.userId = userId;
    this.onlineUsers.add(userId);
    // Per-user room: lets server code emit user-scoped events (e.g.
    // channel.joined when membership changes) without bookkeeping a
    // userId→sockets map. All of this user's sockets receive the event.
    client.join(`user:${userId}`);
    this.server.emit('presence.online', {
      userId,
      onlineCount: this.onlineUsers.size,
      occurredAt: new Date().toISOString(),
    });
  }

  handleDisconnect(client: Socket): void {
    this.logger.log(`socket disconnected: ${client.id}`);

    const userId = typeof client.data.userId === 'string' ? client.data.userId : `anon:${client.id}`;
    this.onlineUsers.delete(userId);
    this.server.emit('presence.offline', {
      userId,
      onlineCount: this.onlineUsers.size,
      occurredAt: new Date().toISOString(),
    });
  }

  @SubscribeMessage('join_channel')
  joinChannel(
    @ConnectedSocket() client: Socket,
    @MessageBody() body: { channelId?: string },
  ): { ok: boolean } {
    if (!body?.channelId) return { ok: false };
    client.join(`channel:${body.channelId}`);
    return { ok: true };
  }

  @SubscribeMessage('leave_channel')
  leaveChannel(
    @ConnectedSocket() client: Socket,
    @MessageBody() body: { channelId?: string },
  ): { ok: boolean } {
    if (!body?.channelId) return { ok: false };
    client.leave(`channel:${body.channelId}`);
    return { ok: true };
  }

  @SubscribeMessage('typing.start')
  typingStart(
    @ConnectedSocket() client: Socket,
    @MessageBody() body: { channelId?: string },
  ): { ok: boolean } {
    if (!body?.channelId) return { ok: false };

    const userId = typeof client.data.userId === 'string' ? client.data.userId : `anon:${client.id}`;
    this.server.to(`channel:${body.channelId}`).emit('typing.start', {
      channelId: body.channelId,
      userId,
      occurredAt: new Date().toISOString(),
    });
    return { ok: true };
  }

  @SubscribeMessage('typing.stop')
  typingStop(
    @ConnectedSocket() client: Socket,
    @MessageBody() body: { channelId?: string },
  ): { ok: boolean } {
    if (!body?.channelId) return { ok: false };

    const userId = typeof client.data.userId === 'string' ? client.data.userId : `anon:${client.id}`;
    this.server.to(`channel:${body.channelId}`).emit('typing.stop', {
      channelId: body.channelId,
      userId,
      occurredAt: new Date().toISOString(),
    });
    return { ok: true };
  }

  emitChannelEvent(channelId: string, event: string, data: Record<string, unknown>): void {
    this.server.to(`channel:${channelId}`).emit(event, data);
  }

  // Emit a user-scoped event to all sockets currently connected for `userId`
  // (via the `user:<userId>` room joined in handleConnection). No-op for
  // offline users — the next connect's initial channel-list fetch covers it.
  emitToUser(userId: string, event: string, data: Record<string, unknown>): void {
    if (!userId) return;
    this.server.to(`user:${userId}`).emit(event, data);
  }

  // Emits message.created per-recipient using the 3-state delivery
  // decision (wake / observer / skip). Skipped recipients receive
  // nothing — used by triage channels to keep non-on-duty / non-mention
  // / non-admin users completely out of the loop.
  async emitMessageCreated(
    channelId: string,
    data: Record<string, unknown>,
    ctx: {
      xType: XType;
      authorUserId: string;
      wakeUserIds: Set<string>;
      mentionUserIds?: Set<string>;
      /** Single Center-scoped admin userId (or null). */
      adminUserId?: string | null;
    },
  ): Promise<void> {
    const sockets = await this.server.in(`channel:${channelId}`).fetchSockets();
    for (const s of sockets) {
      const recipientUserId = typeof s.data.userId === 'string' ? s.data.userId : `anon:${s.id}`;
      const decision = computeDelivery({
        xType: ctx.xType,
        recipientUserId,
        authorUserId: ctx.authorUserId,
        wakeUserIds: ctx.wakeUserIds,
        mentionUserIds: ctx.mentionUserIds,
        adminUserId: ctx.adminUserId,
      });
      if (decision === 'skip') continue;
      s.emit('message.created', {
        ...data,
        channelId,
        wakeup: decision === 'wake',
        xType: ctx.xType,
      });
    }
  }

  // discuss/work + /ack: exactly one recipient (the new current speaker) gets
  // wakeup=true; everyone else false. One message-id; metadata at push only.
  async emitMessageTargeted(
    channelId: string,
    data: Record<string, unknown>,
    wakeupUserId: string | null,
  ): Promise<void> {
    const sockets = await this.server.in(`channel:${channelId}`).fetchSockets();
    for (const s of sockets) {
      const recipientUserId = typeof s.data.userId === 'string' ? s.data.userId : `anon:${s.id}`;
      const wakeup = wakeupUserId !== null && recipientUserId === wakeupUserId;
      s.emit('message.created', { ...data, channelId, wakeup });
    }
  }
}