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';

// Wakeup for non-rotating channels only (general/report/triage/custom).
// discuss/work go through TurnService + emitMessageTargeted, never here.
// Precedence:
//  1. the author never gets woken by their own message
//  2. triage/custom: only wake users in the channel's wake_mapping
//     (mentions change nothing here)
//  3. general: if the message has an at-list, wake only the at'd users;
//     otherwise wake everyone
//  4. report (and anything else): wake nobody
export function computeWakeup(args: {
  xType: XType;
  recipientUserId: string;
  authorUserId: string;
  wakeUserIds: Set<string>;
  mentionUserIds?: Set<string>;
}): boolean {
  const { xType, recipientUserId, authorUserId, wakeUserIds, mentionUserIds } = args;
  if (recipientUserId === authorUserId) return false;
  switch (xType) {
    case 'general':
      if (mentionUserIds && mentionUserIds.size > 0) {
        return mentionUserIds.has(recipientUserId);
      }
      return true;
    case 'triage':
    case 'custom':
      return wakeUserIds.has(recipientUserId);
    case 'dm':
      // 1:1 conversation: every non-author participant is always woken.
      return true;
    default:
      return false;
  }
}

@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);
    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);
  }

  // Emits message.created per-recipient so each carries its own `wakeup` flag.
  async emitMessageCreated(
    channelId: string,
    data: Record<string, unknown>,
    ctx: {
      xType: XType;
      authorUserId: string;
      wakeUserIds: Set<string>;
      mentionUserIds?: Set<string>;
    },
  ): 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 = computeWakeup({
        xType: ctx.xType,
        recipientUserId,
        authorUserId: ctx.authorUserId,
        wakeUserIds: ctx.wakeUserIds,
        mentionUserIds: ctx.mentionUserIds,
      });
      s.emit('message.created', { ...data, channelId, wakeup, 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 });
    }
  }
}