import {
  Body,
  ConflictException,
  Controller,
  Delete,
  ForbiddenException,
  Get,
  Headers,
  NotFoundException,
  Param,
  Patch,
  Post,
  Query,
  Req,
} from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { DataSource, Repository } from 'typeorm';
import { CreateMessageDto } from './dto.create-message.dto.js';
import { Channel } from '../entities/channel.entity.js';
import { ChannelMember } from '../entities/channel-member.entity.js';
import { Message } from '../entities/message.entity.js';
import { IdempotencyRecord } from '../entities/idempotency-record.entity.js';
import { WakeMapping } from '../entities/wake-mapping.entity.js';
import { AdminCacheService } from '../common/admin-cache.service.js';
import { parseSlashCommand } from '../channels/slash-commands.js';
import { parseMentions, extractNameMentions, replaceNameMentions } from '../channels/mentions.js';
import { resolveUserNames } from '../common/center-auth.js';
import { TurnService } from '../channels/turn.service.js';
import { EventsService } from '../events/events.service.js';
import { clampLimit, computeNextExpectedSeq } from './pagination.util.js';
import { RealtimeGateway } from '../realtime/realtime.gateway.js';

const EDIT_WINDOW_MS = 15 * 60 * 1000;
const DEFAULT_PAGE_LIMIT = 50;
const MAX_PAGE_LIMIT = 200;

@Controller('channels/:id/messages')
export class MessagingController {
  constructor(
    private readonly dataSource: DataSource,
    @InjectRepository(Channel)
    private readonly channelRepo: Repository<Channel>,
    @InjectRepository(ChannelMember)
    private readonly memberRepo: Repository<ChannelMember>,
    @InjectRepository(Message)
    private readonly messageRepo: Repository<Message>,
    @InjectRepository(IdempotencyRecord)
    private readonly idemRepo: Repository<IdempotencyRecord>,
    @InjectRepository(WakeMapping)
    private readonly wakeRepo: Repository<WakeMapping>,
    private readonly turn: TurnService,
    private readonly events: EventsService,
    private readonly realtime: RealtimeGateway,
    private readonly adminCache: AdminCacheService,
  ) {}

  private async getIdempotentResponse(
    scope: string,
    idempotencyKey?: string,
  ): Promise<Record<string, unknown> | null> {
    if (!idempotencyKey) return null;
    const row = await this.idemRepo.findOne({ where: { scope, idempotencyKey } });
    return row?.responseBody ?? null;
  }

  private async saveIdempotentResponse(
    scope: string,
    idempotencyKey: string | undefined,
    responseBody: Record<string, unknown>,
  ): Promise<void> {
    if (!idempotencyKey) return;
    const row = this.idemRepo.create({
      scope,
      idempotencyKey,
      responseBody,
    });
    await this.idemRepo.save(row);
  }

  private toView(m: Message) {
    return {
      messageId: m.messageId,
      seq: m.seq,
      content: m.content,
      authorUserId: m.authorUserId,
      replyToMessageId: m.replyToMessageId,
      mentions: m.mentions ?? [],
      attachments: m.attachments ?? [],
      createdAt: m.createdAt.toISOString(),
      editedAt: m.editedAt ? m.editedAt.toISOString() : null,
      deletedAt: m.deletedAt ? m.deletedAt.toISOString() : null,
      isDeleted: m.isDeleted,
    };
  }

  // Channel-participant gate (Guild C-1): public channels are readable/
  // writable by any authenticated user; private channels require explicit
  // channel_members membership. Returns the channel so callers can reuse it.
  private async assertParticipant(channelId: string, userId: string): Promise<Channel> {
    const channel = await this.channelRepo.findOne({ where: { id: channelId } });
    if (!channel) throw new NotFoundException('channel not found');
    if (channel.isPublic) return channel;
    if (!userId) throw new ForbiddenException('not a channel member');
    const member = await this.memberRepo.findOne({ where: { channelId, userId } });
    if (!member) throw new ForbiddenException('not a channel member');
    return channel;
  }

  // Persists one message (allocates a seq under a channel row lock) and
  // returns its view. Used for normal messages and for guild /ack messages.
  private async persistMessage(
    channelId: string,
    input: { authorUserId: string; content: string; clientMessageId?: string | null; replyToMessageId?: string | null; mentions?: string[]; attachments?: Array<{ url: string; name?: string; mimeType?: string }> },
  ): Promise<Message> {
    return this.dataSource.transaction(async (manager) => {
      const channel = await manager.findOne(Channel, {
        where: { id: channelId },
        lock: { mode: 'pessimistic_write' },
      });
      if (!channel) {
        throw new NotFoundException('channel not found');
      }
      const nextSeq = channel.lastSeq + 1;
      channel.lastSeq = nextSeq;
      await manager.save(Channel, channel);

      const messageId = input.clientMessageId ?? `m-${channelId}-${nextSeq}`;
      const row = manager.create(Message, {
        messageId,
        channelId,
        conversationId: null,
        authorUserId: input.authorUserId,
        seq: nextSeq,
        content: input.content,
        replyToMessageId: input.replyToMessageId ?? null,
        mentions: input.mentions ?? [],
        attachments: input.attachments ?? [],
        editedAt: null,
        deletedAt: null,
        isDeleted: false,
      });
      return manager.save(Message, row);
    });
  }

  // Emits a guild-authored /ack message to the channel; wakeup=true only for
  // the new current speaker (null = nobody). One message-id; persisted.
  private async emitAck(channelId: string, wakeupUserId: string | null): Promise<void> {
    const ack = await this.persistMessage(channelId, { authorUserId: 'guild', content: '/ack' });
    const body = this.toView(ack) as Record<string, unknown>;
    await this.events.emit({ eventType: 'message.created', channelId, actorId: 'guild', data: body });
    await this.realtime.emitMessageTargeted(channelId, body, wakeupUserId);
  }

  @Post()
  async create(
    @Param('id') channelId: string,
    @Body() body: CreateMessageDto,
    @Req() req: { userId?: string },
    @Headers('idempotency-key') idempotencyKey?: string,
    @Headers('x-fabric-system-key') systemKey?: string,
  ) {
    const scope = `POST:/channels/${channelId}/messages`;
    const existed = await this.getIdempotentResponse(scope, idempotencyKey);
    if (existed) return existed;

    // Guild C-1: caller must be a participant of the channel, and the
    // author is always the authenticated user — body.authorUserId is
    // ignored so a caller can never post as someone else.
    const userId = String(req.userId ?? '');
    if (!userId) throw new ForbiddenException('missing user');
    const channel = await this.assertParticipant(channelId, userId);
    if (channel.closed) {
      throw new ConflictException({ error: 'channel_closed', message: 'channel is closed' });
    }
    const xType = channel.xType ?? 'general';
    const isRotating = xType === 'discuss' || xType === 'work';

    // announce channels: posts only allowed when the caller presents a
    // valid system key (matches FABRIC_BACKEND_GUILD_SYSTEM_API_KEY env).
    // The ApiKeyGuard has already validated user identity; this is an
    // additional system-only gate on top. Non-system posts are silently
    // discarded (return 403 + log) so misbehaving clients don't pollute
    // the broadcast.
    if (xType === 'announce') {
      const expected = process.env.FABRIC_BACKEND_GUILD_SYSTEM_API_KEY ?? '';
      if (!expected || systemKey !== expected) {
        // log + reject; treat empty env as "no system caller is ever valid"
        throw new ForbiddenException({
          error: 'announce_system_only',
          message: 'announce-type channels accept system-signed posts only',
        });
      }
    }
    const authorUserId = userId;

    // ---- translate <@user.name:NAME> -> <@userId> (outside backticks) via
    // Center before anything else persists/parses the content
    let content = body.content ?? '';
    const names = extractNameMentions(content);
    if (names.length) {
      const map = await resolveUserNames(names);
      content = replaceNameMentions(content, map);
    }

    // ---- command interception: registered slash commands are never delivered
    const cmd = parseSlashCommand(content);
    if (cmd) {
      if (isRotating && cmd.name === 'no-reply') {
        const { ack } = await this.turn.onNoReply(channelId, authorUserId);
        if (ack) await this.emitAck(channelId, ack.wakeupUserId);
      } else if (isRotating && cmd.name === 'force-proceed') {
        const { ack } = await this.turn.onForceProceed(channelId);
        if (ack) await this.emitAck(channelId, ack.wakeupUserId);
      }
      // non-rotating channels (or no effect): swallowed, nothing delivered
      return { status: 'command', command: cmd.name };
    }

    // ---- normal message
    const message = await this.persistMessage(channelId, {
      authorUserId,
      content,
      clientMessageId: body.clientMessageId,
      replyToMessageId: body.replyToMessageId,
      mentions: body.mentions,
      attachments: body.attachments,
    });

    const responseBody = this.toView(message) as Record<string, unknown>;
    await this.saveIdempotentResponse(scope, idempotencyKey, responseBody);

    await this.events.emit({
      eventType: 'message.created',
      channelId,
      actorId: authorUserId,
      data: responseBody,
    });

    // mentions: <@id> outside backtick spans (post name-translation)
    const mentionIds = parseMentions(content);

    if (isRotating) {
      // discuss/work: rotation (incl. mention sub-frames) picks the target
      const decision = await this.turn.onNormalMessage(channelId, authorUserId, mentionIds);
      await this.realtime.emitMessageTargeted(channelId, responseBody, decision.wakeupUserId);
    } else {
      // general/report/triage/custom: 3-state delivery
      // (wake / observer / skip) — see realtime.gateway.computeDelivery.
      // Center-scoped admin (cached, 1d TTL) gets `observer` on triage.
      const wakeRows = await this.wakeRepo.find({ where: { channelId } });
      const wakeUserIds = new Set(wakeRows.map((w) => w.userId));
      const mentionUserIds = new Set(mentionIds.filter((id) => id !== authorUserId));
      const admin = await this.adminCache.get();
      await this.realtime.emitMessageCreated(channelId, responseBody, {
        xType,
        authorUserId,
        wakeUserIds,
        mentionUserIds,
        adminUserId: admin?.userId ?? null,
      });
    }

    return responseBody;
  }

  @Patch(':messageId')
  async edit(
    @Param('id') channelId: string,
    @Param('messageId') messageId: string,
    @Body() body: { content?: string },
    @Req() req: { userId?: string },
    @Headers('idempotency-key') idempotencyKey?: string,
  ) {
    const scope = `PATCH:/channels/${channelId}/messages/${messageId}`;
    const existed = await this.getIdempotentResponse(scope, idempotencyKey);
    if (existed) return existed;

    // Guild C-1: participant + author-ownership.
    const userId = String(req.userId ?? '');
    if (!userId) throw new ForbiddenException('missing user');
    await this.assertParticipant(channelId, userId);

    const item = await this.messageRepo.findOne({ where: { channelId, messageId } });
    if (!item) return { status: 'not_found' };
    if (item.authorUserId !== userId) {
      throw new ForbiddenException('not the message author');
    }

    const now = Date.now();
    const createdAt = new Date(item.createdAt).getTime();
    if (now - createdAt > EDIT_WINDOW_MS) {
      return { status: 'edit_window_expired', messageId };
    }

    item.content = body.content ?? item.content;
    item.editedAt = new Date();
    const saved = await this.messageRepo.save(item);
    const responseBody = this.toView(saved) as Record<string, unknown>;
    await this.saveIdempotentResponse(scope, idempotencyKey, responseBody);

    await this.events.emit({
      eventType: 'message.updated',
      channelId,
      actorId: saved.authorUserId,
      data: responseBody,
    });
    this.realtime.emitChannelEvent(channelId, 'message.updated', responseBody);

    return responseBody;
  }

  @Delete(':messageId')
  async remove(
    @Param('id') channelId: string,
    @Param('messageId') messageId: string,
    @Req() req: { userId?: string },
    @Headers('idempotency-key') idempotencyKey?: string,
  ) {
    const scope = `DELETE:/channels/${channelId}/messages/${messageId}`;
    const existed = await this.getIdempotentResponse(scope, idempotencyKey);
    if (existed) return existed;

    // Guild C-1: participant + author-ownership.
    const userId = String(req.userId ?? '');
    if (!userId) throw new ForbiddenException('missing user');
    await this.assertParticipant(channelId, userId);

    const item = await this.messageRepo.findOne({ where: { channelId, messageId } });
    if (!item) return { status: 'not_found' };
    if (item.authorUserId !== userId) {
      throw new ForbiddenException('not the message author');
    }

    item.isDeleted = true;
    item.deletedAt = new Date();
    item.content = '[deleted]';
    item.mentions = [];
    item.attachments = [];
    await this.messageRepo.save(item);

    const responseBody = {
      status: 'deleted',
      mode: 'soft',
      messageId,
    } as Record<string, unknown>;
    await this.saveIdempotentResponse(scope, idempotencyKey, responseBody);

    await this.events.emit({
      eventType: 'message.deleted',
      channelId,
      actorId: item.authorUserId,
      data: {
        messageId,
        seq: item.seq,
        deletedAt: item.deletedAt?.toISOString() ?? null,
      },
    });
    this.realtime.emitChannelEvent(channelId, 'message.deleted', {
      messageId,
      seq: item.seq,
      deletedAt: item.deletedAt?.toISOString() ?? null,
    });

    return responseBody;
  }

  @Get()
  async listBySeq(
    @Param('id') channelId: string,
    @Req() req: { userId?: string },
    @Query('seq_from') seqFrom?: string,
    @Query('seq_to') seqTo?: string,
    @Query('limit') limit?: string,
  ) {
    // Guild C-1: only participants may read channel history.
    const userId = String(req.userId ?? '');
    if (!userId) throw new ForbiddenException('missing user');
    const from = seqFrom ? Number(seqFrom) : 1;
    const to = seqTo ? Number(seqTo) : Number.MAX_SAFE_INTEGER;
    const safeLimit = clampLimit(limit, DEFAULT_PAGE_LIMIT, MAX_PAGE_LIMIT);

    if (from > to) {
      return {
        items: [],
        page: {
          seqFrom: from,
          seqTo: to,
          limit: safeLimit,
          returned: 0,
          hasMore: false,
          nextExpectedSeq: from,
          highestCommittedSeq: 0,
        },
      };
    }

    const channel = await this.assertParticipant(channelId, userId);

    const qb = this.messageRepo
      .createQueryBuilder('m')
      .where('m.channelId = :channelId', { channelId })
      .andWhere('m.seq >= :from', { from })
      .andWhere('m.seq <= :to', { to })
      .orderBy('m.seq', 'ASC');

    const total = await qb.getCount();
    const rows = await qb.limit(safeLimit).getMany();
    const items = rows.map((m) => this.toView(m));

    const nextExpectedSeq = computeNextExpectedSeq(
      from,
      rows.map((row) => row.seq),
    );

    return {
      items,
      page: {
        seqFrom: from,
        seqTo: to,
        limit: safeLimit,
        returned: items.length,
        hasMore: total > items.length,
        nextExpectedSeq,
        highestCommittedSeq: channel.lastSeq,
      },
    };
  }
}