import { Inject, Injectable, Logger } from '@nestjs/common';
import { ChatChannelType, SyncOperation } from '@prisma/client';
import { PrismaClient } from '../prisma/prisma.module';
import { SyncService } from '../sync/sync.service';
import type { ChatCaller } from '../chat/chat.service';
import { PUSH_PROVIDER, PushNotification, PushProvider } from './push-provider';

@Injectable()
export class PushService {
  private readonly logger = new Logger(PushService.name);

  constructor(
    private readonly prisma: PrismaClient,
    private readonly sync: SyncService,
    @Inject(PUSH_PROVIDER) private readonly provider: PushProvider,
  ) {}

  /// Upsert a device token for the current caller (team user or guest).
  async register(token: string, platform: string, caller: ChatCaller) {
    const owner =
      caller.kind === 'user'
        ? { userId: caller.user.userId, guestAccountId: null }
        : { userId: null, guestAccountId: caller.guest.guestId };
    const row = await this.prisma.deviceToken.upsert({
      where: { token },
      create: { token, platform, ...owner },
      update: { platform, lastSeenAt: new Date(), ...owner },
    });
    await this.sync.capture('DeviceToken', SyncOperation.UPDATE, row.id, row);
    return { ok: true };
  }

  async unregister(token: string) {
    const existing = await this.prisma.deviceToken.findUnique({ where: { token } });
    if (!existing) return { ok: true };
    await this.prisma.deviceToken.delete({ where: { token } });
    await this.sync.capture('DeviceToken', SyncOperation.DELETE, existing.id, {
      id: existing.id,
    });
    return { ok: true };
  }

  /// Fan a chat message out as a push to everyone who can read the channel,
  /// minus the sender. Best-effort — never throws into the caller.
  async notifyChannel(
    channelId: string,
    notification: PushNotification,
    exclude: { userId?: string | null; guestId?: string | null } = {},
  ): Promise<void> {
    try {
      const channel = await this.prisma.chatChannel.findUnique({
        where: { id: channelId },
        include: { participants: { select: { userId: true, guestAccountId: true } } },
      });
      if (!channel) return;

      const { userIds, guestIds } = await this.audience(channel);
      const tokens = await this.prisma.deviceToken.findMany({
        where: {
          OR: [
            userIds.length ? { userId: { in: userIds } } : undefined,
            guestIds.length ? { guestAccountId: { in: guestIds } } : undefined,
          ].filter(Boolean) as object[],
          NOT: {
            OR: [
              exclude.userId ? { userId: exclude.userId } : undefined,
              exclude.guestId ? { guestAccountId: exclude.guestId } : undefined,
            ].filter(Boolean) as object[],
          },
        },
        select: { token: true },
      });
      if (tokens.length === 0) return;

      const { invalidTokens } = await this.provider.sendToTokens(
        tokens.map((t) => t.token),
        notification,
      );
      if (invalidTokens.length) {
        await this.prisma.deviceToken.deleteMany({
          where: { token: { in: invalidTokens } },
        });
      }
    } catch (err) {
      this.logger.warn(`notifyChannel failed: ${(err as Error).message}`);
    }
  }

  private async audience(channel: {
    kcId: string;
    type: ChatChannelType;
    gemeindeId: string | null;
    participants: { userId: string | null; guestAccountId: string | null }[];
  }): Promise<{ userIds: string[]; guestIds: string[] }> {
    if (channel.type === ChatChannelType.DIREKT) {
      return {
        userIds: channel.participants.map((p) => p.userId).filter((id): id is string => !!id),
        guestIds: [],
      };
    }

    if (channel.type === ChatChannelType.GRUPPE) {
      return {
        userIds: channel.participants.map((p) => p.userId).filter((id): id is string => !!id),
        guestIds: channel.participants
          .map((p) => p.guestAccountId)
          .filter((id): id is string => !!id),
      };
    }

    const ltUsers = await this.prisma.user.findMany({
      where: {
        OR: [
          { isLeitungsteam: true },
          { memberships: { some: { kcId: channel.kcId, role: 'LEITUNGSTEAM' } } },
        ],
      },
      select: { id: true },
    });
    const ltIds = ltUsers.map((u) => u.id);

    if (channel.type === ChatChannelType.LT_UEBERGREIFEND) {
      return { userIds: ltIds, guestIds: [] };
    }

    if (channel.type === ChatChannelType.GEMEINDE_GRUPPE) {
      const [members, guests] = await Promise.all([
        this.prisma.membership.findMany({
          where: {
            kcId: channel.kcId,
            gemeindeId: channel.gemeindeId,
            status: 'ACTIVE',
          },
          select: { userId: true },
        }),
        this.prisma.guestAccount.findMany({
          where: { kcId: channel.kcId, gemeindeId: channel.gemeindeId },
          select: { id: true },
        }),
      ]);
      return {
        userIds: [...new Set([...ltIds, ...members.map((m) => m.userId)])],
        guestIds: guests.map((g) => g.id),
      };
    }

    // BROADCAST: everyone in the KC.
    const [members, guests] = await Promise.all([
      this.prisma.membership.findMany({
        where: { kcId: channel.kcId, status: 'ACTIVE' },
        select: { userId: true },
      }),
      this.prisma.guestAccount.findMany({
        where: { kcId: channel.kcId },
        select: { id: true },
      }),
    ]);
    return {
      userIds: [...new Set([...ltIds, ...members.map((m) => m.userId)])],
      guestIds: guests.map((g) => g.id),
    };
  }
}