import {
  BadRequestException,
  ForbiddenException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { Tenant } from './tenant.entity';
import { TenantSetting } from './tenant-setting.entity';
import { TenantMember } from './tenant-member.entity';
import { I18nService } from '../i18n/i18n.service';
import { UserRole } from '../user/user-role.enum';

@Injectable()
export class TenantService {
  public static readonly DEFAULT_TENANT_NAME = 'Default';

  constructor(
    @InjectRepository(Tenant)
    private readonly tenantRepository: Repository<Tenant>,
    @InjectRepository(TenantSetting)
    private readonly tenantSettingRepository: Repository<TenantSetting>,
    @InjectRepository(TenantMember)
    private readonly tenantMemberRepository: Repository<TenantMember>,
    private readonly i18nService: I18nService,
  ) {}

  async findAll(
    page?: number,
    limit?: number,
  ): Promise<{ data: Tenant[]; total: number } | Tenant[]> {
    const queryBuilder = this.tenantRepository
      .createQueryBuilder('tenant')
      .leftJoinAndSelect('tenant.members', 'members')
      .leftJoinAndSelect('members.user', 'user')
      .orderBy('tenant.createdAt', 'ASC');

    if (page !== undefined && limit !== undefined) {
      const [data, total] = await queryBuilder
        .skip((page - 1) * limit)
        .take(limit)
        .getManyAndCount();
      return { data, total };
    }

    return queryBuilder.getMany();
  }

  async findById(id: string): Promise<Tenant> {
    const tenant = await this.tenantRepository.findOneBy({ id });
    if (!tenant)
      throw new NotFoundException(
        this.i18nService.getMessage('tenantNotFound'),
      );
    return tenant;
  }

  async findByName(name: string): Promise<Tenant | null> {
    return this.tenantRepository.findOneBy({ name });
  }

  async create(
    name: string,
    domain?: string,
    parentId?: string,
    isSystem: boolean = false,
  ): Promise<Tenant> {
    const tenant = this.tenantRepository.create({
      name,
      domain,
      parentId,
      isSystem,
    });
    return this.tenantRepository.save(tenant);
  }

  async update(id: string, data: Partial<Tenant>): Promise<Tenant> {
    await this.tenantRepository.update(id, data);
    return this.findById(id);
  }

  async remove(id: string): Promise<void> {
    await this.tenantRepository.delete(id);
  }

  async getSettings(tenantId: string): Promise<TenantSetting | null> {
    return this.tenantSettingRepository.findOneBy({ tenantId });
  }

  async updateSettings(
    tenantId: string,
    data: Partial<TenantSetting>,
  ): Promise<TenantSetting> {
    let setting = await this.tenantSettingRepository.findOneBy({ tenantId });
    if (!setting) {
      setting = this.tenantSettingRepository.create({ tenantId, ...data });
    } else {
      if (data.enabledModelIds) {
        if (
          setting.selectedLLMId &&
          !data.enabledModelIds.includes(setting.selectedLLMId)
        ) {
          data.selectedLLMId = null as any;
        }
        if (
          setting.selectedEmbeddingId &&
          !data.enabledModelIds.includes(setting.selectedEmbeddingId)
        ) {
          data.selectedEmbeddingId = null as any;
        }
        if (
          setting.selectedRerankId &&
          !data.enabledModelIds.includes(setting.selectedRerankId)
        ) {
          data.selectedRerankId = null as any;
        }
        if (
          setting.selectedVisionId &&
          !data.enabledModelIds.includes(setting.selectedVisionId)
        ) {
          data.selectedVisionId = null as any;
        }
      }
      Object.assign(setting, data);
    }
    return this.tenantSettingRepository.save(setting);
  }

  async updateMemberRole(
    tenantId: string,
    userId: string,
    role: string,
  ): Promise<TenantMember> {
    const existing = await this.tenantMemberRepository.findOneBy({
      tenantId,
      userId,
    });
    if (!existing) {
      throw new ForbiddenException(`Member not found in this organization`);
    }
    existing.role = role as any;
    return this.tenantMemberRepository.save(existing);
  }

  async addMember(
    tenantId: string,
    userId: string,
    role: string = 'USER',
  ): Promise<TenantMember> {
    const existing = await this.tenantMemberRepository.findOneBy({
      tenantId,
      userId,
    });
    if (existing) {
      existing.role = role as any;
      return this.tenantMemberRepository.save(existing);
    }
    const member = this.tenantMemberRepository.create({
      tenantId,
      userId,
      role: role as any,
    });
    return this.tenantMemberRepository.save(member);
  }

  async removeMember(tenantId: string, userId: string): Promise<void> {
    await this.tenantMemberRepository.delete({ tenantId, userId });
  }

  async getMembers(
    tenantId: string,
    page?: number,
    limit?: number,
  ): Promise<{ data: TenantMember[]; total: number }> {
    const queryBuilder = this.tenantMemberRepository
      .createQueryBuilder('member')
      .leftJoinAndSelect('member.user', 'user')
      .where('member.tenantId = :tenantId', { tenantId })
      .select([
        'member',
        'user.id',
        'user.username',
        'user.displayName',
        'user.isAdmin',
      ])
      .orderBy('member.createdAt', 'DESC');

    if (page !== undefined && limit !== undefined) {
      const [data, total] = await queryBuilder
        .skip((page - 1) * limit)
        .take(limit)
        .getManyAndCount();
      return { data, total };
    }

    const [data, total] = await queryBuilder.getManyAndCount();
    return { data, total };
  }

  /**
   * Ensure a "Default" tenant exists for data migration purposes.
   * Called during app bootstrap.
   */
  async ensureDefaultTenant(): Promise<Tenant> {
    let defaultTenant = await this.findByName(
      TenantService.DEFAULT_TENANT_NAME,
    );
    if (!defaultTenant) {
      defaultTenant = await this.create(
        TenantService.DEFAULT_TENANT_NAME,
        'default.localhost',
        undefined,
        true,
      );
    } else if (!defaultTenant.isSystem) {
      defaultTenant.isSystem = true;
      await this.tenantRepository.save(defaultTenant);
    }
    return defaultTenant;
  }

  async getMemberIds(tenantId: string): Promise<string[]> {
    const members = await this.tenantMemberRepository.find({
      where: { tenantId },
      select: ['userId'],
    });
    return members.map((m) => m.userId);
  }

  /**
   * Check if a user can access a tenant's resources.
   * Returns true if:
   * 1. Target tenant matches user's primary/current tenantId
   * 2. User is a member of the target tenant (any role)
   * 3. (Optional/Future) User is a global SUPER_ADMIN
   */
  async canAccessTenant(
    userId: string,
    targetTenantId: string,
    currentTenantId?: string,
  ): Promise<boolean> {
    // Case 1: Direct match with current/active tenant
    if (currentTenantId && currentTenantId === targetTenantId) {
      return true;
    }

    // Case 2: Global Super Admin check
    const user = await this.tenantMemberRepository.query(
      'SELECT isAdmin FROM users WHERE id = ?',
      [userId],
    );
    if (user && user[0] && user[0].isAdmin) {
      return true;
    }

    // Case 3: Hierarchical check (Direct membership or Parent Admin)
    let checkTenantId = targetTenantId;
    const seenTenantIds = new Set<string>();

    while (checkTenantId && !seenTenantIds.has(checkTenantId)) {
      seenTenantIds.add(checkTenantId);

      const membership = await this.tenantMemberRepository.findOneBy({
        userId,
        tenantId: checkTenantId,
      });

      if (membership) {
        // If it's the exact target tenant, any membership role works
        if (checkTenantId === targetTenantId) {
          return true;
        }
        // If it's an ancestor, user must be a TENANT_ADMIN or SUPER_ADMIN of that ancestor
        if (
          membership.role === UserRole.TENANT_ADMIN ||
          membership.role === UserRole.SUPER_ADMIN
        ) {
          return true;
        }
      }

      // Move up to parent
      const tenant = await this.tenantRepository.findOneBy({
        id: checkTenantId,
      });
      checkTenantId = tenant?.parentId as string;
    }

    return false;
  }

  /**
   * Determine the user's role in a specific tenant.
   * Checks for global SUPER_ADMIN status first.
   */
  async getUserRole(userId: string, tenantId: string): Promise<UserRole> {
    // 1. Check if user is a global SUPER_ADMIN
    const user = await this.tenantRepository.query(
      'SELECT isAdmin FROM users WHERE id = ?',
      [userId],
    );

    if (user && user[0] && user[0].isAdmin) {
      return UserRole.SUPER_ADMIN;
    }

    // 2. Check for tenant-specific role
    const membership = await this.tenantMemberRepository.findOneBy({
      userId,
      tenantId,
    });

    if (membership) {
      return membership.role;
    }

    // Default to USER
    return UserRole.USER;
  }
}