import { Injectable, Scope, Inject } from '@nestjs/common';
import { REQUEST } from '@nestjs/core';
import { In } from 'typeorm';
import { Request } from 'express';
import { DepartmentsService } from '../departments/departments.service';

export interface CampusRequest extends Request {
  user?: {
    id: number;
    isSuperAdmin?: boolean;
  };
  campusScope?: CampusScope;
}

@Injectable({ scope: Scope.REQUEST })
export class CampusScope {
  constructor(
    @Inject(REQUEST) private req: CampusRequest,
    private departmentsService: DepartmentsService,
  ) {}

  get userId(): number | undefined {
    return this.req.user?.id;
  }

  get isSuperAdmin(): boolean {
    return this.req.user?.isSuperAdmin ?? false;
  }

  get currentDepartmentId(): number | null {
    const raw = this.req.headers?.['x-campus-id'];
    if (raw === undefined) return null;
    const str = Array.isArray(raw) ? raw[0] : raw;
    if (!str) return null;
    const id = parseInt(str, 10);
    return Number.isNaN(id) ? null : id;
  }

  /** Appends departmentId filter. No campus selected = no filtering for super admin; empty result for others. */
  async filter<T extends Record<string, unknown>>(where: T): Promise<T> {
    if (this.isSuperAdmin && !this.currentDepartmentId) {
      return where;
    }

    const ids = await this.getEffectiveScopeIds();
    if (ids.length === 0) {
      // Non-super-admin with no scoping → match nothing, never leak unfiltered data
      if (!this.isSuperAdmin) {
        return { ...where, departmentId: In([]) };
      }
      return where;
    }

    return { ...where, departmentId: In(ids) };
  }

  /** Returns department IDs for QueryBuilder .andWhere(). null = no filtering. */
  async getScopeDepartmentIds(): Promise<number[] | null> {
    if (this.isSuperAdmin && !this.currentDepartmentId) return null;
    const ids = await this.getEffectiveScopeIds();
    return ids.length > 0 ? ids : null;
  }

  private async getEffectiveScopeIds(): Promise<number[]> {
    if (this.currentDepartmentId) {
      return this.departmentsService.getDescendantIds(this.currentDepartmentId);
    }

    if (!this.userId) return [];

    const userDeptIds = await this.departmentsService.getUserDepartments(this.userId);
    const allIds = await Promise.all(
      userDeptIds.map((id) => this.departmentsService.getDescendantIds(id)),
    );
    return [...new Set(allIds.flat())];
  }
}