import {
  CanActivate,
  ExecutionContext,
  Injectable,
  ServiceUnavailableException,
  SetMetadata,
} from '@nestjs/common';
import { Reflector } from '@nestjs/core';

import { SetupStateService } from './setup-state.service';

const SETUP_EXEMPT_KEY = 'setupExempt';

/**
 * Marks routes that stay reachable while the instance still requires the
 * first-run setup: the wizard itself, health probes, and the session
 * routes (so a mid-wizard admin who lost the cookie can sign back in).
 */
export const SetupExempt = (): MethodDecorator & ClassDecorator =>
  SetMetadata(SETUP_EXEMPT_KEY, true);

/**
 * Global first-line guard (registered before AuthGuard via module order):
 * while setup is pending every non-exempt route answers 503
 * `setup_required`, so clients — including anonymous ones — always learn
 * the instance state instead of a misleading 401 (issue #80).
 */
@Injectable()
export class SetupGuard implements CanActivate {
  constructor(
    private readonly reflector: Reflector,
    private readonly state: SetupStateService,
  ) {}

  async canActivate(context: ExecutionContext): Promise<boolean> {
    const exempt = this.reflector.getAllAndOverride<boolean>(SETUP_EXEMPT_KEY, [
      context.getHandler(),
      context.getClass(),
    ]);
    if (exempt) return true;
    if (await this.state.isPending()) {
      throw new ServiceUnavailableException({ code: 'setup_required' });
    }
    return true;
  }
}