import { Injectable } from '@nestjs/common';
import { PassportStrategy } from '@nestjs/passport';
import { ExtractJwt, Strategy } from 'passport-jwt';
import { ConfigService } from '@nestjs/config';

interface JwtPayload {
  sub: string;
  email: string;
  role: string;
  /** Present on impersonation tokens: the acting admin. */
  act?: { sub: string; role: string };
}

@Injectable()
export class JwtStrategy extends PassportStrategy(Strategy) {
  constructor(configService: ConfigService) {
    super({
      jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
      ignoreExpiration: false,
      secretOrKey: configService.getOrThrow<string>('jwt.secret'),
    });
  }

  async validate(payload: JwtPayload) {
    return {
      id: payload.sub,
      email: payload.email,
      role: payload.role,
      // Non-null only while an admin is impersonating this user.
      impersonatedBy: payload.act?.sub ?? null,
      impersonatorRole: payload.act?.role ?? null,
    };
  }
}