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

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,
    private readonly usersService: UsersService,
  ) {
    super({
      jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
      ignoreExpiration: false,
      secretOrKey: configService.getOrThrow<string>('jwt.secret'),
    });
  }

  async validate(payload: JwtPayload) {
    // Resolve the role (and active status) from the database on every request
    // rather than trusting the token. A token's `role` claim is frozen at login,
    // so a role change or deactivation would otherwise stay ineffective until the
    // token expires. `payload.sub` is the impersonated user on impersonation
    // tokens, so this keeps "login as user" working with the target's live role.
    const user = await this.usersService.findById(payload.sub);
    if (!user || !user.isActive) {
      throw new UnauthorizedException();
    }

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