import { BadRequestException, Injectable, UnauthorizedException } from "@nestjs/common";
import { generateSecret, generateURI, verify } from "otplib";
import { usersRepo } from "@eden/database";
import { FieldEncryptionService } from "../crypto/field-encryption.service.js";

const ISSUER = "EDEN";

@Injectable()
export class MfaService {
  constructor(private readonly fieldEncryption: FieldEncryptionService) {}

  /** Stages a new TOTP secret (not yet active — see confirmEnrollment). */
  async startEnrollment(userId: string, email: string): Promise<{ secret: string; otpauthUrl: string }> {
    const secret = generateSecret();
    await usersRepo.setMfaSecret(userId, this.fieldEncryption.encrypt(secret));
    const otpauthUrl = generateURI({ issuer: ISSUER, label: email, secret });
    return { secret, otpauthUrl };
  }

  /** Verifies the first code against the staged secret and flips mfa_enabled on. */
  async confirmEnrollment(userId: string, code: string): Promise<void> {
    const user = await usersRepo.findUserById(userId);
    if (!user?.mfa_secret_encrypted) {
      throw new BadRequestException("Nenhum cadastro de MFA pendente para este usuário");
    }
    if (!(await this.verifyCode(user.mfa_secret_encrypted, code))) {
      throw new BadRequestException("Código inválido");
    }
    await usersRepo.confirmMfaEnrollment(userId);
  }

  /** Requires a currently-valid code — proves the factor, not just an authenticated session. */
  async disable(userId: string, code: string): Promise<void> {
    const user = await usersRepo.findUserById(userId);
    if (!user?.mfa_enabled || !user.mfa_secret_encrypted) {
      throw new BadRequestException("MFA não está habilitado para este usuário");
    }
    if (!(await this.verifyCode(user.mfa_secret_encrypted, code))) {
      throw new UnauthorizedException("Código inválido");
    }
    await usersRepo.disableMfa(userId);
  }

  async verifyCode(encryptedSecret: string, code: string): Promise<boolean> {
    const secret = this.fieldEncryption.decrypt(encryptedSecret);
    const result = await verify({ token: code, secret });
    return result.valid;
  }
}