/**
 * @requires bn.js
 * @requires crypto/public_key
 * @requires crypto/pkcs1
 * @requires enums
 * @requires util
 * @module crypto/signature
*/

import BN from 'bn.js';
import publicKey from './public_key';
import pkcs1 from './pkcs1';
import enums from '../enums';
import util from '../util';

export default {
  /**
   * Verifies the signature provided for data using specified algorithms and public key parameters.
   * See {@link https://tools.ietf.org/html/rfc4880#section-9.1|RFC 4880 9.1}
   * and {@link https://tools.ietf.org/html/rfc4880#section-9.4|RFC 4880 9.4}
   * for public key and hash algorithms.
   * @param {module:enums.publicKey} algo      Public key algorithm
   * @param {module:enums.hash}      hash_algo Hash algorithm
   * @param {Array<module:type/mpi>} msg_MPIs  Algorithm-specific signature parameters
   * @param {Array<module:type/mpi>} pub_MPIs  Algorithm-specific public key parameters
   * @param {Uint8Array}             data      Data for which the signature was created
   * @return {Boolean}                         True if signature is valid
   */
  verify: async function(algo, hash_algo, msg_MPIs, pub_MPIs, data) {
    switch (algo) {
      case enums.publicKey.rsa_encrypt_sign:
      case enums.publicKey.rsa_encrypt:
      case enums.publicKey.rsa_sign: {
        const m = msg_MPIs[0].toBN();
        const n = pub_MPIs[0].toBN();
        const e = pub_MPIs[1].toBN();
        const EM = publicKey.rsa.verify(m, n, e);
        const EM2 = pkcs1.emsa.encode(hash_algo, util.Uint8Array2str(data), n.byteLength());
        return util.hexidump(EM) === EM2;
      }
      case enums.publicKey.dsa: {
        const r = msg_MPIs[0].toBN();
        const s = msg_MPIs[1].toBN();
        const p = pub_MPIs[0].toBN();
        const q = pub_MPIs[1].toBN();
        const g = pub_MPIs[2].toBN();
        const y = pub_MPIs[3].toBN();
        return publicKey.dsa.verify(hash_algo, r, s, data, p, q, g, y);
      }
      case enums.publicKey.ecdsa: {
        const oid = pub_MPIs[0];
        const signature = { r: msg_MPIs[0].toUint8Array(), s: msg_MPIs[1].toUint8Array() };
        const Q = pub_MPIs[1].toUint8Array();
        return publicKey.elliptic.ecdsa.verify(oid, hash_algo, signature, data, Q);
      }
      case enums.publicKey.eddsa: {
        const oid = pub_MPIs[0];
        const signature = { R: msg_MPIs[0].toBN(), S: msg_MPIs[1].toBN() };
        const Q = pub_MPIs[1].toBN();
        return publicKey.elliptic.eddsa.verify(oid, hash_algo, signature, data, Q);
      }
      default:
        throw new Error('Invalid signature algorithm.');
    }
  },

  /**
   * Creates a signature on data using specified algorithms and private key parameters.
   * See {@link https://tools.ietf.org/html/rfc4880#section-9.1|RFC 4880 9.1}
   * and {@link https://tools.ietf.org/html/rfc4880#section-9.4|RFC 4880 9.4}
   * for public key and hash algorithms.
   * @param {module:enums.publicKey} algo       Public key algorithm
   * @param {module:enums.hash}      hash_algo  Hash algorithm
   * @param {Array<module:type/mpi>} key_params Algorithm-specific public and private key parameters
   * @param {Uint8Array}             data       Data to be signed
   * @return {Uint8Array}                       Signature
   */
  sign: async function(algo, hash_algo, key_params, data) {
    switch (algo) {
      case enums.publicKey.rsa_encrypt_sign:
      case enums.publicKey.rsa_encrypt:
      case enums.publicKey.rsa_sign: {
        const n = key_params[0].toBN();
        const e = key_params[1].toBN();
        const d = key_params[2].toBN();
        data = util.Uint8Array2str(data);
        const m = new BN(pkcs1.emsa.encode(hash_algo, data, n.byteLength()), 16);
        const signature = publicKey.rsa.sign(m, n, e, d);
        return util.Uint8Array2MPI(signature);
      }
      case enums.publicKey.dsa: {
        const p = key_params[0].toBN();
        const q = key_params[1].toBN();
        const g = key_params[2].toBN();
        const x = key_params[4].toBN();
        const signature = publicKey.dsa.sign(hash_algo, data, g, p, q, x);
        return util.concatUint8Array([
          util.Uint8Array2MPI(signature.r.toArrayLike(Uint8Array)),
          util.Uint8Array2MPI(signature.s.toArrayLike(Uint8Array))
        ]);
      }
      case enums.publicKey.elgamal: {
        throw new Error('Signing with Elgamal is not defined in the OpenPGP standard.');
      }
      case enums.publicKey.ecdsa: {
        const oid = key_params[0];
        const d = key_params[2].toUint8Array();
        const signature = await publicKey.elliptic.ecdsa.sign(oid, hash_algo, data, d);
        return util.concatUint8Array([
          util.Uint8Array2MPI(signature.r.toArrayLike(Uint8Array)),
          util.Uint8Array2MPI(signature.s.toArrayLike(Uint8Array))
        ]);
      }
      case enums.publicKey.eddsa: {
        const oid = key_params[0];
        const d = key_params[2].toBN();
        const signature = await publicKey.elliptic.eddsa.sign(oid, hash_algo, data, d);
        return util.concatUint8Array([
          util.Uint8Array2MPI(Uint8Array.from(signature.R)),
          util.Uint8Array2MPI(Uint8Array.from(signature.S))
        ]);
      }
      default:
        throw new Error('Invalid signature algorithm.');
    }
  }
};