'use strict';

var RSA = module.exports;
var SSH = require('./ssh.js');
var PEM = require('./pem.js');
var x509 = require('./x509.js');
var ASN1 = require('./asn1.js');
var Enc = require('./encoding.js');

/*global Promise*/
RSA.parse = function parseRsa(opts) {
  return Promise.resolve().then(function () {
    if (!opts || !opts.pem || 'string' !== typeof opts.pem) {
      throw new Error("must pass { pem: pem } as a string");
    }

    var jwk = { kty: 'RSA', n: null, e: null };
    if (0 === opts.pem.indexOf('ssh-rsa ')) {
      return SSH.parse(opts.pem, jwk);
    }
    var pem = opts.pem;
    var block = PEM.parseBlock(pem);
    //var hex = toHex(u8);
    var asn1 = ASN1.parse(block.der);

    var meta = x509.guess(block.der, asn1);

    if ('pkcs1' === meta.format) {
      jwk = RSA.parsePkcs1(block.der, asn1, jwk);
    } else {
      jwk = RSA.parsePkcs8(block.der, asn1, jwk);
    }

    if (opts.public) {
      jwk = {
        kty: jwk.kty
      , n: jwk.n
      , e: jwk.e
      };
    }
    return jwk;
  });
};
RSA.toJwk = RSA.import = RSA.parse;

/*
RSAPrivateKey ::= SEQUENCE {
  version           Version,
  modulus           INTEGER,  -- n
  publicExponent    INTEGER,  -- e
  privateExponent   INTEGER,  -- d
  prime1            INTEGER,  -- p
  prime2            INTEGER,  -- q
  exponent1         INTEGER,  -- d mod (p-1)
  exponent2         INTEGER,  -- d mod (q-1)
  coefficient       INTEGER,  -- (inverse of q) mod p
  otherPrimeInfos   OtherPrimeInfos OPTIONAL
}
*/

RSA.parsePkcs1 = function parseRsaPkcs1(buf, asn1, jwk) {
  if (!asn1.children.every(function(el) {
    return 0x02 === el.type;
  })) {
    throw new Error("not an RSA PKCS#1 public or private key (not all ints)");
  }

  if (2 === asn1.children.length) {

    jwk.n = Enc.bufToUrlBase64(asn1.children[0].value);
    jwk.e = Enc.bufToUrlBase64(asn1.children[1].value);
    return jwk;

  } else if (asn1.children.length >= 9) {
    // the standard allows for "otherPrimeInfos", hence at least 9

    jwk.n = Enc.bufToUrlBase64(asn1.children[1].value);
    jwk.e = Enc.bufToUrlBase64(asn1.children[2].value);
    jwk.d = Enc.bufToUrlBase64(asn1.children[3].value);
    jwk.p = Enc.bufToUrlBase64(asn1.children[4].value);
    jwk.q = Enc.bufToUrlBase64(asn1.children[5].value);
    jwk.dp = Enc.bufToUrlBase64(asn1.children[6].value);
    jwk.dq = Enc.bufToUrlBase64(asn1.children[7].value);
    jwk.qi = Enc.bufToUrlBase64(asn1.children[8].value);
    return jwk;

  } else {
    throw new Error("not an RSA PKCS#1 public or private key (wrong number of ints)");
  }
};

RSA.parsePkcs8 = function parseRsaPkcs8(buf, asn1, jwk) {
  if (2 === asn1.children.length
    && 0x03 === asn1.children[1].type
    && 0x30 === asn1.children[1].value[0]) {

    asn1 = ASN1.parse(asn1.children[1].value);
    jwk.n = Enc.bufToUrlBase64(asn1.children[0].value);
    jwk.e = Enc.bufToUrlBase64(asn1.children[1].value);

  } else if (3 === asn1.children.length
    && 0x04 === asn1.children[2].type
    && 0x30 === asn1.children[2].children[0].type
    && 0x02 === asn1.children[2].children[0].children[0].type) {

    asn1 = asn1.children[2].children[0];
    jwk.n = Enc.bufToUrlBase64(asn1.children[1].value);
    jwk.e = Enc.bufToUrlBase64(asn1.children[2].value);
    jwk.d = Enc.bufToUrlBase64(asn1.children[3].value);
    jwk.p = Enc.bufToUrlBase64(asn1.children[4].value);
    jwk.q = Enc.bufToUrlBase64(asn1.children[5].value);
    jwk.dp = Enc.bufToUrlBase64(asn1.children[6].value);
    jwk.dq = Enc.bufToUrlBase64(asn1.children[7].value);
    jwk.qi = Enc.bufToUrlBase64(asn1.children[8].value);

  } else {
    throw new Error("not an RSA PKCS#8 public or private key (wrong format)");
  }
  return jwk;
};