'use strict';

var EC = module.exports;

var Enc = require('./encoding.js');
var ASN1;
var PEM = require('./pem.js');

// 1.2.840.10045.3.1.7
// prime256v1 (ANSI X9.62 named elliptic curve)
var OBJ_ID_EC  = '06 08 2A8648CE3D030107'.replace(/\s+/g, '').toLowerCase();
// 1.3.132.0.34
// secp384r1 (SECG (Certicom) named elliptic curve)
var OBJ_ID_EC_384 = '06 05 2B81040022'.replace(/\s+/g, '').toLowerCase();

// 1.2.840.10045.2.1
// ecPublicKey (ANSI X9.62 public key type)
var OBJ_ID_EC_PUB = '06 07 2A8648CE3D0201'.replace(/\s+/g, '').toLowerCase();

                      // 19  e  c  d  s  a  -  s  h  a  2  -  n  i  s  t  p  2  5  6
var SSH_EC_P256 = '00000013 65 63 64 73 61 2d 73 68 61 32 2d 6e 69 73 74 70 32 35 36'
  .replace(/\s+/g, '').toLowerCase();

                      // 19  e  c  d  s  a  -  s  h  a  2  -  n  i  s  t  p  3  8  4
var SSH_EC_P384 = '00000013 65 63 64 73 61 2d 73 68 61 32 2d 6e 69 73 74 70 33 38 34'
  .replace(/\s+/g, '').toLowerCase();

// The one good thing that came from the b***kchain hysteria: good EC documentation
// https://davidederosa.com/basic-blockchain-programming/elliptic-curve-keys/

EC.parseSec1 = function parseEcOnlyPrivkey(u8, jwk) {
  var index = 7;
  var len = 32;
  var olen = OBJ_ID_EC.length/2;

  if ("P-384" === jwk.crv) {
    olen = OBJ_ID_EC_384.length/2;
    index = 8;
    len = 48;
  }
  if (len !== u8[index - 1]) {
    throw new Error("Unexpected bitlength " + len);
  }

  // private part is d
  var d = u8.slice(index, index + len);
  // compression bit index
  var ci = index + len + 2 + olen + 2 + 3;
  var c = u8[ci];
  var x, y;

  if (0x04 === c) {
    y = u8.slice(ci + 1 + len, ci + 1 + len + len);
  } else if (0x02 !== c) {
    throw new Error("not a supported EC private key");
  }
  x = u8.slice(ci + 1, ci + 1 + len);

  return {
    kty: jwk.kty
  , crv: jwk.crv
  , d: Enc.bufToUrlBase64(d)
  //, dh: Enc.bufToHex(d)
  , x: Enc.bufToUrlBase64(x)
  //, xh: Enc.bufToHex(x)
  , y: Enc.bufToUrlBase64(y)
  //, yh: Enc.bufToHex(y)
  };
};

EC.parsePkcs8 = function parseEcPkcs8(u8, jwk) {
  var index = 24 + (OBJ_ID_EC.length/2);
  var len = 32;
  if ("P-384" === jwk.crv) {
    index = 24 + (OBJ_ID_EC_384.length/2) + 2;
    len = 48;
  }

  //console.log(index, u8.slice(index));
  if (0x04 !== u8[index]) {
    //console.log(jwk);
    throw new Error("privkey not found");
  }
  var d = u8.slice(index+2, index+2+len);
  var ci = index+2+len+5;
  var xi = ci+1;
  var x = u8.slice(xi, xi + len);
  var yi = xi+len;
  var y;
  if (0x04 === u8[ci]) {
    y = u8.slice(yi, yi + len);
  } else if (0x02 !== u8[ci]) {
    throw new Error("invalid compression bit (expected 0x04 or 0x02)");
  }

  return {
    kty: jwk.kty
  , crv: jwk.crv
  , d: Enc.bufToUrlBase64(d)
  //, dh: Enc.bufToHex(d)
  , x: Enc.bufToUrlBase64(x)
  //, xh: Enc.bufToHex(x)
  , y: Enc.bufToUrlBase64(y)
  //, yh: Enc.bufToHex(y)
  };
};

EC.parseSpki = function parsePem(u8, jwk) {
  var ci = 16 + OBJ_ID_EC.length/2;
  var len = 32;

  if ("P-384" === jwk.crv) {
    ci = 16 + OBJ_ID_EC_384.length/2;
    len = 48;
  }

  var c = u8[ci];
  var xi = ci + 1;
  var x = u8.slice(xi, xi + len);
  var yi = xi + len;
  var y;
  if (0x04 === c) {
    y = u8.slice(yi, yi + len);
  } else if (0x02 !== c) {
    throw new Error("not a supported EC private key");
  }

  return {
    kty: jwk.kty
  , crv: jwk.crv
  , x: Enc.bufToUrlBase64(x)
  //, xh: Enc.bufToHex(x)
  , y: Enc.bufToUrlBase64(y)
  //, yh: Enc.bufToHex(y)
  };
};
EC.parsePkix = EC.parseSpki;

EC.parseSsh = function (pem) {
  var jwk = { kty: 'EC', crv: null, x: null, y: null };
  var b64 = pem.split(/\s+/g)[1];
  var buf = Buffer.from(b64, 'base64');
  var hex = Enc.bufToHex(buf);
  var index = 40;
  var len;
  if (0 === hex.indexOf(SSH_EC_P256)) {
    jwk.crv = 'P-256';
    len = 32;
  } else if (0 === hex.indexOf(SSH_EC_P384)) {
    jwk.crv = 'P-384';
    len = 48;
  }
  var x = buf.slice(index, index + len);
  var y = buf.slice(index + len, index + len + len);
  jwk.x = Enc.bufToUrlBase64(x);
  jwk.y = Enc.bufToUrlBase64(y);
  return jwk;
};

/*global Promise*/
EC.generate = function (opts) {
  return Promise.resolve().then(function () {
    var typ = 'ec';
    var format = opts.format;
    var encoding = opts.encoding;
    var priv;
    var pub = 'spki';

    if (!format) {
      format = 'jwk';
    }
    if (-1 !== [ 'spki', 'pkcs8', 'ssh' ].indexOf(format)) {
      format = 'pkcs8';
    }

    if ('pem' === format) {
      format = 'sec1';
      encoding = 'pem';
    } else if ('der' === format) {
      format = 'sec1';
      encoding = 'der';
    }

    if ('jwk' === format || 'json' === format) {
      format = 'jwk';
      encoding = 'json';
    } else {
      priv = format;
    }

    if (!encoding) {
      encoding = 'pem';
    }

    if (priv) {
      priv = { type: priv, format: encoding };
      pub = { type: pub, format: encoding };
    } else {
      // jwk
      priv = { type: 'sec1', format: 'pem' };
      pub = { type: 'spki', format: 'pem' };
    }

    return new Promise(function (resolve, reject) {
      return require('crypto').generateKeyPair(typ, {
        namedCurve: opts.crv || opts.namedCurve || 'P-256'
      , privateKeyEncoding: priv
      , publicKeyEncoding: pub
      }, function (err, pubkey, privkey) {
        if (err) { reject(err); }
        resolve({
          private: privkey
        , public: pubkey
        });
      });
    }).then(function (keypair) {
      if ('jwk' === format) {
        return {
          private: EC.importSync({ pem: keypair.private, format: priv.type })
        , public: EC.importSync({ pem: keypair.public, format: pub.type, public: true })
        };
      }

      if ('ssh' !== opts.format) {
        return keypair;
      }

      return {
        private: keypair.private
      , public: EC.exportSync({ jwk: EC.importSync({
          pem: keypair.public, format: format, public: true
        }), format: opts.format, public: true })
      };
    });
  });
};

EC.importSync = function importEcSync(opts) {
  if (!opts || !opts.pem || 'string' !== typeof opts.pem) {
    throw new Error("must pass { pem: pem } as a string");
  }
  if (0 === opts.pem.indexOf('ecdsa-sha2-')) {
    return EC.parseSsh(opts.pem);
  }
  var pem = opts.pem;
  var u8 = PEM.parseBlock(pem).bytes;
  var hex = Enc.bufToHex(u8);
  var jwk = { kty: 'EC', crv: null, x: null, y: null };

  //console.log();
  if (-1 !== hex.indexOf(OBJ_ID_EC)) {
    jwk.crv = "P-256";

    // PKCS8
    if (0x02 === u8[3] && 0x30 === u8[6] && 0x06 === u8[8]) {
      //console.log("PKCS8", u8[3].toString(16), u8[6].toString(16), u8[8].toString(16));
      jwk = EC.parsePkcs8(u8, jwk);
    // EC-only
    } else if (0x02 === u8[2] && 0x04 === u8[5] && 0xA0 === u8[39]) {
      //console.log("EC---", u8[2].toString(16), u8[5].toString(16), u8[39].toString(16));
      jwk = EC.parseSec1(u8, jwk);
    // SPKI/PKIK (Public)
    } else if (0x30 === u8[2] && 0x06 === u8[4] && 0x06 === u8[13]) {
      //console.log("SPKI-", u8[2].toString(16), u8[4].toString(16), u8[13].toString(16));
      jwk = EC.parseSpki(u8, jwk);
    // Error
    } else {
      //console.log("PKCS8", u8[3].toString(16), u8[6].toString(16), u8[8].toString(16));
      //console.log("EC---", u8[2].toString(16), u8[5].toString(16), u8[39].toString(16));
      //console.log("SPKI-", u8[2].toString(16), u8[4].toString(16), u8[13].toString(16));
      throw new Error("unrecognized key format");
    }
  } else if (-1 !== hex.indexOf(OBJ_ID_EC_384)) {
    jwk.crv = "P-384";

    // PKCS8
    if (0x02 === u8[3] && 0x30 === u8[6] && 0x06 === u8[8]) {
      //console.log("PKCS8", u8[3].toString(16), u8[6].toString(16), u8[8].toString(16));
      jwk = EC.parsePkcs8(u8, jwk);
    // EC-only
    } else if (0x02 === u8[3] && 0x04 === u8[6] && 0xA0 === u8[56]) {
      //console.log("EC---", u8[3].toString(16), u8[6].toString(16), u8[56].toString(16));
      jwk = EC.parseSec1(u8, jwk);
    // SPKI/PKIK (Public)
    } else if (0x30 === u8[2] && 0x06 === u8[4] && 0x06 === u8[13]) {
      //console.log("SPKI-", u8[2].toString(16), u8[4].toString(16), u8[13].toString(16));
      jwk = EC.parseSpki(u8, jwk);
    // Error
    } else {
      //console.log("PKCS8", u8[3].toString(16), u8[6].toString(16), u8[8].toString(16));
      //console.log("EC---", u8[3].toString(16), u8[6].toString(16), u8[56].toString(16));
      //console.log("SPKI-", u8[2].toString(16), u8[4].toString(16), u8[13].toString(16));
      throw new Error("unrecognized key format");
    }
  } else {
    throw new Error("Supported key types are P-256 and P-384");
  }
  if (opts.public) {
    if (true !== opts.public) {
      throw new Error("options.public must be either `true` or `false` not ("
        + typeof opts.public + ") '" + opts.public + "'");
    }
    delete jwk.d;
  }
  return jwk;
};
EC.parse = function parseEc(opts) {
  return Promise.resolve().then(function () {
    return EC.importSync(opts);
  });
};
EC.toJwk = EC.import = EC.parse;

EC.exportSync = function (opts) {
  if (!opts || !opts.jwk || 'object' !== typeof opts.jwk) {
    throw new Error("must pass { jwk: jwk } as a JSON object");
  }
  var jwk = JSON.parse(JSON.stringify(opts.jwk));
  var format = opts.format;
  if (opts.public || -1 !== [ 'spki', 'pkix', 'ssh', 'rfc4716' ].indexOf(format)) {
    jwk.d = null;
  }
  if ('EC' !== jwk.kty) {
    throw new Error("options.jwk.kty must be 'EC' for EC keys");
  }
  if (!jwk.d) {
    if (!format || -1 !== [ 'spki', 'pkix' ].indexOf(format)) {
      format = 'spki';
    } else if (-1 !== [ 'ssh', 'rfc4716' ].indexOf(format)) {
      format = 'ssh';
    } else {
      throw new Error("options.format must be 'spki' or 'ssh' for public EC keys, not ("
        + typeof format + ") " + format);
    }
  } else {
    if (!format || 'sec1' === format) {
      format = 'sec1';
    } else if ('pkcs8' !== format) {
      throw new Error("options.format must be 'sec1' or 'pkcs8' for private EC keys, not '" + format + "'");
    }
  }
  if (-1 === [ 'P-256', 'P-384' ].indexOf(jwk.crv)) {
    throw new Error("options.jwk.crv must be either P-256 or P-384 for EC keys, not '" + jwk.crv + "'");
  }
  if (!jwk.y) {
    throw new Error("options.jwk.y must be a urlsafe base64-encoded either P-256 or P-384");
  }

  if ('sec1' === format) {
    return PEM.packBlock({ type: "EC PRIVATE KEY", bytes: EC.packSec1(jwk) });
  } else if ('pkcs8' === format) {
    return PEM.packBlock({ type: "PRIVATE KEY", bytes: EC.packPkcs8(jwk) });
  } else if (-1 !== [ 'spki', 'pkix' ].indexOf(format)) {
    return PEM.packBlock({ type: "PUBLIC KEY", bytes: EC.packSpki(jwk) });
  } else if (-1 !== [ 'ssh', 'rfc4716' ].indexOf(format)) {
    return EC.packSsh(jwk);
  } else {
    throw new Error("Sanity Error: reached unreachable code block with format: " + format);
  }
};
EC.pack = function (opts) {
  return Promise.resolve().then(function () {
    return EC.exportSync(opts);
  });
};

EC.packSec1 = function (jwk) {
  var d = Enc.base64ToHex(jwk.d);
  var x = Enc.base64ToHex(jwk.x);
  var y = Enc.base64ToHex(jwk.y);
  var objId = ('P-256' === jwk.crv) ? OBJ_ID_EC : OBJ_ID_EC_384;
  return Enc.hexToUint8(
    ASN1('30'
    , ASN1.UInt('01')
    , ASN1('04', d)
    , ASN1('A0', objId)
    , ASN1('A1', ASN1.BitStr('04' + x + y)))
  );
};
EC.packPkcs8 = function (jwk) {
  var d = Enc.base64ToHex(jwk.d);
  var x = Enc.base64ToHex(jwk.x);
  var y = Enc.base64ToHex(jwk.y);
  var objId = ('P-256' === jwk.crv) ? OBJ_ID_EC : OBJ_ID_EC_384;
  return Enc.hexToUint8(
    ASN1('30'
    , ASN1.UInt('00')
    , ASN1('30'
      , OBJ_ID_EC_PUB
      , objId
      )
    , ASN1('04'
      , ASN1('30'
        , ASN1.UInt('01')
        , ASN1('04', d)
        , ASN1('A1', ASN1.BitStr('04' + x + y)))))
  );
};
EC.packSpki = function (jwk) {
  var x = Enc.base64ToHex(jwk.x);
  var y = Enc.base64ToHex(jwk.y);
  var objId = ('P-256' === jwk.crv) ? OBJ_ID_EC : OBJ_ID_EC_384;
  return Enc.hexToUint8(
    ASN1('30'
    , ASN1('30'
      , OBJ_ID_EC_PUB
      , objId
      )
    , ASN1.BitStr('04' + x + y))
  );
};
EC.packPkix = EC.packSpki;
EC.packSsh = function (jwk) {
  // Custom SSH format
  var typ = 'ecdsa-sha2-nistp256';
	var a = '32 35 36';
  var b = '41';
  var comment = jwk.crv + '@localhost';
  if ('P-256' !== jwk.crv) {
    typ = 'ecdsa-sha2-nistp384';
    a = '33 38 34';
    b = '61';
  }
  var x = Enc.base64ToHex(jwk.x);
  var y = Enc.base64ToHex(jwk.y);
  var ssh = Enc.hexToUint8(
    ('00 00 00 13 65 63 64 73 61 2d 73 68 61 32 2d 6e 69 73 74 70'
    + a + '00 00 00 08 6e 69 73 74 70' + a + '00 00 00' + b
    + '04' + x + y).replace(/\s+/g, '').toLowerCase()
  );

  return typ + ' ' + Enc.bufToBase64(ssh) + ' ' + comment;
};

//
// A dumbed-down, minimal ASN.1 packer
//

// Almost every ASN.1 type that's important for CSR
// can be represented generically with only a few rules.
ASN1 = function ASN1(/*type, hexstrings...*/) {
  var args = Array.prototype.slice.call(arguments);
  var typ = args.shift();
  var str = args.join('').replace(/\s+/g, '').toLowerCase();
  var len = (str.length/2);
  var lenlen = 0;
  var hex = typ;

  // We can't have an odd number of hex chars
  if (len !== Math.round(len)) {
    throw new Error("invalid hex");
  }

  // The first byte of any ASN.1 sequence is the type (Sequence, Integer, etc)
  // The second byte is either the size of the value, or the size of its size

  // 1. If the second byte is < 0x80 (128) it is considered the size
  // 2. If it is > 0x80 then it describes the number of bytes of the size
  //    ex: 0x82 means the next 2 bytes describe the size of the value
  // 3. The special case of exactly 0x80 is "indefinite" length (to end-of-file)

  if (len > 127) {
    lenlen += 1;
    while (len > 255) {
      lenlen += 1;
      len = len >> 8;
    }
  }

  if (lenlen) { hex += Enc.numToHex(0x80 + lenlen); }
  return hex + Enc.numToHex(str.length/2) + str;
};

// The Integer type has some special rules
ASN1.UInt = function UINT() {
  var str = Array.prototype.slice.call(arguments).join('');
  var first = parseInt(str.slice(0, 2), 16);

  // If the first byte is 0x80 or greater, the number is considered negative
  // Therefore we add a '00' prefix if the 0x80 bit is set
  if (0x80 & first) { str = '00' + str; }

  return ASN1('02', str);
};

// The Bit String type also has a special rule
ASN1.BitStr = function BITSTR() {
  var str = Array.prototype.slice.call(arguments).join('');
  // '00' is a mask of how many bits of the next byte to ignore
  return ASN1('03', '00' + str);
};

EC.toPem = EC.export = EC.pack;