/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
;(function (exports) {
'use strict';

if (!exports.Enc) { exports.Enc = {}; }
if (!exports.SSH) { exports.SSH = {}; }

var Enc = exports.Enc;
var SSH = exports.SSH;

SSH.parse = function (ssh) {
  ssh = SSH.parseBlock(ssh);
  ssh = SSH.parseElements(ssh);
  //delete ssh.bytes;
  return SSH.parsePublicKey(ssh);
};

SSH.parseBlock = function (ssh) {
  ssh = ssh.split(/\s+/g);

  return {
    type: ssh[0]
  , bytes: Enc.base64ToBuf(ssh[1])
  , comment: ssh[2]
  };
};

SSH.parseElements = function (ssh) {
  var buf = ssh.bytes;
  var fulllen = buf.byteLength || buf.length;
  var offset = (buf.byteOffset || 0);
  var i = 0;
  var index = 0;
  // using dataview to be browser-compatible (I do want _some_ code reuse)
  var dv = new DataView(buf.buffer.slice(offset, offset + fulllen));
  var els = [];
  var el;
  var len;

  while (index < fulllen) {
    i += 1;
    if (i > 15) { throw new Error("15+ elements, probably not a public ssh key"); }
    len = dv.getUint32(index, false);
    index += 4;
    el = buf.slice(index, index + len);
    // remove BigUInt '00' prefix
    if (0x00 === el[0]) {
      el = el.slice(1);
    }
    els.push(el);
    index += len;
  }
  if (fulllen !== index) {
    throw new Error("invalid ssh public key length \n" + els.map(function (b) {
      return Enc.bufToHex(b);
    }).join('\n'));
  }

  ssh.elements = els;
  return ssh;
};

SSH.parsePublicKey = function (ssh) {
  var els = ssh.elements;
  var typ = Enc.bufToBin(els[0]);
  var len;

  // RSA keys are all the same
  if (SSH.types.rsa === typ) {
    ssh.jwk = {
      kty: 'RSA'
    , n: Enc.bufToUrlBase64(els[2])
    , e: Enc.bufToUrlBase64(els[1])
    };
    return ssh;
  }

  // EC keys are each different
  if (SSH.types.p256 === typ) {
    len = 32;
    ssh.jwk = { kty: 'EC', crv: 'P-256' };
  } else if (SSH.types.p384 === typ) {
    len = 48;
    ssh.jwk = { kty: 'EC', crv: 'P-384' };
  } else {
    throw new Error("Unsupported ssh public key type: "
      + Enc.bufToBin(els[0]));
  }

  // els[1] is just a repeat of a subset of els[0]
  var x = els[2].slice(1, 1 + len);
  var y = els[2].slice(1 + len, 1 + len + len);

  // I don't think EC keys use 0x00 padding, but just in case
  while (0x00 === x[0]) { x = x.slice(1); }
  while (0x00 === y[0]) { y = y.slice(1); }

  ssh.jwk.x = Enc.bufToUrlBase64(x);
  ssh.jwk.y = Enc.bufToUrlBase64(y);

  return ssh;
};

SSH.types = {
  // 19 '00000013'
  // e c d s a - s h a 2 - n i s t p 2 5 6
  // 65636473612d736861322d6e69737470323536
  // 6e69737470323536
  p256: 'ecdsa-sha2-nistp256'

  // 19 '00000013'
  // e c d s a - s h a 2 - n i s t p 3 8 4
  // 65636473612d736861322d6e69737470333834
  // 6e69737470323536
, p384: 'ecdsa-sha2-nistp384'

  // 7 '00000007'
  // s s h - r s a
  // 7373682d727361
, rsa: 'ssh-rsa'
};

Enc.base64ToBuf = function (b64) {
  return Enc.binToBuf(atob(b64));
};

Enc.binToBuf = function (bin) {
  var arr = bin.split('').map(function (ch) {
    return ch.charCodeAt(0);
  });
  return 'undefined' !== typeof Uint8Array ? new Uint8Array(arr) : arr;
};

Enc.bufToBase64 = function (u8) {
  var bin = '';
  u8.forEach(function (i) {
    bin += String.fromCharCode(i);
  });
  return btoa(bin);
};

Enc.bufToBin = function (buf) {
  var bin = '';
  // cannot use .map() because Uint8Array would return only 0s
  buf.forEach(function (ch) {
    bin += String.fromCharCode(ch);
  });
  return bin;
};

Enc.bufToUrlBase64 = function (u8) {
  return Enc.bufToBase64(u8)
    .replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '');
};

Enc.urlBase64ToBase64 = function urlsafeBase64ToBase64(str) {
  var r = str % 4;
  if (2 === r) {
    str += '==';
  } else if (3 === r) {
    str += '=';
  }
  return str.replace(/-/g, '+').replace(/_/g, '/');
};

}('undefined' !== typeof window ? window : module.exports));