'use strict'

var config = require('config')
var crypto = require('crypto')
var fs = require('fs')
var openssl = require('openssl-wrapper')
var path = require('path')
var ursa = require('ursa')

var logger = require('./logger')

var certDir = path.join(__dirname, '..', config.get('storage.certs'))
var algorithm = 'aes-256-ctr'

var peertubeCrypto = {
  checkSignature: checkSignature,
  createCertsIfNotExist: createCertsIfNotExist,
  decrypt: decrypt,
  encrypt: encrypt,
  getCertDir: getCertDir,
  sign: sign
}

function checkSignature (public_key, raw_data, hex_signature) {
  var crt = ursa.createPublicKey(public_key)
  var is_valid = crt.hashAndVerify('sha256', new Buffer(raw_data).toString('hex'), hex_signature, 'hex')
  return is_valid
}

function createCertsIfNotExist (callback) {
  certsExist(function (exist) {
    if (exist === true) {
      return callback(null)
    }

    createCerts(function (err) {
      return callback(err)
    })
  })
}

function decrypt (key, data, callback) {
  fs.readFile(getCertDir() + 'peertube.key.pem', function (err, file) {
    if (err) return callback(err)

    var my_private_key = ursa.createPrivateKey(file)
    var decrypted_key = my_private_key.decrypt(key, 'hex', 'utf8')
    var decrypted_data = symetricDecrypt(data, decrypted_key)

    return callback(null, decrypted_data)
  })
}

function encrypt (public_key, data, callback) {
  var crt = ursa.createPublicKey(public_key)

  symetricEncrypt(data, function (err, dataEncrypted) {
    if (err) return callback(err)

    var key = crt.encrypt(dataEncrypted.password, 'utf8', 'hex')
    var encrypted = {
      data: dataEncrypted.crypted,
      key: key
    }

    callback(null, encrypted)
  })
}

function getCertDir () {
  return certDir
}

function sign (data) {
  var myKey = ursa.createPrivateKey(fs.readFileSync(certDir + 'peertube.key.pem'))
  var signature = myKey.hashAndSign('sha256', data, 'utf8', 'hex')

  return signature
}

// ---------------------------------------------------------------------------

module.exports = peertubeCrypto

// ---------------------------------------------------------------------------

function certsExist (callback) {
  fs.exists(certDir + 'peertube.key.pem', function (exists) {
    return callback(exists)
  })
}

function createCerts (callback) {
  certsExist(function (exist) {
    if (exist === true) {
      var string = 'Certs already exist.'
      logger.warning(string)
      return callback(new Error(string))
    }

    logger.info('Generating a RSA key...')
    openssl.exec('genrsa', { 'out': certDir + 'peertube.key.pem', '2048': false }, function (err) {
      if (err) {
        logger.error('Cannot create private key on this pod.')
        return callback(err)
      }
      logger.info('RSA key generated.')

      logger.info('Manage public key...')
      openssl.exec('rsa', { 'in': certDir + 'peertube.key.pem', 'pubout': true, 'out': certDir + 'peertube.pub' }, function (err) {
        if (err) {
          logger.error('Cannot create public key on this pod.')
          return callback(err)
        }

        logger.info('Public key managed.')
        return callback(null)
      })
    })
  })
}

function generatePassword (callback) {
  crypto.randomBytes(32, function (err, buf) {
    if (err) return callback(err)

    callback(null, buf.toString('utf8'))
  })
}

function symetricDecrypt (text, password) {
  var decipher = crypto.createDecipher(algorithm, password)
  var dec = decipher.update(text, 'hex', 'utf8')
  dec += decipher.final('utf8')
  return dec
}

function symetricEncrypt (text, callback) {
  generatePassword(function (err, password) {
    if (err) return callback(err)

    var cipher = crypto.createCipher(algorithm, password)
    var crypted = cipher.update(text, 'utf8', 'hex')
    crypted += cipher.final('hex')
    callback(null, { crypted: crypted, password: password })
  })
}