gem 'ed25519', '~> 1.2'
gem 'bcrypt_pbkdf', '~> 1.0' unless RUBY_PLATFORM == "java"

require 'ed25519'

require 'base64'

require 'net/ssh/transport/cipher_factory'
require 'net/ssh/authentication/pub_key_fingerprint'
require 'bcrypt_pbkdf' unless RUBY_PLATFORM == "java"

module Net
  module SSH
    module Authentication
      module ED25519
        class SigningKeyFromFile < SimpleDelegator
          def initialize(pk,sk)
            key = ::Ed25519::SigningKey.from_keypair(sk)
            raise ArgumentError, "pk does not match sk" unless pk == key.verify_key.to_bytes

            super(key)
          end
        end

        class OpenSSHPrivateKeyLoader
          CipherFactory = Net::SSH::Transport::CipherFactory

          MBEGIN = "-----BEGIN OPENSSH PRIVATE KEY-----\n"
          MEND = "-----END OPENSSH PRIVATE KEY-----"
          MAGIC = "openssh-key-v1"

          class DecryptError < ArgumentError
            def initialize(message, encrypted_key: false)
              super(message)
              @encrypted_key = encrypted_key
            end

            def encrypted_key?
              return @encrypted_key
            end
          end

          def self.read(datafull, password)
            datafull = datafull.strip
            raise ArgumentError.new("Expected #{MBEGIN} at start of private key") unless datafull.start_with?(MBEGIN)
            raise ArgumentError.new("Expected #{MEND} at end of private key") unless datafull.end_with?(MEND)
            datab64 = datafull[MBEGIN.size...-MEND.size]
            data = Base64.decode64(datab64)
            raise ArgumentError.new("Expected #{MAGIC} at start of decoded private key") unless data.start_with?(MAGIC)
            buffer = Net::SSH::Buffer.new(data[MAGIC.size + 1..-1])

            ciphername = buffer.read_string
            raise ArgumentError.new("#{ciphername} in private key is not supported") unless
              CipherFactory.supported?(ciphername)

            kdfname = buffer.read_string
            raise ArgumentError.new("Expected #{kdfname} to be or none or bcrypt") unless %w[none bcrypt].include?(kdfname)

            kdfopts = Net::SSH::Buffer.new(buffer.read_string)
            num_keys = buffer.read_long
            raise ArgumentError.new("Only 1 key is supported in ssh keys #{num_keys} was in private key") unless num_keys == 1
            _pubkey = buffer.read_string

            len = buffer.read_long

            keylen, blocksize, ivlen = CipherFactory.get_lengths(ciphername, iv_len: true)
            raise ArgumentError.new("Private key len:#{len} is not a multiple of #{blocksize}") if
              ((len < blocksize) || ((blocksize > 0) && (len % blocksize) != 0))

            if kdfname == 'bcrypt'
              salt = kdfopts.read_string
              rounds = kdfopts.read_long

              raise "BCryptPbkdf is not implemented for jruby" if RUBY_PLATFORM == "java"
              key = BCryptPbkdf::key(password, salt, keylen + ivlen, rounds)
            else
              key = '\x00' * (keylen + ivlen)
            end

            cipher = CipherFactory.get(ciphername, key: key[0...keylen], iv:key[keylen...keylen + ivlen], decrypt: true)

            decoded = cipher.update(buffer.remainder_as_buffer.to_s)
            decoded << cipher.final

            decoded = Net::SSH::Buffer.new(decoded)
            check1 = decoded.read_long
            check2 = decoded.read_long

            raise DecryptError.new("Decrypt failed on private key", encrypted_key: kdfname == 'bcrypt') if (check1 != check2)

            type_name = decoded.read_string
            case type_name
            when "ssh-ed25519"
              PrivKey.new(decoded)
            else
              decoded.read_private_keyblob(type_name)
            end
          end
        end

        class PubKey
          include Net::SSH::Authentication::PubKeyFingerprint

          attr_reader :verify_key

          def initialize(data)
            @verify_key = ::Ed25519::VerifyKey.new(data)
          end

          def self.read_keyblob(buffer)
            PubKey.new(buffer.read_string)
          end

          def to_blob
            Net::SSH::Buffer.from(:mstring,"ssh-ed25519",:string,@verify_key.to_bytes).to_s
          end

          def ssh_type
            "ssh-ed25519"
          end

          def ssh_signature_type
            ssh_type
          end

          def ssh_do_verify(sig, data, options = {})
            @verify_key.verify(sig,data)
          end

          def to_pem
            # TODO this is not pem
            ssh_type + Base64.encode64(@verify_key.to_bytes)
          end
        end

        class PrivKey
          CipherFactory = Net::SSH::Transport::CipherFactory

          MBEGIN = "-----BEGIN OPENSSH PRIVATE KEY-----\n"
          MEND = "-----END OPENSSH PRIVATE KEY-----\n"
          MAGIC = "openssh-key-v1"

          attr_reader :sign_key

          def initialize(buffer)
            pk = buffer.read_string
            sk = buffer.read_string
            _comment = buffer.read_string

            @pk = pk
            @sign_key = SigningKeyFromFile.new(pk,sk)
          end

          def to_blob
            public_key.to_blob
          end

          def ssh_type
            "ssh-ed25519"
          end

          def ssh_signature_type
            ssh_type
          end

          def public_key
            PubKey.new(@pk)
          end

          def ssh_do_sign(data, sig_alg = nil)
            @sign_key.sign(data)
          end

          def self.read(data, password)
            OpenSSHPrivateKeyLoader.read(data, password)
          end
        end
      end
    end
  end
end