# frozen_string_literal: true

# Copyright (C) 2019-2021 MongoDB Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

module Mongo
  module Crypt
    module KMS
      module GCP
        # GCP Cloud Key Management Credentials object contains credentials for
        # using GCP KMS provider.
        #
        # @api private
        class Credentials
          extend Forwardable
          include KMS::Validations

          # @return [ String ] GCP email to authenticate with.
          attr_reader :email

          # @return [ String ] GCP private key, base64 encoded DER format.
          attr_reader :private_key

          # @return [ String | nil ] GCP KMS endpoint.
          attr_reader :endpoint

          # @return [ String | nil ] GCP access token.
          attr_reader :access_token

          # @api private
          def_delegator :@opts, :empty?

          FORMAT_HINT = 'GCP KMS provider options must be in the format: ' +
                        "{ email: 'EMAIL', private_key: 'PRIVATE-KEY' }"

          # Creates an GCP KMS credentials object form a parameters hash.
          #
          # @param [ Hash ] opts A hash that contains credentials for
          #   GCP KMS provider
          # @option opts [ String ] :email GCP email.
          # @option opts [ String ] :private_key GCP private key. This method accepts
          #   private key in either base64 encoded DER format, or PEM format.
          # @option opts [ String | nil ] :endpoint GCP endpoint, optional.
          # @option opts [ String | nil ] :access_token GCP access token, optional.
          #   If this option is not null, other options are ignored.
          #
          # @raise [ ArgumentError ] If required options are missing or incorrectly
          #   formatted.
          def initialize(opts)
            @opts = opts
            return if empty?

            if opts[:access_token]
              @access_token = opts[:access_token]
            else
              @email = validate_param(:email, opts, FORMAT_HINT)
              @private_key = begin
                private_key_opt = validate_param(:private_key, opts, FORMAT_HINT)
                if BSON::Environment.jruby?
                  # We cannot really validate private key on JRuby, so we assume
                  # it is in base64 encoded DER format.
                  private_key_opt
                else
                  # Check if private key is in PEM format.
                  pkey = OpenSSL::PKey::RSA.new(private_key_opt)
                  # PEM it is, need to be converted to base64 encoded DER.
                  der = if pkey.respond_to?(:private_to_der)
                          pkey.private_to_der
                        else
                          pkey.to_der
                        end
                  Base64.encode64(der)
                end
              rescue OpenSSL::PKey::RSAError
                # Check if private key is in DER.
                begin
                  OpenSSL::PKey.read(Base64.decode64(private_key_opt))
                  # Private key is fine, use it.
                  private_key_opt
                rescue OpenSSL::PKey::PKeyError
                  raise ArgumentError.new(
                    'The private_key option must be either either base64 encoded DER format, or PEM format.'
                  )
                end
              end

              @endpoint = validate_param(
                :endpoint, opts, FORMAT_HINT, required: false
              )
            end
          end

          # Convert credentials object to a BSON document in libmongocrypt format.
          #
          # @return [ BSON::Document ] Azure KMS credentials in libmongocrypt format.
          def to_document
            return BSON::Document.new if empty?

            if access_token
              BSON::Document.new({ accessToken: access_token })
            else
              BSON::Document.new({
                                   email: email,
                                   privateKey: BSON::Binary.new(private_key, :generic),
                                 }).tap do |bson|
                bson.update({ endpoint: endpoint }) unless endpoint.nil?
              end
            end
          end
        end
      end
    end
  end
end
