#--
# Copyright 2014 Google Inc. All rights reserved.
#
# 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.

require "pathname"
require "digest/md5"
require "digest/crc32c"
require "gcloud/storage/errors"

module Gcloud
  module Storage
    class File
      ##
      # Verifies downloaded files by creating an MD5 or CRC32c hash digest
      # and comparing the value to the one from the Storage API.
      module Verifier #:nodoc:
        def self.verify_md5! gcloud_file, local_file
          gcloud_digest = gcloud_file.md5
          local_digest = md5_for local_file
          if gcloud_digest != local_digest
            fail FileVerificationError.for_md5(gcloud_digest, local_digest)
          end
        end

        def self.verify_crc32c! gcloud_file, local_file
          gcloud_digest = gcloud_file.crc32c
          local_digest = crc32c_for local_file
          if gcloud_digest != local_digest
            fail FileVerificationError.for_md5(gcloud_digest, local_digest)
          end
        end

        def self.verify_md5 gcloud_file, local_file
          gcloud_file.md5 == md5_for(local_file)
        end

        def self.verify_crc32c gcloud_file, local_file
          gcloud_file.crc32c == crc32c_for(local_file)
        end

        def self.md5_for local_file
          ::File.open(Pathname(local_file).to_path, "rb") do |f|
            ::Digest::MD5.base64digest f.read
          end
        end

        def self.crc32c_for local_file
          ::File.open(Pathname(local_file).to_path, "rb") do |f|
            ::Digest::CRC32c.base64digest f.read
          end
        end
      end
    end
  end
end