require "google/cloud/storage"
require "active_support/core_ext/object/to_query"

module ActiveStorage
  # Wraps the Google Cloud Storage as a Active Storage service. See `ActiveStorage::Service` for the generic API
  # documentation that applies to all services.
  class Service::GCSService < Service
    attr_reader :client, :bucket

    def initialize(project:, keyfile:, bucket:)
      @client = Google::Cloud::Storage.new(project: project, keyfile: keyfile)
      @bucket = @client.bucket(bucket)
    end

    def upload(key, io, checksum: nil)
      instrument :upload, key, checksum: checksum do
        begin
          bucket.create_file(io, key, md5: checksum)
        rescue Google::Cloud::InvalidArgumentError
          raise ActiveStorage::IntegrityError
        end
      end
    end

    # FIXME: Add streaming when given a block
    def download(key)
      instrument :download, key do
        io = file_for(key).download
        io.rewind
        io.read
      end
    end

    def delete(key)
      instrument :delete, key do
        file_for(key).try(:delete)
      end
    end

    def exist?(key)
      instrument :exist, key do |payload|
        answer = file_for(key).present?
        payload[:exist] = answer
        answer
      end
    end

    def url(key, expires_in:, disposition:, filename:, content_type:)
      instrument :url, key do |payload|
        generated_url = file_for(key).signed_url expires: expires_in, query: {
          "response-content-disposition" => "#{disposition}; filename=\"#{filename}\"",
          "response-content-type" => content_type
        }

        payload[:url] = generated_url

        generated_url
      end
    end

    def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
      instrument :url, key do |payload|
        generated_url = bucket.signed_url key, method: "PUT", expires: expires_in,
          content_type: content_type, content_md5: checksum

        payload[:url] = generated_url

        generated_url
      end
    end

    def headers_for_direct_upload(key, content_type:, checksum:, **)
      { "Content-Type" => content_type, "Content-MD5" => checksum }
    end

    private
      def file_for(key)
        bucket.file(key)
      end
  end
end