# frozen_string_literal: true

# Copyright 2018 Google LLC
#
# 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
#
#     https://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 "delegate"

module Google
  module Cloud
    module Bigtable
      class Instance
        ##
        # Instance::List is a special-case array with additional
        # values and failed_locations.
        class List < DelegateClass(::Array)
          # @private
          # The gRPC Service object.
          attr_accessor :service

          ##
          # If not empty, indicates that more records match
          # the request and this value should be passed to continue.
          attr_accessor :token

          ##
          # Locations from which instance information could not be retrieved,
          # due to an outage or some other transient condition.
          # Instances whose clusters are all in one of the failed locations
          # may be missing from `instances`, and instances with at least one
          # cluster in a failed location may only have partial information returned.
          attr_accessor :failed_locations

          # @private
          # Creates a new Instance::List with an array of
          # Instance instances.
          def initialize arr = []
            super arr
          end

          ##
          # Whether there is a next page of instances.
          #
          # @return [Boolean]
          #
          # @example
          #   require "google/cloud/bigtable"
          #
          #   bigtable = Google::Cloud::Bigtable.new
          #
          #   instances = bigtable.instances
          #   if instances.next?
          #     next_instances = instances.next
          #   end
          #
          def next?
            !token.nil?
          end

          ##
          # Retrieves the next page of instances.
          #
          # @return [Instance::List] The list of instances.
          #
          # @example
          #   require "google/cloud/bigtable"
          #
          #   bigtable = Google::Cloud::Bigtable.new
          #
          #   instances = bigtable.instances
          #   if instances.next?
          #     next_instances = instances.next
          #   end
          #
          def next
            return nil unless next?
            ensure_service!
            grpc = service.list_instances token: token
            next_list = self.class.from_grpc grpc, service
            next_list.failed_locations.concat(failed_locations.map(&:to_s)) if failed_locations
            next_list
          end

          ##
          # Retrieves remaining results by repeatedly invoking {#next} until
          # {#next?} returns `false`. Calls the given block once for each
          # result, which is passed as the argument to the block.
          #
          # An enumerator is returned if no block is given.
          #
          # This method will make repeated API calls until all remaining results
          # are retrieved (unlike `#each`, for example, which merely iterates
          # over the results returned by a single API call). Use with caution.
          #
          # @yield [instance] The block for accessing each instance.
          # @yieldparam [Instance] instance The instance object.
          #
          # @return [Enumerator]
          #
          # @example Iterating each instance by passing a block:
          #   require "google/cloud/bigtable"
          #
          #   bigtable = Google::Cloud::Bigtable.new
          #
          #   bigtable.instances.all do |instance|
          #     puts instance.instance_id
          #   end
          #
          # @example Using the enumerator by not passing a block:
          #   require "google/cloud/bigtable"
          #
          #   bigtable = Google::Cloud::Bigtable.new
          #
          #   all_instance_ids = bigtable.instances.all.map do |instance|
          #     puts instance.instance_id
          #   end
          #
          def all
            return enum_for :all unless block_given?

            results = self
            loop do
              results.each { |r| yield r }
              break unless results.next?
              results = results.next
            end
          end

          # @private
          # New Instance::List from a Google::Bigtable::Admin::V2::Instance object.
          def self.from_grpc grpc, service
            instances = List.new(Array(grpc.instances).map do |instance|
              Instance.from_grpc instance, service
            end)
            token = grpc.next_page_token
            token = nil if token == ""
            instances.token = token
            instances.service = service
            instances.failed_locations = grpc.failed_locations.map(&:to_s)
            instances
          end

          protected

          # Raises an error unless an active service is available.
          def ensure_service!
            raise "Must have active connection" unless service
          end
        end
      end
    end
  end
end