# Copyright 2015 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 "delegate"

module Gcloud
  module Bigquery
    class Table
      ##
      # Table::List is a special case Array with additional values.
      class List < DelegateClass(::Array)
        ##
        # If not empty, indicates that there are more records that match
        # the request and this value should be passed to continue.
        attr_accessor :token

        # A hash of this page of results.
        attr_accessor :etag

        # Total number of tables in this collection.
        attr_accessor :total

        ##
        # @private Create a new Table::List with an array of tables.
        def initialize arr = []
          super arr
        end

        ##
        # Whether there is a next page of tables.
        #
        # @return [Boolean]
        #
        # @example
        #   require "gcloud"
        #
        #   gcloud = Gcloud.new
        #   bigquery = gcloud.bigquery
        #   dataset = bigquery.dataset "my_dataset"
        #
        #   tables = dataset.tables
        #   if tables.next?
        #     next_tables = tables.next
        #   end
        #
        def next?
          !token.nil?
        end

        ##
        # Retrieve the next page of tables.
        #
        # @return [Table::List]
        #
        # @example
        #   require "gcloud"
        #
        #   gcloud = Gcloud.new
        #   bigquery = gcloud.bigquery
        #   dataset = bigquery.dataset "my_dataset"
        #
        #   tables = dataset.tables
        #   if tables.next?
        #     next_tables = tables.next
        #   end
        #
        def next
          return nil unless next?
          ensure_service!
          options = { token: token, max: @max }
          gapi = @service.list_tables @dataset_id, options
          self.class.from_gapi gapi, @service, @dataset_id, @max
        end

        ##
        # Retrieves all tables by repeatedly loading {#next} until {#next?}
        # returns `false`. Calls the given block once for each table, which is
        # passed as the parameter.
        #
        # An Enumerator is returned if no block is given.
        #
        # This method may make several API calls until all tables are retrieved.
        # Be sure to use as narrow a search criteria as possible. Please use
        # with caution.
        #
        # @param [Integer] request_limit The upper limit of API requests to make
        #   to load all tables. Default is no limit.
        # @yield [table] The block for accessing each table.
        # @yieldparam [Table] table The table object.
        #
        # @return [Enumerator]
        #
        # @example Iterating each result by passing a block:
        #   require "gcloud"
        #
        #   gcloud = Gcloud.new
        #   bigquery = gcloud.bigquery
        #   dataset = bigquery.dataset "my_dataset"
        #
        #   dataset.tables.all do |table|
        #     puts table.name
        #   end
        #
        # @example Using the enumerator by not passing a block:
        #   require "gcloud"
        #
        #   gcloud = Gcloud.new
        #   bigquery = gcloud.bigquery
        #   dataset = bigquery.dataset "my_dataset"
        #
        #   all_names = dataset.tables.all.map do |table|
        #     table.name
        #   end
        #
        # @example Limit the number of API requests made:
        #   require "gcloud"
        #
        #   gcloud = Gcloud.new
        #   bigquery = gcloud.bigquery
        #   dataset = bigquery.dataset "my_dataset"
        #
        #   dataset.tables.all(request_limit: 10) do |table|
        #     puts table.name
        #   end
        #
        def all request_limit: nil
          request_limit = request_limit.to_i if request_limit
          unless block_given?
            return enum_for(:all, request_limit: request_limit)
          end
          results = self
          loop do
            results.each { |r| yield r }
            if request_limit
              request_limit -= 1
              break if request_limit < 0
            end
            break unless results.next?
            results = results.next
          end
        end

        ##
        # @private New Table::List from a response object.
        def self.from_gapi gapi_list, service, dataset_id = nil, max = nil
          tables = List.new(Array(gapi_list.tables).map do |gapi_object|
            Table.from_gapi gapi_object, service
          end)
          tables.instance_variable_set :@token,      gapi_list.next_page_token
          tables.instance_variable_set :@etag,       gapi_list.etag
          tables.instance_variable_set :@total,      gapi_list.total_items
          tables.instance_variable_set :@service,    service
          tables.instance_variable_set :@dataset_id, dataset_id
          tables.instance_variable_set :@max,        max
          tables
        end

        protected

        ##
        # Raise an error unless an active service is available.
        def ensure_service!
          fail "Must have active connection" unless @service
        end
      end
    end
  end
end