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# frozen_string_literal: true
module Gitlab
module Pagination
module Keyset
class Pager < Gitlab::Pagination::Base
attr_reader :request
def initialize(request)
@request = request
end
def paginate(relation, _params = {})
# Validate assumption: The last two columns must match the page order_by
validate_order!(relation)
relation.limit(page.per_page) # rubocop: disable CodeReuse/ActiveRecord
end
def finalize(records)
apply_headers(records.last)
end
private
def apply_headers(last_record_in_page)
return unless last_record_in_page
lower_bounds = last_record_in_page&.slice(page.order_by.keys)
next_page = page.next(lower_bounds)
request.apply_headers(next_page)
end
def page
@page ||= request.page
end
def validate_order!(rel)
present_order = rel.order_values.map { |val| [val.expr.name.to_sym, val.direction] }.last(2).to_h
unless page.order_by == present_order
raise ArgumentError, "Page's order_by does not match the relation's order: #{present_order} vs #{page.order_by}"
end
end
end
end
end
end
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