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# frozen_string_literal: true
class FetchResourceService < BaseService
include JsonLdHelper
ACCEPT_HEADER = 'application/activity+json, application/ld+json; profile="https://www.w3.org/ns/activitystreams", text/html;q=0.1'
attr_reader :response_code
def call(url)
return if url.blank?
process(url)
rescue HTTP::Error, OpenSSL::SSL::SSLError, Addressable::URI::InvalidURIError, Mastodon::HostValidationError, Mastodon::LengthValidationError => e
Rails.logger.debug { "Error fetching resource #{@url}: #{e}" }
nil
end
private
def process(url, terminal = false)
@url = url
perform_request { |response| process_response(response, terminal) }
end
def perform_request(&block)
Request.new(:get, @url).tap do |request|
request.add_headers('Accept' => ACCEPT_HEADER)
# In a real setting we want to sign all outgoing requests,
# in case the remote server has secure mode enabled and requires
# authentication on all resources. However, during development,
# sending request signatures with an inaccessible host is useless
# and prevents even public resources from being fetched, so
# don't do it
request.on_behalf_of(Account.representative) unless Rails.env.development?
end.perform(&block)
end
def process_response(response, terminal = false)
@response_code = response.code
return nil if response.code != 200
if ['application/activity+json', 'application/ld+json'].include?(response.mime_type)
body = response.body_with_limit
json = body_to_json(body)
[json['id'], { prefetched_body: body, id: true }] if supported_context?(json) && (equals_or_includes_any?(json['type'], ActivityPub::FetchRemoteActorService::SUPPORTED_TYPES) || expected_type?(json))
elsif !terminal
link_header = response['Link'] && parse_link_header(response)
if link_header&.find_link(%w(rel alternate))
process_link_headers(link_header)
elsif response.mime_type == 'text/html'
process_html(response)
end
end
end
def expected_type?(json)
equals_or_includes_any?(json['type'], ActivityPub::Activity::Create::SUPPORTED_TYPES + ActivityPub::Activity::Create::CONVERTED_TYPES)
end
def process_html(response)
page = Nokogiri::HTML(response.body_with_limit)
json_link = page.xpath('//link[@rel="alternate"]').find { |link| ['application/activity+json', 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'].include?(link['type']) }
process(json_link['href'], terminal: true) unless json_link.nil?
end
def process_link_headers(link_header)
json_link = link_header.find_link(%w(rel alternate), %w(type application/activity+json)) || link_header.find_link(%w(rel alternate), ['type', 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'])
process(json_link.href, terminal: true) unless json_link.nil?
end
def parse_link_header(response)
LinkHeader.parse(response['Link'].is_a?(Array) ? response['Link'].first : response['Link'])
end
end
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