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- # frozen_string_literal: true
- class Webfinger
- class Error < StandardError; end
- class GoneError < Error; end
- class RedirectError < StandardError; end
- class Response
- def initialize(body)
- @json = Oj.load(body, mode: :strict)
- end
- def subject
- @json['subject']
- end
- def link(rel, attribute)
- links.dig(rel, attribute)
- end
- private
- def links
- @links ||= @json['links'].map { |link| [link['rel'], link] }.to_h
- end
- end
- def initialize(uri)
- _, @domain = uri.split('@')
- raise ArgumentError, 'Webfinger requested for local account' if @domain.nil?
- @uri = uri
- end
- def perform
- Response.new(body_from_webfinger)
- rescue Oj::ParseError
- raise Webfinger::Error, "Invalid JSON in response for #{@uri}"
- rescue Addressable::URI::InvalidURIError
- raise Webfinger::Error, "Invalid URI for #{@uri}"
- end
- private
- def body_from_webfinger(url = standard_url, use_fallback = true)
- webfinger_request(url).perform do |res|
- if res.code == 200
- res.body_with_limit
- elsif res.code == 404 && use_fallback
- body_from_host_meta
- elsif res.code == 410
- raise Webfinger::GoneError, "#{@uri} is gone from the server"
- else
- raise Webfinger::Error, "Request for #{@uri} returned HTTP #{res.code}"
- end
- end
- end
- def body_from_host_meta
- host_meta_request.perform do |res|
- if res.code == 200
- body_from_webfinger(url_from_template(res.body_with_limit), false)
- else
- raise Webfinger::Error, "Request for #{@uri} returned HTTP #{res.code}"
- end
- end
- end
- def url_from_template(str)
- link = Nokogiri::XML(str).at_xpath('//xmlns:Link[@rel="lrdd"]')
- if link.present?
- link['template'].gsub('{uri}', @uri)
- else
- raise Webfinger::Error, "Request for #{@uri} returned host-meta without link to Webfinger"
- end
- rescue Nokogiri::XML::XPath::SyntaxError
- raise Webfinger::Error, "Invalid XML encountered in host-meta for #{@uri}"
- end
- def host_meta_request
- Request.new(:get, host_meta_url).add_headers('Accept' => 'application/xrd+xml, application/xml, text/xml')
- end
- def webfinger_request(url)
- Request.new(:get, url).add_headers('Accept' => 'application/jrd+json, application/json')
- end
- def standard_url
- "https://#{@domain}/.well-known/webfinger?resource=#{@uri}"
- end
- def host_meta_url
- "https://#{@domain}/.well-known/host-meta"
- end
- end
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