added helper for checking if a DID is known by pds/relay

lib/didkit/did.rb

@@ -1,8 +1,11 @@
 require_relative 'errors'
+require_relative 'requests'
 require_relative 'resolver'
 
 module DIDKit
   class DID
+    include Requests
+
     def self.resolve_handle(handle)
       Resolver.new.resolve_handle(handle)
     end
@@ -38,6 +41,34 @@ def web_domain
       did.gsub(/^did\:web\:/, '') if type == :web
     end
 
+    def is_known_by_relay?(relay, options = {})
+      relay_host = relay.include?('://') ? URI(relay).origin : "https://#{relay}"
+      url = URI("#{relay_host}/xrpc/com.atproto.sync.getLatestCommit")
+      url.query = URI.encode_www_form(:did => did)
+
+      response = get_response(url, { timeout: 30, max_redirects: 5 }.merge(options))
+      status = response.code.to_i
+      is_json = (response['Content-Type'] =~ /^application\/json(;.*)?$/)
+
+      if status == 200
+        true
+      elsif status == 400 && is_json && JSON.parse(response.body)['error'] == 'RepoNotFound'
+        false
+      elsif status == 404 && is_json && JSON.parse(response.body)['error']
+        false
+      else
+        raise APIError.new(response)
+      end
+    end
+
+    def account_exists?
+      doc = get_document
+      return false if doc.pds_endpoint.nil?
+
+      pds_host = URI(doc.pds_endpoint).origin
+      is_known_by_relay?(pds_host, timeout: 10)
+    end
+
     def ==(other)
       if other.is_a?(String)
         self.did == other

lib/didkit/errors.rb

@@ -1,4 +1,21 @@
 module DIDKit
   class DIDError < StandardError
   end
+
+  class APIError < StandardError
+    attr_reader :response
+
+    def initialize(response)
+      @response = response
+      super("APIError: #{response}")
+    end
+
+    def status
+      response.code.to_i
+    end
+
+    def body
+      response.body
+    end
+  end
 end