1 files changed, 52 insertions, 0 deletions
diff --git a/app/helpers/jsonld_helper.rb b/app/helpers/jsonld_helper.rb
new file mode 100644
index 000000000..d82a07332
--- /dev/null
+++ b/app/helpers/jsonld_helper.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+module JsonLdHelper
+  def equals_or_includes?(haystack, needle)
+    haystack.is_a?(Array) ? haystack.include?(needle) : haystack == needle
+  end
+
+  def first_of_value(value)
+    value.is_a?(Array) ? value.first : value
+  end
+
+  def value_or_id(value)
+    value.is_a?(String) || value.nil? ? value : value['id']
+  end
+
+  def supported_context?(json)
+    !json.nil? && equals_or_includes?(json['@context'], ActivityPub::TagManager::CONTEXT)
+  end
+
+  def canonicalize(json)
+    graph = RDF::Graph.new << JSON::LD::API.toRdf(json)
+    graph.dump(:normalize)
+  end
+
+  def fetch_resource(uri)
+    response = build_request(uri).perform
+    return if response.code != 200
+    body_to_json(response.to_s)
+  end
+
+  def body_to_json(body)
+    body.is_a?(String) ? Oj.load(body, mode: :strict) : body
+  rescue Oj::ParseError
+    nil
+  end
+
+  def merge_context(context, new_context)
+    if context.is_a?(Array)
+      context << new_context
+    else
+      [context, new_context]
+    end
+  end
+
+  private
+
+  def build_request(uri)
+    request = Request.new(:get, uri)
+    request.add_headers('Accept' => 'application/activity+json, application/ld+json')
+    request
+  end
+end