Refactor #internal_parse

Add a guard for PublicSuffix makes #valid? simpler. Introduce a helper
method to keep things tidy.

lib/twingly/url.rb

@@ -24,22 +24,26 @@ def self.parse(potential_url)
     end
 
     def self.internal_parse(potential_url)
-      if potential_url.is_a?(Addressable::URI)
-        addressable_uri = potential_url
-      else
-        addressable_uri = Addressable::URI.heuristic_parse(potential_url)
-      end
-
+      addressable_uri = to_addressable_uri(potential_url)
       raise Twingly::Error::ParseError if addressable_uri.nil?
 
       public_suffix_domain = PublicSuffix.parse(addressable_uri.display_uri.host)
+      raise Twingly::Error::ParseError if public_suffix_domain.nil?
 
       self.new(addressable_uri, public_suffix_domain)
     rescue Addressable::URI::InvalidURIError, PublicSuffix::DomainInvalid => error
       error.extend(Twingly::URL::Error)
       raise
     end
 
+    def self.to_addressable_uri(potential_url)
+     if potential_url.is_a?(Addressable::URI)
+        potential_url
+      else
+        Addressable::URI.heuristic_parse(potential_url)
+      end
+    end
+
     def initialize(addressable_uri, public_suffix_domain)
       unless addressable_uri.is_a?(Addressable::URI)
         raise ArgumentError, "First parameter must be an Addressable::URI"
@@ -123,7 +127,7 @@ def normalized_path
     end
 
     def valid?
-      addressable_uri && public_suffix_domain && SCHEMES.include?(normalized_scheme)
+      SCHEMES.include?(normalized_scheme)
     end
 
     def <=>(other)

spec/lib/twingly/url_spec.rb

@@ -104,6 +104,20 @@ def valid_urls
     end
   end
 
+  describe ".to_addressable_uri" do
+    let(:adressable_uri) { Addressable::URI.parse(test_url) }
+
+    context "when given Addressable::URI" do
+      subject { described_class.to_addressable_uri(adressable_uri) }
+      it { is_expected.to eq(adressable_uri) }
+    end
+
+    context "when given string" do
+      subject { described_class.to_addressable_uri(test_url) }
+      it { is_expected.to eq(adressable_uri) }
+    end
+  end
+
   describe "#initialize" do
     context "when given input parameters of wrong types" do
       it "raises an error" do