#3928 Zxcvbn service to compute password complexity

app/services/zxcvbn_service.rb

@@ -0,0 +1,23 @@
+class ZxcvbnService
+  def initialize(password)
+    @password = password
+  end
+
+  def complexity
+    wxcvbn = compute_zxcvbn
+    score = wxcvbn.score
+    length = @password.blank? ? 0 : @password.length
+    vulnerabilities = wxcvbn.match_sequence.map { |m| m.matched_word.nil? ? m.token : m.matched_word }.select { |s| s.length > 2 }.join(', ')
+    [score, vulnerabilities, length]
+  end
+
+  def score
+    compute_zxcvbn.score
+  end
+
+  private
+
+  def compute_zxcvbn
+    Zxcvbn.test(@password, [], ZXCVBN_DICTIONNARIES)
+  end
+end