Add kanji and emoji support

app/lib/permalink_normalizer.rb

@@ -0,0 +1,16 @@
+class PermalinkNormalizer
+  attr_accessor :text, :max_length
+
+  def initialize(text, max_length: 50)
+    self.text = text
+    self.max_length = max_length
+  end
+
+  def normalize
+    text
+      .gsub(/((?!\p{Alnum}|\p{So}).)+/, "-")
+      .delete_prefix("-")
+      .delete_suffix("-")
+      .downcase[0..max_length - 1]
+  end
+end

app/models/concerns/permalinkable.rb

@@ -10,7 +10,7 @@ module Permalinkable
 
   def generate_permalink(count = 0)
     column_value = attributes.fetch(self.class.permalink_column)
-    new_permalink = column_value.parameterize[0..49]
+    new_permalink = PermalinkNormalizer.new(column_value).normalize
 
     if count > 0
       new_permalink += "-#{count}"

spec/lib/permalink_normalizer_spec.rb

@@ -0,0 +1,48 @@
+# coding: utf-8
+require 'rails_helper'
+
+RSpec.describe PermalinkNormalizer do
+  describe "#normalize" do
+    subject { PermalinkNormalizer.new(text, max_length: 50).normalize }
+
+    let(:text) { "Hello world!" }
+
+    it { is_expected.to eql("hello-world") }
+
+    context "with a very long title" do
+      let(:text) { "x" * 200 }
+
+      it { is_expected.to eql("x" * 50) }
+    end
+
+    context "with bad characters at start and end" do
+      let(:text) { "~ hello world ~" }
+
+      it { is_expected.to eql("hello-world") }
+    end
+
+    context "with numbers" do
+      let(:text) { "3 days ago" }
+
+      it { is_expected.to eql("3-days-ago") }
+    end
+
+    context "with diacritics" do
+      let(:text) { "naïve café" }
+
+      it { is_expected.to eql("naïve-café") }
+    end
+
+    context "with kanji and kana" do
+      let(:text) { "初めまして、ダニエルです。" }
+
+      it { is_expected.to eql("初めまして-ダニエルです") }
+    end
+
+    context "with emoji" do
+      let(:text) { "💎 is a gemstone 😃" }
+
+      it { is_expected.to eql("💎-is-a-gemstone-😃") }
+    end
+  end
+end

spec/models/article_spec.rb

@@ -9,16 +9,6 @@
       FactoryBot.build(:article, title: "Hello world!", category: category)
     }
 
-    it { is_expected.to eql("hello-world") }
-
-    context "with a very long title" do
-      let(:article) {
-        FactoryBot.build_stubbed(:article, title: "x" * 200)
-      }
-
-      it { is_expected.to eql("x" * 50) }
-    end
-
     context "with existing article having the same title" do
       before do
         FactoryBot.create(:article, title: "Hello world!", category: category)