Use charlock_holmes instead of nkf at FetchLinkCardService (#4080)

* Specs for language detection

* Use CharlockHolmes instead of NKF

* Correct mistakes

* Correct style

* Set hint_enc instead of falling back and strip_tags

* Improve specs

* Add dependencies

spec/services/fetch_link_card_service_spec.rb

@@ -8,6 +8,10 @@ RSpec.describe FetchLinkCardService do
     stub_request(:get, 'http://example.xn--fiqs8s/').to_return(request_fixture('idn.txt'))
     stub_request(:head, 'http://example.com/sjis').to_return(status: 200, headers: { 'Content-Type' => 'text/html' })
     stub_request(:get, 'http://example.com/sjis').to_return(request_fixture('sjis.txt'))
+    stub_request(:head, 'http://example.com/sjis_with_wrong_charset').to_return(status: 200, headers: { 'Content-Type' => 'text/html' })
+    stub_request(:get, 'http://example.com/sjis_with_wrong_charset').to_return(request_fixture('sjis_with_wrong_charset.txt'))
+    stub_request(:head, 'http://example.com/koi8-r').to_return(status: 200, headers: { 'Content-Type' => 'text/html' })
+    stub_request(:get, 'http://example.com/koi8-r').to_return(request_fixture('koi8-r.txt'))
     stub_request(:head, 'https://github.com/qbi/WannaCry').to_return(status: 404)
 
     subject.call(status)
@@ -27,6 +31,25 @@ RSpec.describe FetchLinkCardService do
 
       it 'works with SJIS' do
         expect(a_request(:get, 'http://example.com/sjis')).to have_been_made.at_least_once
+        expect(status.preview_card.title).to eq("SJISのページ")
+      end
+    end
+
+    context do
+      let(:status) { Fabricate(:status, text: 'Check out http://example.com/sjis_with_wrong_charset') }
+
+      it 'works with SJIS even with wrong charset header' do
+        expect(a_request(:get, 'http://example.com/sjis_with_wrong_charset')).to have_been_made.at_least_once
+        expect(status.preview_card.title).to eq("SJISのページ")
+      end
+    end
+
+    context do
+      let(:status) { Fabricate(:status, text: 'Check out http://example.com/koi8-r') }
+
+      it 'works with koi8-r' do
+        expect(a_request(:get, 'http://example.com/koi8-r')).to have_been_made.at_least_once
+        expect(status.preview_card.title).to eq("Московя начинаетъ только въ XVI ст. привлекать внимане иностранцевъ.")
       end
     end
   end