Use string-direction gem for rtl detection

closes #7181

Changelog.md

 # 0.6.2.0
 
 ## Refactor
+* Use string-direction gem for rtl detection [#7181](https://github.com/diaspora/diaspora/pull/7181)
 
 ## Bug fixes
 * Fix fetching comments after fetching likes [#7167](https://github.com/diaspora/diaspora/pull/7167)

Gemfile

@@ -135,6 +135,10 @@ gem "twitter-text",      "1.14.0"
 gem "ruby-oembed",       "0.10.1"
 gem "open_graph_reader", "0.6.1"
 
+# RTL support
+
+gem "string-direction", "1.2.0"
+
 # Security Headers
 
 gem "secure_headers", "3.5.0"

Gemfile.lock

@@ -819,6 +819,8 @@ GEM
       activesupport (>= 3.0)
       sprockets (>= 2.8, < 4.0)
     state_machine (1.2.0)
+    string-direction (1.2.0)
+      yard (~> 0.8)
     swd (1.0.1)
       activesupport (>= 3)
       attr_required (>= 0.0.5)
@@ -1031,6 +1033,7 @@ DEPENDENCIES
   spring (= 2.0.0)
   spring-commands-cucumber (= 1.0.1)
   spring-commands-rspec (= 1.0.4)
+  string-direction (= 1.2.0)
   test_after_commit (= 1.1.0)
   timecop (= 0.8.1)
   turbo_dev_assets (= 0.0.2)
@@ -1046,4 +1049,4 @@ DEPENDENCIES
   will_paginate (= 3.1.5)
 
 BUNDLED WITH
-   1.13.5
+   1.13.6

lib/direction_detector.rb

@@ -2,36 +2,16 @@
 #   Copyright (c) 2010-2011, Diaspora Inc.  This file is
 #   licensed under the Affero General Public License version 3 or later.  See
 #   the COPYRIGHT file.
-# Deeply inspired by https://gitorious.org/statusnet/mainline/blobs/master/plugins/DirectionDetector/DirectionDetectorPlugin.php
 
 class String
-  RTL_RANGES = [
-      [1536, 1791], # arabic, persian, urdu, kurdish, ...
-      [65136, 65279], # arabic peresent 2
-      [64336, 65023], # arabic peresent 1
-      [1424, 1535], # hebrew
-      [64256, 64335], # hebrew peresent
-      [1792, 1871], # syriac
-      [1920, 1983], # thaana
-      [1984, 2047], # nko
-      [11568, 11647] # tifinagh
-    ]
   RTL_CLEANER_REGEXES = [ /@[^ ]+|#[^ ]+/u, # mention, tag
       /^RT[: ]{1}| RT | RT: |[♺♻:]/u # retweet
     ]
 
   def is_rtl?
     return false if self.strip.empty?
-    count = 0
-    self.split(" ").each do |word|
-      if starts_with_rtl_char?(word)
-        count += 1
-      else
-        count -= 1
-      end
-    end
-    return true if count > 0 # more than half of the words are rtl words
-    return starts_with_rtl_char?(self) # otherwise let the first word decide
+    detector = StringDirection::Detector.new(:dominant)
+    detector.rtl? self
   end
 
   # Diaspora specific
@@ -42,14 +22,4 @@ class String
     end
     string.is_rtl?
   end
-
-  def starts_with_rtl_char?(string = self)
-    stripped = string.strip
-    return false if stripped.empty?
-    char = stripped.unpack('U*').first
-    RTL_RANGES.each do |limit|
-      return true if char >= limit[0] && char <= limit[1]
-    end
-    return false
-  end
 end

spec/lib/direction_detector_spec.rb

@@ -24,29 +24,6 @@ describe String do
   let(:hebrew_arabic) { "#{hebrew} #{arabic}" }
 
 
-  describe "#stats_with_rtl_char?" do
-    it 'returns true or false correctly' do
-      expect(english.starts_with_rtl_char?).to be false
-      expect(chinese.starts_with_rtl_char?).to be false
-      expect(arabic.starts_with_rtl_char?).to be true
-      expect(hebrew.starts_with_rtl_char?).to be true
-      expect(hebrew_arabic.starts_with_rtl_char?).to be true
-    end
-
-    it 'only looks at the first char' do
-      expect(english_chinese.starts_with_rtl_char?).to be false
-      expect(chinese_english.starts_with_rtl_char?).to be false
-      expect(english_arabic.starts_with_rtl_char?).to be false
-      expect(hebrew_english.starts_with_rtl_char?).to be true
-      expect(arabic_chinese.starts_with_rtl_char?).to be true
-    end
-    
-    it 'ignores whitespaces' do
-      expect(" \n \r \t".starts_with_rtl_char?).to be false
-      expect(" #{arabic} ".starts_with_rtl_char?).to be true
-    end
-  end
-
   describe "#is_rtl?" do
     it 'returns true or false correctly' do
       expect(english.is_rtl?).to be false
@@ -65,17 +42,16 @@ describe String do
       expect("#{english} #{arabic} #{arabic}".is_rtl?).to be true
     end
 
-    it "fallbacks to the first word if there's no majority" do
-      expect(hebrew_english.is_rtl?).to be true
-      expect(english_hebrew.is_rtl?).to be false
-      expect(arabic_english.is_rtl?).to be true
-      expect(english_arabic.is_rtl?).to be false
-    end
-
     it 'ignores whitespaces' do
       expect(" \n \r \t".is_rtl?).to be false
       expect(" #{arabic} ".is_rtl?).to be true
     end
+
+    it "ignores byte order marks" do
+      expect("\u{feff}".is_rtl?).to be false
+      expect("\u{feff}#{arabic}".is_rtl?).to be true
+      expect("\u{feff}#{english}".is_rtl?).to be false
+    end
   end
 
   describe '#cleaned_is_rtl?' do