Move flat_hash to I18nContent model

also add unit tests for this function and a description
into the model of the behaviour of the function

app/controllers/admin/site_customization/information_texts_controller.rb

@@ -66,17 +66,11 @@ class Admin::SiteCustomization::InformationTextsController < Admin::SiteCustomiz
       translations = I18n.backend.send(:translations)[locale.to_sym]
 
       translations.each do |k, v|
-        @content[k.to_s] = flat_hash(v).keys
-                                       .map { |s| @existing_keys["#{k.to_s}.#{s}"].nil? ?
-                                              I18nContent.new(key: "#{k.to_s}.#{s}") :
-                                              @existing_keys["#{k.to_s}.#{s}"] }
+        @content[k.to_s] = I18nContent.flat_hash(v).keys
+                                      .map { |s| @existing_keys["#{k.to_s}.#{s}"].nil? ?
+                                                 I18nContent.new(key: "#{k.to_s}.#{s}") :
+                                                 @existing_keys["#{k.to_s}.#{s}"] }
       end
     end
 
-    def flat_hash(h, f = nil, g = {})
-      return g.update({ f => h }) unless h.is_a? Hash
-      h.each { |k, r| flat_hash(r, [f,k].compact.join('.'), g) }
-      return g
-    end
-
 end

app/models/i18n_content.rb

@@ -7,4 +7,35 @@ class I18nContent < ActiveRecord::Base
   translates :value, touch: true
   globalize_accessors locales: [:en, :es, :fr, :nl]
 
+  # flat_hash function returns a flattened hash, a hash of a single
+  # level of profundity in which each key is composed from the
+  # keys of the original hash (whose value is not a hash) by
+  # typing in the key the route from the first level of the
+  # original hash
+  #
+  # examples
+  # hash = {'key1' => 'value1',
+  #         'key2' => {'key3' => 'value2',
+  #                    'key4' => {'key5' => 'value3'}}}
+  #
+  # I18nContent.flat_hash(hash) = {"key1"=>"value1",
+  #                                "key2.key3"=>"value2",
+  #                                "key2.key4.key5"=>"value3"}
+  #
+  # I18nContent.flat_hash(hash, 'string') = {"string.key1"=>"value1",
+  #                                          "string.key2.key3"=>"value2",
+  #                                          "string.key2.key4.key5"=>"value3"}
+  #
+  # I18nContent.flat_hash(hash, 'string', {'key6' => "value4"}) =
+  #                                         {'key6' => "value4",
+  #                                          "string.key1"=>"value1",
+  #                                          "string.key2.key3"=>"value2",
+  #                                          "string.key2.key4.key5"=>"value3"}
+
+  def self.flat_hash(h, f = nil, g = {})
+    return g.update({ f => h }) unless h.is_a? Hash
+    h.each { |k, r| flat_hash(r, [f,k].compact.join('.'), g) }
+    return g
+  end
+
 end

spec/models/i18n_content_spec.rb

@@ -73,4 +73,36 @@ RSpec.describe I18nContent, type: :model do
       expect(i18n_content.value).to eq('Texto en español')
     end
   end
+
+  context 'flat_hash' do
+
+    it 'using one parameter' do
+      expect(I18nContent.flat_hash(nil)).to eq({nil=>nil})
+      expect(I18nContent.flat_hash('string')).to eq({nil=>'string'})
+      expect(I18nContent.flat_hash({w: 'string'})).to eq({"w" => 'string'})
+      expect(I18nContent.flat_hash({w: {p: 'string'}})).to eq({"w.p" => 'string'})
+    end
+
+    it 'using the two first parameters' do
+      expect(I18nContent.flat_hash('string', 'f')).to eq({'f'=>'string'})
+      expect(I18nContent.flat_hash(nil, 'f')).to eq({"f" => nil})
+      expect(I18nContent.flat_hash({w: 'string'}, 'f')).to eq({"f.w" => 'string'})
+      expect(I18nContent.flat_hash({w: {p: 'string'}}, 'f')).to eq({"f.w.p" => 'string'})
+    end
+
+    it 'using the first and last parameters' do
+      expect {I18nContent.flat_hash('string', nil, 'not hash')}.to raise_error NoMethodError
+      expect(I18nContent.flat_hash(nil, nil, {q: 'other string'})).to eq({q: 'other string', nil => nil})
+      expect(I18nContent.flat_hash({w: 'string'}, nil, {q: 'other string'})).to eq({q: 'other string', "w" => 'string'})
+      expect(I18nContent.flat_hash({w: {p: 'string'}}, nil, {q: 'other string'})).to eq({q: 'other string', "w.p" => 'string'})
+    end
+
+    it 'using all parameters' do
+      expect {I18nContent.flat_hash('string', 'f', 'not hash')}.to raise_error NoMethodError
+      expect(I18nContent.flat_hash(nil, 'f', {q: 'other string'})).to eq({q: 'other string', "f" => nil})
+      expect(I18nContent.flat_hash({w: 'string'}, 'f', {q: 'other string'})).to eq({q: 'other string', "f.w" => 'string'})
+      expect(I18nContent.flat_hash({w: {p: 'string'}}, 'f', {q: 'other string'})).to eq({q: 'other string', "f.w.p" => 'string'})
+    end
+
+  end
 end