1 files changed, 89 insertions, 0 deletions
diff --git a/app/controllers/concerns/theming_concern.rb b/app/controllers/concerns/theming_concern.rb
new file mode 100644
index 000000000..f993a81d7
--- /dev/null
+++ b/app/controllers/concerns/theming_concern.rb
@@ -0,0 +1,89 @@
+# frozen_string_literal: true
+
+module ThemingConcern
+  extend ActiveSupport::Concern
+
+  def use_pack(pack_name)
+    @core = resolve_pack_with_common(Themes.instance.core, pack_name)
+    @theme = resolve_pack_with_common(Themes.instance.flavour(current_flavour), pack_name, current_skin)
+  end
+
+  private
+
+  def current_flavour
+    [current_user&.setting_flavour, Setting.flavour, 'glitch', 'vanilla'].find { |flavour| Themes.instance.flavours.include?(flavour) }
+  end
+
+  def current_skin
+    skins = Themes.instance.skins_for(current_flavour)
+    [current_user&.setting_skin, Setting.skin, 'default'].find { |skin| skins.include?(skin) }
+  end
+
+  def valid_pack_data?(data, pack_name)
+    data['pack'].is_a?(Hash) && data['pack'][pack_name].present?
+  end
+
+  def nil_pack(data)
+    {
+      use_common: true,
+      flavour: data['name'],
+      pack: nil,
+      preload: nil,
+      skin: nil,
+      supported_locales: data['locales'],
+    }
+  end
+
+  def pack(data, pack_name, skin)
+    pack_data = {
+      use_common: true,
+      flavour: data['name'],
+      pack: pack_name,
+      preload: nil,
+      skin: nil,
+      supported_locales: data['locales'],
+    }
+
+    return pack_data unless data['pack'][pack_name].is_a?(Hash)
+
+    pack_data[:use_common] = false if data['pack'][pack_name]['use_common'] == false
+    pack_data[:pack] = nil unless data['pack'][pack_name]['filename']
+
+    preloads = data['pack'][pack_name]['preload']
+    pack_data[:preload] = [preloads] if preloads.is_a?(String)
+    pack_data[:preload] = preloads if preloads.is_a?(Array)
+
+    if skin != 'default' && data['skin'][skin]
+      pack_data[:skin] = skin if data['skin'][skin].include?(pack_name)
+    elsif data['pack'][pack_name]['stylesheet']
+      pack_data[:skin] = 'default'
+    end
+
+    pack_data
+  end
+
+  def resolve_pack(data, pack_name, skin)
+    return pack(data, pack_name, skin) if valid_pack_data?(data, pack_name)
+    return if data['name'].blank?
+
+    fallbacks = []
+    if data.key?('fallback')
+      fallbacks = data['fallback'] if data['fallback'].is_a?(Array)
+      fallbacks = [data['fallback']] if data['fallback'].is_a?(String)
+    elsif data['name'] != Setting.default_settings['flavour']
+      fallbacks = [Setting.default_settings['flavour']]
+    end
+
+    fallbacks.each do |fallback|
+      return resolve_pack(Themes.instance.flavour(fallback), pack_name) if Themes.instance.flavour(fallback)
+    end
+
+    nil
+  end
+
+  def resolve_pack_with_common(data, pack_name, skin = 'default')
+    result = resolve_pack(data, pack_name, skin) || nil_pack(data)
+    result[:common] = resolve_pack(data, 'common', skin) if result.delete(:use_common)
+    result
+  end
+end