FEATURE: Native theme support

This feature introduces the concept of themes. Themes are an evolution
of site customizations.

Themes introduce two very big conceptual changes:

- A theme may include other "child themes", children can include grand
children and so on.

- A theme may specify a color scheme

The change does away with the idea of "enabled" color schemes.

It also adds a bunch of big niceties like

- You can source a theme from a git repo

- History for themes is much improved

- You can only have a single enabled theme. Themes can be selected by
    users, if you opt for it.

On a technical level this change comes with a whole bunch of goodies

- All CSS is now compiled using a custom pipeline that uses libsass
    see /lib/stylesheet

- There is a single pipeline for css compilation (in the past we used
    one for customizations and another one for the rest of the app

- The stylesheet pipeline is now divorced of sprockets, there is no
   reliance on sprockets for CSS bundling

- CSS is generated with source maps everywhere (including themes) this
    makes debugging much easier

- Our "live reloader" is smarter and avoid a flash of unstyled content
   we run a file watcher in "puma" in dev so you no longer need to run
   rake autospec to watch for CSS changes

app/serializers/color_scheme_color_serializer.rb

@@ -6,6 +6,11 @@ class ColorSchemeColorSerializer < ApplicationSerializer
   end
 
   def default_hex
-    ColorScheme.base_colors[object.name]
+    if object.color_scheme
+      object.color_scheme.base_colors[object.name]
+    else
+      # it is a base color so it is already default
+      object.hex
+    end
   end
 end

app/serializers/color_scheme_serializer.rb

@@ -1,8 +1,4 @@
 class ColorSchemeSerializer < ApplicationSerializer
-  attributes :id, :name, :enabled, :is_base
+  attributes :id, :name, :is_base, :base_scheme_id
   has_many :colors, serializer: ColorSchemeColorSerializer, embed: :objects
-
-  def base
-    object.is_base || false
-  end
 end

app/serializers/site_customization_serializer.rb

@@ -1,7 +0,0 @@
-class SiteCustomizationSerializer < ApplicationSerializer
-
-  attributes :id, :name, :key, :enabled, :created_at, :updated_at,
-             :stylesheet, :header, :footer, :top,
-             :mobile_stylesheet, :mobile_header, :mobile_footer, :mobile_top,
-             :head_tag, :body_tag, :embedded_css
-end

app/serializers/site_serializer.rb

@@ -24,13 +24,25 @@ class SiteSerializer < ApplicationSerializer
              :tags_filter_regexp,
              :top_tags,
              :wizard_required,
-             :topic_featured_link_allowed_category_ids
+             :topic_featured_link_allowed_category_ids,
+             :user_themes
 
   has_many :categories, serializer: BasicCategorySerializer, embed: :objects
   has_many :trust_levels, embed: :objects
   has_many :archetypes, embed: :objects, serializer: ArchetypeSerializer
   has_many :user_fields, embed: :objects, serialzer: UserFieldSerializer
 
+  def user_themes
+    cache_fragment("user_themes") do
+      Theme.where('key = :default OR user_selectable',
+                    default: SiteSetting.default_theme_key)
+           .order(:name)
+           .pluck(:key, :name)
+           .map{|k,n| {theme_key: k, name: n, default: k == SiteSetting.default_theme_key}}
+           .as_json
+    end
+  end
+
   def groups
     cache_fragment("group_names") do
       Group.order(:name).pluck(:id,:name).map { |id,name| { id: id, name: name } }.as_json

app/serializers/theme_serializer.rb

@@ -0,0 +1,42 @@
+class ThemeFieldSerializer < ApplicationSerializer
+  attributes :name, :target, :value
+
+  def target
+    case object.target
+    when 0 then "common"
+    when 1 then "desktop"
+    when 2 then "mobile"
+    end
+  end
+end
+
+class ChildThemeSerializer < ApplicationSerializer
+  attributes :id, :name, :key, :created_at, :updated_at, :default
+
+  def include_default?
+    object.key == SiteSetting.default_theme_key
+  end
+
+  def default
+    true
+  end
+end
+
+class RemoteThemeSerializer < ApplicationSerializer
+  attributes :id, :remote_url, :remote_version, :local_version, :about_url,
+             :license_url, :commits_behind, :remote_updated_at, :updated_at
+
+  # wow, AMS has some pretty nutty logic where it tries to find the path here
+  # from action dispatch, tell it not to
+  def about_url
+    object.about_url
+  end
+end
+
+class ThemeSerializer < ChildThemeSerializer
+  attributes :color_scheme, :color_scheme_id, :user_selectable, :remote_theme_id
+
+  has_many :theme_fields, serializer: ThemeFieldSerializer, embed: :objects
+  has_many :child_themes, serializer: ChildThemeSerializer, embed: :objects
+  has_one :remote_theme, serializer: RemoteThemeSerializer, embed: :objects
+end

app/serializers/user_history_serializer.rb

@@ -12,7 +12,8 @@ class UserHistorySerializer < ApplicationSerializer
              :post_id,
              :category_id,
              :action,
-             :custom_type
+             :custom_type,
+             :id
 
   has_one :acting_user, serializer: BasicUserSerializer, embed: :objects
   has_one :target_user, serializer: BasicUserSerializer, embed: :objects