discourse/app/models/theme.rb

require_dependency 'distributed_cache'
require_dependency 'stylesheet/compiler'
require_dependency 'stylesheet/manager'

class Theme < ActiveRecord::Base

  ALLOWED_FIELDS = %w{scss head_tag header after_header body_tag footer}

  @cache = DistributedCache.new('theme')

  belongs_to :color_scheme
  has_many :theme_fields, dependent: :destroy
  has_many :child_theme_relation, class_name: 'ChildTheme', foreign_key: 'parent_theme_id', dependent: :destroy
  has_many :child_themes, through: :child_theme_relation, source: :child_theme
  belongs_to :remote_theme

  before_create do
    self.key ||= SecureRandom.uuid
    true
  end

  after_save do
    changed_fields.each(&:save!)
    changed_fields.clear

    Theme.expire_site_cache! if user_selectable_changed?

    @dependant_themes = nil
    @included_themes = nil
  end

  after_save do
    remove_from_cache!
    notify_scheme_change if color_scheme_id_changed?
  end

  after_destroy do
    remove_from_cache!
    if SiteSetting.default_theme_key == self.key
      Theme.clear_default!
    end
  end

  after_commit ->(theme) do
    theme.notify_theme_change
  end, on: :update

  def self.expire_site_cache!
    Site.clear_anon_cache!
    ApplicationSerializer.expire_cache_fragment!("user_themes")
  end

  def self.clear_default!
    SiteSetting.default_theme_key = ""
    expire_site_cache!
  end

  def set_default!
    SiteSetting.default_theme_key = key
    Theme.expire_site_cache!
  end

  def self.lookup_field(key, target, field)
    return if key.blank?

    cache_key = "#{key}:#{target}:#{field}:#{ThemeField::COMPILER_VERSION}"
    lookup = @cache[cache_key]
    return lookup.html_safe if lookup

    target = target.to_sym
    theme = find_by(key: key)

    val = theme.resolve_baked_field(target, field) if theme

    (@cache[cache_key] = val || "").html_safe
  end

  def self.remove_from_cache!(themes=nil)
    clear_cache!
  end

  def self.clear_cache!
    @cache.clear
  end


  def self.targets
    @targets ||= Enum.new(common: 0, desktop: 1, mobile: 2)
  end


  def notify_scheme_change(clear_manager_cache=true)
    Stylesheet::Manager.cache.clear if clear_manager_cache
    message = refresh_message_for_targets(["desktop", "mobile", "admin"], self.color_scheme_id, self, Rails.env.development?)
    MessageBus.publish('/file-change', message)
  end

  def notify_theme_change
    Stylesheet::Manager.clear_theme_cache!

    themes = [self] + dependant_themes

    message = themes.map do |theme|
      refresh_message_for_targets([:mobile_theme,:desktop_theme], theme.id, theme)
    end.compact.flatten
    MessageBus.publish('/file-change', message)
  end

  def refresh_message_for_targets(targets, id, theme, add_cache_breaker=false)
    targets.map do |target|
      link = Stylesheet::Manager.stylesheet_link_tag(target.to_sym, 'all', theme.key)
      if link
        href = link.split(/["']/)[1]
        if add_cache_breaker
          href << (href.include?("?") ? "&" : "?")
          href << SecureRandom.hex
        end
        {
          name: "/stylesheets/#{target}#{id ? "_#{id}": ""}",
          new_href: href
        }
      end
    end
  end

  def dependant_themes
    @dependant_themes ||= resolve_dependant_themes(:up)
  end

  def included_themes
    @included_themes ||= resolve_dependant_themes(:down)
  end

  def resolve_dependant_themes(direction)

    select_field,where_field=nil

    if direction == :up
      select_field = "parent_theme_id"
      where_field = "child_theme_id"
    elsif direction == :down
      select_field = "child_theme_id"
      where_field = "parent_theme_id"
    else
      raise "Unknown direction"
    end

    themes = []
    return [] unless id

    uniq = Set.new
    uniq << id

    iterations = 0
    added = [id]

    while added.length > 0 && iterations < 5

      iterations += 1

      new_themes = Theme.where("id in (SELECT #{select_field}
                                  FROM child_themes
                                  WHERE #{where_field} in (?))", added).to_a

      added = []
      new_themes.each do |theme|
        unless uniq.include?(theme.id)
          added << theme.id
          uniq << theme.id
          themes << theme
        end
      end

    end

    themes
  end

  def resolve_baked_field(target, name)
    list_baked_fields(target,name).map{|f| f.value_baked || f.value}.join("\n")
  end

  def list_baked_fields(target, name)

    target = target.to_sym

    theme_ids = [self.id] + (included_themes.map(&:id) || [])
    fields = ThemeField.where(target: [Theme.targets[target], Theme.targets[:common]])
                       .where(name: name.to_s)
                       .includes(:theme)
                       .joins("JOIN (
                             SELECT #{theme_ids.map.with_index{|id,idx| "#{id} AS theme_id, #{idx} AS sort_column"}.join(" UNION ALL SELECT ")}
                            ) as X ON X.theme_id = theme_fields.theme_id")
                       .order('sort_column, target')
    fields.each(&:ensure_baked!)
    fields
  end

  def remove_from_cache!
    self.class.remove_from_cache!
  end

  def changed_fields
    @changed_fields ||= []
  end

  def set_field(target, name, value)
    name = name.to_s

    target_id = Theme.targets[target.to_sym]
    raise "Unknown target #{target} passed to set field" unless target_id

    field = theme_fields.find{|f| f.name==name && f.target == target_id}
    if field
      if value.blank?
        field.destroy
      else
        if field.value != value
          field.value = value
          changed_fields << field
        end
      end
    else
      theme_fields.build(target: target_id, value: value, name: name) if value.present?
    end
  end

  def add_child_theme!(theme)
    child_theme_relation.create!(child_theme_id: theme.id)
    @included_themes = nil
    child_themes.reload
    save!
  end
end

# == Schema Information
#
# Table name: themes
#
#  id               :integer          not null, primary key
#  name             :string           not null
#  user_id          :integer          not null
#  key              :string           not null
#  created_at       :datetime         not null
#  updated_at       :datetime         not null
#  compiler_version :integer          default(0), not null
#  user_selectable  :boolean          default(FALSE), not null
#  hidden           :boolean          default(FALSE), not null
#  color_scheme_id  :integer
#  remote_theme_id  :integer
#
# Indexes
#
#  index_themes_on_key              (key)
#  index_themes_on_remote_theme_id  (remote_theme_id) UNIQUE
#