# frozen_string_literal: true

module Decidim
  # Asset router provides global access to the asset routes for assets saved
  # through ActiveStorage. This handles the different cases for routing to the
  # remote routes when using an assets CDN or to local routes when using the
  # local disk storage driver.
  class AssetRouter
    # Initializes the router.
    #
    # @param [ActiveStorage::Attached, ActiveStorage::Blob] The asset to route
    #   to
    def initialize(asset)
      @asset = asset
    end

    # Generates the correct URL to the asset with the provided options.
    #
    # @param options The options for the URL that are the normal route options
    #   Rails route helpers accept
    def url(**options)
      if asset.is_a? ActiveStorage::Attached
        routes.rails_blob_url(asset.blob, **default_options.merge(options))
      else
        routes.rails_representation_url(asset, **default_options.merge(options))
      end
    end

    private

    attr_reader :asset

    # Provides the route helpers depending on whether the URL is generated to
    # the local host or an external CDN (remote).
    #
    # @return [Module, Decidim::EngineRouter] The correct route helpers based
    #   on the configuration
    def routes
      @routes ||=
        if remote?
          Rails.application.routes.url_helpers
        else
          EngineRouter.new("main_app", {})
        end
    end

    # Determines whether the assets call should be to a remote CDN or to the
    # local server based on the storage options.
    #
    # @return [Boolean] A boolean indicating whether the assets are served
    #   through a remote CDN
    def remote?
      remote_storage_options.present?
    end

    # Determines the default options to be passed to the route helper. For the
    # remote storage, returns the remote storage options and for the local disk
    # storage returns an empty hash.
    #
    # @return [Hash] The default options hash to pass to the route helper
    def default_options
      @default_options ||=
        if remote?
          remote_storage_options
        else
          {}
        end
    end

    # The remote storage options when using a remote CDN. An empty hash in case
    # using the local disk storage.
    #
    # @return [Hash] The remote storage options hash
    def remote_storage_options
      @remote_storage_options ||= {
        host: Rails.application.secrets.dig(:storage, :cdn_host)
      }.compact
    end
  end
end