module ActiveResource
  module Singleton
    extend ActiveSupport::Concern

    module ClassMethods
      attr_writer :singleton_name

      def singleton_name
        @singleton_name ||= model_name.element
      end

      # Gets the singleton path for the object.  If the +query_options+ parameter is omitted, Rails
      # will split from the \prefix options.
      #
      # ==== Options
      # +prefix_options+ - A \hash to add a \prefix to the request for nested URLs (e.g., <tt>:account_id => 19</tt>
      #                    would yield a URL like <tt>/accounts/19/purchases.json</tt>).
      # +query_options+ - A \hash to add items to the query string for the request.
      #
      # ==== Examples
      #   Weather.singleton_path
      #   # => /weather.json
      #
      #   class Inventory < ActiveResource::Base
      #     self.site =   "https://37s.sunrise.com"
      #     self.prefix = "/products/:product_id/"
      #   end
      #
      #   Inventory.singleton_path(:product_id => 5)
      #   # => /products/5/inventory.json
      #
      #   Inventory.singleton_path({:product_id => 5}, {:sold => true})
      #   # => /products/5/inventory.json?sold=true
      #
      def singleton_path(prefix_options = {}, query_options = nil)
        check_prefix_options(prefix_options)

        prefix_options, query_options = split_options(prefix_options) if query_options.nil?
        "#{prefix(prefix_options)}#{singleton_name}.#{format.extension}#{query_string(query_options)}"
      end

      # Core method for finding singleton resources.
      #
      # ==== Arguments
      # Takes a single argument of options
      #
      # ==== Options
      # * <tt>:params</tt> - Sets the query and \prefix (nested URL) parameters.
      #
      # ==== Examples
      #   Weather.find
      #   # => GET /weather.json
      #
      #   Weather.find(:params => {:degrees => 'fahrenheit'})
      #   # => GET /weather.json?degrees=fahrenheit
      #
      # == Failure or missing data
      #   A failure to find the requested object raises a ResourceNotFound
      #   exception.
      #
      #   Inventory.find
      #   # => raises ResourceNotFound
      def find(options = {})
        find_singleton(options)
      end

      private

      # Find singleton resource
      def find_singleton(options)
        prefix_options, query_options = split_options(options[:params])

        path = singleton_path(prefix_options, query_options)
        resp = self.format.decode(self.connection.get(path, self.headers).body)
        instantiate_record(resp, {})
      end
    end

    # Deletes the resource from the remove service.
    #
    # ==== Examples
    #   weather = Weather.find
    #   weather.destroy
    #   Weather.find # 404 (Resource Not Found)
    def destroy
      connection.delete(singleton_path, self.class.headers)
    end

    protected

    # Update the resource on the remote service
    def update
      connection.put(singleton_path(prefix_options), encode, self.class.headers).tap do |response|
        load_attributes_from_response(response)
      end
    end

    # Create (i.e. \save to the remote service) the \new resource.
    def create
      connection.post(singleton_path, encode, self.class.headers).tap do |response|
        self.id = id_from_response(response)
        load_attributes_from_response(response)
      end
    end

    private

    def singleton_path(options = nil)
      self.class.singleton_path(options || prefix_options)
    end
  end
end