module CachedResource
  # The Caching module is included in ActiveResource and
  # handles caching and recaching of responses.
  module Caching
    extend ActiveSupport::Concern

    included do
      class << self
        alias_method_chain :find, :cache
      end
    end

    module ClassMethods
      # find a resource using the cache or resend the request
      # if :reload is set to true or caching is disabled
      def find_with_cache(*arguments)
        arguments << {} unless arguments.last.is_a?(Hash)
        should_reload = arguments.last.delete(:reload) || !cached_resource.enabled
        arguments.pop if arguments.last.empty?
        key = cache_key(arguments)

        begin
          (should_reload ? find_via_reload(key, *arguments) : find_via_cache(key, *arguments))
        rescue ActiveResource::ServerError, ActiveResource::ConnectionError, SocketError => e
          raise(e)
        end
      end

      private

      # try to find a cached response for the given key.  If
      # no cache entry exists, send a new request.
      def find_via_cache(key, *arguments)
        result = cached_resource.cache.read(key).try(:dup)
        result && cached_resource.logger.info("#{CachedResource::Configuration::LOGGER_PREFIX} READ #{key} for #{arguments.inspect}")
        result || find_via_reload(key, *arguments)
      end

      # re/send the request to fetch the resource. Cache the response
      # for the request.
      def find_via_reload(key, *arguments)
        result = find_without_cache(*arguments)
        cached_resource.cache.write(key, result, :expires_in => cached_resource.ttl)
        cached_resource.logger.info("#{CachedResource::Configuration::LOGGER_PREFIX} WRITE #{key} for #{arguments.inspect}")
        result
      end

      # generate the request cache key
      def cache_key(*arguments)
        "#{name.parameterize.gsub("-", "/")}/#{arguments.join('/')}".downcase
      end

    end
  end
end