require 'ostruct'

module FactoryDataPreloader
  class PreloaderAlreadyDefinedError < StandardError; end
  class PreloadedRecordNotFound < StandardError; end

  class FactoryData
    @@preloaded_cache = nil
    @@preloaded_data_deleted = nil
    @@single_test_cache = {}
    @@preloaders = []
  
    class << self

      def preload(model_type, options = {}, &proc)
        raise PreloaderAlreadyDefinedError.new, "You have already defined the preloader for #{model_type.to_s}" if @@preloaders.map(&:model_type).include?(model_type)
      
        model_class = options[:model_class] || model_type.to_s.singularize.classify.constantize
        depends_on = [options[:depends_on]].compact.flatten
        @@preloaders << FactoryDataPreloader::Preloader.new(model_type, model_class, proc, @@preloaders.size, depends_on)

        class << self; self; end.class_eval do
          define_method model_type do |key|
            get_record(model_type, model_class, key)
          end
        end
      end

      def delete_preload_data!
        # make sure this only runs once...
        return unless @@preloaded_data_deleted.nil?
    
        # the preloaders are listed in the parent -> child table order,
        # so we need to delete them in reverse.
        @@preloaders.sort.reverse.each do |preloader|
          preloader.model_class.delete_all
        end
    
        @@preloaded_data_deleted = true
      end

      def preload_data!
        return unless @@preloaded_cache.nil? # make sure the data is only preloaded once.
        @@preloaded_cache = {}
    
        @@preloaders.sort.each do |preloader|
          cache = @@preloaded_cache[preloader.model_type] ||= {}
          preloader.data.each do |key, record|
            if record.new_record? && !record.save
              puts "\nError preloading factory data.  #{preloader.model_class.to_s} :#{key.to_s} could not be saved.  Errors: "
              puts pretty_error_messages(record)
              puts "\n\n"
              next
            end
        
            cache[key] = record.id
          end
        end
      end
  
      def reset_cache!
        @@single_test_cache = {}
      end

      private

      def get_record(type, model_class, key)
        @@single_test_cache[type] ||= {}
        @@single_test_cache[type][key] ||= begin
          record = model_class.find_by_id(@@preloaded_cache[type][key])
          raise PreloadedRecordNotFound.new, "Could not find a record for FactoryData.#{type}(:#{key})." unless record
          record
        end
      end
    
      # Borrowed from shoulda: http://github.com/thoughtbot/shoulda/blob/e02228d45a879ff92cb72b84f5fccc6a5f856a65/lib/shoulda/active_record/helpers.rb#L4-9
      def pretty_error_messages(obj)
        obj.errors.map do |a, m|
          msg = "#{a} #{m}"
          msg << " (#{obj.send(a).inspect})" unless a.to_sym == :base
        end
      end
    end
  end
end

# alias this class so that apps that use it don't have to use the fully qualified name.
FactoryData = FactoryDataPreloader::FactoryData