require 'digest/md5'

# TODO: we should do a PR to the HER project which includes
# smarter filtering and more reliable caching
# Before doing so, we make the filtering behavior customizable
# (E.g.: configure name of filter/sort/limit keys)
module Her
  module Model
    class Relation
      def initialize(parent)
        @parent = parent
        @params = {}
      end

      # Fetch a collection of resources
      def fetch
        path = @parent.build_request_path(@params)
        method = @parent.method_for(:find)
        @parent.request(@params.merge(:_method => method, :_path => path)) do |parsed_data, response|
          @parent.new_collection(parsed_data)
        end
      end

      # Override Her::Model::Relation#where
      # to follow jsonapi.org standards
      # Use filter instead of raw parameters
      def where(params = {})
        return self if !params || params.empty?
        self.params[:filter] ||= {}
        self.params[:filter].merge!(params)
        self
      end
      alias all where

      # E.g:
      # Product.order_by('created_at.desc','name.asc')
      def order_by(*args)
        return self if args.empty?
        self.params[:sort] = [self.params[:sort],args].flatten.compact.uniq
        self
      end
      alias sort_by order_by

      # ActiveRecord-like order
      # Product.order("created_at DESC, name ASC")
      def order(string_query)
        return self if !string_query || string_query.empty?
        args = string_query.split(',').map do |q|
          field, direction = q.strip.split(/\s+/).compact
          [field, direction ? direction.downcase : nil].join('.')
        end
        self.order_by(*args)
      end
      alias sort order

      # Limit the number of results returned
      def limit(max = nil)
        return self if !max
        self.params[:limit] = max
        self
      end

      # Skip result rows
      def skip(nrows = nil)
        return self if !nrows
        self.params[:skip] = nrows
        self
      end

      # Reset the query parameters
      def reset_params
        @params.clear
      end

      # Refetch the relation
      def reload
        fetch
      end

      # Hold the scopes defined on Her::Model classes
      # E.g.: scope :admin, -> { where(admin: 1) }
      def self.scopes
        @scopes ||= {}
      end

      private
        def query_checkum
          Digest::MD5.hexdigest(Marshal.dump(@params))
        end
    end
  end
end