module JsonApiClient
  module Parsers
    class Parser
      class << self
        def parse(klass, response)
          data = response.body.present? ? response.body : {}

          ResultSet.new.tap do |result_set|
            result_set.record_class = klass
            result_set.uri = response.env[:url]
            handle_json_api(result_set, data)
            handle_data(result_set, data)
            handle_errors(result_set, data)
            handle_meta(result_set, data)
            handle_links(result_set, data)
            handle_relationships(result_set, data)
            handle_pagination(result_set, data)
            handle_included(result_set, data)
          end
        end

        #
        # Given a resource hash, returns a Resource.new friendly hash
        # which flattens the attributes in w/ id and type.
        #
        # Example:
        #
        # Given:
        #  {
        #    id: 1.
        #    type: 'person',
        #    attributes: {
        #      first_name: 'Jeff',
        #      last_name: 'Ching'
        #    },
        #    links: {...},
        #    relationships: {...}
        #  }
        #
        # Returns:
        #  {
        #    id: 1,
        #    type: 'person',
        #    first_name: 'Jeff',
        #    last_name: 'Ching'
        #    links: {...},
        #    relationships: {...}
        #  }
        #
        #
        def parameters_from_resource(params)
          attrs = params.slice('id', 'links', 'meta', 'type', 'relationships')
          attrs.merge(params.fetch('attributes', {}))
        end

        private

        def handle_json_api(result_set, data)
          result_set.implementation = Implementation.new(data.fetch("jsonapi", {}))
        end

        def handle_data(result_set, data)
          # all data lives under the "data" attribute
          results = data.fetch("data", [])

          # we will treat everything as an Array
          results = [results] unless results.is_a?(Array)
          resources = results.map do |res|
            resource = result_set.record_class.load(parameters_from_resource(res))
            resource.last_result_set = result_set
            resource
          end
          result_set.concat(resources)
        end

        def handle_errors(result_set, data)
          result_set.errors = ErrorCollector.new(data.fetch("errors", []))
        end

        def handle_meta(result_set, data)
          result_set.meta = MetaData.new(data.fetch("meta", {}))
        end

        def handle_links(result_set, data)
          result_set.links = Linking::TopLevelLinks.new(result_set.record_class, data.fetch("links", {}))
        end

        def handle_relationships(result_set, data)
          result_set.relationships = Relationships::TopLevelRelations.new(result_set.record_class, data.fetch("relationships", {}))
        end

        def handle_pagination(result_set, data)
          result_set.pages = result_set.record_class.paginator.new(result_set, data)
        end

        def handle_included(result_set, data)
          result_set.included = IncludedData.new(result_set, data.fetch("included", []))
        end
      end
    end
  end
end