plexus/yaks

module Yaks
  module Reader
    class Hal
      include Util

      def call(parsed_json, _env = {})
        attributes = parsed_json.dup
        links      = convert_links(attributes.delete('_links') || {})
        embedded   = convert_embedded(attributes.delete('_embedded') || {})

        Resource.new(
          type: attributes.delete('type') || type_from_links(links),
          attributes: Util.symbolize_keys(attributes),
          links: links,
          subresources: embedded
        )
      end

      def type_from_links(links)
        profile = links.detect {|l| l.rel?(:profile)}
        profile.uri[/\w+$/] if profile
      end

      def convert_links(links)
        links.flat_map do |rel, link|
          array(link).map do |l|
            options = symbolize_keys(slice_hash(l, 'title', 'templated'))
            # if it looks like a keyword we'll assume it's a registered rel type
            rel = rel.to_sym if rel =~ /\A\w+\z/
            Resource::Link.new(rel: rel, uri: l['href'], options: options)
          end
        end
      end

      def array(x)
        x.instance_of?(Array) ? x : [x]
      end

      def convert_embedded(embedded)
        embedded.flat_map do |rel, resource|
          case resource
          when nil
            NullResource.new
          when Array
            if resource.empty?
              NullResource.new(collection: true)
            else
              CollectionResource.new(
                members: resource.map { |r|
                  call(r).with(type: Util.singularize(rel[/\w+$/]))
                }
              )
            end
          else
            call(resource)
          end.with(rels: [rel])
        end
      end
    end
  end
end