ruby-json-schema/json-schema

require 'json-schema/attribute'
require 'json-schema/errors/schema_error'
require 'json-schema/util/uri'

module JSON
  class Schema
    class RefAttribute < Attribute
      def self.validate(current_schema, data, fragments, processor, validator, options = {})
        uri, schema = get_referenced_uri_and_schema(current_schema.schema, current_schema, validator)

        if schema
          schema.validate(data, fragments, processor, options)
        elsif uri
          message = "The referenced schema '#{uri.to_s}' cannot be found"
          validation_error(processor, message, fragments, current_schema, self, options[:record_errors])
        else
          message = "The property '#{build_fragment(fragments)}' was not a valid schema"
          validation_error(processor, message, fragments, current_schema, self, options[:record_errors])
        end
      end

      def self.get_referenced_uri_and_schema(s, current_schema, validator)
        uri, schema = nil, nil

        temp_uri = JSON::Util::URI.normalize_ref(s['$ref'], current_schema.uri)

        # Grab the parent schema from the schema list
        schema_key = temp_uri.to_s.split('#')[0] + '#'

        ref_schema = JSON::Validator.schema_for_uri(schema_key)

        if ref_schema
          # Perform fragment resolution to retrieve the appropriate level for the schema
          target_schema = ref_schema.schema
          fragments = JSON::Util::URI.parse(JSON::Util::URI.unescape_uri(temp_uri)).fragment.split('/')
          fragment_path = ''
          fragments.each do |fragment|
            if fragment && fragment != ''
              fragment = fragment.gsub('~0', '~').gsub('~1', '/')
              if target_schema.is_a?(Array)
                target_schema = target_schema[fragment.to_i]
              else
                target_schema = target_schema[fragment]
              end
              fragment_path = fragment_path + "/#{fragment}"
              if target_schema.nil?
                raise SchemaError, "The fragment '#{fragment_path}' does not exist on schema #{ref_schema.uri.to_s}"
              end
            end
          end

          # We have the schema finally, build it and validate!
          uri = temp_uri
          schema = JSON::Schema.new(target_schema, temp_uri, validator)
        end

        [uri, schema]
      end
    end
  end
end