Share behaviour between schema objects

This sets up the ability for shared code between Schema objects and
providing customisation for ones of different OpenAPI versions.

It marks a direction towards modelling the specification of JSON Schema
2020-12 JSON Schema Validation [1] specifically rather trying to
understand how different dialects could be used. My expectation is that
it is very much an edge case that someone would use another dialect and
it seems incredibly hard to consider how they can be supported.

This also has a rename of Schema::OasDialect3_1 to Schema::V3_1.
I don't think we'll ever try to model other dialects so I think it's
best to have a single class to try model the schemas for 3.1 and
hopefully later versions.

[1]: https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-validation-01

WIP

Author: kevindew

json-schema-for-3.1.md

@@ -6,7 +6,7 @@ Things have got complex with schemas in OpenAPI 3.1
 
 How things might work:
 
-- when a schema factory is created, it determines whether the dialect is suported
+- when a schema factory is created, it determines whether the dialect is supported
 - it then creates a factory based on the dialect
 - if there is a reference in it this is resolved
 - there could be complexities in the resolving process because of the id field - does it become relative to this?
@@ -90,3 +90,17 @@ additionalProperties: single json schema
 
 unevaluatedItems - single schema
 unevaluatedProperties: single schema
+
+
+## Returning to this in 2025
+
+Assumption: it'll be extremely rare for usage of the advanced schema fields like dynamicRefs and dynamicAnchors, let's see what we can implement that meets most use cases and hopefully doesn't crash on complex ones
+
+Current idea is create a Schema::Common which can share methods between both schema objects that are shared, then add distinctions for differences
+
+At point of shutting down on 10th January 2025 I was wondering about how schemas merge. I also decided to defer thinking about referenceable node object factory.
+
+I learnt that merging seems largely undefined in JSON Schema, as far as I can tell and I'm just going with a strategy of most recent field wins.
+
+I've set up a Node::Schema class for common schema methods and Node::Schema::v3_0 and v3_1Up classes for specific changes. Need to flesh out
+tests and then behaviour that differs between them

lib/openapi3_parser/node/schema.rb

@@ -1,8 +1,250 @@
 # frozen_string_literal: true
 
+require "openapi3_parser/node/object"
+
 module Openapi3Parser
   module Node
-    module Schema
+    # Base class for common behaviour between Schema objects of different
+    # OpenAPI versions. It is expected to be treated as an abstract class
+    #
+    # rubocop:disable Metrics/ClassLength
+    class Schema < Node::Object
+      # This is used to provide a name for the schema based on it's position in
+      # an OpenAPI document.
+      #
+      # For example it's common to have an OpenAPI document structured like so:
+      # components:
+      #   schemas:
+      #     Product:
+      #       properties:
+      #         product_id:
+      #           type: string
+      #         description:
+      #           type: string
+      #
+      # and there is then implied meaning in the field name of Product, ie
+      # that schema now represents a product. This data is not easily or
+      # consistently made available as it is part of the path to the data
+      # rather than the data itself. Instead the field that would be more
+      # appropriate would be "title" within a schema.
+      #
+      # As this is a common pattern in OpenAPI docs this provides a method
+      # to look up this contextual name of the schema so it can be referenced
+      # when working with the document, it only considers a field to be
+      # name if it is within a group called schemas (as is the case
+      # in #/components/schemas)
+      #
+      # @return [String, nil]
+      def name
+        segments = node_context.source_locations.first.pointer.segments
+        segments[-1] if segments[-2] == "schemas"
+      end
+
+      # @return [String, nil]
+      def title
+        self["title"]
+      end
+
+      # @return [Numeric, nil]
+      def multiple_of
+        self["multipleOf"]
+      end
+
+      # @return [Integer, nil]
+      def maximum
+        self["maximum"]
+      end
+
+      # @return [Boolean]
+      def exclusive_maximum?
+        self["exclusiveMaximum"]
+      end
+
+      # @return [Integer, nil]
+      def minimum
+        self["minimum"]
+      end
+
+      # @return [Boolean]
+      def exclusive_minimum?
+        self["exclusiveMinimum"]
+      end
+
+      # @return [Integer, nil]
+      def max_length
+        self["maxLength"]
+      end
+
+      # @return [Integer]
+      def min_length
+        self["minLength"]
+      end
+
+      # @return [String, nil]
+      def pattern
+        self["pattern"]
+      end
+
+      # @return [Integer, nil]
+      def max_items
+        self["maxItems"]
+      end
+
+      # @return [Integer]
+      def min_items
+        self["minItems"]
+      end
+
+      # @return [Boolean]
+      def unique_items?
+        self["uniqueItems"]
+      end
+
+      # @return [Integer, nil]
+      def max_properties
+        self["maxProperties"]
+      end
+
+      # @return [Integer]
+      def min_properties
+        self["minProperties"]
+      end
+
+      # @return [Node::Array<String>, nil]
+      def required
+        self["required"]
+      end
+
+      # Returns whether a property is a required field or not. Can accept the
+      # property name or a schema
+      #
+      # @param [String, Schema] property
+      # @return [Boolean]
+      def requires?(property)
+        if property.is_a?(self.class)
+          # compare node_context of objects to ensure references aren't treated
+          # as equal - only direct properties of this object will pass.
+          properties.to_h
+                    .select { |k, _| required.to_a.include?(k) }
+                    .any? { |_, schema| schema.node_context == property.node_context }
+        else
+          required.to_a.include?(property)
+        end
+      end
+
+      # @return [Node::Array<Object>, nil]
+      def enum
+        self["enum"]
+      end
+
+      # @return [String, nil]
+      def type
+        self["type"]
+      end
+
+      # @return [Node::Array<Schema>, nil]
+      def all_of
+        self["allOf"]
+      end
+
+      # @return [Node::Array<Schema>, nil]
+      def one_of
+        self["oneOf"]
+      end
+
+      # @return [Node::Array<Schema>, nil]
+      def any_of
+        self["anyOf"]
+      end
+
+      # @return [Schema, nil]
+      def not
+        self["not"]
+      end
+
+      # @return [Schema, nil]
+      def items
+        self["items"]
+      end
+
+      # @return [Map<String, Schema>]
+      def properties
+        self["properties"]
+      end
+
+      # @return [Boolean]
+      def additional_properties?
+        self["additionalProperties"] != false
+      end
+
+      # @return [Schema, nil]
+      def additional_properties_schema
+        properties = self["additionalProperties"]
+        return if [true, false].include?(properties)
+
+        properties
+      end
+
+      # @return [String, nil]
+      def description
+        self["description"]
+      end
+
+      # @return [String, nil]
+      def description_html
+        render_markdown(description)
+      end
+
+      # @return [String, nil]
+      def format
+        self["format"]
+      end
+
+      # @return [Any]
+      def default
+        self["default"]
+      end
+
+      # @return [Boolean]
+      def nullable?
+        self["nullable"]
+      end
+
+      # @return [Discriminator, nil]
+      def discriminator
+        self["discriminator"]
+      end
+
+      # @return [Boolean]
+      def read_only?
+        self["readOnly"]
+      end
+
+      # @return [Boolean]
+      def write_only?
+        self["writeOnly"]
+      end
+
+      # @return [Xml, nil]
+      def xml
+        self["xml"]
+      end
+
+      # @return [ExternalDocumentation, nil]
+      def external_docs
+        self["externalDocs"]
+      end
+
+      # @return [Any]
+      def example
+        self["example"]
+      end
+
+      # @return [Boolean]
+      def deprecated?
+        self["deprecated"]
+      end
     end
+    # rubocop:enable Metrics/ClassLength
   end
 end