Class: Metaschema::JsonSchemaGenerator

Inherits:
Object
  • Object
show all
Defined in:
lib/metaschema/json_schema_generator.rb

Overview

Generates JSON Schema (draft-07) from a parsed Metaschema document.

Usage:

ms = Metaschema::Root.from_xml(File.read("metaschema.xml"))
schema = JsonSchemaGenerator.generate(ms)
puts JSON.pretty_generate(schema)

The generator walks the metaschema definition tree and emits a JSON Schema with a top-level object for each root assembly, and shared $defs for all referenced types.

Constant Summary collapse

SCHEMA_URI = 
"http://json-schema.org/draft-07/schema#"
TYPE_MAP =

Maps metaschema as-type to JSON Schema type.

{
  "string" => { "type" => "string" },
  "markup-line" => { "type" => "string" },
  "markup-multiline" => { "type" => "string" },
  "boolean" => { "type" => "boolean" },
  "integer" => { "type" => "integer" },
  "positive-integer" => { "type" => "integer", "minimum" => 1 },
  "non-negative-integer" => { "type" => "integer", "minimum" => 0 },
  "decimal" => { "type" => "number" },
  "date" => { "type" => "string", "format" => "date" },
  "date-time" => { "type" => "string", "format" => "date-time" },
  "dateTime" => { "type" => "string", "format" => "date-time" },
  "dateTime-with-timezone" => { "type" => "string",
                                "format" => "date-time" },
  "uri" => { "type" => "string", "format" => "uri" },
  "uri-reference" => { "type" => "string" },
  "uuid" => { "type" => "string",
              "pattern" => "^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$" },
  "base64" => { "type" => "string", "contentEncoding" => "base64" },
  "token" => { "type" => "string" },
  "email" => { "type" => "string", "format" => "email" },
  "ip-v4-address" => { "type" => "string", "format" => "ipv4" },
  "ip-v6-address" => { "type" => "string", "format" => "ipv6" },
}.freeze

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(metaschema, id: nil) ⇒ JsonSchemaGenerator

Returns a new instance of JsonSchemaGenerator.



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# File 'lib/metaschema/json_schema_generator.rb', line 49

def initialize(metaschema, id: nil)
  @metaschema = metaschema
  @id = id
  @definitions = {}
  @field_defs = {}
  @assembly_defs = {}
  @flag_defs = {}
end

Class Method Details

.generate(metaschema, id: nil) ⇒ Object 



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# File 'lib/metaschema/json_schema_generator.rb', line 45

def self.generate(metaschema, id: nil)
  new(metaschema, id: id).generate
end

Instance Method Details

#generate ⇒ Object 



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# File 'lib/metaschema/json_schema_generator.rb', line 58

def generate
  collect_definitions

  @metaschema.define_assembly&.each { |a| build_assembly_schema(a) }
  @metaschema.define_field&.each { |f| build_field_def_schema(f) }
  @metaschema.define_flag&.each { |f| build_flag_schema(f) }

  root_assemblies = (@metaschema.define_assembly || []).select do |a|
    a.root_name&.content
  end
  if root_assemblies.one?
    root = root_assemblies.first
    root_name = root.root_name.content
    @definitions[root.name] || { "type" => "object" }

    schema = {
      "$schema" => SCHEMA_URI,
      "$id" => @id,
      "type" => "object",
      "properties" => { root_name => { "$ref" => "#/$defs/#{root.name}" } },
      "required" => [root_name],
      "additionalProperties" => false,
      "$defs" => @definitions,
    }
    schema.delete("$id") unless @id
    schema
  else
    {
      "$schema" => SCHEMA_URI,
      "$id" => @id,
      "$defs" => @definitions,
    }.compact
  end
end