Make RandomExample/RandomItemGenerator deterministic (use seed)

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 4.1.0
+
+* Add `seed` parameter to `GovukSchemas::RandomExample` to make the random behaviour deterministic. Given the same seed, the same randomised outputs will be returned ([#56](https://github.com/alphagov/govuk_schemas/pull/56)).
+
 # 4.0.1
 
 * Bump the required Ruby version to >= 2.6.x.

govuk_schemas.gemspec

@@ -1,5 +1,3 @@
-# coding: utf-8
-
 lib = File.expand_path("lib", __dir__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require "govuk_schemas/version"

lib/govuk_schemas.rb

@@ -1,6 +1,5 @@
 require "govuk_schemas/version"
 require "govuk_schemas/schema"
-require "govuk_schemas/utils"
 require "govuk_schemas/random_example"
 require "govuk_schemas/document_types"
 require "govuk_schemas/example"

lib/govuk_schemas/random_content_generator.rb

@@ -0,0 +1,126 @@
+module GovukSchemas
+  # @private
+  class RandomContentGenerator
+    WORDS = %w[Lorem ipsum dolor sit amet consectetur adipiscing elit. Ut suscipit at mauris non bibendum. Ut ac massa est. Aenean tempor imperdiet leo vel interdum. Nam sagittis cursus sem ultricies scelerisque. Quisque porttitor risus vel risus finibus eu sollicitudin nisl aliquet. Sed sed lectus ac dolor molestie interdum. Nam molestie pellentesque purus ac vestibulum. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Suspendisse non tempor eros. Mauris eu orci hendrerit volutpat lorem in tristique libero. Duis a nibh nibh.].freeze
+
+    def initialize(random: Random.new)
+      @random = random
+    end
+
+    def string_for_type(type)
+      if type == "date-time"
+        time
+      elsif type == "uri"
+        uri
+      else
+        raise "Unknown attribute type `#{type}`"
+      end
+    end
+
+    def time
+      arbitrary_time = Time.new(2012, 2, 1)
+      (arbitrary_time + @random.rand(0..500_000_000)).iso8601
+    end
+
+    # TODO: make this more random with query string, optional anchor.
+    def uri
+      "http://example.com#{base_path}#{anchor}"
+    end
+
+    def base_path
+      "/" + @random.rand(1..5).times.map { uuid }.join("/")
+    end
+
+    def govuk_subdomain_url
+      subdomain = @random.rand(2..4).times.map {
+        ("a".."z").to_a.sample(@random.rand(3..8), random: @random).join
+      }.join(".")
+      "https://#{subdomain}.gov.uk#{base_path}"
+    end
+
+    def string(minimum_chars = nil, maximum_chars = nil)
+      minimum_chars ||= 0
+      maximum_chars ||= 100
+      WORDS.sample(@random.rand(minimum_chars..maximum_chars), random: @random).join(" ")
+    end
+
+    def bool
+      @random.rand(2) == 1
+    end
+
+    def anchor
+      "##{hex}"
+    end
+
+    def random_identifier(separator:)
+      WORDS.sample(@random.rand(1..10), random: @random)
+        .join("-")
+        .gsub(/[^a-z0-9\-_]+/i, "-")
+        .gsub("-", separator)
+    end
+
+    def uuid
+      # matches uuid regex e.g. e058aad7-ce86-5181-8801-4ddcb3c8f27c
+      # /^[a-f0-9]{8}-[a-f0-9]{4}-[1-5][a-f0-9]{3}-[89ab][a-f0-9]{3}-[a-f0-9]{12}$/
+      "#{hex(8)}-#{hex(4)}-1#{hex(3)}-a#{hex(3)}-#{hex(12)}"
+    end
+
+    def hex(length = 10)
+      length.times.map { bool ? random_letter : random_number }.join("")
+    end
+
+    def string_for_regex(pattern)
+      case pattern.to_s
+      when "^(placeholder|placeholder_.+)$"
+        ["placeholder", "placeholder_#{WORDS.sample(random: @random)}"].sample(random: @random)
+      when "^[a-f0-9]{8}-[a-f0-9]{4}-[1-5][a-f0-9]{3}-[89ab][a-f0-9]{3}-[a-f0-9]{12}$"
+        uuid
+      when "^/(([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})+(/([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)*)?$"
+        base_path
+      when "^[1-9][0-9]{3}[-/](0[1-9]|1[0-2])[-/](0[1-9]|[12][0-9]|3[0-1])$"
+        Date.today.iso8601
+      when "^[1-9][0-9]{3}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[0-1])$"
+        Date.today.iso8601
+      when "^#.+$"
+        anchor
+      when "[a-z-]"
+        random_identifier(separator: "-")
+      when "^[a-z_]+$"
+        random_identifier(separator: "_")
+      when "^/(([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})+(/([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)*)?(\\?([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)?(#([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)?$"
+        base_path
+      when "^https://([a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[A-Za-z0-9])?\\.)+campaign\\.gov\\.uk(/(([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})+(/([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)*)?(\\?([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)?(#([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)?)?$"
+        govuk_subdomain_url
+      when "^https://([a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[A-Za-z0-9])?\\.)*gov\\.uk(/(([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})+(/([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)*)?(\\?([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)?(#([a-zA-Z0-9._~!$&'()*+,;=:@-]|%[0-9a-fA-F]{2})*)?)?$"
+        govuk_subdomain_url
+      when '[a-z0-9\-_]'
+        "#{hex}-#{hex}"
+      else
+        raise <<-DOC
+          Don't know how to generate random string for pattern #{pattern.inspect}
+
+          This propably means you've introduced a new regex in  govuk-content-schemas.
+          Because it's very hard to generate a valid string from a regex alone,
+          we have to specify a method to generate random data for each regex in
+          the schemas.
+
+          To fix this:
+
+          - Add your regex to `lib/govuk_schemas/random.rb`
+        DOC
+      end
+    end
+
+  private
+
+    def random_letter
+      letters = ("a".."f").to_a
+      letters[@random.rand(0..letters.count - 1)]
+    end
+
+    def random_number
+      numbers = ("0".."9").to_a
+      numbers[@random.rand(0..numbers.count - 1)]
+    end
+  end
+end

lib/govuk_schemas/random_example.rb

@@ -1,5 +1,4 @@
-require "govuk_schemas/random"
-require "govuk_schemas/random_item_generator"
+require "govuk_schemas/random_schema_generator"
 require "json-schema"
 require "json"
 
@@ -24,11 +23,17 @@ class RandomExample
     #     schema = GovukSchemas::Schema.find(frontend_schema: "detailed_guide")
     #     GovukSchemas::RandomExample.new(schema: schema).payload
     #
+    # Example with seed (for consistent results):
+    #
+    #     schema = GovukSchemas::Schema.find(frontend_schema: "detailed_guide")
+    #     GovukSchemas::RandomExample.new(schema: schema, seed: 777).payload
+    #     GovukSchemas::RandomExample.new(schema: schema, seed: 777).payload # returns same as above
+    #
     # @param [Hash] schema A JSON schema.
     # @return [GovukSchemas::RandomExample]
-    def initialize(schema:)
+    def initialize(schema:, seed: nil)
       @schema = schema
-      @random_generator = RandomItemGenerator.new(schema: schema)
+      @random_generator = RandomSchemaGenerator.new(schema: schema, seed: seed)
     end
 
     # Returns a new `GovukSchemas::RandomExample` object.