Abstract out Mine Density Validation for Custom Games

Reek prompted me to take this action, with its warning about
Board::Settings having too many methods. This is definitely a good chunk
of logic that is related to Board::Settings, but isn't core to it. i.e.
SRP was being violated before. This also just helps reduce the class
size + cognitive load of opening this file, so I'm in.

Also:
- Reorganize Board::Settings' methods a bit into a more sensible order
  (for me, as of now :P)
- Add a couple of missing tests to Board::SettingsTest

app/models/board/settings.rb

@@ -56,8 +56,8 @@ class Board::Settings
               allow_blank: true,
             }
 
-  unless App.dev_mode? # rubocop:disable Style/IfUnlessModifier
-    validate :validate_mine_density, if: :custom?
+  unless App.dev_mode?
+    validates_with(Board::Settings::MineDensityValidator, if: :custom?)
   end
 
   def self.preset(type)
@@ -66,14 +66,6 @@ def self.preset(type)
     new(type:, **settings_for(type))
   end
 
-  def self.random
-    if Pattern.none? || PercentChance.(PERCENT_CHANCE_FOR_RANDOM_PRESET)
-      preset(PRESETS.keys.sample)
-    else # 10% of the time:
-      random_pattern
-    end
-  end
-
   def self.beginner = new(**settings_for("Beginner"))
   def self.intermediate = new(**settings_for("Intermediate"))
   def self.expert = new(**settings_for("Expert"))
@@ -84,15 +76,12 @@ def self.settings_for(type)
   end
   private_class_method :settings_for
 
-  # Custom Settings: See {RANGES}.
-  def self.custom(**) = new(type: Game::CUSTOM_TYPE, **)
-
-  # Shortcut for Custom Settings: See {RANGES}.
-  #
-  # @example
-  #   Board::Settings[12, 20, 30]
-  def self.[](*args)
-    custom(width: args[0], height: args[1], mines: args[2])
+  def self.random
+    if Pattern.none? || PercentChance.(PERCENT_CHANCE_FOR_RANDOM_PRESET)
+      preset(PRESETS.keys.sample)
+    else # 10% of the time:
+      random_pattern
+    end
   end
 
   def self.random_pattern
@@ -110,13 +99,24 @@ def self.pattern(name)
       mines: pattern.mines)
   end
 
+  # Custom Settings: See {RANGES}.
+  def self.custom(**) = new(type: Game::CUSTOM_TYPE, **)
+
+  # Shortcut for Custom Settings: See {RANGES}.
+  #
+  # @example
+  #   Board::Settings[12, 20, 30]
+  def self.[](*args)
+    custom(width: args[0], height: args[1], mines: args[2])
+  end
+
+  def pattern? = type == Game::PATTERN_TYPE
+  def custom? = type == Game::CUSTOM_TYPE
+
   def to_s = type
   def to_h = { type:, name:, width:, height:, mines: }.tap(&:compact!)
-  def to_a = to_h.values
   def as_json = to_h
-
-  def custom? = type == Game::CUSTOM_TYPE
-  def pattern? = type == Game::PATTERN_TYPE
+  def to_a = to_h.values
 
   private
 
@@ -125,38 +125,4 @@ def inspect_identification = identify(:width, :height, :mines)
   def inspect_name
     pattern? ? "#{type} (#{name.inspect})" : type
   end
-
-  def validate_mine_density
-    return if errors.any?
-
-    if too_sparse?
-      errors.add(
-        :mines,
-        "must be >= #{minimum_mines} "\
-        "(#{minimum_density_percentage} of total area)")
-    end
-
-    if too_dense?
-      errors.add(
-        :mines,
-        "must be <= #{maximum_mines} (#{maximum_density} of total area)")
-    end
-  end
-
-  def area = width * height
-  def density = mines / area.to_f
-
-  def too_sparse? = density < minimum_density
-  def minimum_mines = (area * minimum_density).ceil
-  def minimum_density = RANGES[:mine_density].begin
-  def minimum_density_percentage = to_percentage(minimum_density * 100.0)
-
-  def too_dense? = density > maximum_density
-  def maximum_mines = (area * maximum_density).floor
-  def maximum_density = RANGES[:mine_density].end
-
-  def to_percentage(number, precision: 0, **)
-    ActiveSupport::NumberHelper::NumberToPercentageConverter.convert(
-      number, precision:, **)
-  end
 end

app/models/board/settings/mine_density_validator.rb

@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+# Board::Settings::MineDensityValidator validates Mine Density limits on Custom
+# {Game}s.
+class Board::Settings::MineDensityValidator < ActiveModel::Validator
+  # :reek:UtilityFunction
+  def validate(settings)
+    Validate.(settings)
+  end
+
+  # Board::Settings::MineDensityValidator::Validate performs the actual
+  # Validation for {Board::Settings::MineDensityValidator}.
+  class Validate
+    include CallMethodBehaviors
+
+    def initialize(settings)
+      @settings = settings
+    end
+
+    def call
+      return if errors.any?
+
+      if too_sparse?
+        errors.add(
+          :mines,
+          "must be >= #{minimum_mines} "\
+          "(#{minimum_density_percentage} of total area)")
+      end
+
+      if too_dense?
+        errors.add(
+          :mines,
+          "must be <= #{maximum_mines} (#{maximum_density} of total area)")
+      end
+    end
+
+    private
+
+    attr_reader :settings
+
+    def errors = settings.errors
+
+    def area = settings.width * settings.height
+    def density = settings.mines / area.to_f
+
+    def too_sparse? = density < minimum_density
+    def minimum_mines = (area * minimum_density).ceil
+    def minimum_density = Board::Settings::RANGES[:mine_density].begin
+    def minimum_density_percentage = to_percentage(minimum_density * 100.0)
+
+    def too_dense? = density > maximum_density
+    def maximum_mines = (area * maximum_density).floor
+    def maximum_density = Board::Settings::RANGES[:mine_density].end
+
+    def to_percentage(number, precision: 0, **)
+      ActiveSupport::NumberHelper::NumberToPercentageConverter.convert(
+        number, precision:, **)
+    end
+  end
+end

test/models/board/settings_test.rb

@@ -301,6 +301,26 @@ class Board::SettingsTest < ActiveSupport::TestCase
       end
     end
 
+    describe "#name" do
+      subject { unit_class.beginner }
+
+      context "GIVEN a preset" do
+        subject { unit_class.beginner }
+
+        it "returns nil" do
+          _(subject.name).must_be_nil
+        end
+      end
+
+      context "GIVEN a pattern" do
+        subject { unit_class.pattern("Test Pattern 1") }
+
+        it "returns the expected String" do
+          _(subject.name).must_equal("Test Pattern 1")
+        end
+      end
+    end
+
     describe "#width" do
       subject { unit_class.beginner }
 
@@ -327,34 +347,39 @@ class Board::SettingsTest < ActiveSupport::TestCase
       end
     end
 
-    describe "#to_h" do
+    describe "#custom?" do
       context "GIVEN a preset" do
         subject { unit_class.beginner }
 
-        it "returns the expected Hash" do
-          _(subject.to_h).must_equal(
-            { type: "Beginner", width: 9, height: 9, mines: 10 })
+        it "returns false" do
+          _(subject.custom?).must_equal(false)
         end
       end
 
       context "GIVEN custom attributes" do
         subject { unit_class[6, 6, 9] }
 
-        describe "#to_h" do
-          it "returns the expected Hash" do
-            _(subject.to_h).must_equal(
-              { type: "Custom", width: 6, height: 6, mines: 9 })
-          end
+        it "returns true" do
+          _(subject.custom?).must_equal(true)
         end
       end
     end
 
-    describe "#as_json" do
-      subject { unit_class.beginner }
+    describe "#pattern?" do
+      context "GIVEN a preset" do
+        subject { unit_class.beginner }
 
-      it "returns the expected Hash" do
-        _(subject.as_json).must_equal(
-          { type: "Beginner", width: 9, height: 9, mines: 10 })
+        it "returns false" do
+          _(subject.pattern?).must_equal(false)
+        end
+      end
+
+      context "GIVEN a pattern" do
+        subject { unit_class.pattern("Test Pattern 1") }
+
+        it "returns true" do
+          _(subject.pattern?).must_equal(true)
+        end
       end
     end
 
@@ -376,22 +401,35 @@ class Board::SettingsTest < ActiveSupport::TestCase
       end
     end
 
-    describe "#custom?" do
+    describe "#to_h" do
       context "GIVEN a preset" do
         subject { unit_class.beginner }
 
-        it "returns false" do
-          _(subject.custom?).must_equal(false)
+        it "returns the expected Hash" do
+          _(subject.to_h).must_equal(
+            { type: "Beginner", width: 9, height: 9, mines: 10 })
         end
       end
 
       context "GIVEN custom attributes" do
         subject { unit_class[6, 6, 9] }
 
-        it "returns true" do
-          _(subject.custom?).must_equal(true)
+        describe "#to_h" do
+          it "returns the expected Hash" do
+            _(subject.to_h).must_equal(
+              { type: "Custom", width: 6, height: 6, mines: 9 })
+          end
         end
       end
     end
+
+    describe "#as_json" do
+      subject { unit_class.beginner }
+
+      it "returns the expected Hash" do
+        _(subject.as_json).must_equal(
+          { type: "Beginner", width: 9, height: 9, mines: 10 })
+      end
+    end
   end
 end