Allow configuring default priority value at midpoint of range

lib/delayed/priority.rb

@@ -70,7 +70,7 @@ def names=(names)
 
         @ranges = nil
         @alerts = nil
-        @names = names&.sort_by(&:last)&.to_h&.transform_values { |v| new(v) }
+        @names = names_to_default_priority(names)
       end
 
       def alerts=(alerts)
@@ -82,6 +82,15 @@ def alerts=(alerts)
         @alerts = alerts&.sort_by { |k, _| names.keys.index(k) }&.to_h
       end
 
+      def assign_at_midpoint?
+        @assign_at_midpoint || false
+      end
+
+      def assign_at_midpoint=(assign_at_midpoint=false)
+        @assign_at_midpoint = assign_at_midpoint
+        @assign_at_midpoint
+      end
+
       def ranges
         @ranges ||= names.zip(names.except(names.keys.first)).each_with_object({}) do |((name, lower), (_, upper)), obj|
           obj[name] = (lower...(upper || Float::INFINITY))
@@ -91,7 +100,7 @@ def ranges
       private
 
       def default_names
-        @default_names ||= DEFAULT_NAMES.transform_values { |v| new(v) }
+        @default_names ||= names_to_default_priority(DEFAULT_NAMES)
       end
 
       def default_alerts
@@ -109,6 +118,29 @@ def method_missing(method_name, *args)
           super
         end
       end
+
+      def names_to_default_priority(names)
+        return unless names
+
+        names_to_priority = {}
+
+        if assign_at_midpoint?
+          sorted_priorities_by_name = names&.sort_by(&:last)
+          sorted_priorities_by_name.each.with_index do |(name, priority_value), index|
+            if assign_at_midpoint?
+              (_, next_priority_value) = sorted_priorities_by_name[index+1] || [nil, priority_value + 10]
+              midpoint = priority_value + ((next_priority_value - priority_value).to_f/2.0).ceil
+              names_to_priority[name] = new(midpoint)
+            else
+              names_to_priority[name] = new(priority_value)
+            end
+          end
+        else
+          names_to_priority = names.transform_values { |v| new(v) }
+        end
+
+        names_to_priority.sort_by(&:last).to_h
+      end
     end
 
     attr_reader :value

spec/delayed/priority_spec.rb

@@ -3,8 +3,10 @@
 RSpec.describe Delayed::Priority do
   let(:custom_names) { nil }
   let(:custom_alerts) { nil }
+  let(:assign_at_midpoint) { nil }
 
   around do |example|
+    described_class.assign_at_midpoint = assign_at_midpoint
     described_class.names = custom_names
     described_class.alerts = custom_alerts
     example.run
@@ -43,6 +45,17 @@
       expect(described_class.reporting).to eq 30
     end
 
+    context 'when assign_at_midpoint is set to true' do
+      let(:assign_at_midpoint) { true }
+
+      it 'returns the midpoint value' do
+        expect(described_class.interactive).to eq 5
+        expect(described_class.user_visible).to eq 15
+        expect(described_class.eventual).to eq 25
+        expect(described_class.reporting).to eq 35
+      end
+    end
+
     context 'when customized to high, medium, low' do
       let(:custom_names) { { high: 0, medium: 100, low: 500 } }
 
@@ -81,6 +94,16 @@
           )
         end
       end
+
+      context 'when assign_at_midpoint is set to true' do
+        let(:assign_at_midpoint) { true }
+
+        it 'returns the midpoint value' do
+          expect(described_class.high).to eq 50
+          expect(described_class.medium).to eq 300
+          expect(described_class.low).to eq 505
+        end
+      end
     end
   end