feat: add assignment service

spec/services/auto_assignment/assignment_service_fair_distribution_spec.rb

@@ -0,0 +1,126 @@
+require 'rails_helper'
+
+RSpec.describe AutoAssignment::AssignmentService do
+  let(:account) { create(:account) }
+  let(:inbox) do
+    create(:inbox,
+           account: account,
+           enable_auto_assignment: true,
+           auto_assignment_config: {
+             'fair_distribution_limit' => 2,
+             'fair_distribution_window' => 3600
+           })
+  end
+  let(:service) { described_class.new(inbox: inbox) }
+  let(:agent1) { create(:user, account: account, role: :agent, availability: :online) }
+  let(:agent2) { create(:user, account: account, role: :agent, availability: :online) }
+
+  before do
+    create(:inbox_member, inbox: inbox, user: agent1)
+    create(:inbox_member, inbox: inbox, user: agent2)
+    allow(OnlineStatusTracker).to receive(:get_available_users)
+      .and_return({
+                    agent1.id.to_s => 'online',
+                    agent2.id.to_s => 'online'
+                  })
+    # Clean up Redis keys for this inbox
+    clean_redis_keys
+  end
+
+  after do
+    clean_redis_keys
+  end
+
+  def clean_redis_keys
+    # Clean up assignment keys for both agents
+    pattern1 = "assignment:#{inbox.id}:agent:#{agent1.id}:*"
+    pattern2 = "assignment:#{inbox.id}:agent:#{agent2.id}:*"
+
+    Redis::Alfred.scan_each(match: pattern1) { |key| Redis::Alfred.delete(key) }
+    Redis::Alfred.scan_each(match: pattern2) { |key| Redis::Alfred.delete(key) }
+  end
+
+  def create_test_conversation
+    conversation = build(:conversation, inbox: inbox, assignee: nil, status: :open)
+    allow(conversation).to receive(:run_auto_assignment).and_return(nil)
+    conversation.save!
+    conversation
+  end
+
+  describe 'with fair distribution enabled' do
+    it 'respects the assignment limit per agent' do
+      # Each agent can handle 2 conversations
+      conversations = Array.new(4) { create_test_conversation }
+
+      # First 4 conversations should be assigned (2 per agent)
+      conversations.each do |conv|
+        expect(service.perform_for_conversation(conv)).to be true
+      end
+
+      # Verify distribution
+      assigned_to_agent1 = conversations.count { |c| c.reload.assignee == agent1 }
+      assigned_to_agent2 = conversations.count { |c| c.reload.assignee == agent2 }
+
+      expect(assigned_to_agent1).to eq(2)
+      expect(assigned_to_agent2).to eq(2)
+
+      # Fifth conversation should fail (both agents at limit)
+      fifth_conversation = create_test_conversation
+      expect(service.perform_for_conversation(fifth_conversation)).to be false
+      expect(fifth_conversation.reload.assignee).to be_nil
+    end
+
+    it 'tracks assignments using individual Redis keys' do
+      conversation = create_test_conversation
+      service.perform_for_conversation(conversation)
+
+      # Check that assignment key exists
+      pattern = "assignment:#{inbox.id}:agent:#{conversation.reload.assignee.id}:*"
+      count = Redis::Alfred.keys_count(pattern)
+      expect(count).to eq(1)
+    end
+
+    it 'allows new assignments after window expires' do
+      # Assign 2 conversations to agent1
+      2.times do
+        conversation = create_test_conversation
+        allow(service).to receive(:round_robin_selector).and_return(
+          instance_double(AutoAssignment::RoundRobinSelector, select_agent: agent1)
+        )
+        service.perform_for_conversation(conversation)
+      end
+
+      # Agent1 is now at limit
+      rate_limiter = AutoAssignment::RateLimiter.new(inbox: inbox, agent: agent1)
+      expect(rate_limiter.within_limit?).to be false
+
+      # Clear Redis keys to simulate time window expiry
+      clean_redis_keys
+
+      # Agent1 should be available again
+      expect(rate_limiter.within_limit?).to be true
+
+      # New assignment should work
+      new_conversation = create_test_conversation
+      allow(service).to receive(:round_robin_selector).and_return(
+        instance_double(AutoAssignment::RoundRobinSelector, select_agent: agent1)
+      )
+      expect(service.perform_for_conversation(new_conversation)).to be true
+    end
+  end
+
+  describe 'without fair distribution' do
+    before do
+      inbox.update!(auto_assignment_config: {})
+    end
+
+    it 'assigns without limits' do
+      # Create more conversations than would be allowed with limits
+      5.times do
+        conversation = create_test_conversation
+        expect(service.perform_for_conversation(conversation)).to be true
+        expect(conversation.reload.assignee).not_to be_nil
+      end
+    end
+  end
+end