feat: add base llm service using rubyllm

enterprise/app/services/llm/base_service.rb

@@ -0,0 +1,24 @@
+class Llm::BaseService
+  DEFAULT_MODEL = 'gpt-4o-mini'.freeze
+
+  def initialize
+    setup_ruby_llm
+    setup_model
+  rescue StandardError => e
+    raise "Failed to initialize LLM client: #{e.message}"
+  end
+
+  private
+
+  def setup_ruby_llm
+    api_key = InstallationConfig.find_by!(name: 'CAPTAIN_OPEN_AI_API_KEY').value
+    ::RubyLLM.configure do |config|
+      config.openai_api_key = api_key
+    end
+  end
+
+  def setup_model
+    config_value = InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_MODEL')&.value
+    @model = (config_value.presence || DEFAULT_MODEL)
+  end
+end

spec/enterprise/services/llm/base_service_spec.rb

@@ -0,0 +1,55 @@
+require 'rails_helper'
+
+RSpec.describe Llm::BaseService do
+  describe '#initialize' do
+    let(:api_key) { 'test-key' }
+    let(:model) { 'custom-model' }
+
+    before do
+      create(:installation_config, name: 'CAPTAIN_OPEN_AI_API_KEY', value: api_key)
+    end
+
+    it 'configures RubyLLM with the API key' do
+      expect(RubyLLM).to receive(:configure) do |&block|
+        config = OpenStruct.new
+        block.call(config)
+        expect(config.openai_api_key).to eq(api_key)
+      end
+
+      described_class.new
+    end
+
+    context 'when API key is missing' do
+      before do
+        InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_API_KEY').destroy
+      end
+
+      it 'raises an error' do
+        expect { described_class.new }.to raise_error(
+          RuntimeError,
+          /Failed to initialize LLM client: Couldn't find InstallationConfig/
+        )
+      end
+    end
+
+    context 'when model config exists' do
+      before do
+        create(:installation_config, name: 'CAPTAIN_OPEN_AI_MODEL', value: model)
+      end
+
+      it 'uses the configured model' do
+        allow(RubyLLM).to receive(:configure)
+        service = described_class.new
+        expect(service.instance_variable_get(:@model)).to eq(model)
+      end
+    end
+
+    context 'when model config is missing' do
+      it 'uses the default model' do
+        allow(RubyLLM).to receive(:configure)
+        service = described_class.new
+        expect(service.instance_variable_get(:@model)).to eq(described_class::DEFAULT_MODEL)
+      end
+    end
+  end
+end