feat: Add a tool to search Linear Issues in copilot (#11518)

This PR adds a tool to search Linear issues. If the integration is
enabled for the account, the tool will return results as expected. Also
introduces support for an `active?` method, which allows third-party
Copilot tools to be conditionally enabled based on the status of the
integration on the account.

enterprise/app/services/captain/tool_registry_service.rb

@@ -9,6 +9,8 @@ class Captain::ToolRegistryService
 
   def register_tool(tool_class)
     tool = tool_class.new(@assistant)
+    return unless tool.active?
+
     @tools[tool.name] = tool
     @registered_tools << tool.to_registry_format
   end

enterprise/app/services/captain/tools/base_service.rb

@@ -31,4 +31,8 @@ class Captain::Tools::BaseService
       }
     }
   end
+
+  def active?
+    true
+  end
 end

enterprise/app/services/captain/tools/copilot/search_linear_issues_service.rb

@@ -0,0 +1,77 @@
+class Captain::Tools::Copilot::SearchLinearIssuesService < Captain::Tools::BaseService
+  def name
+    'search_linear_issues'
+  end
+
+  def description
+    'Search Linear issues based on a search term'
+  end
+
+  def parameters
+    {
+      type: 'object',
+      properties: {
+        term: {
+          type: 'string',
+          description: 'The search term to find Linear issues'
+        }
+      },
+      required: %w[term]
+    }
+  end
+
+  def execute(arguments)
+    return 'Linear integration is not enabled' unless active?
+
+    term = arguments['term']
+
+    Rails.logger.info "#{self.class.name}: Service called with the search term #{term}"
+
+    return 'Missing required parameters' if term.blank?
+
+    linear_service = Integrations::Linear::ProcessorService.new(account: @assistant.account)
+    result = linear_service.search_issue(term)
+
+    return result[:error] if result[:error]
+
+    issues = result[:data]
+    return 'No issues found, I should try another similar search term' if issues.blank?
+
+    total_count = issues.length
+
+    <<~RESPONSE
+      Total number of issues: #{total_count}
+      #{issues.map { |issue| format_issue(issue) }.join("\n---\n")}
+    RESPONSE
+  end
+
+  def active?
+    @assistant.account.hooks.find_by(app_id: 'linear').present?
+  end
+
+  private
+
+  def format_issue(issue)
+    <<~ISSUE
+      Title: #{issue['title']}
+      ID: #{issue['id']}
+      State: #{issue['state']['name']}
+      Priority: #{format_priority(issue['priority'])}
+      #{issue['assignee'] ? "Assignee: #{issue['assignee']['name']}" : 'Assignee: Unassigned'}
+      #{issue['description'].present? ? "\nDescription: #{issue['description']}" : ''}
+    ISSUE
+  end
+
+  def format_priority(priority)
+    return 'No priority' if priority.nil?
+
+    case priority
+    when 0 then 'No priority'
+    when 1 then 'Urgent'
+    when 2 then 'High'
+    when 3 then 'Medium'
+    when 4 then 'Low'
+    else 'Unknown'
+    end
+  end
+end