Added current screen endpoint

Necessary to handle the request and response to the current screen API endpoint.

lib/trmnl/api/endpoints/current_screen.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require "pipeable"
+
+module TRMNL
+  module API
+    module Endpoints
+      # Handles API request/response.
+      class CurrentScreen
+        include Dependencies[
+          :client,
+          contract: "contracts.current_screen",
+          model: "models.current_screen"
+        ]
+
+        include Pipeable
+
+        def call token:
+          pipe client.get("current_screen", headers: {"Access-Token" => token}),
+               try(:parse, catch: JSON::ParserError),
+               validate(contract, as: :to_h),
+               to(model, :for)
+        end
+      end
+    end
+  end
+end

spec/lib/trmnl/api/endpoints/current_screen_spec.rb

@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+RSpec.describe TRMNL::API::Endpoints::CurrentScreen do
+  subject(:endpoint) { described_class.new client: }
+
+  include_context "with application dependencies"
+
+  let(:client) { TRMNL::API::Client.new http: }
+
+  describe "#call" do
+    context "with success" do
+      let :http do
+        HTTP::Fake::Client.new do
+          get "/api/current_screen" do
+            headers["Content-Type"] = "application/json"
+            status 200
+
+            <<~JSON
+              {
+                "status": 200,
+                "refresh_rate": 3200,
+                "image_url": "https://test.io/images/test.bmp",
+                "filename": "test.bmp",
+                "rendered_at": null
+              }
+            JSON
+          end
+        end
+      end
+
+      it "answers success" do
+        result = endpoint.call token: "secret"
+
+        expect(result).to be_success(
+          TRMNL::API::Models::CurrentScreen[
+            refresh_rate: 3200,
+            image_url: "https://test.io/images/test.bmp",
+            filename: "test.bmp"
+          ]
+        )
+      end
+    end
+
+    context "with failure" do
+      let :http do
+        HTTP::Fake::Client.new do
+          get "/api/current_screen" do
+            headers["Content-Type"] = "application/json"
+            status 404
+
+            <<~JSON
+              {"error": "Danger!"}
+            JSON
+          end
+        end
+      end
+
+      it "answers error response" do
+        result = described_class.new(client:).call token: "secret"
+        expect(result).to match(Failure(be_a(HTTP::Response)))
+      end
+    end
+  end
+end