Added model contract

Necessary to validate the HTTP response from the Core server.

Milestone: minor

lib/trmnl/api/contracts/model.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+require "dry/schema"
+
+module TRMNL
+  module API
+    module Contracts
+      # Validates API response.
+      Model = Dry::Schema.JSON do
+        required(:data).array(:hash) do
+          required(:name).filled :string
+          required(:label).filled :string
+          required(:description).filled :string
+          required(:colors).filled :integer
+          required(:bit_depth).filled :integer
+          required(:scale_factor) { filled? > int? | float? }
+          required(:rotation).filled :integer
+          required(:mime_type).filled :string
+          required(:width).filled :integer
+          required(:height).filled :integer
+          required(:offset_x).filled :integer
+          required(:offset_y).filled :integer
+          required(:published_at).filled :time
+        end
+      end
+    end
+  end
+end

spec/lib/trmnl/api/contracts/model_spec.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+RSpec.describe TRMNL::API::Contracts::Model do
+  subject(:contract) { described_class }
+
+  let :payload do
+    {
+      name: "test",
+      label: "Test",
+      description: "A test.",
+      colors: 2,
+      bit_depth: 1,
+      scale_factor: 1,
+      rotation: 90,
+      mime_type: "image/png",
+      width: 800,
+      height: 480,
+      offset_x: 10,
+      offset_y: 15,
+      published_at: "2025-07-16T18:18:11+00:00"
+    }
+  end
+
+  describe "#call" do
+    it "validates scale factor is an integer" do
+      expect(contract.call(data: [payload]).to_monad).to be_success
+    end
+
+    it "checks scale factor is a float" do
+      payload[:scale_factor] = 1.5
+      expect(contract.call(data: [payload]).to_monad).to be_success
+    end
+
+    it "answers failure when scale factor is missing" do
+      payload.delete :scale_factor
+
+      expect(contract.call(data: [payload]).errors.to_h).to eq(
+        data: {
+          0 => {
+            scale_factor: ["is missing"]
+          }
+        }
+      )
+    end
+  end
+end