feat: Implement basic general folder support (#2051)

- Related: #1748

tests/ha/entity-state-translation.test.ts

@@ -0,0 +1,88 @@
+import { describe, expect, it, vi } from 'vitest';
+import { getEntityStateTranslation } from '../../src/ha/entity-state-translation';
+import { createHASS, createRegistryEntity, createStateEntity } from '../test-utils';
+
+describe('getEntityStateTranslation', () => {
+  it('returns null if state is missing', () => {
+    expect(getEntityStateTranslation(createHASS(), 'light.office')).toBeNull();
+  });
+
+  it('returns translation_key translation if available', () => {
+    const entity = createRegistryEntity({
+      entity_id: 'light.office',
+      translation_key: 'translation_key',
+    });
+    const hass = createHASS({
+      'light.office': createStateEntity({
+        state: 'on',
+        attributes: {},
+      }),
+    });
+    vi.mocked(hass.localize).mockReturnValue('Translated State');
+
+    expect(getEntityStateTranslation(hass, 'light.office', { entity })).toBe(
+      'Translated State',
+    );
+  });
+
+  it('returns device_class translation if translation_key not available', () => {
+    const entity = createRegistryEntity({
+      entity_id: 'light.office',
+    });
+    const hass = createHASS({
+      'light.office': createStateEntity({
+        state: 'on',
+        attributes: {
+          device_class: 'light',
+        },
+      }),
+    });
+    vi.mocked(hass.localize).mockReturnValue('Translated State');
+
+    expect(getEntityStateTranslation(hass, 'light.office', { entity })).toBe(
+      'Translated State',
+    );
+  });
+
+  it('returns default translation if translation_key not available', () => {
+    const entity = createRegistryEntity({
+      entity_id: 'light.office',
+    });
+    const hass = createHASS({
+      'light.office': createStateEntity({
+        state: 'on',
+      }),
+    });
+    vi.mocked(hass.localize).mockReturnValue('Translated State');
+
+    expect(getEntityStateTranslation(hass, 'light.office', { entity })).toBe(
+      'Translated State',
+    );
+  });
+
+  it('returns raw state if no translation found', () => {
+    const entity = createRegistryEntity({
+      entity_id: 'light.office',
+    });
+    const hass = createHASS({
+      'light.office': createStateEntity({
+        state: 'on',
+      }),
+    });
+    vi.mocked(hass.localize).mockReturnValue('');
+
+    expect(getEntityStateTranslation(hass, 'light.office', { entity })).toBe('on');
+  });
+
+  it('uses passed in state', () => {
+    const entity = createRegistryEntity({
+      entity_id: 'light.office',
+    });
+    const hass = createHASS();
+    vi.mocked(hass.localize).mockReturnValue('');
+
+    expect(
+      getEntityStateTranslation(hass, 'light.office', { entity, state: 'off' }),
+    ).toBe('off');
+  });
+});