feat: config loader with calibration validation

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/config.test.ts

@@ -0,0 +1,43 @@
+import { describe, it, expect, vi, afterEach } from 'vitest';
+import { loadConfig, DEFAULT_RENDER } from './config';
+
+function mockFetch(body: unknown, ok = true) {
+  vi.stubGlobal('fetch', vi.fn().mockResolvedValue({
+    ok,
+    json: () => Promise.resolve(body),
+  }));
+}
+
+afterEach(() => vi.unstubAllGlobals());
+
+describe('loadConfig', () => {
+  it('loads stream URL and fills render defaults', async () => {
+    mockFetch({ streamUrl: 'http://cam/stream' });
+    const cfg = await loadConfig('config.json');
+    expect(cfg.streamUrl).toBe('http://cam/stream');
+    expect(cfg.renderDefaults).toEqual(DEFAULT_RENDER);
+    expect(cfg.calibration).toBeNull();
+  });
+
+  it('keeps a valid calibration', async () => {
+    const calibration = {
+      imagePoints: [[0, 0], [1, 0], [1, 1], [0, 1]],
+      machinePoints: [[0, 0], [1, 0], [1, 1], [0, 1]],
+      homography: [1, 0, 0, 0, 1, 0, 0, 0, 1],
+    };
+    mockFetch({ streamUrl: 'x', calibration });
+    const cfg = await loadConfig('config.json');
+    expect(cfg.calibration).toEqual(calibration);
+  });
+
+  it('drops a malformed calibration to null', async () => {
+    mockFetch({ streamUrl: 'x', calibration: { homography: [1, 2, 3] } });
+    const cfg = await loadConfig('config.json');
+    expect(cfg.calibration).toBeNull();
+  });
+
+  it('throws when the request fails', async () => {
+    mockFetch({}, false);
+    await expect(loadConfig('config.json')).rejects.toThrow();
+  });
+});

src/config.ts

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+import type { AppConfig, Calibration, Mat3, Vec2 } from './types';
+
+export const DEFAULT_RENDER = { cutColor: '#00e5ff', rapidColor: '#ff9800', lineWidth: 1.5 };
+
+function isVec2Array(v: unknown): v is Vec2[] {
+  return Array.isArray(v) && v.every((p) => Array.isArray(p) && p.length === 2 && p.every((n) => typeof n === 'number'));
+}
+
+function parseCalibration(c: unknown): Calibration | null {
+  if (!c || typeof c !== 'object') return null;
+  const obj = c as Record<string, unknown>;
+  if (!isVec2Array(obj.imagePoints) || !isVec2Array(obj.machinePoints)) return null;
+  if (!Array.isArray(obj.homography) || obj.homography.length !== 9) return null;
+  if (!obj.homography.every((n) => typeof n === 'number')) return null;
+  if (obj.imagePoints.length !== obj.machinePoints.length || obj.imagePoints.length < 4) return null;
+  return {
+    imagePoints: obj.imagePoints,
+    machinePoints: obj.machinePoints,
+    homography: obj.homography as Mat3,
+  };
+}
+
+export async function loadConfig(url: string): Promise<AppConfig> {
+  const res = await fetch(url);
+  if (!res.ok) throw new Error(`Failed to load ${url}: ${res.status}`);
+  const raw = (await res.json()) as Record<string, unknown>;
+  return {
+    streamUrl: typeof raw.streamUrl === 'string' ? raw.streamUrl : '',
+    calibration: parseCalibration(raw.calibration),
+    renderDefaults: { ...DEFAULT_RENDER, ...(raw.renderDefaults as object | undefined) },
+  };
+}