refactor: load server settings from JSON configuration

tests/server-config.test.ts

@@ -0,0 +1,33 @@
+import assert from 'node:assert/strict';
+import { mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import test from 'node:test';
+import { loadServerConfig } from '../server/config.ts';
+
+test('server and Mongo verifier can load the documented JSON configuration', () => {
+  const example = new URL('../.config.example.json', import.meta.url);
+  const config = loadServerConfig(example);
+  assert.equal(config.port, 3000);
+  assert.equal(config.visitStore, 'mongo');
+  assert.equal(config.mongoDatabase, 'sunrise');
+  assert.ok(config.allowedOrigins.includes('http://127.0.0.1:3000'));
+});
+
+test('missing or invalid configuration fails without exposing its contents', () => {
+  const directory = mkdtempSync(join(tmpdir(), 'sunrise-config-'));
+  const path = join(directory, '.config.json');
+  try {
+    assert.throws(() => loadServerConfig(path), /Cannot read/);
+    writeFileSync(path, '{"mongoUri":"secret",');
+    assert.throws(() => loadServerConfig(path), /^Error: Invalid JSON in .config.json$/);
+    const example = JSON.parse(readFileSync(new URL('../.config.example.json', import.meta.url), 'utf8'));
+    for (const override of [{ port: '3000' }, { port: 65536 }, { host: '' },
+      { allowedOrigins: 'https://example.com' }, { visitStore: 'invalid' }, { mongoUri: null }]) {
+      writeFileSync(path, JSON.stringify({ ...example, ...override }));
+      assert.throws(() => loadServerConfig(path), /Invalid .config.json field/);
+    }
+  } finally {
+    rmSync(directory, { recursive: true, force: true });
+  }
+});