chore(config): centralize feature settings

lib/config/environment.ts

@@ -0,0 +1,52 @@
+import { z } from "zod";
+
+const nonEmptyString = z.string().trim().min(1);
+const urlString = z.url();
+
+export type Environment = Record<string, string | undefined>;
+
+export function requiredEnvironmentValue(
+  name: string,
+  environment: Environment = process.env,
+) {
+  const parsed = nonEmptyString.safeParse(environment[name]);
+  if (!parsed.success) {
+    throw new Error(`Missing required environment variable: ${name}`);
+  }
+  return parsed.data;
+}
+
+export function optionalEnvironmentValue(
+  name: string,
+  environment: Environment = process.env,
+) {
+  const parsed = nonEmptyString.safeParse(environment[name]);
+  return parsed.success ? parsed.data : null;
+}
+
+export function requiredEnvironmentUrl(
+  name: string,
+  environment: Environment = process.env,
+) {
+  const value = requiredEnvironmentValue(name, environment);
+  const parsed = urlString.safeParse(value);
+  if (!parsed.success) {
+    throw new Error(`Environment variable ${name} must be an absolute URL`);
+  }
+  return parsed.data.replace(/\/$/, "");
+}
+
+export function readFeatureEnvironment<Names extends readonly string[]>(
+  feature: string,
+  names: Names,
+  environment: Environment = process.env,
+): { [Name in Names[number]]: string } {
+  try {
+    return Object.fromEntries(
+      names.map((name) => [name, requiredEnvironmentValue(name, environment)]),
+    ) as { [Name in Names[number]]: string };
+  } catch (error) {
+    const message = error instanceof Error ? error.message : "Invalid configuration";
+    throw new Error(`${feature} is not configured: ${message}`, { cause: error });
+  }
+}