Challenge 1: Type process.env — Possible Solution
====================================================================

import { z } from "zod";

const ConfigSchema = z.object({
  NODE_ENV: z.enum(["development", "production", "test"]),
  PORT: z.coerce.number().int().positive(),
  LOG_LEVEL: z.enum(["debug", "info", "warn", "error"]),
});

type Config = z.infer<typeof ConfigSchema>;

// Example: given these environment variables —
//   NODE_ENV=production
//   PORT=8080
//   LOG_LEVEL=warn
// ConfigSchema.parse(process.env) returns:
//   { NODE_ENV: "production", PORT: 8080, LOG_LEVEL: "warn" }
// Note PORT is the *number* 8080, not the string "8080".

// A quick manual check without needing real env vars:
const parsed = ConfigSchema.parse({
  NODE_ENV: "production",
  PORT: "8080",   // strings are exactly what process.env actually gives you
  LOG_LEVEL: "warn",
});

console.log(typeof parsed.PORT); // "number"
console.log(parsed.LOG_LEVEL);   // "warn"

// Passing an invalid LOG_LEVEL throws immediately:
// ConfigSchema.parse({ NODE_ENV: "production", PORT: "8080", LOG_LEVEL: "verbose" });
// -> ZodError: Invalid enum value. Expected 'debug' | 'info' | 'warn' | 'error', received 'verbose'

WHY THIS WORKS
--------------
- z.coerce.number() converts the string "8080" into the number 8080 as part
  of validation — no separate parseInt() call needed, and it still rejects
  genuinely non-numeric strings like "abc".
- z.enum([...]) restricts LOG_LEVEL to exactly the four allowed literal
  strings — a typo like "wran" fails validation instead of silently being
  accepted as a string.
- `type Config = z.infer<typeof ConfigSchema>` means Config always matches
  the schema exactly — there's no second, hand-written interface that could
  drift out of sync with what's actually validated.