env.ts

/**
 * Environment + origin resolution.
 *
 * This is the single source of truth for two SEO-critical environment facts:
 *
 *   1. Which deployment environment we are in (production | preview | development).
 *   2. The canonical origin to use when building absolute URLs.
 *
 * Why it lives in one place: a preview/staging deploy must *never* emit
 * production canonicals or get indexed. Centralizing the lookup means the
 * canonical builder, sitemap, robots route, and `proxy.ts` all agree.
 *
 * Everything reads `process.env` at call time (not module load) so the values
 * can be overridden per-process at runtime (e.g. `DEPLOY_ENV=preview next start`)
 * and so unit tests can set `process.env.SITE_ORIGIN` before exercising the code.
 */

export type DeployEnv = 'production' | 'preview' | 'development';

/**
 * Default origins per environment. These are illustrative placeholders — a
 * real deployment sets `SITE_ORIGIN` explicitly (see {@link getSiteOrigin}).
 */
export const DEFAULT_ORIGINS: Record<DeployEnv, string> = {
  production: 'https://www.example.com',
  preview: 'https://preview.example.com',
  development: 'http://localhost:3000',
};

/**
 * Resolve the current deployment environment.
 *
 * Honors an explicit `DEPLOY_ENV`, then Vercel's `VERCEL_ENV`, then falls back
 * to `NODE_ENV` (production build => production, otherwise development).
 */
export function getDeployEnv(): DeployEnv {
  const raw = (process.env.DEPLOY_ENV ?? process.env.VERCEL_ENV)?.trim();
  if (raw === 'production' || raw === 'preview' || raw === 'development') {
    return raw;
  }
  return process.env.NODE_ENV === 'production' ? 'production' : 'development';
}

/** True only in the production environment. Drives noindex + robots behavior. */
export function isProduction(): boolean {
  return getDeployEnv() === 'production';
}

/** The default origin for the current environment, ignoring `SITE_ORIGIN`. */
export function resolveDefaultOrigin(): string {
  return DEFAULT_ORIGINS[getDeployEnv()];
}

/**
 * Normalize an origin string to a bare `scheme://host[:port]` with no trailing
 * slash. Returns null if the value is not a valid http/https URL.
 */
function normalizeOrigin(value: string): string | null {
  let parsed: URL;
  try {
    parsed = new URL(value);
  } catch {
    return null;
  }
  if (parsed.protocol !== 'http:' && parsed.protocol !== 'https:') {
    return null;
  }
  return parsed.origin;
}

/**
 * The canonical origin for absolute URLs.
 *
 * Prefers an explicit, valid `SITE_ORIGIN`; otherwise falls back to the
 * environment default. The result never has a trailing slash.
 */
export function getSiteOrigin(): string {
  const explicit = process.env.SITE_ORIGIN?.trim();
  if (explicit) {
    const normalized = normalizeOrigin(explicit);
    if (normalized) return normalized;
  }
  // Fall back to the environment default (also normalized for safety).
  return normalizeOrigin(resolveDefaultOrigin()) ?? DEFAULT_ORIGINS.development;
}