export const DEFAULT_API_BASE_URL = 'https://webhgcgapi.mfcg.me';
export const UPSTREAM_HOP_HEADER = 'x-91dj-upstream';

export interface ApiRequestContext {
  headers: Pick<Headers, 'get'>;
  url?: string;
}

function configuredApiUrl(): string {
  return (process.env.UPSTREAM_API_URL ?? process.env.API_BASE_URL ?? DEFAULT_API_BASE_URL).trim();
}

export function usesCurrentApiOrigin(): boolean {
  return configuredApiUrl() === 'current';
}

/** Resolve each visitor's origin at request time; never store a request host globally. */
export function getApiBaseUrl(request?: ApiRequestContext): string {
  const value = configuredApiUrl();
  if (value === 'current') {
    const incoming = request?.url ? new URL(request.url) : undefined;
    const host = (request?.headers.get('host') || request?.headers.get('x-forwarded-host')?.split(',')[0] || incoming?.host || '').trim();
    const protocol = (request?.headers.get('x-forwarded-proto')?.split(',')[0] || incoming?.protocol.replace(':', '') || 'https').trim();
    if (!host || /[\s,/\\?#@]/.test(host) || !['http', 'https'].includes(protocol)) throw new Error('当前域名接口模式缺少有效的请求域名或协议');
    const origin = new URL(protocol + '://' + host);
    if (origin.username || origin.password || origin.pathname !== '/' || origin.search || origin.hash) throw new Error('当前域名接口地址无效');
    return origin.origin;
  }
  try {
    const url = new URL(value);
    if (!['http:', 'https:'].includes(url.protocol) || url.username || url.password || url.search || url.hash) throw new Error('Invalid upstream');
    return url.href.replace(/\/+$/, '');
  } catch { throw new Error('UPSTREAM_API_URL 必须是有效的 HTTP(S) 接口地址'); }
}