import type { TrustedProxyConfig } from "./trusted-proxy.js";

export function requireTrustedProxyHeaderName(
  name: string,
  optionName: string,
): string {
  const header = name.trim();
  if (!header) {
    throw new Error(`${optionName} must be a non-empty header name.`);
  }

  try {
    new Headers().get(header);
  } catch {
    throw new Error(`${optionName} must be a valid HTTP header name.`);
  }

  return header;
}

export function assertValidTrustedProxyConfig(
  config: TrustedProxyConfig,
): void {
  if (!config) return;

  if (config.hostHeader !== undefined && config.hostHeader !== false) {
    requireTrustedProxyHeaderName(config.hostHeader, "trustedProxy.hostHeader");
  }
  if (config.protocolHeader !== undefined && config.protocolHeader !== false) {
    requireTrustedProxyHeaderName(
      config.protocolHeader,
      "trustedProxy.protocolHeader",
    );
  }
  if (typeof config.clientIp === "object") {
    requireTrustedProxyHeaderName(
      config.clientIp.header,
      "trustedProxy.clientIp.header",
    );
  }
}