/**
 * Contract Headers - Dynamic Version & Canonical Fingerprint
 * 
 * NO HARDCODING: Version comes from package.json, fingerprint from canonical schemas
 */

import { createHash } from "crypto";
import pkg from "../package.json";

/**
 * Emit contract headers with dynamic version and fingerprint
 * SINGLE SOURCE OF TRUTH: No hardcoded values
 */
export function emitContractHeaders(): Record<string, string> {
  const version = pkg.version; // <- Single source of truth from package.json
  
  // Try to get fingerprint from generated file, fallback to package version
  let fingerprint: string;
  try {
    const { CONTRACTS_FINGERPRINT } = require('./fingerprint');
    fingerprint = CONTRACTS_FINGERPRINT;
  } catch {
    // Fallback during development/testing before fingerprint is generated
    fingerprint = `${version}:development`;
  }
  
  return {
    "X-Contracts-Version": version,
    "X-Contracts-Fingerprint": fingerprint,
  };
}

/**
 * Validate that headers match package version (for testing)
 */
export function validateHeadersMatchPackage(): { valid: boolean; errors: string[] } {
  const errors: string[] = [];
  const headers = emitContractHeaders();
  
  if (headers["X-Contracts-Version"] !== pkg.version) {
    errors.push(`Header version ${headers["X-Contracts-Version"]} !== package version ${pkg.version}`);
  }
  
  if (!headers["X-Contracts-Fingerprint"].startsWith(`${pkg.version}:`)) {
    errors.push(`Fingerprint doesn't start with package version: ${headers["X-Contracts-Fingerprint"]}`);
  }
  
  return {
    valid: errors.length === 0,
    errors
  };
}